text: // SPDX-License-Identifier: GPL-2.0
  /*
   *  linux/fs/ext4/inode.c
   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   *  from
   *
   *  linux/fs/minix/inode.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  64-bit file support on 64-bit platforms by Jakub Jelinek
   *	(jj@sunsite.ms.mff.cuni.cz)
   *
   *  Assorted race fixes, rewrite of ext4_get_block() by Al Viro, 2000
   */
  
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/time.h>
  #include <linux/highuid.h>
  #include <linux/pagemap.h>
  #include <linux/dax.h>
  #include <linux/quotaops.h>
  #include <linux/string.h>
  #include <linux/buffer_head.h>
  #include <linux/writeback.h>
  #include <linux/pagevec.h>
  #include <linux/mpage.h>
  #include <linux/namei.h>
  #include <linux/uio.h>
  #include <linux/bio.h>
  #include <linux/workqueue.h>
  #include <linux/kernel.h>
  #include <linux/printk.h>
  #include <linux/slab.h>
  #include <linux/bitops.h>
  #include <linux/iomap.h>
  #include <linux/iversion.h>
  
  #include "ext4_jbd2.h"
  #include "xattr.h"
  #include "acl.h"
  #include "truncate.h"
  
  #include <trace/events/ext4.h>
  
  static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
  			      struct ext4_inode_info *ei)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	__u32 csum;
  	__u16 dummy_csum = 0;
  	int offset = offsetof(struct ext4_inode, i_checksum_lo);
  	unsigned int csum_size = sizeof(dummy_csum);
  
  	csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)raw, offset);
  	csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, csum_size);
  	offset += csum_size;
  	csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
  			   EXT4_GOOD_OLD_INODE_SIZE - offset);
  
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
  		offset = offsetof(struct ext4_inode, i_checksum_hi);
  		csum = ext4_chksum(sbi, csum, (__u8 *)raw +
  				   EXT4_GOOD_OLD_INODE_SIZE,
  				   offset - EXT4_GOOD_OLD_INODE_SIZE);
  		if (EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi)) {
  			csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum,
  					   csum_size);
  			offset += csum_size;
  		}
  		csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
  				   EXT4_INODE_SIZE(inode->i_sb) - offset);
  	}
  
  	return csum;
  }
  
  static int ext4_inode_csum_verify(struct inode *inode, struct ext4_inode *raw,
  				  struct ext4_inode_info *ei)
  {
  	__u32 provided, calculated;
  
  	if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
  	    cpu_to_le32(EXT4_OS_LINUX) ||
  	    !ext4_has_metadata_csum(inode->i_sb))
  		return 1;
  
  	provided = le16_to_cpu(raw->i_checksum_lo);
  	calculated = ext4_inode_csum(inode, raw, ei);
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
  	    EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
  		provided |= ((__u32)le16_to_cpu(raw->i_checksum_hi)) << 16;
  	else
  		calculated &= 0xFFFF;
  
  	return provided == calculated;
  }
  
  void ext4_inode_csum_set(struct inode *inode, struct ext4_inode *raw,
  			 struct ext4_inode_info *ei)
  {
  	__u32 csum;
  
  	if (EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
  	    cpu_to_le32(EXT4_OS_LINUX) ||
  	    !ext4_has_metadata_csum(inode->i_sb))
  		return;
  
  	csum = ext4_inode_csum(inode, raw, ei);
  	raw->i_checksum_lo = cpu_to_le16(csum & 0xFFFF);
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
  	    EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
  		raw->i_checksum_hi = cpu_to_le16(csum >> 16);
  }
  
  static inline int ext4_begin_ordered_truncate(struct inode *inode,
  					      loff_t new_size)
  {
  	trace_ext4_begin_ordered_truncate(inode, new_size);
  	/*
  	 * If jinode is zero, then we never opened the file for
  	 * writing, so there's no need to call
  	 * jbd2_journal_begin_ordered_truncate() since there's no
  	 * outstanding writes we need to flush.
  	 */
  	if (!EXT4_I(inode)->jinode)
  		return 0;
  	return jbd2_journal_begin_ordered_truncate(EXT4_JOURNAL(inode),
  						   EXT4_I(inode)->jinode,
  						   new_size);
  }
  
  static void ext4_invalidatepage(struct page *page, unsigned int offset,
  				unsigned int length);
  static int __ext4_journalled_writepage(struct page *page, unsigned int len);
  static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
  				  int pextents);
  
  /*
   * Test whether an inode is a fast symlink.
   * A fast symlink has its symlink data stored in ext4_inode_info->i_data.
   */
  int ext4_inode_is_fast_symlink(struct inode *inode)
  {
  	if (!(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) {
  		int ea_blocks = EXT4_I(inode)->i_file_acl ?
  				EXT4_CLUSTER_SIZE(inode->i_sb) >> 9 : 0;
  
  		if (ext4_has_inline_data(inode))
  			return 0;
  
  		return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
  	}
  	return S_ISLNK(inode->i_mode) && inode->i_size &&
  	       (inode->i_size < EXT4_N_BLOCKS * 4);
  }
  
  /*
   * Called at the last iput() if i_nlink is zero.
   */
  void ext4_evict_inode(struct inode *inode)
  {
  	handle_t *handle;
  	int err;
  	/*
  	 * Credits for final inode cleanup and freeing:
  	 * sb + inode (ext4_orphan_del()), block bitmap, group descriptor
  	 * (xattr block freeing), bitmap, group descriptor (inode freeing)
  	 */
  	int extra_credits = 6;
  	struct ext4_xattr_inode_array *ea_inode_array = NULL;
  	bool freeze_protected = false;
  
  	trace_ext4_evict_inode(inode);
  
  	if (inode->i_nlink) {
  		/*
  		 * When journalling data dirty buffers are tracked only in the
  		 * journal. So although mm thinks everything is clean and
  		 * ready for reaping the inode might still have some pages to
  		 * write in the running transaction or waiting to be
  		 * checkpointed. Thus calling jbd2_journal_invalidatepage()
  		 * (via truncate_inode_pages()) to discard these buffers can
  		 * cause data loss. Also even if we did not discard these
  		 * buffers, we would have no way to find them after the inode
  		 * is reaped and thus user could see stale data if he tries to
  		 * read them before the transaction is checkpointed. So be
  		 * careful and force everything to disk here... We use
  		 * ei->i_datasync_tid to store the newest transaction
  		 * containing inode's data.
  		 *
  		 * Note that directories do not have this problem because they
  		 * don't use page cache.
  		 */
  		if (inode->i_ino != EXT4_JOURNAL_INO &&
  		    ext4_should_journal_data(inode) &&
  		    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode)) &&
  		    inode->i_data.nrpages) {
  			journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  			tid_t commit_tid = EXT4_I(inode)->i_datasync_tid;
  
  			jbd2_complete_transaction(journal, commit_tid);
  			filemap_write_and_wait(&inode->i_data);
  		}
  		truncate_inode_pages_final(&inode->i_data);
  
  		goto no_delete;
  	}
  
  	if (is_bad_inode(inode))
  		goto no_delete;
  	dquot_initialize(inode);
  
  	if (ext4_should_order_data(inode))
  		ext4_begin_ordered_truncate(inode, 0);
  	truncate_inode_pages_final(&inode->i_data);
  
  	/*
  	 * For inodes with journalled data, transaction commit could have
  	 * dirtied the inode. Flush worker is ignoring it because of I_FREEING
  	 * flag but we still need to remove the inode from the writeback lists.
  	 */
  	if (!list_empty_careful(&inode->i_io_list)) {
  		WARN_ON_ONCE(!ext4_should_journal_data(inode));
  		inode_io_list_del(inode);
  	}
  
  	/*
  	 * Protect us against freezing - iput() caller didn't have to have any
  	 * protection against it. When we are in a running transaction though,
  	 * we are already protected against freezing and we cannot grab further
  	 * protection due to lock ordering constraints.
  	 */
  	if (!ext4_journal_current_handle()) {
  		sb_start_intwrite(inode->i_sb);
  		freeze_protected = true;
  	}
  
  	if (!IS_NOQUOTA(inode))
  		extra_credits += EXT4_MAXQUOTAS_DEL_BLOCKS(inode->i_sb);
  
  	/*
  	 * Block bitmap, group descriptor, and inode are accounted in both
  	 * ext4_blocks_for_truncate() and extra_credits. So subtract 3.
  	 */
  	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE,
  			 ext4_blocks_for_truncate(inode) + extra_credits - 3);
  	if (IS_ERR(handle)) {
  		ext4_std_error(inode->i_sb, PTR_ERR(handle));
  		/*
  		 * If we're going to skip the normal cleanup, we still need to
  		 * make sure that the in-core orphan linked list is properly
  		 * cleaned up.
  		 */
  		ext4_orphan_del(NULL, inode);
  		if (freeze_protected)
  			sb_end_intwrite(inode->i_sb);
  		goto no_delete;
  	}
  
  	if (IS_SYNC(inode))
  		ext4_handle_sync(handle);
  
  	/*
  	 * Set inode->i_size to 0 before calling ext4_truncate(). We need
  	 * special handling of symlinks here because i_size is used to
  	 * determine whether ext4_inode_info->i_data contains symlink data or
  	 * block mappings. Setting i_size to 0 will remove its fast symlink
  	 * status. Erase i_data so that it becomes a valid empty block map.
  	 */
  	if (ext4_inode_is_fast_symlink(inode))
  		memset(EXT4_I(inode)->i_data, 0, sizeof(EXT4_I(inode)->i_data));
  	inode->i_size = 0;
  	err = ext4_mark_inode_dirty(handle, inode);
  	if (err) {
  		ext4_warning(inode->i_sb,
  			     "couldn't mark inode dirty (err %d)", err);
  		goto stop_handle;
  	}
  	if (inode->i_blocks) {
  		err = ext4_truncate(inode);
  		if (err) {
  			ext4_error_err(inode->i_sb, -err,
  				       "couldn't truncate inode %lu (err %d)",
  				       inode->i_ino, err);
  			goto stop_handle;
  		}
  	}
  
  	/* Remove xattr references. */
  	err = ext4_xattr_delete_inode(handle, inode, &ea_inode_array,
  				      extra_credits);
  	if (err) {
  		ext4_warning(inode->i_sb, "xattr delete (err %d)", err);
  stop_handle:
  		ext4_journal_stop(handle);
  		ext4_orphan_del(NULL, inode);
  		if (freeze_protected)
  			sb_end_intwrite(inode->i_sb);
  		ext4_xattr_inode_array_free(ea_inode_array);
  		goto no_delete;
  	}
  
  	/*
  	 * Kill off the orphan record which ext4_truncate created.
  	 * AKPM: I think this can be inside the above `if'.
  	 * Note that ext4_orphan_del() has to be able to cope with the
  	 * deletion of a non-existent orphan - this is because we don't
  	 * know if ext4_truncate() actually created an orphan record.
  	 * (Well, we could do this if we need to, but heck - it works)
  	 */
  	ext4_orphan_del(handle, inode);
  	EXT4_I(inode)->i_dtime	= (__u32)ktime_get_real_seconds();
  
  	/*
  	 * One subtle ordering requirement: if anything has gone wrong
  	 * (transaction abort, IO errors, whatever), then we can still
  	 * do these next steps (the fs will already have been marked as
  	 * having errors), but we can't free the inode if the mark_dirty
  	 * fails.
  	 */
  	if (ext4_mark_inode_dirty(handle, inode))
  		/* If that failed, just do the required in-core inode clear. */
  		ext4_clear_inode(inode);
  	else
  		ext4_free_inode(handle, inode);
  	ext4_journal_stop(handle);
  	if (freeze_protected)
  		sb_end_intwrite(inode->i_sb);
  	ext4_xattr_inode_array_free(ea_inode_array);
  	return;
  no_delete:
  	if (!list_empty(&EXT4_I(inode)->i_fc_list))
  		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM);
  	ext4_clear_inode(inode);	/* We must guarantee clearing of inode... */
  }
  
  #ifdef CONFIG_QUOTA
  qsize_t *ext4_get_reserved_space(struct inode *inode)
  {
  	return &EXT4_I(inode)->i_reserved_quota;
  }
  #endif
  
  /*
   * Called with i_data_sem down, which is important since we can call
   * ext4_discard_preallocations() from here.
   */
  void ext4_da_update_reserve_space(struct inode *inode,
  					int used, int quota_claim)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct ext4_inode_info *ei = EXT4_I(inode);
  
  	spin_lock(&ei->i_block_reservation_lock);
  	trace_ext4_da_update_reserve_space(inode, used, quota_claim);
  	if (unlikely(used > ei->i_reserved_data_blocks)) {
  		ext4_warning(inode->i_sb, "%s: ino %lu, used %d "
  			 "with only %d reserved data blocks",
  			 __func__, inode->i_ino, used,
  			 ei->i_reserved_data_blocks);
  		WARN_ON(1);
  		used = ei->i_reserved_data_blocks;
  	}
  
  	/* Update per-inode reservations */
  	ei->i_reserved_data_blocks -= used;
  	percpu_counter_sub(&sbi->s_dirtyclusters_counter, used);
  
  	spin_unlock(&ei->i_block_reservation_lock);
  
  	/* Update quota subsystem for data blocks */
  	if (quota_claim)
  		dquot_claim_block(inode, EXT4_C2B(sbi, used));
  	else {
  		/*
  		 * We did fallocate with an offset that is already delayed
  		 * allocated. So on delayed allocated writeback we should
  		 * not re-claim the quota for fallocated blocks.
  		 */
  		dquot_release_reservation_block(inode, EXT4_C2B(sbi, used));
  	}
  
  	/*
  	 * If we have done all the pending block allocations and if
  	 * there aren't any writers on the inode, we can discard the
  	 * inode's preallocations.
  	 */
  	if ((ei->i_reserved_data_blocks == 0) &&
  	    !inode_is_open_for_write(inode))
  		ext4_discard_preallocations(inode, 0);
  }
  
  static int __check_block_validity(struct inode *inode, const char *func,
  				unsigned int line,
  				struct ext4_map_blocks *map)
  {
  	if (ext4_has_feature_journal(inode->i_sb) &&
  	    (inode->i_ino ==
  	     le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
  		return 0;
  	if (!ext4_inode_block_valid(inode, map->m_pblk, map->m_len)) {
  		ext4_error_inode(inode, func, line, map->m_pblk,
  				 "lblock %lu mapped to illegal pblock %llu "
  				 "(length %d)", (unsigned long) map->m_lblk,
  				 map->m_pblk, map->m_len);
  		return -EFSCORRUPTED;
  	}
  	return 0;
  }
  
  int ext4_issue_zeroout(struct inode *inode, ext4_lblk_t lblk, ext4_fsblk_t pblk,
  		       ext4_lblk_t len)
  {
  	int ret;
  
  	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
  		return fscrypt_zeroout_range(inode, lblk, pblk, len);
  
  	ret = sb_issue_zeroout(inode->i_sb, pblk, len, GFP_NOFS);
  	if (ret > 0)
  		ret = 0;
  
  	return ret;
  }
  
  #define check_block_validity(inode, map)	\
  	__check_block_validity((inode), __func__, __LINE__, (map))
  
  #ifdef ES_AGGRESSIVE_TEST
  static void ext4_map_blocks_es_recheck(handle_t *handle,
  				       struct inode *inode,
  				       struct ext4_map_blocks *es_map,
  				       struct ext4_map_blocks *map,
  				       int flags)
  {
  	int retval;
  
  	map->m_flags = 0;
  	/*
  	 * There is a race window that the result is not the same.
  	 * e.g. xfstests #223 when dioread_nolock enables.  The reason
  	 * is that we lookup a block mapping in extent status tree with
  	 * out taking i_data_sem.  So at the time the unwritten extent
  	 * could be converted.
  	 */
  	down_read(&EXT4_I(inode)->i_data_sem);
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
  		retval = ext4_ext_map_blocks(handle, inode, map, 0);
  	} else {
  		retval = ext4_ind_map_blocks(handle, inode, map, 0);
  	}
  	up_read((&EXT4_I(inode)->i_data_sem));
  
  	/*
  	 * We don't check m_len because extent will be collpased in status
  	 * tree.  So the m_len might not equal.
  	 */
  	if (es_map->m_lblk != map->m_lblk ||
  	    es_map->m_flags != map->m_flags ||
  	    es_map->m_pblk != map->m_pblk) {
  		printk("ES cache assertion failed for inode: %lu "
  		       "es_cached ex [%d/%d/%llu/%x] != "
  		       "found ex [%d/%d/%llu/%x] retval %d flags %x\n",
  		       inode->i_ino, es_map->m_lblk, es_map->m_len,
  		       es_map->m_pblk, es_map->m_flags, map->m_lblk,
  		       map->m_len, map->m_pblk, map->m_flags,
  		       retval, flags);
  	}
  }
  #endif /* ES_AGGRESSIVE_TEST */
  
  /*
   * The ext4_map_blocks() function tries to look up the requested blocks,
   * and returns if the blocks are already mapped.
   *
   * Otherwise it takes the write lock of the i_data_sem and allocate blocks
   * and store the allocated blocks in the result buffer head and mark it
   * mapped.
   *
   * If file type is extents based, it will call ext4_ext_map_blocks(),
   * Otherwise, call with ext4_ind_map_blocks() to handle indirect mapping
   * based files
   *
   * On success, it returns the number of blocks being mapped or allocated.  if
   * create==0 and the blocks are pre-allocated and unwritten, the resulting @map
   * is marked as unwritten. If the create == 1, it will mark @map as mapped.
   *
   * It returns 0 if plain look up failed (blocks have not been allocated), in
   * that case, @map is returned as unmapped but we still do fill map->m_len to
   * indicate the length of a hole starting at map->m_lblk.
   *
   * It returns the error in case of allocation failure.
   */
  int ext4_map_blocks(handle_t *handle, struct inode *inode,
  		    struct ext4_map_blocks *map, int flags)
  {
  	struct extent_status es;
  	int retval;
  	int ret = 0;
  #ifdef ES_AGGRESSIVE_TEST
  	struct ext4_map_blocks orig_map;
  
  	memcpy(&orig_map, map, sizeof(*map));
  #endif
  
  	map->m_flags = 0;
  	ext_debug(inode, "flag 0x%x, max_blocks %u, logical block %lu\n",
  		  flags, map->m_len, (unsigned long) map->m_lblk);
  
  	/*
  	 * ext4_map_blocks returns an int, and m_len is an unsigned int
  	 */
  	if (unlikely(map->m_len > INT_MAX))
  		map->m_len = INT_MAX;
  
  	/* We can handle the block number less than EXT_MAX_BLOCKS */
  	if (unlikely(map->m_lblk >= EXT_MAX_BLOCKS))
  		return -EFSCORRUPTED;
  
  	/* Lookup extent status tree firstly */
  	if (!(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) &&
  	    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
  		if (ext4_es_is_written(&es) || ext4_es_is_unwritten(&es)) {
  			map->m_pblk = ext4_es_pblock(&es) +
  					map->m_lblk - es.es_lblk;
  			map->m_flags |= ext4_es_is_written(&es) ?
  					EXT4_MAP_MAPPED : EXT4_MAP_UNWRITTEN;
  			retval = es.es_len - (map->m_lblk - es.es_lblk);
  			if (retval > map->m_len)
  				retval = map->m_len;
  			map->m_len = retval;
  		} else if (ext4_es_is_delayed(&es) || ext4_es_is_hole(&es)) {
  			map->m_pblk = 0;
  			retval = es.es_len - (map->m_lblk - es.es_lblk);
  			if (retval > map->m_len)
  				retval = map->m_len;
  			map->m_len = retval;
  			retval = 0;
  		} else {
  			BUG();
  		}
  #ifdef ES_AGGRESSIVE_TEST
  		ext4_map_blocks_es_recheck(handle, inode, map,
  					   &orig_map, flags);
  #endif
  		goto found;
  	}
  
  	/*
  	 * Try to see if we can get the block without requesting a new
  	 * file system block.
  	 */
  	down_read(&EXT4_I(inode)->i_data_sem);
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
  		retval = ext4_ext_map_blocks(handle, inode, map, 0);
  	} else {
  		retval = ext4_ind_map_blocks(handle, inode, map, 0);
  	}
  	if (retval > 0) {
  		unsigned int status;
  
  		if (unlikely(retval != map->m_len)) {
  			ext4_warning(inode->i_sb,
  				     "ES len assertion failed for inode "
  				     "%lu: retval %d != map->m_len %d",
  				     inode->i_ino, retval, map->m_len);
  			WARN_ON(1);
  		}
  
  		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
  				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
  		if (!(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
  		    !(status & EXTENT_STATUS_WRITTEN) &&
  		    ext4_es_scan_range(inode, &ext4_es_is_delayed, map->m_lblk,
  				       map->m_lblk + map->m_len - 1))
  			status |= EXTENT_STATUS_DELAYED;
  		ret = ext4_es_insert_extent(inode, map->m_lblk,
  					    map->m_len, map->m_pblk, status);
  		if (ret < 0)
  			retval = ret;
  	}
  	up_read((&EXT4_I(inode)->i_data_sem));
  
  found:
  	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
  		ret = check_block_validity(inode, map);
  		if (ret != 0)
  			return ret;
  	}
  
  	/* If it is only a block(s) look up */
  	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
  		return retval;
  
  	/*
  	 * Returns if the blocks have already allocated
  	 *
  	 * Note that if blocks have been preallocated
  	 * ext4_ext_get_block() returns the create = 0
  	 * with buffer head unmapped.
  	 */
  	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED)
  		/*
  		 * If we need to convert extent to unwritten
  		 * we continue and do the actual work in
  		 * ext4_ext_map_blocks()
  		 */
  		if (!(flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN))
  			return retval;
  
  	/*
  	 * Here we clear m_flags because after allocating an new extent,
  	 * it will be set again.
  	 */
  	map->m_flags &= ~EXT4_MAP_FLAGS;
  
  	/*
  	 * New blocks allocate and/or writing to unwritten extent
  	 * will possibly result in updating i_data, so we take
  	 * the write lock of i_data_sem, and call get_block()
  	 * with create == 1 flag.
  	 */
  	down_write(&EXT4_I(inode)->i_data_sem);
  
  	/*
  	 * We need to check for EXT4 here because migrate
  	 * could have changed the inode type in between
  	 */
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
  		retval = ext4_ext_map_blocks(handle, inode, map, flags);
  	} else {
  		retval = ext4_ind_map_blocks(handle, inode, map, flags);
  
  		if (retval > 0 && map->m_flags & EXT4_MAP_NEW) {
  			/*
  			 * We allocated new blocks which will result in
  			 * i_data's format changing.  Force the migrate
  			 * to fail by clearing migrate flags
  			 */
  			ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
  		}
  
  		/*
  		 * Update reserved blocks/metadata blocks after successful
  		 * block allocation which had been deferred till now. We don't
  		 * support fallocate for non extent files. So we can update
  		 * reserve space here.
  		 */
  		if ((retval > 0) &&
  			(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE))
  			ext4_da_update_reserve_space(inode, retval, 1);
  	}
  
  	if (retval > 0) {
  		unsigned int status;
  
  		if (unlikely(retval != map->m_len)) {
  			ext4_warning(inode->i_sb,
  				     "ES len assertion failed for inode "
  				     "%lu: retval %d != map->m_len %d",
  				     inode->i_ino, retval, map->m_len);
  			WARN_ON(1);
  		}
  
  		/*
  		 * We have to zeroout blocks before inserting them into extent
  		 * status tree. Otherwise someone could look them up there and
  		 * use them before they are really zeroed. We also have to
  		 * unmap metadata before zeroing as otherwise writeback can
  		 * overwrite zeros with stale data from block device.
  		 */
  		if (flags & EXT4_GET_BLOCKS_ZERO &&
  		    map->m_flags & EXT4_MAP_MAPPED &&
  		    map->m_flags & EXT4_MAP_NEW) {
  			ret = ext4_issue_zeroout(inode, map->m_lblk,
  						 map->m_pblk, map->m_len);
  			if (ret) {
  				retval = ret;
  				goto out_sem;
  			}
  		}
  
  		/*
  		 * If the extent has been zeroed out, we don't need to update
  		 * extent status tree.
  		 */
  		if ((flags & EXT4_GET_BLOCKS_PRE_IO) &&
  		    ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
  			if (ext4_es_is_written(&es))
  				goto out_sem;
  		}
  		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
  				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
  		if (!(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
  		    !(status & EXTENT_STATUS_WRITTEN) &&
  		    ext4_es_scan_range(inode, &ext4_es_is_delayed, map->m_lblk,
  				       map->m_lblk + map->m_len - 1))
  			status |= EXTENT_STATUS_DELAYED;
  		ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
  					    map->m_pblk, status);
  		if (ret < 0) {
  			retval = ret;
  			goto out_sem;
  		}
  	}
  
  out_sem:
  	up_write((&EXT4_I(inode)->i_data_sem));
  	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
  		ret = check_block_validity(inode, map);
  		if (ret != 0)
  			return ret;
  
  		/*
  		 * Inodes with freshly allocated blocks where contents will be
  		 * visible after transaction commit must be on transaction's
  		 * ordered data list.
  		 */
  		if (map->m_flags & EXT4_MAP_NEW &&
  		    !(map->m_flags & EXT4_MAP_UNWRITTEN) &&
  		    !(flags & EXT4_GET_BLOCKS_ZERO) &&
  		    !ext4_is_quota_file(inode) &&
  		    ext4_should_order_data(inode)) {
  			loff_t start_byte =
  				(loff_t)map->m_lblk << inode->i_blkbits;
  			loff_t length = (loff_t)map->m_len << inode->i_blkbits;
  
  			if (flags & EXT4_GET_BLOCKS_IO_SUBMIT)
  				ret = ext4_jbd2_inode_add_wait(handle, inode,
  						start_byte, length);
  			else
  				ret = ext4_jbd2_inode_add_write(handle, inode,
  						start_byte, length);
  			if (ret)
  				return ret;
  		}
  		ext4_fc_track_range(handle, inode, map->m_lblk,
  			    map->m_lblk + map->m_len - 1);
  	}
  
  	if (retval < 0)
  		ext_debug(inode, "failed with err %d\n", retval);
  	return retval;
  }
  
  /*
   * Update EXT4_MAP_FLAGS in bh->b_state. For buffer heads attached to pages
   * we have to be careful as someone else may be manipulating b_state as well.
   */
  static void ext4_update_bh_state(struct buffer_head *bh, unsigned long flags)
  {
  	unsigned long old_state;
  	unsigned long new_state;
  
  	flags &= EXT4_MAP_FLAGS;
  
  	/* Dummy buffer_head? Set non-atomically. */
  	if (!bh->b_page) {
  		bh->b_state = (bh->b_state & ~EXT4_MAP_FLAGS) | flags;
  		return;
  	}
  	/*
  	 * Someone else may be modifying b_state. Be careful! This is ugly but
  	 * once we get rid of using bh as a container for mapping information
  	 * to pass to / from get_block functions, this can go away.
  	 */
  	do {
  		old_state = READ_ONCE(bh->b_state);
  		new_state = (old_state & ~EXT4_MAP_FLAGS) | flags;
  	} while (unlikely(
  		 cmpxchg(&bh->b_state, old_state, new_state) != old_state));
  }
  
  static int _ext4_get_block(struct inode *inode, sector_t iblock,
  			   struct buffer_head *bh, int flags)
  {
  	struct ext4_map_blocks map;
  	int ret = 0;
  
  	if (ext4_has_inline_data(inode))
  		return -ERANGE;
  
  	map.m_lblk = iblock;
  	map.m_len = bh->b_size >> inode->i_blkbits;
  
  	ret = ext4_map_blocks(ext4_journal_current_handle(), inode, &map,
  			      flags);
  	if (ret > 0) {
  		map_bh(bh, inode->i_sb, map.m_pblk);
  		ext4_update_bh_state(bh, map.m_flags);
  		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
  		ret = 0;
  	} else if (ret == 0) {
  		/* hole case, need to fill in bh->b_size */
  		bh->b_size = inode->i_sb->s_blocksize * map.m_len;
  	}
  	return ret;
  }
  
  int ext4_get_block(struct inode *inode, sector_t iblock,
  		   struct buffer_head *bh, int create)
  {
  	return _ext4_get_block(inode, iblock, bh,
  			       create ? EXT4_GET_BLOCKS_CREATE : 0);
  }
  
  /*
   * Get block function used when preparing for buffered write if we require
   * creating an unwritten extent if blocks haven't been allocated.  The extent
   * will be converted to written after the IO is complete.
   */
  int ext4_get_block_unwritten(struct inode *inode, sector_t iblock,
  			     struct buffer_head *bh_result, int create)
  {
  	ext4_debug("ext4_get_block_unwritten: inode %lu, create flag %d\n",
  		   inode->i_ino, create);
  	return _ext4_get_block(inode, iblock, bh_result,
  			       EXT4_GET_BLOCKS_IO_CREATE_EXT);
  }
  
  /* Maximum number of blocks we map for direct IO at once. */
  #define DIO_MAX_BLOCKS 4096
  
  /*
   * `handle' can be NULL if create is zero
   */
  struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
  				ext4_lblk_t block, int map_flags)
  {
  	struct ext4_map_blocks map;
  	struct buffer_head *bh;
  	int create = map_flags & EXT4_GET_BLOCKS_CREATE;
  	int err;
  
  	ASSERT((EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
  		    || handle != NULL || create == 0);
  
  	map.m_lblk = block;
  	map.m_len = 1;
  	err = ext4_map_blocks(handle, inode, &map, map_flags);
  
  	if (err == 0)
  		return create ? ERR_PTR(-ENOSPC) : NULL;
  	if (err < 0)
  		return ERR_PTR(err);
  
  	bh = sb_getblk(inode->i_sb, map.m_pblk);
  	if (unlikely(!bh))
  		return ERR_PTR(-ENOMEM);
  	if (map.m_flags & EXT4_MAP_NEW) {
  		ASSERT(create != 0);
  		ASSERT((EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
  			    || (handle != NULL));
  
  		/*
  		 * Now that we do not always journal data, we should
  		 * keep in mind whether this should always journal the
  		 * new buffer as metadata.  For now, regular file
  		 * writes use ext4_get_block instead, so it's not a
  		 * problem.
  		 */
  		lock_buffer(bh);
  		BUFFER_TRACE(bh, "call get_create_access");
  		err = ext4_journal_get_create_access(handle, inode->i_sb, bh,
  						     EXT4_JTR_NONE);
  		if (unlikely(err)) {
  			unlock_buffer(bh);
  			goto errout;
  		}
  		if (!buffer_uptodate(bh)) {
  			memset(bh->b_data, 0, inode->i_sb->s_blocksize);
  			set_buffer_uptodate(bh);
  		}
  		unlock_buffer(bh);
  		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
  		err = ext4_handle_dirty_metadata(handle, inode, bh);
  		if (unlikely(err))
  			goto errout;
  	} else
  		BUFFER_TRACE(bh, "not a new buffer");
  	return bh;
  errout:
  	brelse(bh);
  	return ERR_PTR(err);
  }
  
  struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
  			       ext4_lblk_t block, int map_flags)
  {
  	struct buffer_head *bh;
  	int ret;
  
  	bh = ext4_getblk(handle, inode, block, map_flags);
  	if (IS_ERR(bh))
  		return bh;
  	if (!bh || ext4_buffer_uptodate(bh))
  		return bh;
  
  	ret = ext4_read_bh_lock(bh, REQ_META | REQ_PRIO, true);
  	if (ret) {
  		put_bh(bh);
  		return ERR_PTR(ret);
  	}
  	return bh;
  }
  
  /* Read a contiguous batch of blocks. */
  int ext4_bread_batch(struct inode *inode, ext4_lblk_t block, int bh_count,
  		     bool wait, struct buffer_head **bhs)
  {
  	int i, err;
  
  	for (i = 0; i < bh_count; i++) {
  		bhs[i] = ext4_getblk(NULL, inode, block + i, 0 /* map_flags */);
  		if (IS_ERR(bhs[i])) {
  			err = PTR_ERR(bhs[i]);
  			bh_count = i;
  			goto out_brelse;
  		}
  	}
  
  	for (i = 0; i < bh_count; i++)
  		/* Note that NULL bhs[i] is valid because of holes. */
  		if (bhs[i] && !ext4_buffer_uptodate(bhs[i]))
  			ext4_read_bh_lock(bhs[i], REQ_META | REQ_PRIO, false);
  
  	if (!wait)
  		return 0;
  
  	for (i = 0; i < bh_count; i++)
  		if (bhs[i])
  			wait_on_buffer(bhs[i]);
  
  	for (i = 0; i < bh_count; i++) {
  		if (bhs[i] && !buffer_uptodate(bhs[i])) {
  			err = -EIO;
  			goto out_brelse;
  		}
  	}
  	return 0;
  
  out_brelse:
  	for (i = 0; i < bh_count; i++) {
  		brelse(bhs[i]);
  		bhs[i] = NULL;
  	}
  	return err;
  }
  
  int ext4_walk_page_buffers(handle_t *handle, struct inode *inode,
  			   struct buffer_head *head,
  			   unsigned from,
  			   unsigned to,
  			   int *partial,
  			   int (*fn)(handle_t *handle, struct inode *inode,
  				     struct buffer_head *bh))
  {
  	struct buffer_head *bh;
  	unsigned block_start, block_end;
  	unsigned blocksize = head->b_size;
  	int err, ret = 0;
  	struct buffer_head *next;
  
  	for (bh = head, block_start = 0;
  	     ret == 0 && (bh != head || !block_start);
  	     block_start = block_end, bh = next) {
  		next = bh->b_this_page;
  		block_end = block_start + blocksize;
  		if (block_end <= from || block_start >= to) {
  			if (partial && !buffer_uptodate(bh))
  				*partial = 1;
  			continue;
  		}
  		err = (*fn)(handle, inode, bh);
  		if (!ret)
  			ret = err;
  	}
  	return ret;
  }
  
  /*
   * To preserve ordering, it is essential that the hole instantiation and
   * the data write be encapsulated in a single transaction.  We cannot
   * close off a transaction and start a new one between the ext4_get_block()
   * and the commit_write().  So doing the jbd2_journal_start at the start of
   * prepare_write() is the right place.
   *
   * Also, this function can nest inside ext4_writepage().  In that case, we
   * *know* that ext4_writepage() has generated enough buffer credits to do the
   * whole page.  So we won't block on the journal in that case, which is good,
   * because the caller may be PF_MEMALLOC.
   *
   * By accident, ext4 can be reentered when a transaction is open via
   * quota file writes.  If we were to commit the transaction while thus
   * reentered, there can be a deadlock - we would be holding a quota
   * lock, and the commit would never complete if another thread had a
   * transaction open and was blocking on the quota lock - a ranking
   * violation.
   *
   * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
   * will _not_ run commit under these circumstances because handle->h_ref
   * is elevated.  We'll still have enough credits for the tiny quotafile
   * write.
   */
  int do_journal_get_write_access(handle_t *handle, struct inode *inode,
  				struct buffer_head *bh)
  {
  	int dirty = buffer_dirty(bh);
  	int ret;
  
  	if (!buffer_mapped(bh) || buffer_freed(bh))
  		return 0;
  	/*
  	 * __block_write_begin() could have dirtied some buffers. Clean
  	 * the dirty bit as jbd2_journal_get_write_access() could complain
  	 * otherwise about fs integrity issues. Setting of the dirty bit
  	 * by __block_write_begin() isn't a real problem here as we clear
  	 * the bit before releasing a page lock and thus writeback cannot
  	 * ever write the buffer.
  	 */
  	if (dirty)
  		clear_buffer_dirty(bh);
  	BUFFER_TRACE(bh, "get write access");
  	ret = ext4_journal_get_write_access(handle, inode->i_sb, bh,
  					    EXT4_JTR_NONE);
  	if (!ret && dirty)
  		ret = ext4_handle_dirty_metadata(handle, NULL, bh);
  	return ret;
  }
  
  #ifdef CONFIG_FS_ENCRYPTION
  static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
  				  get_block_t *get_block)
  {
  	unsigned from = pos & (PAGE_SIZE - 1);
  	unsigned to = from + len;
  	struct inode *inode = page->mapping->host;
  	unsigned block_start, block_end;
  	sector_t block;
  	int err = 0;
  	unsigned blocksize = inode->i_sb->s_blocksize;
  	unsigned bbits;
  	struct buffer_head *bh, *head, *wait[2];
  	int nr_wait = 0;
  	int i;
  
  	BUG_ON(!PageLocked(page));
  	BUG_ON(from > PAGE_SIZE);
  	BUG_ON(to > PAGE_SIZE);
  	BUG_ON(from > to);
  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, blocksize, 0);
  	head = page_buffers(page);
  	bbits = ilog2(blocksize);
  	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
  
  	for (bh = head, block_start = 0; bh != head || !block_start;
  	    block++, block_start = block_end, bh = bh->b_this_page) {
  		block_end = block_start + blocksize;
  		if (block_end <= from || block_start >= to) {
  			if (PageUptodate(page)) {
  				set_buffer_uptodate(bh);
  			}
  			continue;
  		}
  		if (buffer_new(bh))
  			clear_buffer_new(bh);
  		if (!buffer_mapped(bh)) {
  			WARN_ON(bh->b_size != blocksize);
  			err = get_block(inode, block, bh, 1);
  			if (err)
  				break;
  			if (buffer_new(bh)) {
  				if (PageUptodate(page)) {
  					clear_buffer_new(bh);
  					set_buffer_uptodate(bh);
  					mark_buffer_dirty(bh);
  					continue;
  				}
  				if (block_end > to || block_start < from)
  					zero_user_segments(page, to, block_end,
  							   block_start, from);
  				continue;
  			}
  		}
  		if (PageUptodate(page)) {
  			set_buffer_uptodate(bh);
  			continue;
  		}
  		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
  		    !buffer_unwritten(bh) &&
  		    (block_start < from || block_end > to)) {
  			ext4_read_bh_lock(bh, 0, false);
  			wait[nr_wait++] = bh;
  		}
  	}
  	/*
  	 * If we issued read requests, let them complete.
  	 */
  	for (i = 0; i < nr_wait; i++) {
  		wait_on_buffer(wait[i]);
  		if (!buffer_uptodate(wait[i]))
  			err = -EIO;
  	}
  	if (unlikely(err)) {
  		page_zero_new_buffers(page, from, to);
  	} else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
  		for (i = 0; i < nr_wait; i++) {
  			int err2;
  
  			err2 = fscrypt_decrypt_pagecache_blocks(page, blocksize,
  								bh_offset(wait[i]));
  			if (err2) {
  				clear_buffer_uptodate(wait[i]);
  				err = err2;
  			}
  		}
  	}
  
  	return err;
  }
  #endif
  
  static int ext4_write_begin(struct file *file, struct address_space *mapping,
  			    loff_t pos, unsigned len, unsigned flags,
  			    struct page **pagep, void **fsdata)
  {
  	struct inode *inode = mapping->host;
  	int ret, needed_blocks;
  	handle_t *handle;
  	int retries = 0;
  	struct page *page;
  	pgoff_t index;
  	unsigned from, to;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	trace_ext4_write_begin(inode, pos, len, flags);
  	/*
  	 * Reserve one block more for addition to orphan list in case
  	 * we allocate blocks but write fails for some reason
  	 */
  	needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
  	index = pos >> PAGE_SHIFT;
  	from = pos & (PAGE_SIZE - 1);
  	to = from + len;
  
  	if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
  		ret = ext4_try_to_write_inline_data(mapping, inode, pos, len,
  						    flags, pagep);
  		if (ret < 0)
  			return ret;
  		if (ret == 1)
  			return 0;
  	}
  
  	/*
  	 * grab_cache_page_write_begin() can take a long time if the
  	 * system is thrashing due to memory pressure, or if the page
  	 * is being written back.  So grab it first before we start
  	 * the transaction handle.  This also allows us to allocate
  	 * the page (if needed) without using GFP_NOFS.
  	 */
  retry_grab:
  	page = grab_cache_page_write_begin(mapping, index, flags);
  	if (!page)
  		return -ENOMEM;
  	unlock_page(page);
  
  retry_journal:
  	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE, needed_blocks);
  	if (IS_ERR(handle)) {
  		put_page(page);
  		return PTR_ERR(handle);
  	}
  
  	lock_page(page);
  	if (page->mapping != mapping) {
  		/* The page got truncated from under us */
  		unlock_page(page);
  		put_page(page);
  		ext4_journal_stop(handle);
  		goto retry_grab;
  	}
  	/* In case writeback began while the page was unlocked */
  	wait_for_stable_page(page);
  
  #ifdef CONFIG_FS_ENCRYPTION
  	if (ext4_should_dioread_nolock(inode))
  		ret = ext4_block_write_begin(page, pos, len,
  					     ext4_get_block_unwritten);
  	else
  		ret = ext4_block_write_begin(page, pos, len,
  					     ext4_get_block);
  #else
  	if (ext4_should_dioread_nolock(inode))
  		ret = __block_write_begin(page, pos, len,
  					  ext4_get_block_unwritten);
  	else
  		ret = __block_write_begin(page, pos, len, ext4_get_block);
  #endif
  	if (!ret && ext4_should_journal_data(inode)) {
  		ret = ext4_walk_page_buffers(handle, inode,
  					     page_buffers(page), from, to, NULL,
  					     do_journal_get_write_access);
  	}
  
  	if (ret) {
  		bool extended = (pos + len > inode->i_size) &&
  				!ext4_verity_in_progress(inode);
  
  		unlock_page(page);
  		/*
  		 * __block_write_begin may have instantiated a few blocks
  		 * outside i_size.  Trim these off again. Don't need
  		 * i_size_read because we hold i_mutex.
  		 *
  		 * Add inode to orphan list in case we crash before
  		 * truncate finishes
  		 */
  		if (extended && ext4_can_truncate(inode))
  			ext4_orphan_add(handle, inode);
  
  		ext4_journal_stop(handle);
  		if (extended) {
  			ext4_truncate_failed_write(inode);
  			/*
  			 * If truncate failed early the inode might
  			 * still be on the orphan list; we need to
  			 * make sure the inode is removed from the
  			 * orphan list in that case.
  			 */
  			if (inode->i_nlink)
  				ext4_orphan_del(NULL, inode);
  		}
  
  		if (ret == -ENOSPC &&
  		    ext4_should_retry_alloc(inode->i_sb, &retries))
  			goto retry_journal;
  		put_page(page);
  		return ret;
  	}
  	*pagep = page;
  	return ret;
  }
  
  /* For write_end() in data=journal mode */
  static int write_end_fn(handle_t *handle, struct inode *inode,
  			struct buffer_head *bh)
  {
  	int ret;
  	if (!buffer_mapped(bh) || buffer_freed(bh))
  		return 0;
  	set_buffer_uptodate(bh);
  	ret = ext4_handle_dirty_metadata(handle, NULL, bh);
  	clear_buffer_meta(bh);
  	clear_buffer_prio(bh);
  	return ret;
  }
  
  /*
   * We need to pick up the new inode size which generic_commit_write gave us
   * `file' can be NULL - eg, when called from page_symlink().
   *
   * ext4 never places buffers on inode->i_mapping->private_list.  metadata
   * buffers are managed internally.
   */
  static int ext4_write_end(struct file *file,
  			  struct address_space *mapping,
  			  loff_t pos, unsigned len, unsigned copied,
  			  struct page *page, void *fsdata)
  {
  	handle_t *handle = ext4_journal_current_handle();
  	struct inode *inode = mapping->host;
  	loff_t old_size = inode->i_size;
  	int ret = 0, ret2;
  	int i_size_changed = 0;
  	bool verity = ext4_verity_in_progress(inode);
  
  	trace_ext4_write_end(inode, pos, len, copied);
  
  	if (ext4_has_inline_data(inode))
  		return ext4_write_inline_data_end(inode, pos, len, copied, page);
  
  	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
  	/*
  	 * it's important to update i_size while still holding page lock:
  	 * page writeout could otherwise come in and zero beyond i_size.
  	 *
  	 * If FS_IOC_ENABLE_VERITY is running on this inode, then Merkle tree
  	 * blocks are being written past EOF, so skip the i_size update.
  	 */
  	if (!verity)
  		i_size_changed = ext4_update_inode_size(inode, pos + copied);
  	unlock_page(page);
  	put_page(page);
  
  	if (old_size < pos && !verity)
  		pagecache_isize_extended(inode, old_size, pos);
  	/*
  	 * Don't mark the inode dirty under page lock. First, it unnecessarily
  	 * makes the holding time of page lock longer. Second, it forces lock
  	 * ordering of page lock and transaction start for journaling
  	 * filesystems.
  	 */
  	if (i_size_changed)
  		ret = ext4_mark_inode_dirty(handle, inode);
  
  	if (pos + len > inode->i_size && !verity && ext4_can_truncate(inode))
  		/* if we have allocated more blocks and copied
  		 * less. We will have blocks allocated outside
  		 * inode->i_size. So truncate them
  		 */
  		ext4_orphan_add(handle, inode);
  
  	ret2 = ext4_journal_stop(handle);
  	if (!ret)
  		ret = ret2;
  
  	if (pos + len > inode->i_size && !verity) {
  		ext4_truncate_failed_write(inode);
  		/*
  		 * If truncate failed early the inode might still be
  		 * on the orphan list; we need to make sure the inode
  		 * is removed from the orphan list in that case.
  		 */
  		if (inode->i_nlink)
  			ext4_orphan_del(NULL, inode);
  	}
  
  	return ret ? ret : copied;
  }
  
  /*
   * This is a private version of page_zero_new_buffers() which doesn't
   * set the buffer to be dirty, since in data=journalled mode we need
   * to call ext4_handle_dirty_metadata() instead.
   */
  static void ext4_journalled_zero_new_buffers(handle_t *handle,
  					    struct inode *inode,
  					    struct page *page,
  					    unsigned from, unsigned to)
  {
  	unsigned int block_start = 0, block_end;
  	struct buffer_head *head, *bh;
  
  	bh = head = page_buffers(page);
  	do {
  		block_end = block_start + bh->b_size;
  		if (buffer_new(bh)) {
  			if (block_end > from && block_start < to) {
  				if (!PageUptodate(page)) {
  					unsigned start, size;
  
  					start = max(from, block_start);
  					size = min(to, block_end) - start;
  
  					zero_user(page, start, size);
  					write_end_fn(handle, inode, bh);
  				}
  				clear_buffer_new(bh);
  			}
  		}
  		block_start = block_end;
  		bh = bh->b_this_page;
  	} while (bh != head);
  }
  
  static int ext4_journalled_write_end(struct file *file,
  				     struct address_space *mapping,
  				     loff_t pos, unsigned len, unsigned copied,
  				     struct page *page, void *fsdata)
  {
  	handle_t *handle = ext4_journal_current_handle();
  	struct inode *inode = mapping->host;
  	loff_t old_size = inode->i_size;
  	int ret = 0, ret2;
  	int partial = 0;
  	unsigned from, to;
  	int size_changed = 0;
  	bool verity = ext4_verity_in_progress(inode);
  
  	trace_ext4_journalled_write_end(inode, pos, len, copied);
  	from = pos & (PAGE_SIZE - 1);
  	to = from + len;
  
  	BUG_ON(!ext4_handle_valid(handle));
  
  	if (ext4_has_inline_data(inode))
  		return ext4_write_inline_data_end(inode, pos, len, copied, page);
  
  	if (unlikely(copied < len) && !PageUptodate(page)) {
  		copied = 0;
  		ext4_journalled_zero_new_buffers(handle, inode, page, from, to);
  	} else {
  		if (unlikely(copied < len))
  			ext4_journalled_zero_new_buffers(handle, inode, page,
  							 from + copied, to);
  		ret = ext4_walk_page_buffers(handle, inode, page_buffers(page),
  					     from, from + copied, &partial,
  					     write_end_fn);
  		if (!partial)
  			SetPageUptodate(page);
  	}
  	if (!verity)
  		size_changed = ext4_update_inode_size(inode, pos + copied);
  	ext4_set_inode_state(inode, EXT4_STATE_JDATA);
  	EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
  	unlock_page(page);
  	put_page(page);
  
  	if (old_size < pos && !verity)
  		pagecache_isize_extended(inode, old_size, pos);
  
  	if (size_changed) {
  		ret2 = ext4_mark_inode_dirty(handle, inode);
  		if (!ret)
  			ret = ret2;
  	}
  
  	if (pos + len > inode->i_size && !verity && ext4_can_truncate(inode))
  		/* if we have allocated more blocks and copied
  		 * less. We will have blocks allocated outside
  		 * inode->i_size. So truncate them
  		 */
  		ext4_orphan_add(handle, inode);
  
  	ret2 = ext4_journal_stop(handle);
  	if (!ret)
  		ret = ret2;
  	if (pos + len > inode->i_size && !verity) {
  		ext4_truncate_failed_write(inode);
  		/*
  		 * If truncate failed early the inode might still be
  		 * on the orphan list; we need to make sure the inode
  		 * is removed from the orphan list in that case.
  		 */
  		if (inode->i_nlink)
  			ext4_orphan_del(NULL, inode);
  	}
  
  	return ret ? ret : copied;
  }
  
  /*
   * Reserve space for a single cluster
   */
  static int ext4_da_reserve_space(struct inode *inode)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	int ret;
  
  	/*
  	 * We will charge metadata quota at writeout time; this saves
  	 * us from metadata over-estimation, though we may go over by
  	 * a small amount in the end.  Here we just reserve for data.
  	 */
  	ret = dquot_reserve_block(inode, EXT4_C2B(sbi, 1));
  	if (ret)
  		return ret;
  
  	spin_lock(&ei->i_block_reservation_lock);
  	if (ext4_claim_free_clusters(sbi, 1, 0)) {
  		spin_unlock(&ei->i_block_reservation_lock);
  		dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
  		return -ENOSPC;
  	}
  	ei->i_reserved_data_blocks++;
  	trace_ext4_da_reserve_space(inode);
  	spin_unlock(&ei->i_block_reservation_lock);
  
  	return 0;       /* success */
  }
  
  void ext4_da_release_space(struct inode *inode, int to_free)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct ext4_inode_info *ei = EXT4_I(inode);
  
  	if (!to_free)
  		return;		/* Nothing to release, exit */
  
  	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
  
  	trace_ext4_da_release_space(inode, to_free);
  	if (unlikely(to_free > ei->i_reserved_data_blocks)) {
  		/*
  		 * if there aren't enough reserved blocks, then the
  		 * counter is messed up somewhere.  Since this
  		 * function is called from invalidate page, it's
  		 * harmless to return without any action.
  		 */
  		ext4_warning(inode->i_sb, "ext4_da_release_space: "
  			 "ino %lu, to_free %d with only %d reserved "
  			 "data blocks", inode->i_ino, to_free,
  			 ei->i_reserved_data_blocks);
  		WARN_ON(1);
  		to_free = ei->i_reserved_data_blocks;
  	}
  	ei->i_reserved_data_blocks -= to_free;
  
  	/* update fs dirty data blocks counter */
  	percpu_counter_sub(&sbi->s_dirtyclusters_counter, to_free);
  
  	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
  
  	dquot_release_reservation_block(inode, EXT4_C2B(sbi, to_free));
  }
  
  /*
   * Delayed allocation stuff
   */
  
  struct mpage_da_data {
  	struct inode *inode;
  	struct writeback_control *wbc;
  
  	pgoff_t first_page;	/* The first page to write */
  	pgoff_t next_page;	/* Current page to examine */
  	pgoff_t last_page;	/* Last page to examine */
  	/*
  	 * Extent to map - this can be after first_page because that can be
  	 * fully mapped. We somewhat abuse m_flags to store whether the extent
  	 * is delalloc or unwritten.
  	 */
  	struct ext4_map_blocks map;
  	struct ext4_io_submit io_submit;	/* IO submission data */
  	unsigned int do_map:1;
  	unsigned int scanned_until_end:1;
  };
  
  static void mpage_release_unused_pages(struct mpage_da_data *mpd,
  				       bool invalidate)
  {
  	int nr_pages, i;
  	pgoff_t index, end;
  	struct pagevec pvec;
  	struct inode *inode = mpd->inode;
  	struct address_space *mapping = inode->i_mapping;
  
  	/* This is necessary when next_page == 0. */
  	if (mpd->first_page >= mpd->next_page)
  		return;
  
  	mpd->scanned_until_end = 0;
  	index = mpd->first_page;
  	end   = mpd->next_page - 1;
  	if (invalidate) {
  		ext4_lblk_t start, last;
  		start = index << (PAGE_SHIFT - inode->i_blkbits);
  		last = end << (PAGE_SHIFT - inode->i_blkbits);
  		ext4_es_remove_extent(inode, start, last - start + 1);
  	}
  
  	pagevec_init(&pvec);
  	while (index <= end) {
  		nr_pages = pagevec_lookup_range(&pvec, mapping, &index, end);
  		if (nr_pages == 0)
  			break;
  		for (i = 0; i < nr_pages; i++) {
  			struct page *page = pvec.pages[i];
  
  			BUG_ON(!PageLocked(page));
  			BUG_ON(PageWriteback(page));
  			if (invalidate) {
  				if (page_mapped(page))
  					clear_page_dirty_for_io(page);
  				block_invalidatepage(page, 0, PAGE_SIZE);
  				ClearPageUptodate(page);
  			}
  			unlock_page(page);
  		}
  		pagevec_release(&pvec);
  	}
  }
  
  static void ext4_print_free_blocks(struct inode *inode)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct super_block *sb = inode->i_sb;
  	struct ext4_inode_info *ei = EXT4_I(inode);
  
  	ext4_msg(sb, KERN_CRIT, "Total free blocks count %lld",
  	       EXT4_C2B(EXT4_SB(inode->i_sb),
  			ext4_count_free_clusters(sb)));
  	ext4_msg(sb, KERN_CRIT, "Free/Dirty block details");
  	ext4_msg(sb, KERN_CRIT, "free_blocks=%lld",
  	       (long long) EXT4_C2B(EXT4_SB(sb),
  		percpu_counter_sum(&sbi->s_freeclusters_counter)));
  	ext4_msg(sb, KERN_CRIT, "dirty_blocks=%lld",
  	       (long long) EXT4_C2B(EXT4_SB(sb),
  		percpu_counter_sum(&sbi->s_dirtyclusters_counter)));
  	ext4_msg(sb, KERN_CRIT, "Block reservation details");
  	ext4_msg(sb, KERN_CRIT, "i_reserved_data_blocks=%u",
  		 ei->i_reserved_data_blocks);
  	return;
  }
  
  static int ext4_bh_delay_or_unwritten(handle_t *handle, struct inode *inode,
  				      struct buffer_head *bh)
  {
  	return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
  }
  
  /*
   * ext4_insert_delayed_block - adds a delayed block to the extents status
   *                             tree, incrementing the reserved cluster/block
   *                             count or making a pending reservation
   *                             where needed
   *
   * @inode - file containing the newly added block
   * @lblk - logical block to be added
   *
   * Returns 0 on success, negative error code on failure.
   */
  static int ext4_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	int ret;
  	bool allocated = false;
  	bool reserved = false;
  
  	/*
  	 * If the cluster containing lblk is shared with a delayed,
  	 * written, or unwritten extent in a bigalloc file system, it's
  	 * already been accounted for and does not need to be reserved.
  	 * A pending reservation must be made for the cluster if it's
  	 * shared with a written or unwritten extent and doesn't already
  	 * have one.  Written and unwritten extents can be purged from the
  	 * extents status tree if the system is under memory pressure, so
  	 * it's necessary to examine the extent tree if a search of the
  	 * extents status tree doesn't get a match.
  	 */
  	if (sbi->s_cluster_ratio == 1) {
  		ret = ext4_da_reserve_space(inode);
  		if (ret != 0)   /* ENOSPC */
  			goto errout;
  		reserved = true;
  	} else {   /* bigalloc */
  		if (!ext4_es_scan_clu(inode, &ext4_es_is_delonly, lblk)) {
  			if (!ext4_es_scan_clu(inode,
  					      &ext4_es_is_mapped, lblk)) {
  				ret = ext4_clu_mapped(inode,
  						      EXT4_B2C(sbi, lblk));
  				if (ret < 0)
  					goto errout;
  				if (ret == 0) {
  					ret = ext4_da_reserve_space(inode);
  					if (ret != 0)   /* ENOSPC */
  						goto errout;
  					reserved = true;
  				} else {
  					allocated = true;
  				}
  			} else {
  				allocated = true;
  			}
  		}
  	}
  
  	ret = ext4_es_insert_delayed_block(inode, lblk, allocated);
  	if (ret && reserved)
  		ext4_da_release_space(inode, 1);
  
  errout:
  	return ret;
  }
  
  /*
   * This function is grabs code from the very beginning of
   * ext4_map_blocks, but assumes that the caller is from delayed write
   * time. This function looks up the requested blocks and sets the
   * buffer delay bit under the protection of i_data_sem.
   */
  static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
  			      struct ext4_map_blocks *map,
  			      struct buffer_head *bh)
  {
  	struct extent_status es;
  	int retval;
  	sector_t invalid_block = ~((sector_t) 0xffff);
  #ifdef ES_AGGRESSIVE_TEST
  	struct ext4_map_blocks orig_map;
  
  	memcpy(&orig_map, map, sizeof(*map));
  #endif
  
  	if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
  		invalid_block = ~0;
  
  	map->m_flags = 0;
  	ext_debug(inode, "max_blocks %u, logical block %lu\n", map->m_len,
  		  (unsigned long) map->m_lblk);
  
  	/* Lookup extent status tree firstly */
  	if (ext4_es_lookup_extent(inode, iblock, NULL, &es)) {
  		if (ext4_es_is_hole(&es)) {
  			retval = 0;
  			down_read(&EXT4_I(inode)->i_data_sem);
  			goto add_delayed;
  		}
  
  		/*
  		 * the buffer head associated with a delayed and not unwritten
  		 * block found in the extent status cache must contain an
  		 * invalid block number and have its BH_New and BH_Delay bits
  		 * set, reflecting the state assigned when the block was
  		 * initially delayed allocated
  		 */
  		if (ext4_es_is_delonly(&es)) {
  			BUG_ON(bh->b_blocknr != invalid_block);
  			BUG_ON(!buffer_new(bh));
  			BUG_ON(!buffer_delay(bh));
  			return 0;
  		}
  
  		map->m_pblk = ext4_es_pblock(&es) + iblock - es.es_lblk;
  		retval = es.es_len - (iblock - es.es_lblk);
  		if (retval > map->m_len)
  			retval = map->m_len;
  		map->m_len = retval;
  		if (ext4_es_is_written(&es))
  			map->m_flags |= EXT4_MAP_MAPPED;
  		else if (ext4_es_is_unwritten(&es))
  			map->m_flags |= EXT4_MAP_UNWRITTEN;
  		else
  			BUG();
  
  #ifdef ES_AGGRESSIVE_TEST
  		ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
  #endif
  		return retval;
  	}
  
  	/*
  	 * Try to see if we can get the block without requesting a new
  	 * file system block.
  	 */
  	down_read(&EXT4_I(inode)->i_data_sem);
  	if (ext4_has_inline_data(inode))
  		retval = 0;
  	else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		retval = ext4_ext_map_blocks(NULL, inode, map, 0);
  	else
  		retval = ext4_ind_map_blocks(NULL, inode, map, 0);
  
  add_delayed:
  	if (retval == 0) {
  		int ret;
  
  		/*
  		 * XXX: __block_prepare_write() unmaps passed block,
  		 * is it OK?
  		 */
  
  		ret = ext4_insert_delayed_block(inode, map->m_lblk);
  		if (ret != 0) {
  			retval = ret;
  			goto out_unlock;
  		}
  
  		map_bh(bh, inode->i_sb, invalid_block);
  		set_buffer_new(bh);
  		set_buffer_delay(bh);
  	} else if (retval > 0) {
  		int ret;
  		unsigned int status;
  
  		if (unlikely(retval != map->m_len)) {
  			ext4_warning(inode->i_sb,
  				     "ES len assertion failed for inode "
  				     "%lu: retval %d != map->m_len %d",
  				     inode->i_ino, retval, map->m_len);
  			WARN_ON(1);
  		}
  
  		status = map->m_flags & EXT4_MAP_UNWRITTEN ?
  				EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
  		ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
  					    map->m_pblk, status);
  		if (ret != 0)
  			retval = ret;
  	}
  
  out_unlock:
  	up_read((&EXT4_I(inode)->i_data_sem));
  
  	return retval;
  }
  
  /*
   * This is a special get_block_t callback which is used by
   * ext4_da_write_begin().  It will either return mapped block or
   * reserve space for a single block.
   *
   * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set.
   * We also have b_blocknr = -1 and b_bdev initialized properly
   *
   * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set.
   * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev
   * initialized properly.
   */
  int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
  			   struct buffer_head *bh, int create)
  {
  	struct ext4_map_blocks map;
  	int ret = 0;
  
  	BUG_ON(create == 0);
  	BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
  
  	map.m_lblk = iblock;
  	map.m_len = 1;
  
  	/*
  	 * first, we need to know whether the block is allocated already
  	 * preallocated blocks are unmapped but should treated
  	 * the same as allocated blocks.
  	 */
  	ret = ext4_da_map_blocks(inode, iblock, &map, bh);
  	if (ret <= 0)
  		return ret;
  
  	map_bh(bh, inode->i_sb, map.m_pblk);
  	ext4_update_bh_state(bh, map.m_flags);
  
  	if (buffer_unwritten(bh)) {
  		/* A delayed write to unwritten bh should be marked
  		 * new and mapped.  Mapped ensures that we don't do
  		 * get_block multiple times when we write to the same
  		 * offset and new ensures that we do proper zero out
  		 * for partial write.
  		 */
  		set_buffer_new(bh);
  		set_buffer_mapped(bh);
  	}
  	return 0;
  }
  
  static int bget_one(handle_t *handle, struct inode *inode,
  		    struct buffer_head *bh)
  {
  	get_bh(bh);
  	return 0;
  }
  
  static int bput_one(handle_t *handle, struct inode *inode,
  		    struct buffer_head *bh)
  {
  	put_bh(bh);
  	return 0;
  }
  
  static int __ext4_journalled_writepage(struct page *page,
  				       unsigned int len)
  {
  	struct address_space *mapping = page->mapping;
  	struct inode *inode = mapping->host;
  	struct buffer_head *page_bufs = NULL;
  	handle_t *handle = NULL;
  	int ret = 0, err = 0;
  	int inline_data = ext4_has_inline_data(inode);
  	struct buffer_head *inode_bh = NULL;
  
  	ClearPageChecked(page);
  
  	if (inline_data) {
  		BUG_ON(page->index != 0);
  		BUG_ON(len > ext4_get_max_inline_size(inode));
  		inode_bh = ext4_journalled_write_inline_data(inode, len, page);
  		if (inode_bh == NULL)
  			goto out;
  	} else {
  		page_bufs = page_buffers(page);
  		if (!page_bufs) {
  			BUG();
  			goto out;
  		}
  		ext4_walk_page_buffers(handle, inode, page_bufs, 0, len,
  				       NULL, bget_one);
  	}
  	/*
  	 * We need to release the page lock before we start the
  	 * journal, so grab a reference so the page won't disappear
  	 * out from under us.
  	 */
  	get_page(page);
  	unlock_page(page);
  
  	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
  				    ext4_writepage_trans_blocks(inode));
  	if (IS_ERR(handle)) {
  		ret = PTR_ERR(handle);
  		put_page(page);
  		goto out_no_pagelock;
  	}
  	BUG_ON(!ext4_handle_valid(handle));
  
  	lock_page(page);
  	put_page(page);
  	if (page->mapping != mapping) {
  		/* The page got truncated from under us */
  		ext4_journal_stop(handle);
  		ret = 0;
  		goto out;
  	}
  
  	if (inline_data) {
  		ret = ext4_mark_inode_dirty(handle, inode);
  	} else {
  		ret = ext4_walk_page_buffers(handle, inode, page_bufs, 0, len,
  					     NULL, do_journal_get_write_access);
  
  		err = ext4_walk_page_buffers(handle, inode, page_bufs, 0, len,
  					     NULL, write_end_fn);
  	}
  	if (ret == 0)
  		ret = err;
  	err = ext4_jbd2_inode_add_write(handle, inode, page_offset(page), len);
  	if (ret == 0)
  		ret = err;
  	EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
  	err = ext4_journal_stop(handle);
  	if (!ret)
  		ret = err;
  
  	ext4_set_inode_state(inode, EXT4_STATE_JDATA);
  out:
  	unlock_page(page);
  out_no_pagelock:
  	if (!inline_data && page_bufs)
  		ext4_walk_page_buffers(NULL, inode, page_bufs, 0, len,
  				       NULL, bput_one);
  	brelse(inode_bh);
  	return ret;
  }
  
  /*
   * Note that we don't need to start a transaction unless we're journaling data
   * because we should have holes filled from ext4_page_mkwrite(). We even don't
   * need to file the inode to the transaction's list in ordered mode because if
   * we are writing back data added by write(), the inode is already there and if
   * we are writing back data modified via mmap(), no one guarantees in which
   * transaction the data will hit the disk. In case we are journaling data, we
   * cannot start transaction directly because transaction start ranks above page
   * lock so we have to do some magic.
   *
   * This function can get called via...
   *   - ext4_writepages after taking page lock (have journal handle)
   *   - journal_submit_inode_data_buffers (no journal handle)
   *   - shrink_page_list via the kswapd/direct reclaim (no journal handle)
   *   - grab_page_cache when doing write_begin (have journal handle)
   *
   * We don't do any block allocation in this function. If we have page with
   * multiple blocks we need to write those buffer_heads that are mapped. This
   * is important for mmaped based write. So if we do with blocksize 1K
   * truncate(f, 1024);
   * a = mmap(f, 0, 4096);
   * a[0] = 'a';
   * truncate(f, 4096);
   * we have in the page first buffer_head mapped via page_mkwrite call back
   * but other buffer_heads would be unmapped but dirty (dirty done via the
   * do_wp_page). So writepage should write the first block. If we modify
   * the mmap area beyond 1024 we will again get a page_fault and the
   * page_mkwrite callback will do the block allocation and mark the
   * buffer_heads mapped.
   *
   * We redirty the page if we have any buffer_heads that is either delay or
   * unwritten in the page.
   *
   * We can get recursively called as show below.
   *
   *	ext4_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
   *		ext4_writepage()
   *
   * But since we don't do any block allocation we should not deadlock.
   * Page also have the dirty flag cleared so we don't get recurive page_lock.
   */
  static int ext4_writepage(struct page *page,
  			  struct writeback_control *wbc)
  {
  	int ret = 0;
  	loff_t size;
  	unsigned int len;
  	struct buffer_head *page_bufs = NULL;
  	struct inode *inode = page->mapping->host;
  	struct ext4_io_submit io_submit;
  	bool keep_towrite = false;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) {
  		inode->i_mapping->a_ops->invalidatepage(page, 0, PAGE_SIZE);
  		unlock_page(page);
  		return -EIO;
  	}
  
  	trace_ext4_writepage(page);
  	size = i_size_read(inode);
  	if (page->index == size >> PAGE_SHIFT &&
  	    !ext4_verity_in_progress(inode))
  		len = size & ~PAGE_MASK;
  	else
  		len = PAGE_SIZE;
  
  	page_bufs = page_buffers(page);
  	/*
  	 * We cannot do block allocation or other extent handling in this
  	 * function. If there are buffers needing that, we have to redirty
  	 * the page. But we may reach here when we do a journal commit via
  	 * journal_submit_inode_data_buffers() and in that case we must write
  	 * allocated buffers to achieve data=ordered mode guarantees.
  	 *
  	 * Also, if there is only one buffer per page (the fs block
  	 * size == the page size), if one buffer needs block
  	 * allocation or needs to modify the extent tree to clear the
  	 * unwritten flag, we know that the page can't be written at
  	 * all, so we might as well refuse the write immediately.
  	 * Unfortunately if the block size != page size, we can't as
  	 * easily detect this case using ext4_walk_page_buffers(), but
  	 * for the extremely common case, this is an optimization that
  	 * skips a useless round trip through ext4_bio_write_page().
  	 */
  	if (ext4_walk_page_buffers(NULL, inode, page_bufs, 0, len, NULL,
  				   ext4_bh_delay_or_unwritten)) {
  		redirty_page_for_writepage(wbc, page);
  		if ((current->flags & PF_MEMALLOC) ||
  		    (inode->i_sb->s_blocksize == PAGE_SIZE)) {
  			/*
  			 * For memory cleaning there's no point in writing only
  			 * some buffers. So just bail out. Warn if we came here
  			 * from direct reclaim.
  			 */
  			WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD))
  							== PF_MEMALLOC);
  			unlock_page(page);
  			return 0;
  		}
  		keep_towrite = true;
  	}
  
  	if (PageChecked(page) && ext4_should_journal_data(inode))
  		/*
  		 * It's mmapped pagecache.  Add buffers and journal it.  There
  		 * doesn't seem much point in redirtying the page here.
  		 */
  		return __ext4_journalled_writepage(page, len);
  
  	ext4_io_submit_init(&io_submit, wbc);
  	io_submit.io_end = ext4_init_io_end(inode, GFP_NOFS);
  	if (!io_submit.io_end) {
  		redirty_page_for_writepage(wbc, page);
  		unlock_page(page);
  		return -ENOMEM;
  	}
  	ret = ext4_bio_write_page(&io_submit, page, len, keep_towrite);
  	ext4_io_submit(&io_submit);
  	/* Drop io_end reference we got from init */
  	ext4_put_io_end_defer(io_submit.io_end);
  	return ret;
  }
  
  static int mpage_submit_page(struct mpage_da_data *mpd, struct page *page)
  {
  	int len;
  	loff_t size;
  	int err;
  
  	BUG_ON(page->index != mpd->first_page);
  	clear_page_dirty_for_io(page);
  	/*
  	 * We have to be very careful here!  Nothing protects writeback path
  	 * against i_size changes and the page can be writeably mapped into
  	 * page tables. So an application can be growing i_size and writing
  	 * data through mmap while writeback runs. clear_page_dirty_for_io()
  	 * write-protects our page in page tables and the page cannot get
  	 * written to again until we release page lock. So only after
  	 * clear_page_dirty_for_io() we are safe to sample i_size for
  	 * ext4_bio_write_page() to zero-out tail of the written page. We rely
  	 * on the barrier provided by TestClearPageDirty in
  	 * clear_page_dirty_for_io() to make sure i_size is really sampled only
  	 * after page tables are updated.
  	 */
  	size = i_size_read(mpd->inode);
  	if (page->index == size >> PAGE_SHIFT &&
  	    !ext4_verity_in_progress(mpd->inode))
  		len = size & ~PAGE_MASK;
  	else
  		len = PAGE_SIZE;
  	err = ext4_bio_write_page(&mpd->io_submit, page, len, false);
  	if (!err)
  		mpd->wbc->nr_to_write--;
  	mpd->first_page++;
  
  	return err;
  }
  
  #define BH_FLAGS (BIT(BH_Unwritten) | BIT(BH_Delay))
  
  /*
   * mballoc gives us at most this number of blocks...
   * XXX: That seems to be only a limitation of ext4_mb_normalize_request().
   * The rest of mballoc seems to handle chunks up to full group size.
   */
  #define MAX_WRITEPAGES_EXTENT_LEN 2048
  
  /*
   * mpage_add_bh_to_extent - try to add bh to extent of blocks to map
   *
   * @mpd - extent of blocks
   * @lblk - logical number of the block in the file
   * @bh - buffer head we want to add to the extent
   *
   * The function is used to collect contig. blocks in the same state. If the
   * buffer doesn't require mapping for writeback and we haven't started the
   * extent of buffers to map yet, the function returns 'true' immediately - the
   * caller can write the buffer right away. Otherwise the function returns true
   * if the block has been added to the extent, false if the block couldn't be
   * added.
   */
  static bool mpage_add_bh_to_extent(struct mpage_da_data *mpd, ext4_lblk_t lblk,
  				   struct buffer_head *bh)
  {
  	struct ext4_map_blocks *map = &mpd->map;
  
  	/* Buffer that doesn't need mapping for writeback? */
  	if (!buffer_dirty(bh) || !buffer_mapped(bh) ||
  	    (!buffer_delay(bh) && !buffer_unwritten(bh))) {
  		/* So far no extent to map => we write the buffer right away */
  		if (map->m_len == 0)
  			return true;
  		return false;
  	}
  
  	/* First block in the extent? */
  	if (map->m_len == 0) {
  		/* We cannot map unless handle is started... */
  		if (!mpd->do_map)
  			return false;
  		map->m_lblk = lblk;
  		map->m_len = 1;
  		map->m_flags = bh->b_state & BH_FLAGS;
  		return true;
  	}
  
  	/* Don't go larger than mballoc is willing to allocate */
  	if (map->m_len >= MAX_WRITEPAGES_EXTENT_LEN)
  		return false;
  
  	/* Can we merge the block to our big extent? */
  	if (lblk == map->m_lblk + map->m_len &&
  	    (bh->b_state & BH_FLAGS) == map->m_flags) {
  		map->m_len++;
  		return true;
  	}
  	return false;
  }
  
  /*
   * mpage_process_page_bufs - submit page buffers for IO or add them to extent
   *
   * @mpd - extent of blocks for mapping
   * @head - the first buffer in the page
   * @bh - buffer we should start processing from
   * @lblk - logical number of the block in the file corresponding to @bh
   *
   * Walk through page buffers from @bh upto @head (exclusive) and either submit
   * the page for IO if all buffers in this page were mapped and there's no
   * accumulated extent of buffers to map or add buffers in the page to the
   * extent of buffers to map. The function returns 1 if the caller can continue
   * by processing the next page, 0 if it should stop adding buffers to the
   * extent to map because we cannot extend it anymore. It can also return value
   * < 0 in case of error during IO submission.
   */
  static int mpage_process_page_bufs(struct mpage_da_data *mpd,
  				   struct buffer_head *head,
  				   struct buffer_head *bh,
  				   ext4_lblk_t lblk)
  {
  	struct inode *inode = mpd->inode;
  	int err;
  	ext4_lblk_t blocks = (i_size_read(inode) + i_blocksize(inode) - 1)
  							>> inode->i_blkbits;
  
  	if (ext4_verity_in_progress(inode))
  		blocks = EXT_MAX_BLOCKS;
  
  	do {
  		BUG_ON(buffer_locked(bh));
  
  		if (lblk >= blocks || !mpage_add_bh_to_extent(mpd, lblk, bh)) {
  			/* Found extent to map? */
  			if (mpd->map.m_len)
  				return 0;
  			/* Buffer needs mapping and handle is not started? */
  			if (!mpd->do_map)
  				return 0;
  			/* Everything mapped so far and we hit EOF */
  			break;
  		}
  	} while (lblk++, (bh = bh->b_this_page) != head);
  	/* So far everything mapped? Submit the page for IO. */
  	if (mpd->map.m_len == 0) {
  		err = mpage_submit_page(mpd, head->b_page);
  		if (err < 0)
  			return err;
  	}
  	if (lblk >= blocks) {
  		mpd->scanned_until_end = 1;
  		return 0;
  	}
  	return 1;
  }
  
  /*
   * mpage_process_page - update page buffers corresponding to changed extent and
   *		       may submit fully mapped page for IO
   *
   * @mpd		- description of extent to map, on return next extent to map
   * @m_lblk	- logical block mapping.
   * @m_pblk	- corresponding physical mapping.
   * @map_bh	- determines on return whether this page requires any further
   *		  mapping or not.
   * Scan given page buffers corresponding to changed extent and update buffer
   * state according to new extent state.
   * We map delalloc buffers to their physical location, clear unwritten bits.
   * If the given page is not fully mapped, we update @map to the next extent in
   * the given page that needs mapping & return @map_bh as true.
   */
  static int mpage_process_page(struct mpage_da_data *mpd, struct page *page,
  			      ext4_lblk_t *m_lblk, ext4_fsblk_t *m_pblk,
  			      bool *map_bh)
  {
  	struct buffer_head *head, *bh;
  	ext4_io_end_t *io_end = mpd->io_submit.io_end;
  	ext4_lblk_t lblk = *m_lblk;
  	ext4_fsblk_t pblock = *m_pblk;
  	int err = 0;
  	int blkbits = mpd->inode->i_blkbits;
  	ssize_t io_end_size = 0;
  	struct ext4_io_end_vec *io_end_vec = ext4_last_io_end_vec(io_end);
  
  	bh = head = page_buffers(page);
  	do {
  		if (lblk < mpd->map.m_lblk)
  			continue;
  		if (lblk >= mpd->map.m_lblk + mpd->map.m_len) {
  			/*
  			 * Buffer after end of mapped extent.
  			 * Find next buffer in the page to map.
  			 */
  			mpd->map.m_len = 0;
  			mpd->map.m_flags = 0;
  			io_end_vec->size += io_end_size;
  			io_end_size = 0;
  
  			err = mpage_process_page_bufs(mpd, head, bh, lblk);
  			if (err > 0)
  				err = 0;
  			if (!err && mpd->map.m_len && mpd->map.m_lblk > lblk) {
  				io_end_vec = ext4_alloc_io_end_vec(io_end);
  				if (IS_ERR(io_end_vec)) {
  					err = PTR_ERR(io_end_vec);
  					goto out;
  				}
  				io_end_vec->offset = (loff_t)mpd->map.m_lblk << blkbits;
  			}
  			*map_bh = true;
  			goto out;
  		}
  		if (buffer_delay(bh)) {
  			clear_buffer_delay(bh);
  			bh->b_blocknr = pblock++;
  		}
  		clear_buffer_unwritten(bh);
  		io_end_size += (1 << blkbits);
  	} while (lblk++, (bh = bh->b_this_page) != head);
  
  	io_end_vec->size += io_end_size;
  	io_end_size = 0;
  	*map_bh = false;
  out:
  	*m_lblk = lblk;
  	*m_pblk = pblock;
  	return err;
  }
  
  /*
   * mpage_map_buffers - update buffers corresponding to changed extent and
   *		       submit fully mapped pages for IO
   *
   * @mpd - description of extent to map, on return next extent to map
   *
   * Scan buffers corresponding to changed extent (we expect corresponding pages
   * to be already locked) and update buffer state according to new extent state.
   * We map delalloc buffers to their physical location, clear unwritten bits,
   * and mark buffers as uninit when we perform writes to unwritten extents
   * and do extent conversion after IO is finished. If the last page is not fully
   * mapped, we update @map to the next extent in the last page that needs
   * mapping. Otherwise we submit the page for IO.
   */
  static int mpage_map_and_submit_buffers(struct mpage_da_data *mpd)
  {
  	struct pagevec pvec;
  	int nr_pages, i;
  	struct inode *inode = mpd->inode;
  	int bpp_bits = PAGE_SHIFT - inode->i_blkbits;
  	pgoff_t start, end;
  	ext4_lblk_t lblk;
  	ext4_fsblk_t pblock;
  	int err;
  	bool map_bh = false;
  
  	start = mpd->map.m_lblk >> bpp_bits;
  	end = (mpd->map.m_lblk + mpd->map.m_len - 1) >> bpp_bits;
  	lblk = start << bpp_bits;
  	pblock = mpd->map.m_pblk;
  
  	pagevec_init(&pvec);
  	while (start <= end) {
  		nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
  						&start, end);
  		if (nr_pages == 0)
  			break;
  		for (i = 0; i < nr_pages; i++) {
  			struct page *page = pvec.pages[i];
  
  			err = mpage_process_page(mpd, page, &lblk, &pblock,
  						 &map_bh);
  			/*
  			 * If map_bh is true, means page may require further bh
  			 * mapping, or maybe the page was submitted for IO.
  			 * So we return to call further extent mapping.
  			 */
  			if (err < 0 || map_bh)
  				goto out;
  			/* Page fully mapped - let IO run! */
  			err = mpage_submit_page(mpd, page);
  			if (err < 0)
  				goto out;
  		}
  		pagevec_release(&pvec);
  	}
  	/* Extent fully mapped and matches with page boundary. We are done. */
  	mpd->map.m_len = 0;
  	mpd->map.m_flags = 0;
  	return 0;
  out:
  	pagevec_release(&pvec);
  	return err;
  }
  
  static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
  {
  	struct inode *inode = mpd->inode;
  	struct ext4_map_blocks *map = &mpd->map;
  	int get_blocks_flags;
  	int err, dioread_nolock;
  
  	trace_ext4_da_write_pages_extent(inode, map);
  	/*
  	 * Call ext4_map_blocks() to allocate any delayed allocation blocks, or
  	 * to convert an unwritten extent to be initialized (in the case
  	 * where we have written into one or more preallocated blocks).  It is
  	 * possible that we're going to need more metadata blocks than
  	 * previously reserved. However we must not fail because we're in
  	 * writeback and there is nothing we can do about it so it might result
  	 * in data loss.  So use reserved blocks to allocate metadata if
  	 * possible.
  	 *
  	 * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE if
  	 * the blocks in question are delalloc blocks.  This indicates
  	 * that the blocks and quotas has already been checked when
  	 * the data was copied into the page cache.
  	 */
  	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
  			   EXT4_GET_BLOCKS_METADATA_NOFAIL |
  			   EXT4_GET_BLOCKS_IO_SUBMIT;
  	dioread_nolock = ext4_should_dioread_nolock(inode);
  	if (dioread_nolock)
  		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
  	if (map->m_flags & BIT(BH_Delay))
  		get_blocks_flags |= EXT4_GET_BLOCKS_DELALLOC_RESERVE;
  
  	err = ext4_map_blocks(handle, inode, map, get_blocks_flags);
  	if (err < 0)
  		return err;
  	if (dioread_nolock && (map->m_flags & EXT4_MAP_UNWRITTEN)) {
  		if (!mpd->io_submit.io_end->handle &&
  		    ext4_handle_valid(handle)) {
  			mpd->io_submit.io_end->handle = handle->h_rsv_handle;
  			handle->h_rsv_handle = NULL;
  		}
  		ext4_set_io_unwritten_flag(inode, mpd->io_submit.io_end);
  	}
  
  	BUG_ON(map->m_len == 0);
  	return 0;
  }
  
  /*
   * mpage_map_and_submit_extent - map extent starting at mpd->lblk of length
   *				 mpd->len and submit pages underlying it for IO
   *
   * @handle - handle for journal operations
   * @mpd - extent to map
   * @give_up_on_write - we set this to true iff there is a fatal error and there
   *                     is no hope of writing the data. The caller should discard
   *                     dirty pages to avoid infinite loops.
   *
   * The function maps extent starting at mpd->lblk of length mpd->len. If it is
   * delayed, blocks are allocated, if it is unwritten, we may need to convert
   * them to initialized or split the described range from larger unwritten
   * extent. Note that we need not map all the described range since allocation
   * can return less blocks or the range is covered by more unwritten extents. We
   * cannot map more because we are limited by reserved transaction credits. On
   * the other hand we always make sure that the last touched page is fully
   * mapped so that it can be written out (and thus forward progress is
   * guaranteed). After mapping we submit all mapped pages for IO.
   */
  static int mpage_map_and_submit_extent(handle_t *handle,
  				       struct mpage_da_data *mpd,
  				       bool *give_up_on_write)
  {
  	struct inode *inode = mpd->inode;
  	struct ext4_map_blocks *map = &mpd->map;
  	int err;
  	loff_t disksize;
  	int progress = 0;
  	ext4_io_end_t *io_end = mpd->io_submit.io_end;
  	struct ext4_io_end_vec *io_end_vec;
  
  	io_end_vec = ext4_alloc_io_end_vec(io_end);
  	if (IS_ERR(io_end_vec))
  		return PTR_ERR(io_end_vec);
  	io_end_vec->offset = ((loff_t)map->m_lblk) << inode->i_blkbits;
  	do {
  		err = mpage_map_one_extent(handle, mpd);
  		if (err < 0) {
  			struct super_block *sb = inode->i_sb;
  
  			if (ext4_forced_shutdown(EXT4_SB(sb)) ||
  			    ext4_test_mount_flag(sb, EXT4_MF_FS_ABORTED))
  				goto invalidate_dirty_pages;
  			/*
  			 * Let the uper layers retry transient errors.
  			 * In the case of ENOSPC, if ext4_count_free_blocks()
  			 * is non-zero, a commit should free up blocks.
  			 */
  			if ((err == -ENOMEM) ||
  			    (err == -ENOSPC && ext4_count_free_clusters(sb))) {
  				if (progress)
  					goto update_disksize;
  				return err;
  			}
  			ext4_msg(sb, KERN_CRIT,
  				 "Delayed block allocation failed for "
  				 "inode %lu at logical offset %llu with"
  				 " max blocks %u with error %d",
  				 inode->i_ino,
  				 (unsigned long long)map->m_lblk,
  				 (unsigned)map->m_len, -err);
  			ext4_msg(sb, KERN_CRIT,
  				 "This should not happen!! Data will "
  				 "be lost\n");
  			if (err == -ENOSPC)
  				ext4_print_free_blocks(inode);
  		invalidate_dirty_pages:
  			*give_up_on_write = true;
  			return err;
  		}
  		progress = 1;
  		/*
  		 * Update buffer state, submit mapped pages, and get us new
  		 * extent to map
  		 */
  		err = mpage_map_and_submit_buffers(mpd);
  		if (err < 0)
  			goto update_disksize;
  	} while (map->m_len);
  
  update_disksize:
  	/*
  	 * Update on-disk size after IO is submitted.  Races with
  	 * truncate are avoided by checking i_size under i_data_sem.
  	 */
  	disksize = ((loff_t)mpd->first_page) << PAGE_SHIFT;
  	if (disksize > READ_ONCE(EXT4_I(inode)->i_disksize)) {
  		int err2;
  		loff_t i_size;
  
  		down_write(&EXT4_I(inode)->i_data_sem);
  		i_size = i_size_read(inode);
  		if (disksize > i_size)
  			disksize = i_size;
  		if (disksize > EXT4_I(inode)->i_disksize)
  			EXT4_I(inode)->i_disksize = disksize;
  		up_write(&EXT4_I(inode)->i_data_sem);
  		err2 = ext4_mark_inode_dirty(handle, inode);
  		if (err2) {
  			ext4_error_err(inode->i_sb, -err2,
  				       "Failed to mark inode %lu dirty",
  				       inode->i_ino);
  		}
  		if (!err)
  			err = err2;
  	}
  	return err;
  }
  
  /*
   * Calculate the total number of credits to reserve for one writepages
   * iteration. This is called from ext4_writepages(). We map an extent of
   * up to MAX_WRITEPAGES_EXTENT_LEN blocks and then we go on and finish mapping
   * the last partial page. So in total we can map MAX_WRITEPAGES_EXTENT_LEN +
   * bpp - 1 blocks in bpp different extents.
   */
  static int ext4_da_writepages_trans_blocks(struct inode *inode)
  {
  	int bpp = ext4_journal_blocks_per_page(inode);
  
  	return ext4_meta_trans_blocks(inode,
  				MAX_WRITEPAGES_EXTENT_LEN + bpp - 1, bpp);
  }
  
  /*
   * mpage_prepare_extent_to_map - find & lock contiguous range of dirty pages
   * 				 and underlying extent to map
   *
   * @mpd - where to look for pages
   *
   * Walk dirty pages in the mapping. If they are fully mapped, submit them for
   * IO immediately. When we find a page which isn't mapped we start accumulating
   * extent of buffers underlying these pages that needs mapping (formed by
   * either delayed or unwritten buffers). We also lock the pages containing
   * these buffers. The extent found is returned in @mpd structure (starting at
   * mpd->lblk with length mpd->len blocks).
   *
   * Note that this function can attach bios to one io_end structure which are
   * neither logically nor physically contiguous. Although it may seem as an
   * unnecessary complication, it is actually inevitable in blocksize < pagesize
   * case as we need to track IO to all buffers underlying a page in one io_end.
   */
  static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
  {
  	struct address_space *mapping = mpd->inode->i_mapping;
  	struct pagevec pvec;
  	unsigned int nr_pages;
  	long left = mpd->wbc->nr_to_write;
  	pgoff_t index = mpd->first_page;
  	pgoff_t end = mpd->last_page;
  	xa_mark_t tag;
  	int i, err = 0;
  	int blkbits = mpd->inode->i_blkbits;
  	ext4_lblk_t lblk;
  	struct buffer_head *head;
  
  	if (mpd->wbc->sync_mode == WB_SYNC_ALL || mpd->wbc->tagged_writepages)
  		tag = PAGECACHE_TAG_TOWRITE;
  	else
  		tag = PAGECACHE_TAG_DIRTY;
  
  	pagevec_init(&pvec);
  	mpd->map.m_len = 0;
  	mpd->next_page = index;
  	while (index <= end) {
  		nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
  				tag);
  		if (nr_pages == 0)
  			break;
  
  		for (i = 0; i < nr_pages; i++) {
  			struct page *page = pvec.pages[i];
  
  			/*
  			 * Accumulated enough dirty pages? This doesn't apply
  			 * to WB_SYNC_ALL mode. For integrity sync we have to
  			 * keep going because someone may be concurrently
  			 * dirtying pages, and we might have synced a lot of
  			 * newly appeared dirty pages, but have not synced all
  			 * of the old dirty pages.
  			 */
  			if (mpd->wbc->sync_mode == WB_SYNC_NONE && left <= 0)
  				goto out;
  
  			/* If we can't merge this page, we are done. */
  			if (mpd->map.m_len > 0 && mpd->next_page != page->index)
  				goto out;
  
  			lock_page(page);
  			/*
  			 * If the page is no longer dirty, or its mapping no
  			 * longer corresponds to inode we are writing (which
  			 * means it has been truncated or invalidated), or the
  			 * page is already under writeback and we are not doing
  			 * a data integrity writeback, skip the page
  			 */
  			if (!PageDirty(page) ||
  			    (PageWriteback(page) &&
  			     (mpd->wbc->sync_mode == WB_SYNC_NONE)) ||
  			    unlikely(page->mapping != mapping)) {
  				unlock_page(page);
  				continue;
  			}
  
  			wait_on_page_writeback(page);
  			BUG_ON(PageWriteback(page));
  
  			if (mpd->map.m_len == 0)
  				mpd->first_page = page->index;
  			mpd->next_page = page->index + 1;
  			/* Add all dirty buffers to mpd */
  			lblk = ((ext4_lblk_t)page->index) <<
  				(PAGE_SHIFT - blkbits);
  			head = page_buffers(page);
  			err = mpage_process_page_bufs(mpd, head, head, lblk);
  			if (err <= 0)
  				goto out;
  			err = 0;
  			left--;
  		}
  		pagevec_release(&pvec);
  		cond_resched();
  	}
  	mpd->scanned_until_end = 1;
  	return 0;
  out:
  	pagevec_release(&pvec);
  	return err;
  }
  
  static int ext4_writepages(struct address_space *mapping,
  			   struct writeback_control *wbc)
  {
  	pgoff_t	writeback_index = 0;
  	long nr_to_write = wbc->nr_to_write;
  	int range_whole = 0;
  	int cycled = 1;
  	handle_t *handle = NULL;
  	struct mpage_da_data mpd;
  	struct inode *inode = mapping->host;
  	int needed_blocks, rsv_blocks = 0, ret = 0;
  	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
  	struct blk_plug plug;
  	bool give_up_on_write = false;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	percpu_down_read(&sbi->s_writepages_rwsem);
  	trace_ext4_writepages(inode, wbc);
  
  	/*
  	 * No pages to write? This is mainly a kludge to avoid starting
  	 * a transaction for special inodes like journal inode on last iput()
  	 * because that could violate lock ordering on umount
  	 */
  	if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
  		goto out_writepages;
  
  	if (ext4_should_journal_data(inode)) {
  		ret = generic_writepages(mapping, wbc);
  		goto out_writepages;
  	}
  
  	/*
  	 * If the filesystem has aborted, it is read-only, so return
  	 * right away instead of dumping stack traces later on that
  	 * will obscure the real source of the problem.  We test
  	 * EXT4_MF_FS_ABORTED instead of sb->s_flag's SB_RDONLY because
  	 * the latter could be true if the filesystem is mounted
  	 * read-only, and in that case, ext4_writepages should
  	 * *never* be called, so if that ever happens, we would want
  	 * the stack trace.
  	 */
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(mapping->host->i_sb)) ||
  		     ext4_test_mount_flag(inode->i_sb, EXT4_MF_FS_ABORTED))) {
  		ret = -EROFS;
  		goto out_writepages;
  	}
  
  	/*
  	 * If we have inline data and arrive here, it means that
  	 * we will soon create the block for the 1st page, so
  	 * we'd better clear the inline data here.
  	 */
  	if (ext4_has_inline_data(inode)) {
  		/* Just inode will be modified... */
  		handle = ext4_journal_start(inode, EXT4_HT_INODE, 1);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			goto out_writepages;
  		}
  		BUG_ON(ext4_test_inode_state(inode,
  				EXT4_STATE_MAY_INLINE_DATA));
  		ext4_destroy_inline_data(handle, inode);
  		ext4_journal_stop(handle);
  	}
  
  	if (ext4_should_dioread_nolock(inode)) {
  		/*
  		 * We may need to convert up to one extent per block in
  		 * the page and we may dirty the inode.
  		 */
  		rsv_blocks = 1 + ext4_chunk_trans_blocks(inode,
  						PAGE_SIZE >> inode->i_blkbits);
  	}
  
  	if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
  		range_whole = 1;
  
  	if (wbc->range_cyclic) {
  		writeback_index = mapping->writeback_index;
  		if (writeback_index)
  			cycled = 0;
  		mpd.first_page = writeback_index;
  		mpd.last_page = -1;
  	} else {
  		mpd.first_page = wbc->range_start >> PAGE_SHIFT;
  		mpd.last_page = wbc->range_end >> PAGE_SHIFT;
  	}
  
  	mpd.inode = inode;
  	mpd.wbc = wbc;
  	ext4_io_submit_init(&mpd.io_submit, wbc);
  retry:
  	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
  		tag_pages_for_writeback(mapping, mpd.first_page, mpd.last_page);
  	blk_start_plug(&plug);
  
  	/*
  	 * First writeback pages that don't need mapping - we can avoid
  	 * starting a transaction unnecessarily and also avoid being blocked
  	 * in the block layer on device congestion while having transaction
  	 * started.
  	 */
  	mpd.do_map = 0;
  	mpd.scanned_until_end = 0;
  	mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
  	if (!mpd.io_submit.io_end) {
  		ret = -ENOMEM;
  		goto unplug;
  	}
  	ret = mpage_prepare_extent_to_map(&mpd);
  	/* Unlock pages we didn't use */
  	mpage_release_unused_pages(&mpd, false);
  	/* Submit prepared bio */
  	ext4_io_submit(&mpd.io_submit);
  	ext4_put_io_end_defer(mpd.io_submit.io_end);
  	mpd.io_submit.io_end = NULL;
  	if (ret < 0)
  		goto unplug;
  
  	while (!mpd.scanned_until_end && wbc->nr_to_write > 0) {
  		/* For each extent of pages we use new io_end */
  		mpd.io_submit.io_end = ext4_init_io_end(inode, GFP_KERNEL);
  		if (!mpd.io_submit.io_end) {
  			ret = -ENOMEM;
  			break;
  		}
  
  		/*
  		 * We have two constraints: We find one extent to map and we
  		 * must always write out whole page (makes a difference when
  		 * blocksize < pagesize) so that we don't block on IO when we
  		 * try to write out the rest of the page. Journalled mode is
  		 * not supported by delalloc.
  		 */
  		BUG_ON(ext4_should_journal_data(inode));
  		needed_blocks = ext4_da_writepages_trans_blocks(inode);
  
  		/* start a new transaction */
  		handle = ext4_journal_start_with_reserve(inode,
  				EXT4_HT_WRITE_PAGE, needed_blocks, rsv_blocks);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			ext4_msg(inode->i_sb, KERN_CRIT, "%s: jbd2_start: "
  			       "%ld pages, ino %lu; err %d", __func__,
  				wbc->nr_to_write, inode->i_ino, ret);
  			/* Release allocated io_end */
  			ext4_put_io_end(mpd.io_submit.io_end);
  			mpd.io_submit.io_end = NULL;
  			break;
  		}
  		mpd.do_map = 1;
  
  		trace_ext4_da_write_pages(inode, mpd.first_page, mpd.wbc);
  		ret = mpage_prepare_extent_to_map(&mpd);
  		if (!ret && mpd.map.m_len)
  			ret = mpage_map_and_submit_extent(handle, &mpd,
  					&give_up_on_write);
  		/*
  		 * Caution: If the handle is synchronous,
  		 * ext4_journal_stop() can wait for transaction commit
  		 * to finish which may depend on writeback of pages to
  		 * complete or on page lock to be released.  In that
  		 * case, we have to wait until after we have
  		 * submitted all the IO, released page locks we hold,
  		 * and dropped io_end reference (for extent conversion
  		 * to be able to complete) before stopping the handle.
  		 */
  		if (!ext4_handle_valid(handle) || handle->h_sync == 0) {
  			ext4_journal_stop(handle);
  			handle = NULL;
  			mpd.do_map = 0;
  		}
  		/* Unlock pages we didn't use */
  		mpage_release_unused_pages(&mpd, give_up_on_write);
  		/* Submit prepared bio */
  		ext4_io_submit(&mpd.io_submit);
  
  		/*
  		 * Drop our io_end reference we got from init. We have
  		 * to be careful and use deferred io_end finishing if
  		 * we are still holding the transaction as we can
  		 * release the last reference to io_end which may end
  		 * up doing unwritten extent conversion.
  		 */
  		if (handle) {
  			ext4_put_io_end_defer(mpd.io_submit.io_end);
  			ext4_journal_stop(handle);
  		} else
  			ext4_put_io_end(mpd.io_submit.io_end);
  		mpd.io_submit.io_end = NULL;
  
  		if (ret == -ENOSPC && sbi->s_journal) {
  			/*
  			 * Commit the transaction which would
  			 * free blocks released in the transaction
  			 * and try again
  			 */
  			jbd2_journal_force_commit_nested(sbi->s_journal);
  			ret = 0;
  			continue;
  		}
  		/* Fatal error - ENOMEM, EIO... */
  		if (ret)
  			break;
  	}
  unplug:
  	blk_finish_plug(&plug);
  	if (!ret && !cycled && wbc->nr_to_write > 0) {
  		cycled = 1;
  		mpd.last_page = writeback_index - 1;
  		mpd.first_page = 0;
  		goto retry;
  	}
  
  	/* Update index */
  	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
  		/*
  		 * Set the writeback_index so that range_cyclic
  		 * mode will write it back later
  		 */
  		mapping->writeback_index = mpd.first_page;
  
  out_writepages:
  	trace_ext4_writepages_result(inode, wbc, ret,
  				     nr_to_write - wbc->nr_to_write);
  	percpu_up_read(&sbi->s_writepages_rwsem);
  	return ret;
  }
  
  static int ext4_dax_writepages(struct address_space *mapping,
  			       struct writeback_control *wbc)
  {
  	int ret;
  	long nr_to_write = wbc->nr_to_write;
  	struct inode *inode = mapping->host;
  	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	percpu_down_read(&sbi->s_writepages_rwsem);
  	trace_ext4_writepages(inode, wbc);
  
  	ret = dax_writeback_mapping_range(mapping, sbi->s_daxdev, wbc);
  	trace_ext4_writepages_result(inode, wbc, ret,
  				     nr_to_write - wbc->nr_to_write);
  	percpu_up_read(&sbi->s_writepages_rwsem);
  	return ret;
  }
  
  static int ext4_nonda_switch(struct super_block *sb)
  {
  	s64 free_clusters, dirty_clusters;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  
  	/*
  	 * switch to non delalloc mode if we are running low
  	 * on free block. The free block accounting via percpu
  	 * counters can get slightly wrong with percpu_counter_batch getting
  	 * accumulated on each CPU without updating global counters
  	 * Delalloc need an accurate free block accounting. So switch
  	 * to non delalloc when we are near to error range.
  	 */
  	free_clusters =
  		percpu_counter_read_positive(&sbi->s_freeclusters_counter);
  	dirty_clusters =
  		percpu_counter_read_positive(&sbi->s_dirtyclusters_counter);
  	/*
  	 * Start pushing delalloc when 1/2 of free blocks are dirty.
  	 */
  	if (dirty_clusters && (free_clusters < 2 * dirty_clusters))
  		try_to_writeback_inodes_sb(sb, WB_REASON_FS_FREE_SPACE);
  
  	if (2 * free_clusters < 3 * dirty_clusters ||
  	    free_clusters < (dirty_clusters + EXT4_FREECLUSTERS_WATERMARK)) {
  		/*
  		 * free block count is less than 150% of dirty blocks
  		 * or free blocks is less than watermark
  		 */
  		return 1;
  	}
  	return 0;
  }
  
  static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
  			       loff_t pos, unsigned len, unsigned flags,
  			       struct page **pagep, void **fsdata)
  {
  	int ret, retries = 0;
  	struct page *page;
  	pgoff_t index;
  	struct inode *inode = mapping->host;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	index = pos >> PAGE_SHIFT;
  
  	if (ext4_nonda_switch(inode->i_sb) || S_ISLNK(inode->i_mode) ||
  	    ext4_verity_in_progress(inode)) {
  		*fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
  		return ext4_write_begin(file, mapping, pos,
  					len, flags, pagep, fsdata);
  	}
  	*fsdata = (void *)0;
  	trace_ext4_da_write_begin(inode, pos, len, flags);
  
  	if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
  		ret = ext4_da_write_inline_data_begin(mapping, inode,
  						      pos, len, flags,
  						      pagep, fsdata);
  		if (ret < 0)
  			return ret;
  		if (ret == 1)
  			return 0;
  	}
  
  retry:
  	page = grab_cache_page_write_begin(mapping, index, flags);
  	if (!page)
  		return -ENOMEM;
  
  	/* In case writeback began while the page was unlocked */
  	wait_for_stable_page(page);
  
  #ifdef CONFIG_FS_ENCRYPTION
  	ret = ext4_block_write_begin(page, pos, len,
  				     ext4_da_get_block_prep);
  #else
  	ret = __block_write_begin(page, pos, len, ext4_da_get_block_prep);
  #endif
  	if (ret < 0) {
  		unlock_page(page);
  		put_page(page);
  		/*
  		 * block_write_begin may have instantiated a few blocks
  		 * outside i_size.  Trim these off again. Don't need
  		 * i_size_read because we hold inode lock.
  		 */
  		if (pos + len > inode->i_size)
  			ext4_truncate_failed_write(inode);
  
  		if (ret == -ENOSPC &&
  		    ext4_should_retry_alloc(inode->i_sb, &retries))
  			goto retry;
  		return ret;
  	}
  
  	*pagep = page;
  	return ret;
  }
  
  /*
   * Check if we should update i_disksize
   * when write to the end of file but not require block allocation
   */
  static int ext4_da_should_update_i_disksize(struct page *page,
  					    unsigned long offset)
  {
  	struct buffer_head *bh;
  	struct inode *inode = page->mapping->host;
  	unsigned int idx;
  	int i;
  
  	bh = page_buffers(page);
  	idx = offset >> inode->i_blkbits;
  
  	for (i = 0; i < idx; i++)
  		bh = bh->b_this_page;
  
  	if (!buffer_mapped(bh) || (buffer_delay(bh)) || buffer_unwritten(bh))
  		return 0;
  	return 1;
  }
  
  static int ext4_da_write_end(struct file *file,
  			     struct address_space *mapping,
  			     loff_t pos, unsigned len, unsigned copied,
  			     struct page *page, void *fsdata)
  {
  	struct inode *inode = mapping->host;
  	loff_t new_i_size;
  	unsigned long start, end;
  	int write_mode = (int)(unsigned long)fsdata;
  
  	if (write_mode == FALL_BACK_TO_NONDELALLOC)
  		return ext4_write_end(file, mapping, pos,
  				      len, copied, page, fsdata);
  
  	trace_ext4_da_write_end(inode, pos, len, copied);
  
  	if (write_mode != CONVERT_INLINE_DATA &&
  	    ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA) &&
  	    ext4_has_inline_data(inode))
  		return ext4_write_inline_data_end(inode, pos, len, copied, page);
  
  	start = pos & (PAGE_SIZE - 1);
  	end = start + copied - 1;
  
  	/*
  	 * Since we are holding inode lock, we are sure i_disksize <=
  	 * i_size. We also know that if i_disksize < i_size, there are
  	 * delalloc writes pending in the range upto i_size. If the end of
  	 * the current write is <= i_size, there's no need to touch
  	 * i_disksize since writeback will push i_disksize upto i_size
  	 * eventually. If the end of the current write is > i_size and
  	 * inside an allocated block (ext4_da_should_update_i_disksize()
  	 * check), we need to update i_disksize here as neither
  	 * ext4_writepage() nor certain ext4_writepages() paths not
  	 * allocating blocks update i_disksize.
  	 *
  	 * Note that we defer inode dirtying to generic_write_end() /
  	 * ext4_da_write_inline_data_end().
  	 */
  	new_i_size = pos + copied;
  	if (copied && new_i_size > inode->i_size &&
  	    ext4_da_should_update_i_disksize(page, end))
  		ext4_update_i_disksize(inode, new_i_size);
  
  	return generic_write_end(file, mapping, pos, len, copied, page, fsdata);
  }
  
  /*
   * Force all delayed allocation blocks to be allocated for a given inode.
   */
  int ext4_alloc_da_blocks(struct inode *inode)
  {
  	trace_ext4_alloc_da_blocks(inode);
  
  	if (!EXT4_I(inode)->i_reserved_data_blocks)
  		return 0;
  
  	/*
  	 * We do something simple for now.  The filemap_flush() will
  	 * also start triggering a write of the data blocks, which is
  	 * not strictly speaking necessary (and for users of
  	 * laptop_mode, not even desirable).  However, to do otherwise
  	 * would require replicating code paths in:
  	 *
  	 * ext4_writepages() ->
  	 *    write_cache_pages() ---> (via passed in callback function)
  	 *        __mpage_da_writepage() -->
  	 *           mpage_add_bh_to_extent()
  	 *           mpage_da_map_blocks()
  	 *
  	 * The problem is that write_cache_pages(), located in
  	 * mm/page-writeback.c, marks pages clean in preparation for
  	 * doing I/O, which is not desirable if we're not planning on
  	 * doing I/O at all.
  	 *
  	 * We could call write_cache_pages(), and then redirty all of
  	 * the pages by calling redirty_page_for_writepage() but that
  	 * would be ugly in the extreme.  So instead we would need to
  	 * replicate parts of the code in the above functions,
  	 * simplifying them because we wouldn't actually intend to
  	 * write out the pages, but rather only collect contiguous
  	 * logical block extents, call the multi-block allocator, and
  	 * then update the buffer heads with the block allocations.
  	 *
  	 * For now, though, we'll cheat by calling filemap_flush(),
  	 * which will map the blocks, and start the I/O, but not
  	 * actually wait for the I/O to complete.
  	 */
  	return filemap_flush(inode->i_mapping);
  }
  
  /*
   * bmap() is special.  It gets used by applications such as lilo and by
   * the swapper to find the on-disk block of a specific piece of data.
   *
   * Naturally, this is dangerous if the block concerned is still in the
   * journal.  If somebody makes a swapfile on an ext4 data-journaling
   * filesystem and enables swap, then they may get a nasty shock when the
   * data getting swapped to that swapfile suddenly gets overwritten by
   * the original zero's written out previously to the journal and
   * awaiting writeback in the kernel's buffer cache.
   *
   * So, if we see any bmap calls here on a modified, data-journaled file,
   * take extra steps to flush any blocks which might be in the cache.
   */
  static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
  {
  	struct inode *inode = mapping->host;
  	journal_t *journal;
  	int err;
  
  	/*
  	 * We can get here for an inline file via the FIBMAP ioctl
  	 */
  	if (ext4_has_inline_data(inode))
  		return 0;
  
  	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
  			test_opt(inode->i_sb, DELALLOC)) {
  		/*
  		 * With delalloc we want to sync the file
  		 * so that we can make sure we allocate
  		 * blocks for file
  		 */
  		filemap_write_and_wait(mapping);
  	}
  
  	if (EXT4_JOURNAL(inode) &&
  	    ext4_test_inode_state(inode, EXT4_STATE_JDATA)) {
  		/*
  		 * This is a REALLY heavyweight approach, but the use of
  		 * bmap on dirty files is expected to be extremely rare:
  		 * only if we run lilo or swapon on a freshly made file
  		 * do we expect this to happen.
  		 *
  		 * (bmap requires CAP_SYS_RAWIO so this does not
  		 * represent an unprivileged user DOS attack --- we'd be
  		 * in trouble if mortal users could trigger this path at
  		 * will.)
  		 *
  		 * NB. EXT4_STATE_JDATA is not set on files other than
  		 * regular files.  If somebody wants to bmap a directory
  		 * or symlink and gets confused because the buffer
  		 * hasn't yet been flushed to disk, they deserve
  		 * everything they get.
  		 */
  
  		ext4_clear_inode_state(inode, EXT4_STATE_JDATA);
  		journal = EXT4_JOURNAL(inode);
  		jbd2_journal_lock_updates(journal);
  		err = jbd2_journal_flush(journal, 0);
  		jbd2_journal_unlock_updates(journal);
  
  		if (err)
  			return 0;
  	}
  
  	return iomap_bmap(mapping, block, &ext4_iomap_ops);
  }
  
  static int ext4_readpage(struct file *file, struct page *page)
  {
  	int ret = -EAGAIN;
  	struct inode *inode = page->mapping->host;
  
  	trace_ext4_readpage(page);
  
  	if (ext4_has_inline_data(inode))
  		ret = ext4_readpage_inline(inode, page);
  
  	if (ret == -EAGAIN)
  		return ext4_mpage_readpages(inode, NULL, page);
  
  	return ret;
  }
  
  static void ext4_readahead(struct readahead_control *rac)
  {
  	struct inode *inode = rac->mapping->host;
  
  	/* If the file has inline data, no need to do readahead. */
  	if (ext4_has_inline_data(inode))
  		return;
  
  	ext4_mpage_readpages(inode, rac, NULL);
  }
  
  static void ext4_invalidatepage(struct page *page, unsigned int offset,
  				unsigned int length)
  {
  	trace_ext4_invalidatepage(page, offset, length);
  
  	/* No journalling happens on data buffers when this function is used */
  	WARN_ON(page_has_buffers(page) && buffer_jbd(page_buffers(page)));
  
  	block_invalidatepage(page, offset, length);
  }
  
  static int __ext4_journalled_invalidatepage(struct page *page,
  					    unsigned int offset,
  					    unsigned int length)
  {
  	journal_t *journal = EXT4_JOURNAL(page->mapping->host);
  
  	trace_ext4_journalled_invalidatepage(page, offset, length);
  
  	/*
  	 * If it's a full truncate we just forget about the pending dirtying
  	 */
  	if (offset == 0 && length == PAGE_SIZE)
  		ClearPageChecked(page);
  
  	return jbd2_journal_invalidatepage(journal, page, offset, length);
  }
  
  /* Wrapper for aops... */
  static void ext4_journalled_invalidatepage(struct page *page,
  					   unsigned int offset,
  					   unsigned int length)
  {
  	WARN_ON(__ext4_journalled_invalidatepage(page, offset, length) < 0);
  }
  
  static int ext4_releasepage(struct page *page, gfp_t wait)
  {
  	journal_t *journal = EXT4_JOURNAL(page->mapping->host);
  
  	trace_ext4_releasepage(page);
  
  	/* Page has dirty journalled data -> cannot release */
  	if (PageChecked(page))
  		return 0;
  	if (journal)
  		return jbd2_journal_try_to_free_buffers(journal, page);
  	else
  		return try_to_free_buffers(page);
  }
  
  static bool ext4_inode_datasync_dirty(struct inode *inode)
  {
  	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  
  	if (journal) {
  		if (jbd2_transaction_committed(journal,
  			EXT4_I(inode)->i_datasync_tid))
  			return false;
  		if (test_opt2(inode->i_sb, JOURNAL_FAST_COMMIT))
  			return !list_empty(&EXT4_I(inode)->i_fc_list);
  		return true;
  	}
  
  	/* Any metadata buffers to write? */
  	if (!list_empty(&inode->i_mapping->private_list))
  		return true;
  	return inode->i_state & I_DIRTY_DATASYNC;
  }
  
  static void ext4_set_iomap(struct inode *inode, struct iomap *iomap,
  			   struct ext4_map_blocks *map, loff_t offset,
  			   loff_t length)
  {
  	u8 blkbits = inode->i_blkbits;
  
  	/*
  	 * Writes that span EOF might trigger an I/O size update on completion,
  	 * so consider them to be dirty for the purpose of O_DSYNC, even if
  	 * there is no other metadata changes being made or are pending.
  	 */
  	iomap->flags = 0;
  	if (ext4_inode_datasync_dirty(inode) ||
  	    offset + length > i_size_read(inode))
  		iomap->flags |= IOMAP_F_DIRTY;
  
  	if (map->m_flags & EXT4_MAP_NEW)
  		iomap->flags |= IOMAP_F_NEW;
  
  	iomap->bdev = inode->i_sb->s_bdev;
  	iomap->dax_dev = EXT4_SB(inode->i_sb)->s_daxdev;
  	iomap->offset = (u64) map->m_lblk << blkbits;
  	iomap->length = (u64) map->m_len << blkbits;
  
  	if ((map->m_flags & EXT4_MAP_MAPPED) &&
  	    !ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		iomap->flags |= IOMAP_F_MERGED;
  
  	/*
  	 * Flags passed to ext4_map_blocks() for direct I/O writes can result
  	 * in m_flags having both EXT4_MAP_MAPPED and EXT4_MAP_UNWRITTEN bits
  	 * set. In order for any allocated unwritten extents to be converted
  	 * into written extents correctly within the ->end_io() handler, we
  	 * need to ensure that the iomap->type is set appropriately. Hence, the
  	 * reason why we need to check whether the EXT4_MAP_UNWRITTEN bit has
  	 * been set first.
  	 */
  	if (map->m_flags & EXT4_MAP_UNWRITTEN) {
  		iomap->type = IOMAP_UNWRITTEN;
  		iomap->addr = (u64) map->m_pblk << blkbits;
  	} else if (map->m_flags & EXT4_MAP_MAPPED) {
  		iomap->type = IOMAP_MAPPED;
  		iomap->addr = (u64) map->m_pblk << blkbits;
  	} else {
  		iomap->type = IOMAP_HOLE;
  		iomap->addr = IOMAP_NULL_ADDR;
  	}
  }
  
  static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
  			    unsigned int flags)
  {
  	handle_t *handle;
  	u8 blkbits = inode->i_blkbits;
  	int ret, dio_credits, m_flags = 0, retries = 0;
  
  	/*
  	 * Trim the mapping request to the maximum value that we can map at
  	 * once for direct I/O.
  	 */
  	if (map->m_len > DIO_MAX_BLOCKS)
  		map->m_len = DIO_MAX_BLOCKS;
  	dio_credits = ext4_chunk_trans_blocks(inode, map->m_len);
  
  retry:
  	/*
  	 * Either we allocate blocks and then don't get an unwritten extent, so
  	 * in that case we have reserved enough credits. Or, the blocks are
  	 * already allocated and unwritten. In that case, the extent conversion
  	 * fits into the credits as well.
  	 */
  	handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, dio_credits);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  
  	/*
  	 * DAX and direct I/O are the only two operations that are currently
  	 * supported with IOMAP_WRITE.
  	 */
  	WARN_ON(!IS_DAX(inode) && !(flags & IOMAP_DIRECT));
  	if (IS_DAX(inode))
  		m_flags = EXT4_GET_BLOCKS_CREATE_ZERO;
  	/*
  	 * We use i_size instead of i_disksize here because delalloc writeback
  	 * can complete at any point during the I/O and subsequently push the
  	 * i_disksize out to i_size. This could be beyond where direct I/O is
  	 * happening and thus expose allocated blocks to direct I/O reads.
  	 */
  	else if (((loff_t)map->m_lblk << blkbits) >= i_size_read(inode))
  		m_flags = EXT4_GET_BLOCKS_CREATE;
  	else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		m_flags = EXT4_GET_BLOCKS_IO_CREATE_EXT;
  
  	ret = ext4_map_blocks(handle, inode, map, m_flags);
  
  	/*
  	 * We cannot fill holes in indirect tree based inodes as that could
  	 * expose stale data in the case of a crash. Use the magic error code
  	 * to fallback to buffered I/O.
  	 */
  	if (!m_flags && !ret)
  		ret = -ENOTBLK;
  
  	ext4_journal_stop(handle);
  	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
  		goto retry;
  
  	return ret;
  }
  
  
  static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
  		unsigned flags, struct iomap *iomap, struct iomap *srcmap)
  {
  	int ret;
  	struct ext4_map_blocks map;
  	u8 blkbits = inode->i_blkbits;
  
  	if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
  		return -EINVAL;
  
  	if (WARN_ON_ONCE(ext4_has_inline_data(inode)))
  		return -ERANGE;
  
  	/*
  	 * Calculate the first and last logical blocks respectively.
  	 */
  	map.m_lblk = offset >> blkbits;
  	map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
  			  EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
  
  	if (flags & IOMAP_WRITE) {
  		/*
  		 * We check here if the blocks are already allocated, then we
  		 * don't need to start a journal txn and we can directly return
  		 * the mapping information. This could boost performance
  		 * especially in multi-threaded overwrite requests.
  		 */
  		if (offset + length <= i_size_read(inode)) {
  			ret = ext4_map_blocks(NULL, inode, &map, 0);
  			if (ret > 0 && (map.m_flags & EXT4_MAP_MAPPED))
  				goto out;
  		}
  		ret = ext4_iomap_alloc(inode, &map, flags);
  	} else {
  		ret = ext4_map_blocks(NULL, inode, &map, 0);
  	}
  
  	if (ret < 0)
  		return ret;
  out:
  	ext4_set_iomap(inode, iomap, &map, offset, length);
  
  	return 0;
  }
  
  static int ext4_iomap_overwrite_begin(struct inode *inode, loff_t offset,
  		loff_t length, unsigned flags, struct iomap *iomap,
  		struct iomap *srcmap)
  {
  	int ret;
  
  	/*
  	 * Even for writes we don't need to allocate blocks, so just pretend
  	 * we are reading to save overhead of starting a transaction.
  	 */
  	flags &= ~IOMAP_WRITE;
  	ret = ext4_iomap_begin(inode, offset, length, flags, iomap, srcmap);
  	WARN_ON_ONCE(iomap->type != IOMAP_MAPPED);
  	return ret;
  }
  
  static int ext4_iomap_end(struct inode *inode, loff_t offset, loff_t length,
  			  ssize_t written, unsigned flags, struct iomap *iomap)
  {
  	/*
  	 * Check to see whether an error occurred while writing out the data to
  	 * the allocated blocks. If so, return the magic error code so that we
  	 * fallback to buffered I/O and attempt to complete the remainder of
  	 * the I/O. Any blocks that may have been allocated in preparation for
  	 * the direct I/O will be reused during buffered I/O.
  	 */
  	if (flags & (IOMAP_WRITE | IOMAP_DIRECT) && written == 0)
  		return -ENOTBLK;
  
  	return 0;
  }
  
  const struct iomap_ops ext4_iomap_ops = {
  	.iomap_begin		= ext4_iomap_begin,
  	.iomap_end		= ext4_iomap_end,
  };
  
  const struct iomap_ops ext4_iomap_overwrite_ops = {
  	.iomap_begin		= ext4_iomap_overwrite_begin,
  	.iomap_end		= ext4_iomap_end,
  };
  
  static bool ext4_iomap_is_delalloc(struct inode *inode,
  				   struct ext4_map_blocks *map)
  {
  	struct extent_status es;
  	ext4_lblk_t offset = 0, end = map->m_lblk + map->m_len - 1;
  
  	ext4_es_find_extent_range(inode, &ext4_es_is_delayed,
  				  map->m_lblk, end, &es);
  
  	if (!es.es_len || es.es_lblk > end)
  		return false;
  
  	if (es.es_lblk > map->m_lblk) {
  		map->m_len = es.es_lblk - map->m_lblk;
  		return false;
  	}
  
  	offset = map->m_lblk - es.es_lblk;
  	map->m_len = es.es_len - offset;
  
  	return true;
  }
  
  static int ext4_iomap_begin_report(struct inode *inode, loff_t offset,
  				   loff_t length, unsigned int flags,
  				   struct iomap *iomap, struct iomap *srcmap)
  {
  	int ret;
  	bool delalloc = false;
  	struct ext4_map_blocks map;
  	u8 blkbits = inode->i_blkbits;
  
  	if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
  		return -EINVAL;
  
  	if (ext4_has_inline_data(inode)) {
  		ret = ext4_inline_data_iomap(inode, iomap);
  		if (ret != -EAGAIN) {
  			if (ret == 0 && offset >= iomap->length)
  				ret = -ENOENT;
  			return ret;
  		}
  	}
  
  	/*
  	 * Calculate the first and last logical block respectively.
  	 */
  	map.m_lblk = offset >> blkbits;
  	map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
  			  EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
  
  	/*
  	 * Fiemap callers may call for offset beyond s_bitmap_maxbytes.
  	 * So handle it here itself instead of querying ext4_map_blocks().
  	 * Since ext4_map_blocks() will warn about it and will return
  	 * -EIO error.
  	 */
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
  		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  		if (offset >= sbi->s_bitmap_maxbytes) {
  			map.m_flags = 0;
  			goto set_iomap;
  		}
  	}
  
  	ret = ext4_map_blocks(NULL, inode, &map, 0);
  	if (ret < 0)
  		return ret;
  	if (ret == 0)
  		delalloc = ext4_iomap_is_delalloc(inode, &map);
  
  set_iomap:
  	ext4_set_iomap(inode, iomap, &map, offset, length);
  	if (delalloc && iomap->type == IOMAP_HOLE)
  		iomap->type = IOMAP_DELALLOC;
  
  	return 0;
  }
  
  const struct iomap_ops ext4_iomap_report_ops = {
  	.iomap_begin = ext4_iomap_begin_report,
  };
  
  /*
   * Pages can be marked dirty completely asynchronously from ext4's journalling
   * activity.  By filemap_sync_pte(), try_to_unmap_one(), etc.  We cannot do
   * much here because ->set_page_dirty is called under VFS locks.  The page is
   * not necessarily locked.
   *
   * We cannot just dirty the page and leave attached buffers clean, because the
   * buffers' dirty state is "definitive".  We cannot just set the buffers dirty
   * or jbddirty because all the journalling code will explode.
   *
   * So what we do is to mark the page "pending dirty" and next time writepage
   * is called, propagate that into the buffers appropriately.
   */
  static int ext4_journalled_set_page_dirty(struct page *page)
  {
  	SetPageChecked(page);
  	return __set_page_dirty_nobuffers(page);
  }
  
  static int ext4_set_page_dirty(struct page *page)
  {
  	WARN_ON_ONCE(!PageLocked(page) && !PageDirty(page));
  	WARN_ON_ONCE(!page_has_buffers(page));
  	return __set_page_dirty_buffers(page);
  }
  
  static int ext4_iomap_swap_activate(struct swap_info_struct *sis,
  				    struct file *file, sector_t *span)
  {
  	return iomap_swapfile_activate(sis, file, span,
  				       &ext4_iomap_report_ops);
  }
  
  static const struct address_space_operations ext4_aops = {
  	.readpage		= ext4_readpage,
  	.readahead		= ext4_readahead,
  	.writepage		= ext4_writepage,
  	.writepages		= ext4_writepages,
  	.write_begin		= ext4_write_begin,
  	.write_end		= ext4_write_end,
  	.set_page_dirty		= ext4_set_page_dirty,
  	.bmap			= ext4_bmap,
  	.invalidatepage		= ext4_invalidatepage,
  	.releasepage		= ext4_releasepage,
  	.direct_IO		= noop_direct_IO,
  	.migratepage		= buffer_migrate_page,
  	.is_partially_uptodate  = block_is_partially_uptodate,
  	.error_remove_page	= generic_error_remove_page,
  	.swap_activate		= ext4_iomap_swap_activate,
  };
  
  static const struct address_space_operations ext4_journalled_aops = {
  	.readpage		= ext4_readpage,
  	.readahead		= ext4_readahead,
  	.writepage		= ext4_writepage,
  	.writepages		= ext4_writepages,
  	.write_begin		= ext4_write_begin,
  	.write_end		= ext4_journalled_write_end,
  	.set_page_dirty		= ext4_journalled_set_page_dirty,
  	.bmap			= ext4_bmap,
  	.invalidatepage		= ext4_journalled_invalidatepage,
  	.releasepage		= ext4_releasepage,
  	.direct_IO		= noop_direct_IO,
  	.is_partially_uptodate  = block_is_partially_uptodate,
  	.error_remove_page	= generic_error_remove_page,
  	.swap_activate		= ext4_iomap_swap_activate,
  };
  
  static const struct address_space_operations ext4_da_aops = {
  	.readpage		= ext4_readpage,
  	.readahead		= ext4_readahead,
  	.writepage		= ext4_writepage,
  	.writepages		= ext4_writepages,
  	.write_begin		= ext4_da_write_begin,
  	.write_end		= ext4_da_write_end,
  	.set_page_dirty		= ext4_set_page_dirty,
  	.bmap			= ext4_bmap,
  	.invalidatepage		= ext4_invalidatepage,
  	.releasepage		= ext4_releasepage,
  	.direct_IO		= noop_direct_IO,
  	.migratepage		= buffer_migrate_page,
  	.is_partially_uptodate  = block_is_partially_uptodate,
  	.error_remove_page	= generic_error_remove_page,
  	.swap_activate		= ext4_iomap_swap_activate,
  };
  
  static const struct address_space_operations ext4_dax_aops = {
  	.writepages		= ext4_dax_writepages,
  	.direct_IO		= noop_direct_IO,
  	.set_page_dirty		= __set_page_dirty_no_writeback,
  	.bmap			= ext4_bmap,
  	.invalidatepage		= noop_invalidatepage,
  	.swap_activate		= ext4_iomap_swap_activate,
  };
  
  void ext4_set_aops(struct inode *inode)
  {
  	switch (ext4_inode_journal_mode(inode)) {
  	case EXT4_INODE_ORDERED_DATA_MODE:
  	case EXT4_INODE_WRITEBACK_DATA_MODE:
  		break;
  	case EXT4_INODE_JOURNAL_DATA_MODE:
  		inode->i_mapping->a_ops = &ext4_journalled_aops;
  		return;
  	default:
  		BUG();
  	}
  	if (IS_DAX(inode))
  		inode->i_mapping->a_ops = &ext4_dax_aops;
  	else if (test_opt(inode->i_sb, DELALLOC))
  		inode->i_mapping->a_ops = &ext4_da_aops;
  	else
  		inode->i_mapping->a_ops = &ext4_aops;
  }
  
  static int __ext4_block_zero_page_range(handle_t *handle,
  		struct address_space *mapping, loff_t from, loff_t length)
  {
  	ext4_fsblk_t index = from >> PAGE_SHIFT;
  	unsigned offset = from & (PAGE_SIZE-1);
  	unsigned blocksize, pos;
  	ext4_lblk_t iblock;
  	struct inode *inode = mapping->host;
  	struct buffer_head *bh;
  	struct page *page;
  	int err = 0;
  
  	page = find_or_create_page(mapping, from >> PAGE_SHIFT,
  				   mapping_gfp_constraint(mapping, ~__GFP_FS));
  	if (!page)
  		return -ENOMEM;
  
  	blocksize = inode->i_sb->s_blocksize;
  
  	iblock = index << (PAGE_SHIFT - inode->i_sb->s_blocksize_bits);
  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, blocksize, 0);
  
  	/* Find the buffer that contains "offset" */
  	bh = page_buffers(page);
  	pos = blocksize;
  	while (offset >= pos) {
  		bh = bh->b_this_page;
  		iblock++;
  		pos += blocksize;
  	}
  	if (buffer_freed(bh)) {
  		BUFFER_TRACE(bh, "freed: skip");
  		goto unlock;
  	}
  	if (!buffer_mapped(bh)) {
  		BUFFER_TRACE(bh, "unmapped");
  		ext4_get_block(inode, iblock, bh, 0);
  		/* unmapped? It's a hole - nothing to do */
  		if (!buffer_mapped(bh)) {
  			BUFFER_TRACE(bh, "still unmapped");
  			goto unlock;
  		}
  	}
  
  	/* Ok, it's mapped. Make sure it's up-to-date */
  	if (PageUptodate(page))
  		set_buffer_uptodate(bh);
  
  	if (!buffer_uptodate(bh)) {
  		err = ext4_read_bh_lock(bh, 0, true);
  		if (err)
  			goto unlock;
  		if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
  			/* We expect the key to be set. */
  			BUG_ON(!fscrypt_has_encryption_key(inode));
  			err = fscrypt_decrypt_pagecache_blocks(page, blocksize,
  							       bh_offset(bh));
  			if (err) {
  				clear_buffer_uptodate(bh);
  				goto unlock;
  			}
  		}
  	}
  	if (ext4_should_journal_data(inode)) {
  		BUFFER_TRACE(bh, "get write access");
  		err = ext4_journal_get_write_access(handle, inode->i_sb, bh,
  						    EXT4_JTR_NONE);
  		if (err)
  			goto unlock;
  	}
  	zero_user(page, offset, length);
  	BUFFER_TRACE(bh, "zeroed end of block");
  
  	if (ext4_should_journal_data(inode)) {
  		err = ext4_handle_dirty_metadata(handle, inode, bh);
  	} else {
  		err = 0;
  		mark_buffer_dirty(bh);
  		if (ext4_should_order_data(inode))
  			err = ext4_jbd2_inode_add_write(handle, inode, from,
  					length);
  	}
  
  unlock:
  	unlock_page(page);
  	put_page(page);
  	return err;
  }
  
  /*
   * ext4_block_zero_page_range() zeros out a mapping of length 'length'
   * starting from file offset 'from'.  The range to be zero'd must
   * be contained with in one block.  If the specified range exceeds
   * the end of the block it will be shortened to end of the block
   * that corresponds to 'from'
   */
  static int ext4_block_zero_page_range(handle_t *handle,
  		struct address_space *mapping, loff_t from, loff_t length)
  {
  	struct inode *inode = mapping->host;
  	unsigned offset = from & (PAGE_SIZE-1);
  	unsigned blocksize = inode->i_sb->s_blocksize;
  	unsigned max = blocksize - (offset & (blocksize - 1));
  
  	/*
  	 * correct length if it does not fall between
  	 * 'from' and the end of the block
  	 */
  	if (length > max || length < 0)
  		length = max;
  
  	if (IS_DAX(inode)) {
  		return iomap_zero_range(inode, from, length, NULL,
  					&ext4_iomap_ops);
  	}
  	return __ext4_block_zero_page_range(handle, mapping, from, length);
  }
  
  /*
   * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
   * up to the end of the block which corresponds to `from'.
   * This required during truncate. We need to physically zero the tail end
   * of that block so it doesn't yield old data if the file is later grown.
   */
  static int ext4_block_truncate_page(handle_t *handle,
  		struct address_space *mapping, loff_t from)
  {
  	unsigned offset = from & (PAGE_SIZE-1);
  	unsigned length;
  	unsigned blocksize;
  	struct inode *inode = mapping->host;
  
  	/* If we are processing an encrypted inode during orphan list handling */
  	if (IS_ENCRYPTED(inode) && !fscrypt_has_encryption_key(inode))
  		return 0;
  
  	blocksize = inode->i_sb->s_blocksize;
  	length = blocksize - (offset & (blocksize - 1));
  
  	return ext4_block_zero_page_range(handle, mapping, from, length);
  }
  
  int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
  			     loff_t lstart, loff_t length)
  {
  	struct super_block *sb = inode->i_sb;
  	struct address_space *mapping = inode->i_mapping;
  	unsigned partial_start, partial_end;
  	ext4_fsblk_t start, end;
  	loff_t byte_end = (lstart + length - 1);
  	int err = 0;
  
  	partial_start = lstart & (sb->s_blocksize - 1);
  	partial_end = byte_end & (sb->s_blocksize - 1);
  
  	start = lstart >> sb->s_blocksize_bits;
  	end = byte_end >> sb->s_blocksize_bits;
  
  	/* Handle partial zero within the single block */
  	if (start == end &&
  	    (partial_start || (partial_end != sb->s_blocksize - 1))) {
  		err = ext4_block_zero_page_range(handle, mapping,
  						 lstart, length);
  		return err;
  	}
  	/* Handle partial zero out on the start of the range */
  	if (partial_start) {
  		err = ext4_block_zero_page_range(handle, mapping,
  						 lstart, sb->s_blocksize);
  		if (err)
  			return err;
  	}
  	/* Handle partial zero out on the end of the range */
  	if (partial_end != sb->s_blocksize - 1)
  		err = ext4_block_zero_page_range(handle, mapping,
  						 byte_end - partial_end,
  						 partial_end + 1);
  	return err;
  }
  
  int ext4_can_truncate(struct inode *inode)
  {
  	if (S_ISREG(inode->i_mode))
  		return 1;
  	if (S_ISDIR(inode->i_mode))
  		return 1;
  	if (S_ISLNK(inode->i_mode))
  		return !ext4_inode_is_fast_symlink(inode);
  	return 0;
  }
  
  /*
   * We have to make sure i_disksize gets properly updated before we truncate
   * page cache due to hole punching or zero range. Otherwise i_disksize update
   * can get lost as it may have been postponed to submission of writeback but
   * that will never happen after we truncate page cache.
   */
  int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
  				      loff_t len)
  {
  	handle_t *handle;
  	int ret;
  
  	loff_t size = i_size_read(inode);
  
  	WARN_ON(!inode_is_locked(inode));
  	if (offset > size || offset + len < size)
  		return 0;
  
  	if (EXT4_I(inode)->i_disksize >= size)
  		return 0;
  
  	handle = ext4_journal_start(inode, EXT4_HT_MISC, 1);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  	ext4_update_i_disksize(inode, size);
  	ret = ext4_mark_inode_dirty(handle, inode);
  	ext4_journal_stop(handle);
  
  	return ret;
  }
  
  static void ext4_wait_dax_page(struct inode *inode)
  {
  	filemap_invalidate_unlock(inode->i_mapping);
  	schedule();
  	filemap_invalidate_lock(inode->i_mapping);
  }
  
  int ext4_break_layouts(struct inode *inode)
  {
  	struct page *page;
  	int error;
  
  	if (WARN_ON_ONCE(!rwsem_is_locked(&inode->i_mapping->invalidate_lock)))
  		return -EINVAL;
  
  	do {
  		page = dax_layout_busy_page(inode->i_mapping);
  		if (!page)
  			return 0;
  
  		error = ___wait_var_event(&page->_refcount,
  				atomic_read(&page->_refcount) == 1,
  				TASK_INTERRUPTIBLE, 0, 0,
  				ext4_wait_dax_page(inode));
  	} while (error == 0);
  
  	return error;
  }
  
  /*
   * ext4_punch_hole: punches a hole in a file by releasing the blocks
   * associated with the given offset and length
   *
   * @inode:  File inode
   * @offset: The offset where the hole will begin
   * @len:    The length of the hole
   *
   * Returns: 0 on success or negative on failure
   */
  
  int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
  {
  	struct super_block *sb = inode->i_sb;
  	ext4_lblk_t first_block, stop_block;
  	struct address_space *mapping = inode->i_mapping;
  	loff_t first_block_offset, last_block_offset;
  	handle_t *handle;
  	unsigned int credits;
  	int ret = 0, ret2 = 0;
  
  	trace_ext4_punch_hole(inode, offset, length, 0);
  
  	ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
  	if (ext4_has_inline_data(inode)) {
  		filemap_invalidate_lock(mapping);
  		ret = ext4_convert_inline_data(inode);
  		filemap_invalidate_unlock(mapping);
  		if (ret)
  			return ret;
  	}
  
  	/*
  	 * Write out all dirty pages to avoid race conditions
  	 * Then release them.
  	 */
  	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
  		ret = filemap_write_and_wait_range(mapping, offset,
  						   offset + length - 1);
  		if (ret)
  			return ret;
  	}
  
  	inode_lock(inode);
  
  	/* No need to punch hole beyond i_size */
  	if (offset >= inode->i_size)
  		goto out_mutex;
  
  	/*
  	 * If the hole extends beyond i_size, set the hole
  	 * to end after the page that contains i_size
  	 */
  	if (offset + length > inode->i_size) {
  		length = inode->i_size +
  		   PAGE_SIZE - (inode->i_size & (PAGE_SIZE - 1)) -
  		   offset;
  	}
  
  	if (offset & (sb->s_blocksize - 1) ||
  	    (offset + length) & (sb->s_blocksize - 1)) {
  		/*
  		 * Attach jinode to inode for jbd2 if we do any zeroing of
  		 * partial block
  		 */
  		ret = ext4_inode_attach_jinode(inode);
  		if (ret < 0)
  			goto out_mutex;
  
  	}
  
  	/* Wait all existing dio workers, newcomers will block on i_mutex */
  	inode_dio_wait(inode);
  
  	/*
  	 * Prevent page faults from reinstantiating pages we have released from
  	 * page cache.
  	 */
  	filemap_invalidate_lock(mapping);
  
  	ret = ext4_break_layouts(inode);
  	if (ret)
  		goto out_dio;
  
  	first_block_offset = round_up(offset, sb->s_blocksize);
  	last_block_offset = round_down((offset + length), sb->s_blocksize) - 1;
  
  	/* Now release the pages and zero block aligned part of pages*/
  	if (last_block_offset > first_block_offset) {
  		ret = ext4_update_disksize_before_punch(inode, offset, length);
  		if (ret)
  			goto out_dio;
  		truncate_pagecache_range(inode, first_block_offset,
  					 last_block_offset);
  	}
  
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		credits = ext4_writepage_trans_blocks(inode);
  	else
  		credits = ext4_blocks_for_truncate(inode);
  	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
  	if (IS_ERR(handle)) {
  		ret = PTR_ERR(handle);
  		ext4_std_error(sb, ret);
  		goto out_dio;
  	}
  
  	ret = ext4_zero_partial_blocks(handle, inode, offset,
  				       length);
  	if (ret)
  		goto out_stop;
  
  	first_block = (offset + sb->s_blocksize - 1) >>
  		EXT4_BLOCK_SIZE_BITS(sb);
  	stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);
  
  	/* If there are blocks to remove, do it */
  	if (stop_block > first_block) {
  
  		down_write(&EXT4_I(inode)->i_data_sem);
  		ext4_discard_preallocations(inode, 0);
  
  		ret = ext4_es_remove_extent(inode, first_block,
  					    stop_block - first_block);
  		if (ret) {
  			up_write(&EXT4_I(inode)->i_data_sem);
  			goto out_stop;
  		}
  
  		if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  			ret = ext4_ext_remove_space(inode, first_block,
  						    stop_block - 1);
  		else
  			ret = ext4_ind_remove_space(handle, inode, first_block,
  						    stop_block);
  
  		up_write(&EXT4_I(inode)->i_data_sem);
  	}
  	ext4_fc_track_range(handle, inode, first_block, stop_block);
  	if (IS_SYNC(inode))
  		ext4_handle_sync(handle);
  
  	inode->i_mtime = inode->i_ctime = current_time(inode);
  	ret2 = ext4_mark_inode_dirty(handle, inode);
  	if (unlikely(ret2))
  		ret = ret2;
  	if (ret >= 0)
  		ext4_update_inode_fsync_trans(handle, inode, 1);
  out_stop:
  	ext4_journal_stop(handle);
  out_dio:
  	filemap_invalidate_unlock(mapping);
  out_mutex:
  	inode_unlock(inode);
  	return ret;
  }
  
  int ext4_inode_attach_jinode(struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	struct jbd2_inode *jinode;
  
  	if (ei->jinode || !EXT4_SB(inode->i_sb)->s_journal)
  		return 0;
  
  	jinode = jbd2_alloc_inode(GFP_KERNEL);
  	spin_lock(&inode->i_lock);
  	if (!ei->jinode) {
  		if (!jinode) {
  			spin_unlock(&inode->i_lock);
  			return -ENOMEM;
  		}
  		ei->jinode = jinode;
  		jbd2_journal_init_jbd_inode(ei->jinode, inode);
  		jinode = NULL;
  	}
  	spin_unlock(&inode->i_lock);
  	if (unlikely(jinode != NULL))
  		jbd2_free_inode(jinode);
  	return 0;
  }
  
  /*
   * ext4_truncate()
   *
   * We block out ext4_get_block() block instantiations across the entire
   * transaction, and VFS/VM ensures that ext4_truncate() cannot run
   * simultaneously on behalf of the same inode.
   *
   * As we work through the truncate and commit bits of it to the journal there
   * is one core, guiding principle: the file's tree must always be consistent on
   * disk.  We must be able to restart the truncate after a crash.
   *
   * The file's tree may be transiently inconsistent in memory (although it
   * probably isn't), but whenever we close off and commit a journal transaction,
   * the contents of (the filesystem + the journal) must be consistent and
   * restartable.  It's pretty simple, really: bottom up, right to left (although
   * left-to-right works OK too).
   *
   * Note that at recovery time, journal replay occurs *before* the restart of
   * truncate against the orphan inode list.
   *
   * The committed inode has the new, desired i_size (which is the same as
   * i_disksize in this case).  After a crash, ext4_orphan_cleanup() will see
   * that this inode's truncate did not complete and it will again call
   * ext4_truncate() to have another go.  So there will be instantiated blocks
   * to the right of the truncation point in a crashed ext4 filesystem.  But
   * that's fine - as long as they are linked from the inode, the post-crash
   * ext4_truncate() run will find them and release them.
   */
  int ext4_truncate(struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	unsigned int credits;
  	int err = 0, err2;
  	handle_t *handle;
  	struct address_space *mapping = inode->i_mapping;
  
  	/*
  	 * There is a possibility that we're either freeing the inode
  	 * or it's a completely new inode. In those cases we might not
  	 * have i_mutex locked because it's not necessary.
  	 */
  	if (!(inode->i_state & (I_NEW|I_FREEING)))
  		WARN_ON(!inode_is_locked(inode));
  	trace_ext4_truncate_enter(inode);
  
  	if (!ext4_can_truncate(inode))
  		goto out_trace;
  
  	if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
  		ext4_set_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
  
  	if (ext4_has_inline_data(inode)) {
  		int has_inline = 1;
  
  		err = ext4_inline_data_truncate(inode, &has_inline);
  		if (err || has_inline)
  			goto out_trace;
  	}
  
  	/* If we zero-out tail of the page, we have to create jinode for jbd2 */
  	if (inode->i_size & (inode->i_sb->s_blocksize - 1)) {
  		if (ext4_inode_attach_jinode(inode) < 0)
  			goto out_trace;
  	}
  
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		credits = ext4_writepage_trans_blocks(inode);
  	else
  		credits = ext4_blocks_for_truncate(inode);
  
  	handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
  	if (IS_ERR(handle)) {
  		err = PTR_ERR(handle);
  		goto out_trace;
  	}
  
  	if (inode->i_size & (inode->i_sb->s_blocksize - 1))
  		ext4_block_truncate_page(handle, mapping, inode->i_size);
  
  	/*
  	 * We add the inode to the orphan list, so that if this
  	 * truncate spans multiple transactions, and we crash, we will
  	 * resume the truncate when the filesystem recovers.  It also
  	 * marks the inode dirty, to catch the new size.
  	 *
  	 * Implication: the file must always be in a sane, consistent
  	 * truncatable state while each transaction commits.
  	 */
  	err = ext4_orphan_add(handle, inode);
  	if (err)
  		goto out_stop;
  
  	down_write(&EXT4_I(inode)->i_data_sem);
  
  	ext4_discard_preallocations(inode, 0);
  
  	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		err = ext4_ext_truncate(handle, inode);
  	else
  		ext4_ind_truncate(handle, inode);
  
  	up_write(&ei->i_data_sem);
  	if (err)
  		goto out_stop;
  
  	if (IS_SYNC(inode))
  		ext4_handle_sync(handle);
  
  out_stop:
  	/*
  	 * If this was a simple ftruncate() and the file will remain alive,
  	 * then we need to clear up the orphan record which we created above.
  	 * However, if this was a real unlink then we were called by
  	 * ext4_evict_inode(), and we allow that function to clean up the
  	 * orphan info for us.
  	 */
  	if (inode->i_nlink)
  		ext4_orphan_del(handle, inode);
  
  	inode->i_mtime = inode->i_ctime = current_time(inode);
  	err2 = ext4_mark_inode_dirty(handle, inode);
  	if (unlikely(err2 && !err))
  		err = err2;
  	ext4_journal_stop(handle);
  
  out_trace:
  	trace_ext4_truncate_exit(inode);
  	return err;
  }
  
  /*
   * ext4_get_inode_loc returns with an extra refcount against the inode's
   * underlying buffer_head on success. If 'in_mem' is true, we have all
   * data in memory that is needed to recreate the on-disk version of this
   * inode.
   */
  static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
  				struct ext4_iloc *iloc, int in_mem,
  				ext4_fsblk_t *ret_block)
  {
  	struct ext4_group_desc	*gdp;
  	struct buffer_head	*bh;
  	ext4_fsblk_t		block;
  	struct blk_plug		plug;
  	int			inodes_per_block, inode_offset;
  
  	iloc->bh = NULL;
  	if (ino < EXT4_ROOT_INO ||
  	    ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))
  		return -EFSCORRUPTED;
  
  	iloc->block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb);
  	gdp = ext4_get_group_desc(sb, iloc->block_group, NULL);
  	if (!gdp)
  		return -EIO;
  
  	/*
  	 * Figure out the offset within the block group inode table
  	 */
  	inodes_per_block = EXT4_SB(sb)->s_inodes_per_block;
  	inode_offset = ((ino - 1) %
  			EXT4_INODES_PER_GROUP(sb));
  	block = ext4_inode_table(sb, gdp) + (inode_offset / inodes_per_block);
  	iloc->offset = (inode_offset % inodes_per_block) * EXT4_INODE_SIZE(sb);
  
  	bh = sb_getblk(sb, block);
  	if (unlikely(!bh))
  		return -ENOMEM;
  	if (ext4_buffer_uptodate(bh))
  		goto has_buffer;
  
  	lock_buffer(bh);
  	if (ext4_buffer_uptodate(bh)) {
  		/* Someone brought it uptodate while we waited */
  		unlock_buffer(bh);
  		goto has_buffer;
  	}
  
  	/*
  	 * If we have all information of the inode in memory and this
  	 * is the only valid inode in the block, we need not read the
  	 * block.
  	 */
  	if (in_mem) {
  		struct buffer_head *bitmap_bh;
  		int i, start;
  
  		start = inode_offset & ~(inodes_per_block - 1);
  
  		/* Is the inode bitmap in cache? */
  		bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp));
  		if (unlikely(!bitmap_bh))
  			goto make_io;
  
  		/*
  		 * If the inode bitmap isn't in cache then the
  		 * optimisation may end up performing two reads instead
  		 * of one, so skip it.
  		 */
  		if (!buffer_uptodate(bitmap_bh)) {
  			brelse(bitmap_bh);
  			goto make_io;
  		}
  		for (i = start; i < start + inodes_per_block; i++) {
  			if (i == inode_offset)
  				continue;
  			if (ext4_test_bit(i, bitmap_bh->b_data))
  				break;
  		}
  		brelse(bitmap_bh);
  		if (i == start + inodes_per_block) {
  			/* all other inodes are free, so skip I/O */
  			memset(bh->b_data, 0, bh->b_size);
  			set_buffer_uptodate(bh);
  			unlock_buffer(bh);
  			goto has_buffer;
  		}
  	}
  
  make_io:
  	/*
  	 * If we need to do any I/O, try to pre-readahead extra
  	 * blocks from the inode table.
  	 */
  	blk_start_plug(&plug);
  	if (EXT4_SB(sb)->s_inode_readahead_blks) {
  		ext4_fsblk_t b, end, table;
  		unsigned num;
  		__u32 ra_blks = EXT4_SB(sb)->s_inode_readahead_blks;
  
  		table = ext4_inode_table(sb, gdp);
  		/* s_inode_readahead_blks is always a power of 2 */
  		b = block & ~((ext4_fsblk_t) ra_blks - 1);
  		if (table > b)
  			b = table;
  		end = b + ra_blks;
  		num = EXT4_INODES_PER_GROUP(sb);
  		if (ext4_has_group_desc_csum(sb))
  			num -= ext4_itable_unused_count(sb, gdp);
  		table += num / inodes_per_block;
  		if (end > table)
  			end = table;
  		while (b <= end)
  			ext4_sb_breadahead_unmovable(sb, b++);
  	}
  
  	/*
  	 * There are other valid inodes in the buffer, this inode
  	 * has in-inode xattrs, or we don't have this inode in memory.
  	 * Read the block from disk.
  	 */
  	trace_ext4_load_inode(sb, ino);
  	ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO, NULL);
  	blk_finish_plug(&plug);
  	wait_on_buffer(bh);
  	ext4_simulate_fail_bh(sb, bh, EXT4_SIM_INODE_EIO);
  	if (!buffer_uptodate(bh)) {
  		if (ret_block)
  			*ret_block = block;
  		brelse(bh);
  		return -EIO;
  	}
  has_buffer:
  	iloc->bh = bh;
  	return 0;
  }
  
  static int __ext4_get_inode_loc_noinmem(struct inode *inode,
  					struct ext4_iloc *iloc)
  {
  	ext4_fsblk_t err_blk;
  	int ret;
  
  	ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, iloc, 0,
  					&err_blk);
  
  	if (ret == -EIO)
  		ext4_error_inode_block(inode, err_blk, EIO,
  					"unable to read itable block");
  
  	return ret;
  }
  
  int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
  {
  	ext4_fsblk_t err_blk;
  	int ret;
  
  	/* We have all inode data except xattrs in memory here. */
  	ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, iloc,
  		!ext4_test_inode_state(inode, EXT4_STATE_XATTR), &err_blk);
  
  	if (ret == -EIO)
  		ext4_error_inode_block(inode, err_blk, EIO,
  					"unable to read itable block");
  
  	return ret;
  }
  
  
  int ext4_get_fc_inode_loc(struct super_block *sb, unsigned long ino,
  			  struct ext4_iloc *iloc)
  {
  	return __ext4_get_inode_loc(sb, ino, iloc, 0, NULL);
  }
  
  static bool ext4_should_enable_dax(struct inode *inode)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  	if (test_opt2(inode->i_sb, DAX_NEVER))
  		return false;
  	if (!S_ISREG(inode->i_mode))
  		return false;
  	if (ext4_should_journal_data(inode))
  		return false;
  	if (ext4_has_inline_data(inode))
  		return false;
  	if (ext4_test_inode_flag(inode, EXT4_INODE_ENCRYPT))
  		return false;
  	if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
  		return false;
  	if (!test_bit(EXT4_FLAGS_BDEV_IS_DAX, &sbi->s_ext4_flags))
  		return false;
  	if (test_opt(inode->i_sb, DAX_ALWAYS))
  		return true;
  
  	return ext4_test_inode_flag(inode, EXT4_INODE_DAX);
  }
  
  void ext4_set_inode_flags(struct inode *inode, bool init)
  {
  	unsigned int flags = EXT4_I(inode)->i_flags;
  	unsigned int new_fl = 0;
  
  	WARN_ON_ONCE(IS_DAX(inode) && init);
  
  	if (flags & EXT4_SYNC_FL)
  		new_fl |= S_SYNC;
  	if (flags & EXT4_APPEND_FL)
  		new_fl |= S_APPEND;
  	if (flags & EXT4_IMMUTABLE_FL)
  		new_fl |= S_IMMUTABLE;
  	if (flags & EXT4_NOATIME_FL)
  		new_fl |= S_NOATIME;
  	if (flags & EXT4_DIRSYNC_FL)
  		new_fl |= S_DIRSYNC;
  
  	/* Because of the way inode_set_flags() works we must preserve S_DAX
  	 * here if already set. */
  	new_fl |= (inode->i_flags & S_DAX);
  	if (init && ext4_should_enable_dax(inode))
  		new_fl |= S_DAX;
  
  	if (flags & EXT4_ENCRYPT_FL)
  		new_fl |= S_ENCRYPTED;
  	if (flags & EXT4_CASEFOLD_FL)
  		new_fl |= S_CASEFOLD;
  	if (flags & EXT4_VERITY_FL)
  		new_fl |= S_VERITY;
  	inode_set_flags(inode, new_fl,
  			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX|
  			S_ENCRYPTED|S_CASEFOLD|S_VERITY);
  }
  
  static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,
  				  struct ext4_inode_info *ei)
  {
  	blkcnt_t i_blocks ;
  	struct inode *inode = &(ei->vfs_inode);
  	struct super_block *sb = inode->i_sb;
  
  	if (ext4_has_feature_huge_file(sb)) {
  		/* we are using combined 48 bit field */
  		i_blocks = ((u64)le16_to_cpu(raw_inode->i_blocks_high)) << 32 |
  					le32_to_cpu(raw_inode->i_blocks_lo);
  		if (ext4_test_inode_flag(inode, EXT4_INODE_HUGE_FILE)) {
  			/* i_blocks represent file system block size */
  			return i_blocks  << (inode->i_blkbits - 9);
  		} else {
  			return i_blocks;
  		}
  	} else {
  		return le32_to_cpu(raw_inode->i_blocks_lo);
  	}
  }
  
  static inline int ext4_iget_extra_inode(struct inode *inode,
  					 struct ext4_inode *raw_inode,
  					 struct ext4_inode_info *ei)
  {
  	__le32 *magic = (void *)raw_inode +
  			EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize;
  
  	if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize + sizeof(__le32) <=
  	    EXT4_INODE_SIZE(inode->i_sb) &&
  	    *magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
  		ext4_set_inode_state(inode, EXT4_STATE_XATTR);
  		return ext4_find_inline_data_nolock(inode);
  	} else
  		EXT4_I(inode)->i_inline_off = 0;
  	return 0;
  }
  
  int ext4_get_projid(struct inode *inode, kprojid_t *projid)
  {
  	if (!ext4_has_feature_project(inode->i_sb))
  		return -EOPNOTSUPP;
  	*projid = EXT4_I(inode)->i_projid;
  	return 0;
  }
  
  /*
   * ext4 has self-managed i_version for ea inodes, it stores the lower 32bit of
   * refcount in i_version, so use raw values if inode has EXT4_EA_INODE_FL flag
   * set.
   */
  static inline void ext4_inode_set_iversion_queried(struct inode *inode, u64 val)
  {
  	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL))
  		inode_set_iversion_raw(inode, val);
  	else
  		inode_set_iversion_queried(inode, val);
  }
  static inline u64 ext4_inode_peek_iversion(const struct inode *inode)
  {
  	if (unlikely(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL))
  		return inode_peek_iversion_raw(inode);
  	else
  		return inode_peek_iversion(inode);
  }
  
  struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
  			  ext4_iget_flags flags, const char *function,
  			  unsigned int line)
  {
  	struct ext4_iloc iloc;
  	struct ext4_inode *raw_inode;
  	struct ext4_inode_info *ei;
  	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  	struct inode *inode;
  	journal_t *journal = EXT4_SB(sb)->s_journal;
  	long ret;
  	loff_t size;
  	int block;
  	uid_t i_uid;
  	gid_t i_gid;
  	projid_t i_projid;
  
  	if ((!(flags & EXT4_IGET_SPECIAL) &&
  	     ((ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO) ||
  	      ino == le32_to_cpu(es->s_usr_quota_inum) ||
  	      ino == le32_to_cpu(es->s_grp_quota_inum) ||
  	      ino == le32_to_cpu(es->s_prj_quota_inum) ||
  	      ino == le32_to_cpu(es->s_orphan_file_inum))) ||
  	    (ino < EXT4_ROOT_INO) ||
  	    (ino > le32_to_cpu(es->s_inodes_count))) {
  		if (flags & EXT4_IGET_HANDLE)
  			return ERR_PTR(-ESTALE);
  		__ext4_error(sb, function, line, false, EFSCORRUPTED, 0,
  			     "inode #%lu: comm %s: iget: illegal inode #",
  			     ino, current->comm);
  		return ERR_PTR(-EFSCORRUPTED);
  	}
  
  	inode = iget_locked(sb, ino);
  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  	if (!(inode->i_state & I_NEW))
  		return inode;
  
  	ei = EXT4_I(inode);
  	iloc.bh = NULL;
  
  	ret = __ext4_get_inode_loc_noinmem(inode, &iloc);
  	if (ret < 0)
  		goto bad_inode;
  	raw_inode = ext4_raw_inode(&iloc);
  
  	if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) {
  		ext4_error_inode(inode, function, line, 0,
  				 "iget: root inode unallocated");
  		ret = -EFSCORRUPTED;
  		goto bad_inode;
  	}
  
  	if ((flags & EXT4_IGET_HANDLE) &&
  	    (raw_inode->i_links_count == 0) && (raw_inode->i_mode == 0)) {
  		ret = -ESTALE;
  		goto bad_inode;
  	}
  
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
  		ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
  		if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
  			EXT4_INODE_SIZE(inode->i_sb) ||
  		    (ei->i_extra_isize & 3)) {
  			ext4_error_inode(inode, function, line, 0,
  					 "iget: bad extra_isize %u "
  					 "(inode size %u)",
  					 ei->i_extra_isize,
  					 EXT4_INODE_SIZE(inode->i_sb));
  			ret = -EFSCORRUPTED;
  			goto bad_inode;
  		}
  	} else
  		ei->i_extra_isize = 0;
  
  	/* Precompute checksum seed for inode metadata */
  	if (ext4_has_metadata_csum(sb)) {
  		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  		__u32 csum;
  		__le32 inum = cpu_to_le32(inode->i_ino);
  		__le32 gen = raw_inode->i_generation;
  		csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum,
  				   sizeof(inum));
  		ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen,
  					      sizeof(gen));
  	}
  
  	if ((!ext4_inode_csum_verify(inode, raw_inode, ei) ||
  	    ext4_simulate_fail(sb, EXT4_SIM_INODE_CRC)) &&
  	     (!(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY))) {
  		ext4_error_inode_err(inode, function, line, 0,
  				EFSBADCRC, "iget: checksum invalid");
  		ret = -EFSBADCRC;
  		goto bad_inode;
  	}
  
  	inode->i_mode = le16_to_cpu(raw_inode->i_mode);
  	i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low);
  	i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);
  	if (ext4_has_feature_project(sb) &&
  	    EXT4_INODE_SIZE(sb) > EXT4_GOOD_OLD_INODE_SIZE &&
  	    EXT4_FITS_IN_INODE(raw_inode, ei, i_projid))
  		i_projid = (projid_t)le32_to_cpu(raw_inode->i_projid);
  	else
  		i_projid = EXT4_DEF_PROJID;
  
  	if (!(test_opt(inode->i_sb, NO_UID32))) {
  		i_uid |= le16_to_cpu(raw_inode->i_uid_high) << 16;
  		i_gid |= le16_to_cpu(raw_inode->i_gid_high) << 16;
  	}
  	i_uid_write(inode, i_uid);
  	i_gid_write(inode, i_gid);
  	ei->i_projid = make_kprojid(&init_user_ns, i_projid);
  	set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
  
  	ext4_clear_state_flags(ei);	/* Only relevant on 32-bit archs */
  	ei->i_inline_off = 0;
  	ei->i_dir_start_lookup = 0;
  	ei->i_dtime = le32_to_cpu(raw_inode->i_dtime);
  	/* We now have enough fields to check if the inode was active or not.
  	 * This is needed because nfsd might try to access dead inodes
  	 * the test is that same one that e2fsck uses
  	 * NeilBrown 1999oct15
  	 */
  	if (inode->i_nlink == 0) {
  		if ((inode->i_mode == 0 ||
  		     !(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_ORPHAN_FS)) &&
  		    ino != EXT4_BOOT_LOADER_INO) {
  			/* this inode is deleted */
  			ret = -ESTALE;
  			goto bad_inode;
  		}
  		/* The only unlinked inodes we let through here have
  		 * valid i_mode and are being read by the orphan
  		 * recovery code: that's fine, we're about to complete
  		 * the process of deleting those.
  		 * OR it is the EXT4_BOOT_LOADER_INO which is
  		 * not initialized on a new filesystem. */
  	}
  	ei->i_flags = le32_to_cpu(raw_inode->i_flags);
  	ext4_set_inode_flags(inode, true);
  	inode->i_blocks = ext4_inode_blocks(raw_inode, ei);
  	ei->i_file_acl = le32_to_cpu(raw_inode->i_file_acl_lo);
  	if (ext4_has_feature_64bit(sb))
  		ei->i_file_acl |=
  			((__u64)le16_to_cpu(raw_inode->i_file_acl_high)) << 32;
  	inode->i_size = ext4_isize(sb, raw_inode);
  	if ((size = i_size_read(inode)) < 0) {
  		ext4_error_inode(inode, function, line, 0,
  				 "iget: bad i_size value: %lld", size);
  		ret = -EFSCORRUPTED;
  		goto bad_inode;
  	}
  	/*
  	 * If dir_index is not enabled but there's dir with INDEX flag set,
  	 * we'd normally treat htree data as empty space. But with metadata
  	 * checksumming that corrupts checksums so forbid that.
  	 */
  	if (!ext4_has_feature_dir_index(sb) && ext4_has_metadata_csum(sb) &&
  	    ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) {
  		ext4_error_inode(inode, function, line, 0,
  			 "iget: Dir with htree data on filesystem without dir_index feature.");
  		ret = -EFSCORRUPTED;
  		goto bad_inode;
  	}
  	ei->i_disksize = inode->i_size;
  #ifdef CONFIG_QUOTA
  	ei->i_reserved_quota = 0;
  #endif
  	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
  	ei->i_block_group = iloc.block_group;
  	ei->i_last_alloc_group = ~0;
  	/*
  	 * NOTE! The in-memory inode i_data array is in little-endian order
  	 * even on big-endian machines: we do NOT byteswap the block numbers!
  	 */
  	for (block = 0; block < EXT4_N_BLOCKS; block++)
  		ei->i_data[block] = raw_inode->i_block[block];
  	INIT_LIST_HEAD(&ei->i_orphan);
  	ext4_fc_init_inode(&ei->vfs_inode);
  
  	/*
  	 * Set transaction id's of transactions that have to be committed
  	 * to finish f[data]sync. We set them to currently running transaction
  	 * as we cannot be sure that the inode or some of its metadata isn't
  	 * part of the transaction - the inode could have been reclaimed and
  	 * now it is reread from disk.
  	 */
  	if (journal) {
  		transaction_t *transaction;
  		tid_t tid;
  
  		read_lock(&journal->j_state_lock);
  		if (journal->j_running_transaction)
  			transaction = journal->j_running_transaction;
  		else
  			transaction = journal->j_committing_transaction;
  		if (transaction)
  			tid = transaction->t_tid;
  		else
  			tid = journal->j_commit_sequence;
  		read_unlock(&journal->j_state_lock);
  		ei->i_sync_tid = tid;
  		ei->i_datasync_tid = tid;
  	}
  
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
  		if (ei->i_extra_isize == 0) {
  			/* The extra space is currently unused. Use it. */
  			BUILD_BUG_ON(sizeof(struct ext4_inode) & 3);
  			ei->i_extra_isize = sizeof(struct ext4_inode) -
  					    EXT4_GOOD_OLD_INODE_SIZE;
  		} else {
  			ret = ext4_iget_extra_inode(inode, raw_inode, ei);
  			if (ret)
  				goto bad_inode;
  		}
  	}
  
  	EXT4_INODE_GET_XTIME(i_ctime, inode, raw_inode);
  	EXT4_INODE_GET_XTIME(i_mtime, inode, raw_inode);
  	EXT4_INODE_GET_XTIME(i_atime, inode, raw_inode);
  	EXT4_EINODE_GET_XTIME(i_crtime, ei, raw_inode);
  
  	if (likely(!test_opt2(inode->i_sb, HURD_COMPAT))) {
  		u64 ivers = le32_to_cpu(raw_inode->i_disk_version);
  
  		if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
  			if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
  				ivers |=
  		    (__u64)(le32_to_cpu(raw_inode->i_version_hi)) << 32;
  		}
  		ext4_inode_set_iversion_queried(inode, ivers);
  	}
  
  	ret = 0;
  	if (ei->i_file_acl &&
  	    !ext4_inode_block_valid(inode, ei->i_file_acl, 1)) {
  		ext4_error_inode(inode, function, line, 0,
  				 "iget: bad extended attribute block %llu",
  				 ei->i_file_acl);
  		ret = -EFSCORRUPTED;
  		goto bad_inode;
  	} else if (!ext4_has_inline_data(inode)) {
  		/* validate the block references in the inode */
  		if (!(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY) &&
  			(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
  			(S_ISLNK(inode->i_mode) &&
  			!ext4_inode_is_fast_symlink(inode)))) {
  			if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  				ret = ext4_ext_check_inode(inode);
  			else
  				ret = ext4_ind_check_inode(inode);
  		}
  	}
  	if (ret)
  		goto bad_inode;
  
  	if (S_ISREG(inode->i_mode)) {
  		inode->i_op = &ext4_file_inode_operations;
  		inode->i_fop = &ext4_file_operations;
  		ext4_set_aops(inode);
  	} else if (S_ISDIR(inode->i_mode)) {
  		inode->i_op = &ext4_dir_inode_operations;
  		inode->i_fop = &ext4_dir_operations;
  	} else if (S_ISLNK(inode->i_mode)) {
  		/* VFS does not allow setting these so must be corruption */
  		if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {
  			ext4_error_inode(inode, function, line, 0,
  					 "iget: immutable or append flags "
  					 "not allowed on symlinks");
  			ret = -EFSCORRUPTED;
  			goto bad_inode;
  		}
  		if (IS_ENCRYPTED(inode)) {
  			inode->i_op = &ext4_encrypted_symlink_inode_operations;
  			ext4_set_aops(inode);
  		} else if (ext4_inode_is_fast_symlink(inode)) {
  			inode->i_link = (char *)ei->i_data;
  			inode->i_op = &ext4_fast_symlink_inode_operations;
  			nd_terminate_link(ei->i_data, inode->i_size,
  				sizeof(ei->i_data) - 1);
  		} else {
  			inode->i_op = &ext4_symlink_inode_operations;
  			ext4_set_aops(inode);
  		}
  		inode_nohighmem(inode);
  	} else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
  	      S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
  		inode->i_op = &ext4_special_inode_operations;
  		if (raw_inode->i_block[0])
  			init_special_inode(inode, inode->i_mode,
  			   old_decode_dev(le32_to_cpu(raw_inode->i_block[0])));
  		else
  			init_special_inode(inode, inode->i_mode,
  			   new_decode_dev(le32_to_cpu(raw_inode->i_block[1])));
  	} else if (ino == EXT4_BOOT_LOADER_INO) {
  		make_bad_inode(inode);
  	} else {
  		ret = -EFSCORRUPTED;
  		ext4_error_inode(inode, function, line, 0,
  				 "iget: bogus i_mode (%o)", inode->i_mode);
  		goto bad_inode;
  	}
  	if (IS_CASEFOLDED(inode) && !ext4_has_feature_casefold(inode->i_sb))
  		ext4_error_inode(inode, function, line, 0,
  				 "casefold flag without casefold feature");
  	brelse(iloc.bh);
  
  	unlock_new_inode(inode);
  	return inode;
  
  bad_inode:
  	brelse(iloc.bh);
  	iget_failed(inode);
  	return ERR_PTR(ret);
  }
  
  static int ext4_inode_blocks_set(handle_t *handle,
  				struct ext4_inode *raw_inode,
  				struct ext4_inode_info *ei)
  {
  	struct inode *inode = &(ei->vfs_inode);
  	u64 i_blocks = READ_ONCE(inode->i_blocks);
  	struct super_block *sb = inode->i_sb;
  
  	if (i_blocks <= ~0U) {
  		/*
  		 * i_blocks can be represented in a 32 bit variable
  		 * as multiple of 512 bytes
  		 */
  		raw_inode->i_blocks_lo   = cpu_to_le32(i_blocks);
  		raw_inode->i_blocks_high = 0;
  		ext4_clear_inode_flag(inode, EXT4_INODE_HUGE_FILE);
  		return 0;
  	}
  
  	/*
  	 * This should never happen since sb->s_maxbytes should not have
  	 * allowed this, sb->s_maxbytes was set according to the huge_file
  	 * feature in ext4_fill_super().
  	 */
  	if (!ext4_has_feature_huge_file(sb))
  		return -EFSCORRUPTED;
  
  	if (i_blocks <= 0xffffffffffffULL) {
  		/*
  		 * i_blocks can be represented in a 48 bit variable
  		 * as multiple of 512 bytes
  		 */
  		raw_inode->i_blocks_lo   = cpu_to_le32(i_blocks);
  		raw_inode->i_blocks_high = cpu_to_le16(i_blocks >> 32);
  		ext4_clear_inode_flag(inode, EXT4_INODE_HUGE_FILE);
  	} else {
  		ext4_set_inode_flag(inode, EXT4_INODE_HUGE_FILE);
  		/* i_block is stored in file system block size */
  		i_blocks = i_blocks >> (inode->i_blkbits - 9);
  		raw_inode->i_blocks_lo   = cpu_to_le32(i_blocks);
  		raw_inode->i_blocks_high = cpu_to_le16(i_blocks >> 32);
  	}
  	return 0;
  }
  
  static void __ext4_update_other_inode_time(struct super_block *sb,
  					   unsigned long orig_ino,
  					   unsigned long ino,
  					   struct ext4_inode *raw_inode)
  {
  	struct inode *inode;
  
  	inode = find_inode_by_ino_rcu(sb, ino);
  	if (!inode)
  		return;
  
  	if (!inode_is_dirtytime_only(inode))
  		return;
  
  	spin_lock(&inode->i_lock);
  	if (inode_is_dirtytime_only(inode)) {
  		struct ext4_inode_info	*ei = EXT4_I(inode);
  
  		inode->i_state &= ~I_DIRTY_TIME;
  		spin_unlock(&inode->i_lock);
  
  		spin_lock(&ei->i_raw_lock);
  		EXT4_INODE_SET_XTIME(i_ctime, inode, raw_inode);
  		EXT4_INODE_SET_XTIME(i_mtime, inode, raw_inode);
  		EXT4_INODE_SET_XTIME(i_atime, inode, raw_inode);
  		ext4_inode_csum_set(inode, raw_inode, ei);
  		spin_unlock(&ei->i_raw_lock);
  		trace_ext4_other_inode_update_time(inode, orig_ino);
  		return;
  	}
  	spin_unlock(&inode->i_lock);
  }
  
  /*
   * Opportunistically update the other time fields for other inodes in
   * the same inode table block.
   */
  static void ext4_update_other_inodes_time(struct super_block *sb,
  					  unsigned long orig_ino, char *buf)
  {
  	unsigned long ino;
  	int i, inodes_per_block = EXT4_SB(sb)->s_inodes_per_block;
  	int inode_size = EXT4_INODE_SIZE(sb);
  
  	/*
  	 * Calculate the first inode in the inode table block.  Inode
  	 * numbers are one-based.  That is, the first inode in a block
  	 * (assuming 4k blocks and 256 byte inodes) is (n*16 + 1).
  	 */
  	ino = ((orig_ino - 1) & ~(inodes_per_block - 1)) + 1;
  	rcu_read_lock();
  	for (i = 0; i < inodes_per_block; i++, ino++, buf += inode_size) {
  		if (ino == orig_ino)
  			continue;
  		__ext4_update_other_inode_time(sb, orig_ino, ino,
  					       (struct ext4_inode *)buf);
  	}
  	rcu_read_unlock();
  }
  
  /*
   * Post the struct inode info into an on-disk inode location in the
   * buffer-cache.  This gobbles the caller's reference to the
   * buffer_head in the inode location struct.
   *
   * The caller must have write access to iloc->bh.
   */
  static int ext4_do_update_inode(handle_t *handle,
  				struct inode *inode,
  				struct ext4_iloc *iloc)
  {
  	struct ext4_inode *raw_inode = ext4_raw_inode(iloc);
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	struct buffer_head *bh = iloc->bh;
  	struct super_block *sb = inode->i_sb;
  	int err = 0, block;
  	int need_datasync = 0, set_large_file = 0;
  	uid_t i_uid;
  	gid_t i_gid;
  	projid_t i_projid;
  
  	spin_lock(&ei->i_raw_lock);
  
  	/*
  	 * For fields not tracked in the in-memory inode, initialise them
  	 * to zero for new inodes.
  	 */
  	if (ext4_test_inode_state(inode, EXT4_STATE_NEW))
  		memset(raw_inode, 0, EXT4_SB(inode->i_sb)->s_inode_size);
  
  	err = ext4_inode_blocks_set(handle, raw_inode, ei);
  
  	raw_inode->i_mode = cpu_to_le16(inode->i_mode);
  	i_uid = i_uid_read(inode);
  	i_gid = i_gid_read(inode);
  	i_projid = from_kprojid(&init_user_ns, ei->i_projid);
  	if (!(test_opt(inode->i_sb, NO_UID32))) {
  		raw_inode->i_uid_low = cpu_to_le16(low_16_bits(i_uid));
  		raw_inode->i_gid_low = cpu_to_le16(low_16_bits(i_gid));
  		/*
  		 * Fix up interoperability with old kernels. Otherwise,
  		 * old inodes get re-used with the upper 16 bits of the
  		 * uid/gid intact.
  		 */
  		if (ei->i_dtime && list_empty(&ei->i_orphan)) {
  			raw_inode->i_uid_high = 0;
  			raw_inode->i_gid_high = 0;
  		} else {
  			raw_inode->i_uid_high =
  				cpu_to_le16(high_16_bits(i_uid));
  			raw_inode->i_gid_high =
  				cpu_to_le16(high_16_bits(i_gid));
  		}
  	} else {
  		raw_inode->i_uid_low = cpu_to_le16(fs_high2lowuid(i_uid));
  		raw_inode->i_gid_low = cpu_to_le16(fs_high2lowgid(i_gid));
  		raw_inode->i_uid_high = 0;
  		raw_inode->i_gid_high = 0;
  	}
  	raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
  
  	EXT4_INODE_SET_XTIME(i_ctime, inode, raw_inode);
  	EXT4_INODE_SET_XTIME(i_mtime, inode, raw_inode);
  	EXT4_INODE_SET_XTIME(i_atime, inode, raw_inode);
  	EXT4_EINODE_SET_XTIME(i_crtime, ei, raw_inode);
  
  	raw_inode->i_dtime = cpu_to_le32(ei->i_dtime);
  	raw_inode->i_flags = cpu_to_le32(ei->i_flags & 0xFFFFFFFF);
  	if (likely(!test_opt2(inode->i_sb, HURD_COMPAT)))
  		raw_inode->i_file_acl_high =
  			cpu_to_le16(ei->i_file_acl >> 32);
  	raw_inode->i_file_acl_lo = cpu_to_le32(ei->i_file_acl);
  	if (READ_ONCE(ei->i_disksize) != ext4_isize(inode->i_sb, raw_inode)) {
  		ext4_isize_set(raw_inode, ei->i_disksize);
  		need_datasync = 1;
  	}
  	if (ei->i_disksize > 0x7fffffffULL) {
  		if (!ext4_has_feature_large_file(sb) ||
  				EXT4_SB(sb)->s_es->s_rev_level ==
  		    cpu_to_le32(EXT4_GOOD_OLD_REV))
  			set_large_file = 1;
  	}
  	raw_inode->i_generation = cpu_to_le32(inode->i_generation);
  	if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
  		if (old_valid_dev(inode->i_rdev)) {
  			raw_inode->i_block[0] =
  				cpu_to_le32(old_encode_dev(inode->i_rdev));
  			raw_inode->i_block[1] = 0;
  		} else {
  			raw_inode->i_block[0] = 0;
  			raw_inode->i_block[1] =
  				cpu_to_le32(new_encode_dev(inode->i_rdev));
  			raw_inode->i_block[2] = 0;
  		}
  	} else if (!ext4_has_inline_data(inode)) {
  		for (block = 0; block < EXT4_N_BLOCKS; block++)
  			raw_inode->i_block[block] = ei->i_data[block];
  	}
  
  	if (likely(!test_opt2(inode->i_sb, HURD_COMPAT))) {
  		u64 ivers = ext4_inode_peek_iversion(inode);
  
  		raw_inode->i_disk_version = cpu_to_le32(ivers);
  		if (ei->i_extra_isize) {
  			if (EXT4_FITS_IN_INODE(raw_inode, ei, i_version_hi))
  				raw_inode->i_version_hi =
  					cpu_to_le32(ivers >> 32);
  			raw_inode->i_extra_isize =
  				cpu_to_le16(ei->i_extra_isize);
  		}
  	}
  
  	if (i_projid != EXT4_DEF_PROJID &&
  	    !ext4_has_feature_project(inode->i_sb))
  		err = err ?: -EFSCORRUPTED;
  
  	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
  	    EXT4_FITS_IN_INODE(raw_inode, ei, i_projid))
  		raw_inode->i_projid = cpu_to_le32(i_projid);
  
  	ext4_inode_csum_set(inode, raw_inode, ei);
  	spin_unlock(&ei->i_raw_lock);
  	if (err) {
  		EXT4_ERROR_INODE(inode, "corrupted inode contents");
  		goto out_brelse;
  	}
  
  	if (inode->i_sb->s_flags & SB_LAZYTIME)
  		ext4_update_other_inodes_time(inode->i_sb, inode->i_ino,
  					      bh->b_data);
  
  	BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
  	err = ext4_handle_dirty_metadata(handle, NULL, bh);
  	if (err)
  		goto out_error;
  	ext4_clear_inode_state(inode, EXT4_STATE_NEW);
  	if (set_large_file) {
  		BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get write access");
  		err = ext4_journal_get_write_access(handle, sb,
  						    EXT4_SB(sb)->s_sbh,
  						    EXT4_JTR_NONE);
  		if (err)
  			goto out_error;
  		lock_buffer(EXT4_SB(sb)->s_sbh);
  		ext4_set_feature_large_file(sb);
  		ext4_superblock_csum_set(sb);
  		unlock_buffer(EXT4_SB(sb)->s_sbh);
  		ext4_handle_sync(handle);
  		err = ext4_handle_dirty_metadata(handle, NULL,
  						 EXT4_SB(sb)->s_sbh);
  	}
  	ext4_update_inode_fsync_trans(handle, inode, need_datasync);
  out_error:
  	ext4_std_error(inode->i_sb, err);
  out_brelse:
  	brelse(bh);
  	return err;
  }
  
  /*
   * ext4_write_inode()
   *
   * We are called from a few places:
   *
   * - Within generic_file_aio_write() -> generic_write_sync() for O_SYNC files.
   *   Here, there will be no transaction running. We wait for any running
   *   transaction to commit.
   *
   * - Within flush work (sys_sync(), kupdate and such).
   *   We wait on commit, if told to.
   *
   * - Within iput_final() -> write_inode_now()
   *   We wait on commit, if told to.
   *
   * In all cases it is actually safe for us to return without doing anything,
   * because the inode has been copied into a raw inode buffer in
   * ext4_mark_inode_dirty().  This is a correctness thing for WB_SYNC_ALL
   * writeback.
   *
   * Note that we are absolutely dependent upon all inode dirtiers doing the
   * right thing: they *must* call mark_inode_dirty() after dirtying info in
   * which we are interested.
   *
   * It would be a bug for them to not do this.  The code:
   *
   *	mark_inode_dirty(inode)
   *	stuff();
   *	inode->i_size = expr;
   *
   * is in error because write_inode() could occur while `stuff()' is running,
   * and the new i_size will be lost.  Plus the inode will no longer be on the
   * superblock's dirty inode list.
   */
  int ext4_write_inode(struct inode *inode, struct writeback_control *wbc)
  {
  	int err;
  
  	if (WARN_ON_ONCE(current->flags & PF_MEMALLOC) ||
  	    sb_rdonly(inode->i_sb))
  		return 0;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	if (EXT4_SB(inode->i_sb)->s_journal) {
  		if (ext4_journal_current_handle()) {
  			jbd_debug(1, "called recursively, non-PF_MEMALLOC!\n");
  			dump_stack();
  			return -EIO;
  		}
  
  		/*
  		 * No need to force transaction in WB_SYNC_NONE mode. Also
  		 * ext4_sync_fs() will force the commit after everything is
  		 * written.
  		 */
  		if (wbc->sync_mode != WB_SYNC_ALL || wbc->for_sync)
  			return 0;
  
  		err = ext4_fc_commit(EXT4_SB(inode->i_sb)->s_journal,
  						EXT4_I(inode)->i_sync_tid);
  	} else {
  		struct ext4_iloc iloc;
  
  		err = __ext4_get_inode_loc_noinmem(inode, &iloc);
  		if (err)
  			return err;
  		/*
  		 * sync(2) will flush the whole buffer cache. No need to do
  		 * it here separately for each inode.
  		 */
  		if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync)
  			sync_dirty_buffer(iloc.bh);
  		if (buffer_req(iloc.bh) && !buffer_uptodate(iloc.bh)) {
  			ext4_error_inode_block(inode, iloc.bh->b_blocknr, EIO,
  					       "IO error syncing inode");
  			err = -EIO;
  		}
  		brelse(iloc.bh);
  	}
  	return err;
  }
  
  /*
   * In data=journal mode ext4_journalled_invalidatepage() may fail to invalidate
   * buffers that are attached to a page stradding i_size and are undergoing
   * commit. In that case we have to wait for commit to finish and try again.
   */
  static void ext4_wait_for_tail_page_commit(struct inode *inode)
  {
  	struct page *page;
  	unsigned offset;
  	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  	tid_t commit_tid = 0;
  	int ret;
  
  	offset = inode->i_size & (PAGE_SIZE - 1);
  	/*
  	 * If the page is fully truncated, we don't need to wait for any commit
  	 * (and we even should not as __ext4_journalled_invalidatepage() may
  	 * strip all buffers from the page but keep the page dirty which can then
  	 * confuse e.g. concurrent ext4_writepage() seeing dirty page without
  	 * buffers). Also we don't need to wait for any commit if all buffers in
  	 * the page remain valid. This is most beneficial for the common case of
  	 * blocksize == PAGESIZE.
  	 */
  	if (!offset || offset > (PAGE_SIZE - i_blocksize(inode)))
  		return;
  	while (1) {
  		page = find_lock_page(inode->i_mapping,
  				      inode->i_size >> PAGE_SHIFT);
  		if (!page)
  			return;
  		ret = __ext4_journalled_invalidatepage(page, offset,
  						PAGE_SIZE - offset);
  		unlock_page(page);
  		put_page(page);
  		if (ret != -EBUSY)
  			return;
  		commit_tid = 0;
  		read_lock(&journal->j_state_lock);
  		if (journal->j_committing_transaction)
  			commit_tid = journal->j_committing_transaction->t_tid;
  		read_unlock(&journal->j_state_lock);
  		if (commit_tid)
  			jbd2_log_wait_commit(journal, commit_tid);
  	}
  }
  
  /*
   * ext4_setattr()
   *
   * Called from notify_change.
   *
   * We want to trap VFS attempts to truncate the file as soon as
   * possible.  In particular, we want to make sure that when the VFS
   * shrinks i_size, we put the inode on the orphan list and modify
   * i_disksize immediately, so that during the subsequent flushing of
   * dirty pages and freeing of disk blocks, we can guarantee that any
   * commit will leave the blocks being flushed in an unused state on
   * disk.  (On recovery, the inode will get truncated and the blocks will
   * be freed, so we have a strong guarantee that no future commit will
   * leave these blocks visible to the user.)
   *
   * Another thing we have to assure is that if we are in ordered mode
   * and inode is still attached to the committing transaction, we must
   * we start writeout of all the dirty pages which are being truncated.
   * This way we are sure that all the data written in the previous
   * transaction are already on disk (truncate waits for pages under
   * writeback).
   *
   * Called with inode->i_mutex down.
   */
  int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
  		 struct iattr *attr)
  {
  	struct inode *inode = d_inode(dentry);
  	int error, rc = 0;
  	int orphan = 0;
  	const unsigned int ia_valid = attr->ia_valid;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return -EPERM;
  
  	if (unlikely(IS_APPEND(inode) &&
  		     (ia_valid & (ATTR_MODE | ATTR_UID |
  				  ATTR_GID | ATTR_TIMES_SET))))
  		return -EPERM;
  
  	error = setattr_prepare(mnt_userns, dentry, attr);
  	if (error)
  		return error;
  
  	error = fscrypt_prepare_setattr(dentry, attr);
  	if (error)
  		return error;
  
  	error = fsverity_prepare_setattr(dentry, attr);
  	if (error)
  		return error;
  
  	if (is_quota_modification(inode, attr)) {
  		error = dquot_initialize(inode);
  		if (error)
  			return error;
  	}
  	ext4_fc_start_update(inode);
  	if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, inode->i_uid)) ||
  	    (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, inode->i_gid))) {
  		handle_t *handle;
  
  		/* (user+group)*(old+new) structure, inode write (sb,
  		 * inode block, ? - but truncate inode update has it) */
  		handle = ext4_journal_start(inode, EXT4_HT_QUOTA,
  			(EXT4_MAXQUOTAS_INIT_BLOCKS(inode->i_sb) +
  			 EXT4_MAXQUOTAS_DEL_BLOCKS(inode->i_sb)) + 3);
  		if (IS_ERR(handle)) {
  			error = PTR_ERR(handle);
  			goto err_out;
  		}
  
  		/* dquot_transfer() calls back ext4_get_inode_usage() which
  		 * counts xattr inode references.
  		 */
  		down_read(&EXT4_I(inode)->xattr_sem);
  		error = dquot_transfer(inode, attr);
  		up_read(&EXT4_I(inode)->xattr_sem);
  
  		if (error) {
  			ext4_journal_stop(handle);
  			ext4_fc_stop_update(inode);
  			return error;
  		}
  		/* Update corresponding info in inode so that everything is in
  		 * one transaction */
  		if (attr->ia_valid & ATTR_UID)
  			inode->i_uid = attr->ia_uid;
  		if (attr->ia_valid & ATTR_GID)
  			inode->i_gid = attr->ia_gid;
  		error = ext4_mark_inode_dirty(handle, inode);
  		ext4_journal_stop(handle);
  		if (unlikely(error)) {
  			ext4_fc_stop_update(inode);
  			return error;
  		}
  	}
  
  	if (attr->ia_valid & ATTR_SIZE) {
  		handle_t *handle;
  		loff_t oldsize = inode->i_size;
  		int shrink = (attr->ia_size < inode->i_size);
  
  		if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
  			struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  			if (attr->ia_size > sbi->s_bitmap_maxbytes) {
  				ext4_fc_stop_update(inode);
  				return -EFBIG;
  			}
  		}
  		if (!S_ISREG(inode->i_mode)) {
  			ext4_fc_stop_update(inode);
  			return -EINVAL;
  		}
  
  		if (IS_I_VERSION(inode) && attr->ia_size != inode->i_size)
  			inode_inc_iversion(inode);
  
  		if (shrink) {
  			if (ext4_should_order_data(inode)) {
  				error = ext4_begin_ordered_truncate(inode,
  							    attr->ia_size);
  				if (error)
  					goto err_out;
  			}
  			/*
  			 * Blocks are going to be removed from the inode. Wait
  			 * for dio in flight.
  			 */
  			inode_dio_wait(inode);
  		}
  
  		filemap_invalidate_lock(inode->i_mapping);
  
  		rc = ext4_break_layouts(inode);
  		if (rc) {
  			filemap_invalidate_unlock(inode->i_mapping);
  			goto err_out;
  		}
  
  		if (attr->ia_size != inode->i_size) {
  			handle = ext4_journal_start(inode, EXT4_HT_INODE, 3);
  			if (IS_ERR(handle)) {
  				error = PTR_ERR(handle);
  				goto out_mmap_sem;
  			}
  			if (ext4_handle_valid(handle) && shrink) {
  				error = ext4_orphan_add(handle, inode);
  				orphan = 1;
  			}
  			/*
  			 * Update c/mtime on truncate up, ext4_truncate() will
  			 * update c/mtime in shrink case below
  			 */
  			if (!shrink) {
  				inode->i_mtime = current_time(inode);
  				inode->i_ctime = inode->i_mtime;
  			}
  
  			if (shrink)
  				ext4_fc_track_range(handle, inode,
  					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
  					inode->i_sb->s_blocksize_bits,
  					(oldsize > 0 ? oldsize - 1 : 0) >>
  					inode->i_sb->s_blocksize_bits);
  			else
  				ext4_fc_track_range(
  					handle, inode,
  					(oldsize > 0 ? oldsize - 1 : oldsize) >>
  					inode->i_sb->s_blocksize_bits,
  					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
  					inode->i_sb->s_blocksize_bits);
  
  			down_write(&EXT4_I(inode)->i_data_sem);
  			EXT4_I(inode)->i_disksize = attr->ia_size;
  			rc = ext4_mark_inode_dirty(handle, inode);
  			if (!error)
  				error = rc;
  			/*
  			 * We have to update i_size under i_data_sem together
  			 * with i_disksize to avoid races with writeback code
  			 * running ext4_wb_update_i_disksize().
  			 */
  			if (!error)
  				i_size_write(inode, attr->ia_size);
  			up_write(&EXT4_I(inode)->i_data_sem);
  			ext4_journal_stop(handle);
  			if (error)
  				goto out_mmap_sem;
  			if (!shrink) {
  				pagecache_isize_extended(inode, oldsize,
  							 inode->i_size);
  			} else if (ext4_should_journal_data(inode)) {
  				ext4_wait_for_tail_page_commit(inode);
  			}
  		}
  
  		/*
  		 * Truncate pagecache after we've waited for commit
  		 * in data=journal mode to make pages freeable.
  		 */
  		truncate_pagecache(inode, inode->i_size);
  		/*
  		 * Call ext4_truncate() even if i_size didn't change to
  		 * truncate possible preallocated blocks.
  		 */
  		if (attr->ia_size <= oldsize) {
  			rc = ext4_truncate(inode);
  			if (rc)
  				error = rc;
  		}
  out_mmap_sem:
  		filemap_invalidate_unlock(inode->i_mapping);
  	}
  
  	if (!error) {
  		setattr_copy(mnt_userns, inode, attr);
  		mark_inode_dirty(inode);
  	}
  
  	/*
  	 * If the call to ext4_truncate failed to get a transaction handle at
  	 * all, we need to clean up the in-core orphan list manually.
  	 */
  	if (orphan && inode->i_nlink)
  		ext4_orphan_del(NULL, inode);
  
  	if (!error && (ia_valid & ATTR_MODE))
  		rc = posix_acl_chmod(mnt_userns, inode, inode->i_mode);
  
  err_out:
  	if  (error)
  		ext4_std_error(inode->i_sb, error);
  	if (!error)
  		error = rc;
  	ext4_fc_stop_update(inode);
  	return error;
  }
  
  int ext4_getattr(struct user_namespace *mnt_userns, const struct path *path,
  		 struct kstat *stat, u32 request_mask, unsigned int query_flags)
  {
  	struct inode *inode = d_inode(path->dentry);
  	struct ext4_inode *raw_inode;
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	unsigned int flags;
  
  	if ((request_mask & STATX_BTIME) &&
  	    EXT4_FITS_IN_INODE(raw_inode, ei, i_crtime)) {
  		stat->result_mask |= STATX_BTIME;
  		stat->btime.tv_sec = ei->i_crtime.tv_sec;
  		stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
  	}
  
  	flags = ei->i_flags & EXT4_FL_USER_VISIBLE;
  	if (flags & EXT4_APPEND_FL)
  		stat->attributes |= STATX_ATTR_APPEND;
  	if (flags & EXT4_COMPR_FL)
  		stat->attributes |= STATX_ATTR_COMPRESSED;
  	if (flags & EXT4_ENCRYPT_FL)
  		stat->attributes |= STATX_ATTR_ENCRYPTED;
  	if (flags & EXT4_IMMUTABLE_FL)
  		stat->attributes |= STATX_ATTR_IMMUTABLE;
  	if (flags & EXT4_NODUMP_FL)
  		stat->attributes |= STATX_ATTR_NODUMP;
  	if (flags & EXT4_VERITY_FL)
  		stat->attributes |= STATX_ATTR_VERITY;
  
  	stat->attributes_mask |= (STATX_ATTR_APPEND |
  				  STATX_ATTR_COMPRESSED |
  				  STATX_ATTR_ENCRYPTED |
  				  STATX_ATTR_IMMUTABLE |
  				  STATX_ATTR_NODUMP |
  				  STATX_ATTR_VERITY);
  
  	generic_fillattr(mnt_userns, inode, stat);
  	return 0;
  }
  
  int ext4_file_getattr(struct user_namespace *mnt_userns,
  		      const struct path *path, struct kstat *stat,
  		      u32 request_mask, unsigned int query_flags)
  {
  	struct inode *inode = d_inode(path->dentry);
  	u64 delalloc_blocks;
  
  	ext4_getattr(mnt_userns, path, stat, request_mask, query_flags);
  
  	/*
  	 * If there is inline data in the inode, the inode will normally not
  	 * have data blocks allocated (it may have an external xattr block).
  	 * Report at least one sector for such files, so tools like tar, rsync,
  	 * others don't incorrectly think the file is completely sparse.
  	 */
  	if (unlikely(ext4_has_inline_data(inode)))
  		stat->blocks += (stat->size + 511) >> 9;
  
  	/*
  	 * We can't update i_blocks if the block allocation is delayed
  	 * otherwise in the case of system crash before the real block
  	 * allocation is done, we will have i_blocks inconsistent with
  	 * on-disk file blocks.
  	 * We always keep i_blocks updated together with real
  	 * allocation. But to not confuse with user, stat
  	 * will return the blocks that include the delayed allocation
  	 * blocks for this file.
  	 */
  	delalloc_blocks = EXT4_C2B(EXT4_SB(inode->i_sb),
  				   EXT4_I(inode)->i_reserved_data_blocks);
  	stat->blocks += delalloc_blocks << (inode->i_sb->s_blocksize_bits - 9);
  	return 0;
  }
  
  static int ext4_index_trans_blocks(struct inode *inode, int lblocks,
  				   int pextents)
  {
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
  		return ext4_ind_trans_blocks(inode, lblocks);
  	return ext4_ext_index_trans_blocks(inode, pextents);
  }
  
  /*
   * Account for index blocks, block groups bitmaps and block group
   * descriptor blocks if modify datablocks and index blocks
   * worse case, the indexs blocks spread over different block groups
   *
   * If datablocks are discontiguous, they are possible to spread over
   * different block groups too. If they are contiguous, with flexbg,
   * they could still across block group boundary.
   *
   * Also account for superblock, inode, quota and xattr blocks
   */
  static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
  				  int pextents)
  {
  	ext4_group_t groups, ngroups = ext4_get_groups_count(inode->i_sb);
  	int gdpblocks;
  	int idxblocks;
  	int ret = 0;
  
  	/*
  	 * How many index blocks need to touch to map @lblocks logical blocks
  	 * to @pextents physical extents?
  	 */
  	idxblocks = ext4_index_trans_blocks(inode, lblocks, pextents);
  
  	ret = idxblocks;
  
  	/*
  	 * Now let's see how many group bitmaps and group descriptors need
  	 * to account
  	 */
  	groups = idxblocks + pextents;
  	gdpblocks = groups;
  	if (groups > ngroups)
  		groups = ngroups;
  	if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
  		gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;
  
  	/* bitmaps and block group descriptor blocks */
  	ret += groups + gdpblocks;
  
  	/* Blocks for super block, inode, quota and xattr blocks */
  	ret += EXT4_META_TRANS_BLOCKS(inode->i_sb);
  
  	return ret;
  }
  
  /*
   * Calculate the total number of credits to reserve to fit
   * the modification of a single pages into a single transaction,
   * which may include multiple chunks of block allocations.
   *
   * This could be called via ext4_write_begin()
   *
   * We need to consider the worse case, when
   * one new block per extent.
   */
  int ext4_writepage_trans_blocks(struct inode *inode)
  {
  	int bpp = ext4_journal_blocks_per_page(inode);
  	int ret;
  
  	ret = ext4_meta_trans_blocks(inode, bpp, bpp);
  
  	/* Account for data blocks for journalled mode */
  	if (ext4_should_journal_data(inode))
  		ret += bpp;
  	return ret;
  }
  
  /*
   * Calculate the journal credits for a chunk of data modification.
   *
   * This is called from DIO, fallocate or whoever calling
   * ext4_map_blocks() to map/allocate a chunk of contiguous disk blocks.
   *
   * journal buffers for data blocks are not included here, as DIO
   * and fallocate do no need to journal data buffers.
   */
  int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)
  {
  	return ext4_meta_trans_blocks(inode, nrblocks, 1);
  }
  
  /*
   * The caller must have previously called ext4_reserve_inode_write().
   * Give this, we know that the caller already has write access to iloc->bh.
   */
  int ext4_mark_iloc_dirty(handle_t *handle,
  			 struct inode *inode, struct ext4_iloc *iloc)
  {
  	int err = 0;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) {
  		put_bh(iloc->bh);
  		return -EIO;
  	}
  	ext4_fc_track_inode(handle, inode);
  
  	if (IS_I_VERSION(inode))
  		inode_inc_iversion(inode);
  
  	/* the do_update_inode consumes one bh->b_count */
  	get_bh(iloc->bh);
  
  	/* ext4_do_update_inode() does jbd2_journal_dirty_metadata */
  	err = ext4_do_update_inode(handle, inode, iloc);
  	put_bh(iloc->bh);
  	return err;
  }
  
  /*
   * On success, We end up with an outstanding reference count against
   * iloc->bh.  This _must_ be cleaned up later.
   */
  
  int
  ext4_reserve_inode_write(handle_t *handle, struct inode *inode,
  			 struct ext4_iloc *iloc)
  {
  	int err;
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;
  
  	err = ext4_get_inode_loc(inode, iloc);
  	if (!err) {
  		BUFFER_TRACE(iloc->bh, "get_write_access");
  		err = ext4_journal_get_write_access(handle, inode->i_sb,
  						    iloc->bh, EXT4_JTR_NONE);
  		if (err) {
  			brelse(iloc->bh);
  			iloc->bh = NULL;
  		}
  	}
  	ext4_std_error(inode->i_sb, err);
  	return err;
  }
  
  static int __ext4_expand_extra_isize(struct inode *inode,
  				     unsigned int new_extra_isize,
  				     struct ext4_iloc *iloc,
  				     handle_t *handle, int *no_expand)
  {
  	struct ext4_inode *raw_inode;
  	struct ext4_xattr_ibody_header *header;
  	unsigned int inode_size = EXT4_INODE_SIZE(inode->i_sb);
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	int error;
  
  	/* this was checked at iget time, but double check for good measure */
  	if ((EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize > inode_size) ||
  	    (ei->i_extra_isize & 3)) {
  		EXT4_ERROR_INODE(inode, "bad extra_isize %u (inode size %u)",
  				 ei->i_extra_isize,
  				 EXT4_INODE_SIZE(inode->i_sb));
  		return -EFSCORRUPTED;
  	}
  	if ((new_extra_isize < ei->i_extra_isize) ||
  	    (new_extra_isize < 4) ||
  	    (new_extra_isize > inode_size - EXT4_GOOD_OLD_INODE_SIZE))
  		return -EINVAL;	/* Should never happen */
  
  	raw_inode = ext4_raw_inode(iloc);
  
  	header = IHDR(inode, raw_inode);
  
  	/* No extended attributes present */
  	if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR) ||
  	    header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC)) {
  		memset((void *)raw_inode + EXT4_GOOD_OLD_INODE_SIZE +
  		       EXT4_I(inode)->i_extra_isize, 0,
  		       new_extra_isize - EXT4_I(inode)->i_extra_isize);
  		EXT4_I(inode)->i_extra_isize = new_extra_isize;
  		return 0;
  	}
  
  	/* try to expand with EAs present */
  	error = ext4_expand_extra_isize_ea(inode, new_extra_isize,
  					   raw_inode, handle);
  	if (error) {
  		/*
  		 * Inode size expansion failed; don't try again
  		 */
  		*no_expand = 1;
  	}
  
  	return error;
  }
  
  /*
   * Expand an inode by new_extra_isize bytes.
   * Returns 0 on success or negative error number on failure.
   */
  static int ext4_try_to_expand_extra_isize(struct inode *inode,
  					  unsigned int new_extra_isize,
  					  struct ext4_iloc iloc,
  					  handle_t *handle)
  {
  	int no_expand;
  	int error;
  
  	if (ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND))
  		return -EOVERFLOW;
  
  	/*
  	 * In nojournal mode, we can immediately attempt to expand
  	 * the inode.  When journaled, we first need to obtain extra
  	 * buffer credits since we may write into the EA block
  	 * with this same handle. If journal_extend fails, then it will
  	 * only result in a minor loss of functionality for that inode.
  	 * If this is felt to be critical, then e2fsck should be run to
  	 * force a large enough s_min_extra_isize.
  	 */
  	if (ext4_journal_extend(handle,
  				EXT4_DATA_TRANS_BLOCKS(inode->i_sb), 0) != 0)
  		return -ENOSPC;
  
  	if (ext4_write_trylock_xattr(inode, &no_expand) == 0)
  		return -EBUSY;
  
  	error = __ext4_expand_extra_isize(inode, new_extra_isize, &iloc,
  					  handle, &no_expand);
  	ext4_write_unlock_xattr(inode, &no_expand);
  
  	return error;
  }
  
  int ext4_expand_extra_isize(struct inode *inode,
  			    unsigned int new_extra_isize,
  			    struct ext4_iloc *iloc)
  {
  	handle_t *handle;
  	int no_expand;
  	int error, rc;
  
  	if (ext4_test_inode_state(inode, EXT4_STATE_NO_EXPAND)) {
  		brelse(iloc->bh);
  		return -EOVERFLOW;
  	}
  
  	handle = ext4_journal_start(inode, EXT4_HT_INODE,
  				    EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
  	if (IS_ERR(handle)) {
  		error = PTR_ERR(handle);
  		brelse(iloc->bh);
  		return error;
  	}
  
  	ext4_write_lock_xattr(inode, &no_expand);
  
  	BUFFER_TRACE(iloc->bh, "get_write_access");
  	error = ext4_journal_get_write_access(handle, inode->i_sb, iloc->bh,
  					      EXT4_JTR_NONE);
  	if (error) {
  		brelse(iloc->bh);
  		goto out_unlock;
  	}
  
  	error = __ext4_expand_extra_isize(inode, new_extra_isize, iloc,
  					  handle, &no_expand);
  
  	rc = ext4_mark_iloc_dirty(handle, inode, iloc);
  	if (!error)
  		error = rc;
  
  out_unlock:
  	ext4_write_unlock_xattr(inode, &no_expand);
  	ext4_journal_stop(handle);
  	return error;
  }
  
  /*
   * What we do here is to mark the in-core inode as clean with respect to inode
   * dirtiness (it may still be data-dirty).
   * This means that the in-core inode may be reaped by prune_icache
   * without having to perform any I/O.  This is a very good thing,
   * because *any* task may call prune_icache - even ones which
   * have a transaction open against a different journal.
   *
   * Is this cheating?  Not really.  Sure, we haven't written the
   * inode out, but prune_icache isn't a user-visible syncing function.
   * Whenever the user wants stuff synced (sys_sync, sys_msync, sys_fsync)
   * we start and wait on commits.
   */
  int __ext4_mark_inode_dirty(handle_t *handle, struct inode *inode,
  				const char *func, unsigned int line)
  {
  	struct ext4_iloc iloc;
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	int err;
  
  	might_sleep();
  	trace_ext4_mark_inode_dirty(inode, _RET_IP_);
  	err = ext4_reserve_inode_write(handle, inode, &iloc);
  	if (err)
  		goto out;
  
  	if (EXT4_I(inode)->i_extra_isize < sbi->s_want_extra_isize)
  		ext4_try_to_expand_extra_isize(inode, sbi->s_want_extra_isize,
  					       iloc, handle);
  
  	err = ext4_mark_iloc_dirty(handle, inode, &iloc);
  out:
  	if (unlikely(err))
  		ext4_error_inode_err(inode, func, line, 0, err,
  					"mark_inode_dirty error");
  	return err;
  }
  
  /*
   * ext4_dirty_inode() is called from __mark_inode_dirty()
   *
   * We're really interested in the case where a file is being extended.
   * i_size has been changed by generic_commit_write() and we thus need
   * to include the updated inode in the current transaction.
   *
   * Also, dquot_alloc_block() will always dirty the inode when blocks
   * are allocated to the file.
   *
   * If the inode is marked synchronous, we don't honour that here - doing
   * so would cause a commit on atime updates, which we don't bother doing.
   * We handle synchronous inodes at the highest possible level.
   */
  void ext4_dirty_inode(struct inode *inode, int flags)
  {
  	handle_t *handle;
  
  	handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  	if (IS_ERR(handle))
  		return;
  	ext4_mark_inode_dirty(handle, inode);
  	ext4_journal_stop(handle);
  }
  
  int ext4_change_inode_journal_flag(struct inode *inode, int val)
  {
  	journal_t *journal;
  	handle_t *handle;
  	int err;
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  	/*
  	 * We have to be very careful here: changing a data block's
  	 * journaling status dynamically is dangerous.  If we write a
  	 * data block to the journal, change the status and then delete
  	 * that block, we risk forgetting to revoke the old log record
  	 * from the journal and so a subsequent replay can corrupt data.
  	 * So, first we make sure that the journal is empty and that
  	 * nobody is changing anything.
  	 */
  
  	journal = EXT4_JOURNAL(inode);
  	if (!journal)
  		return 0;
  	if (is_journal_aborted(journal))
  		return -EROFS;
  
  	/* Wait for all existing dio workers */
  	inode_dio_wait(inode);
  
  	/*
  	 * Before flushing the journal and switching inode's aops, we have
  	 * to flush all dirty data the inode has. There can be outstanding
  	 * delayed allocations, there can be unwritten extents created by
  	 * fallocate or buffered writes in dioread_nolock mode covered by
  	 * dirty data which can be converted only after flushing the dirty
  	 * data (and journalled aops don't know how to handle these cases).
  	 */
  	if (val) {
  		filemap_invalidate_lock(inode->i_mapping);
  		err = filemap_write_and_wait(inode->i_mapping);
  		if (err < 0) {
  			filemap_invalidate_unlock(inode->i_mapping);
  			return err;
  		}
  	}
  
  	percpu_down_write(&sbi->s_writepages_rwsem);
  	jbd2_journal_lock_updates(journal);
  
  	/*
  	 * OK, there are no updates running now, and all cached data is
  	 * synced to disk.  We are now in a completely consistent state
  	 * which doesn't have anything in the journal, and we know that
  	 * no filesystem updates are running, so it is safe to modify
  	 * the inode's in-core data-journaling state flag now.
  	 */
  
  	if (val)
  		ext4_set_inode_flag(inode, EXT4_INODE_JOURNAL_DATA);
  	else {
  		err = jbd2_journal_flush(journal, 0);
  		if (err < 0) {
  			jbd2_journal_unlock_updates(journal);
  			percpu_up_write(&sbi->s_writepages_rwsem);
  			return err;
  		}
  		ext4_clear_inode_flag(inode, EXT4_INODE_JOURNAL_DATA);
  	}
  	ext4_set_aops(inode);
  
  	jbd2_journal_unlock_updates(journal);
  	percpu_up_write(&sbi->s_writepages_rwsem);
  
  	if (val)
  		filemap_invalidate_unlock(inode->i_mapping);
  
  	/* Finally we can mark the inode as dirty. */
  
  	handle = ext4_journal_start(inode, EXT4_HT_INODE, 1);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  
  	ext4_fc_mark_ineligible(inode->i_sb,
  		EXT4_FC_REASON_JOURNAL_FLAG_CHANGE);
  	err = ext4_mark_inode_dirty(handle, inode);
  	ext4_handle_sync(handle);
  	ext4_journal_stop(handle);
  	ext4_std_error(inode->i_sb, err);
  
  	return err;
  }
  
  static int ext4_bh_unmapped(handle_t *handle, struct inode *inode,
  			    struct buffer_head *bh)
  {
  	return !buffer_mapped(bh);
  }
  
  vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
  {
  	struct vm_area_struct *vma = vmf->vma;
  	struct page *page = vmf->page;
  	loff_t size;
  	unsigned long len;
  	int err;
  	vm_fault_t ret;
  	struct file *file = vma->vm_file;
  	struct inode *inode = file_inode(file);
  	struct address_space *mapping = inode->i_mapping;
  	handle_t *handle;
  	get_block_t *get_block;
  	int retries = 0;
  
  	if (unlikely(IS_IMMUTABLE(inode)))
  		return VM_FAULT_SIGBUS;
  
  	sb_start_pagefault(inode->i_sb);
  	file_update_time(vma->vm_file);
  
  	filemap_invalidate_lock_shared(mapping);
  
  	err = ext4_convert_inline_data(inode);
  	if (err)
  		goto out_ret;
  
  	/*
  	 * On data journalling we skip straight to the transaction handle:
  	 * there's no delalloc; page truncated will be checked later; the
  	 * early return w/ all buffers mapped (calculates size/len) can't
  	 * be used; and there's no dioread_nolock, so only ext4_get_block.
  	 */
  	if (ext4_should_journal_data(inode))
  		goto retry_alloc;
  
  	/* Delalloc case is easy... */
  	if (test_opt(inode->i_sb, DELALLOC) &&
  	    !ext4_nonda_switch(inode->i_sb)) {
  		do {
  			err = block_page_mkwrite(vma, vmf,
  						   ext4_da_get_block_prep);
  		} while (err == -ENOSPC &&
  		       ext4_should_retry_alloc(inode->i_sb, &retries));
  		goto out_ret;
  	}
  
  	lock_page(page);
  	size = i_size_read(inode);
  	/* Page got truncated from under us? */
  	if (page->mapping != mapping || page_offset(page) > size) {
  		unlock_page(page);
  		ret = VM_FAULT_NOPAGE;
  		goto out;
  	}
  
  	if (page->index == size >> PAGE_SHIFT)
  		len = size & ~PAGE_MASK;
  	else
  		len = PAGE_SIZE;
  	/*
  	 * Return if we have all the buffers mapped. This avoids the need to do
  	 * journal_start/journal_stop which can block and take a long time
  	 *
  	 * This cannot be done for data journalling, as we have to add the
  	 * inode to the transaction's list to writeprotect pages on commit.
  	 */
  	if (page_has_buffers(page)) {
  		if (!ext4_walk_page_buffers(NULL, inode, page_buffers(page),
  					    0, len, NULL,
  					    ext4_bh_unmapped)) {
  			/* Wait so that we don't change page under IO */
  			wait_for_stable_page(page);
  			ret = VM_FAULT_LOCKED;
  			goto out;
  		}
  	}
  	unlock_page(page);
  	/* OK, we need to fill the hole... */
  	if (ext4_should_dioread_nolock(inode))
  		get_block = ext4_get_block_unwritten;
  	else
  		get_block = ext4_get_block;
  retry_alloc:
  	handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
  				    ext4_writepage_trans_blocks(inode));
  	if (IS_ERR(handle)) {
  		ret = VM_FAULT_SIGBUS;
  		goto out;
  	}
  	/*
  	 * Data journalling can't use block_page_mkwrite() because it
  	 * will set_buffer_dirty() before do_journal_get_write_access()
  	 * thus might hit warning messages for dirty metadata buffers.
  	 */
  	if (!ext4_should_journal_data(inode)) {
  		err = block_page_mkwrite(vma, vmf, get_block);
  	} else {
  		lock_page(page);
  		size = i_size_read(inode);
  		/* Page got truncated from under us? */
  		if (page->mapping != mapping || page_offset(page) > size) {
  			ret = VM_FAULT_NOPAGE;
  			goto out_error;
  		}
  
  		if (page->index == size >> PAGE_SHIFT)
  			len = size & ~PAGE_MASK;
  		else
  			len = PAGE_SIZE;
  
  		err = __block_write_begin(page, 0, len, ext4_get_block);
  		if (!err) {
  			ret = VM_FAULT_SIGBUS;
  			if (ext4_walk_page_buffers(handle, inode,
  					page_buffers(page), 0, len, NULL,
  					do_journal_get_write_access))
  				goto out_error;
  			if (ext4_walk_page_buffers(handle, inode,
  					page_buffers(page), 0, len, NULL,
  					write_end_fn))
  				goto out_error;
  			if (ext4_jbd2_inode_add_write(handle, inode,
  						      page_offset(page), len))
  				goto out_error;
  			ext4_set_inode_state(inode, EXT4_STATE_JDATA);
  		} else {
  			unlock_page(page);
  		}
  	}
  	ext4_journal_stop(handle);
  	if (err == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
  		goto retry_alloc;
  out_ret:
  	ret = block_page_mkwrite_return(err);
  out:
  	filemap_invalidate_unlock_shared(mapping);
  	sb_end_pagefault(inode->i_sb);
  	return ret;
  out_error:
  	unlock_page(page);
  	ext4_journal_stop(handle);
  	goto out;
  }
  