text: /*
   *  linux/fs/ext4/file.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/file.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  ext4 fs regular file handling primitives
   *
   *  64-bit file support on 64-bit platforms by Jakub Jelinek
   *	(jj@sunsite.ms.mff.cuni.cz)
   */
  
  #include <linux/time.h>
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/path.h>
  #include <linux/quotaops.h>
  #include <linux/pagevec.h>
  #include <linux/uio.h>
  #include "ext4.h"
  #include "ext4_jbd2.h"
  #include "xattr.h"
  #include "acl.h"
  
  /*
   * Called when an inode is released. Note that this is different
   * from ext4_file_open: open gets called at every open, but release
   * gets called only when /all/ the files are closed.
   */
  static int ext4_release_file(struct inode *inode, struct file *filp)
  {
  	if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
  		ext4_alloc_da_blocks(inode);
  		ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
  	}
  	/* if we are the last writer on the inode, drop the block reservation */
  	if ((filp->f_mode & FMODE_WRITE) &&
  			(atomic_read(&inode->i_writecount) == 1) &&
  		        !EXT4_I(inode)->i_reserved_data_blocks)
  	{
  		down_write(&EXT4_I(inode)->i_data_sem);
  		ext4_discard_preallocations(inode);
  		up_write(&EXT4_I(inode)->i_data_sem);
  	}
  	if (is_dx(inode) && filp->private_data)
  		ext4_htree_free_dir_info(filp->private_data);
  
  	return 0;
  }
  
  static void ext4_unwritten_wait(struct inode *inode)
  {
  	wait_queue_head_t *wq = ext4_ioend_wq(inode);
  
  	wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
  }
  
  /*
   * This tests whether the IO in question is block-aligned or not.
   * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
   * are converted to written only after the IO is complete.  Until they are
   * mapped, these blocks appear as holes, so dio_zero_block() will assume that
   * it needs to zero out portions of the start and/or end block.  If 2 AIO
   * threads are at work on the same unwritten block, they must be synchronized
   * or one thread will zero the other's data, causing corruption.
   */
  static int
  ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
  {
  	struct super_block *sb = inode->i_sb;
  	int blockmask = sb->s_blocksize - 1;
  
  	if (pos >= i_size_read(inode))
  		return 0;
  
  	if ((pos | iov_iter_alignment(from)) & blockmask)
  		return 1;
  
  	return 0;
  }
  
  static ssize_t
  ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(iocb->ki_filp);
  	struct mutex *aio_mutex = NULL;
  	struct blk_plug plug;
  	int o_direct = iocb->ki_flags & IOCB_DIRECT;
  	int overwrite = 0;
  	ssize_t ret;
  
  	/*
  	 * Unaligned direct AIO must be serialized; see comment above
  	 * In the case of O_APPEND, assume that we must always serialize
  	 */
  	if (o_direct &&
  	    ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
  	    !is_sync_kiocb(iocb) &&
  	    (iocb->ki_flags & IOCB_APPEND ||
  	     ext4_unaligned_aio(inode, from, iocb->ki_pos))) {
  		aio_mutex = ext4_aio_mutex(inode);
  		mutex_lock(aio_mutex);
  		ext4_unwritten_wait(inode);
  	}
  
  	mutex_lock(&inode->i_mutex);
  	ret = generic_write_checks(iocb, from);
  	if (ret <= 0)
  		goto out;
  
  	/*
  	 * If we have encountered a bitmap-format file, the size limit
  	 * is smaller than s_maxbytes, which is for extent-mapped files.
  	 */
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
  		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  		if (iocb->ki_pos >= sbi->s_bitmap_maxbytes) {
  			ret = -EFBIG;
  			goto out;
  		}
  		iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
  	}
  
  	iocb->private = &overwrite;
  	if (o_direct) {
  		size_t length = iov_iter_count(from);
  		loff_t pos = iocb->ki_pos;
  		blk_start_plug(&plug);
  
  		/* check whether we do a DIO overwrite or not */
  		if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
  		    !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
  			struct ext4_map_blocks map;
  			unsigned int blkbits = inode->i_blkbits;
  			int err, len;
  
  			map.m_lblk = pos >> blkbits;
  			map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
  				- map.m_lblk;
  			len = map.m_len;
  
  			err = ext4_map_blocks(NULL, inode, &map, 0);
  			/*
  			 * 'err==len' means that all of blocks has
  			 * been preallocated no matter they are
  			 * initialized or not.  For excluding
  			 * unwritten extents, we need to check
  			 * m_flags.  There are two conditions that
  			 * indicate for initialized extents.  1) If we
  			 * hit extent cache, EXT4_MAP_MAPPED flag is
  			 * returned; 2) If we do a real lookup,
  			 * non-flags are returned.  So we should check
  			 * these two conditions.
  			 */
  			if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
  				overwrite = 1;
  		}
  	}
  
  	ret = __generic_file_write_iter(iocb, from);
  	mutex_unlock(&inode->i_mutex);
  
  	if (ret > 0) {
  		ssize_t err;
  
  		err = generic_write_sync(file, iocb->ki_pos - ret, ret);
  		if (err < 0)
  			ret = err;
  	}
  	if (o_direct)
  		blk_finish_plug(&plug);
  
  	if (aio_mutex)
  		mutex_unlock(aio_mutex);
  	return ret;
  
  out:
  	mutex_unlock(&inode->i_mutex);
  	if (aio_mutex)
  		mutex_unlock(aio_mutex);
  	return ret;
  }
  
  #ifdef CONFIG_FS_DAX
  static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
  	return dax_fault(vma, vmf, ext4_get_block);
  					/* Is this the right get_block? */
  }
  
  static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
  	return dax_mkwrite(vma, vmf, ext4_get_block);
  }
  
  static const struct vm_operations_struct ext4_dax_vm_ops = {
  	.fault		= ext4_dax_fault,
  	.page_mkwrite	= ext4_dax_mkwrite,
  	.pfn_mkwrite	= dax_pfn_mkwrite,
  };
  #else
  #define ext4_dax_vm_ops	ext4_file_vm_ops
  #endif
  
  static const struct vm_operations_struct ext4_file_vm_ops = {
  	.fault		= filemap_fault,
  	.map_pages	= filemap_map_pages,
  	.page_mkwrite   = ext4_page_mkwrite,
  };
  
  static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct inode *inode = file->f_mapping->host;
  
  	if (ext4_encrypted_inode(inode)) {
  		int err = ext4_generate_encryption_key(inode);
  		if (err)
  			return 0;
  	}
  	file_accessed(file);
  	if (IS_DAX(file_inode(file))) {
  		vma->vm_ops = &ext4_dax_vm_ops;
  		vma->vm_flags |= VM_MIXEDMAP;
  	} else {
  		vma->vm_ops = &ext4_file_vm_ops;
  	}
  	return 0;
  }
  
  static int ext4_file_open(struct inode * inode, struct file * filp)
  {
  	struct super_block *sb = inode->i_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct vfsmount *mnt = filp->f_path.mnt;
  	struct path path;
  	char buf[64], *cp;
  	int ret;
  
  	if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
  		     !(sb->s_flags & MS_RDONLY))) {
  		sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
  		/*
  		 * Sample where the filesystem has been mounted and
  		 * store it in the superblock for sysadmin convenience
  		 * when trying to sort through large numbers of block
  		 * devices or filesystem images.
  		 */
  		memset(buf, 0, sizeof(buf));
  		path.mnt = mnt;
  		path.dentry = mnt->mnt_root;
  		cp = d_path(&path, buf, sizeof(buf));
  		if (!IS_ERR(cp)) {
  			handle_t *handle;
  			int err;
  
  			handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
  			if (IS_ERR(handle))
  				return PTR_ERR(handle);
  			BUFFER_TRACE(sbi->s_sbh, "get_write_access");
  			err = ext4_journal_get_write_access(handle, sbi->s_sbh);
  			if (err) {
  				ext4_journal_stop(handle);
  				return err;
  			}
  			strlcpy(sbi->s_es->s_last_mounted, cp,
  				sizeof(sbi->s_es->s_last_mounted));
  			ext4_handle_dirty_super(handle, sb);
  			ext4_journal_stop(handle);
  		}
  	}
  	/*
  	 * Set up the jbd2_inode if we are opening the inode for
  	 * writing and the journal is present
  	 */
  	if (filp->f_mode & FMODE_WRITE) {
  		ret = ext4_inode_attach_jinode(inode);
  		if (ret < 0)
  			return ret;
  	}
  	ret = dquot_file_open(inode, filp);
  	if (!ret && ext4_encrypted_inode(inode)) {
  		ret = ext4_generate_encryption_key(inode);
  		if (ret)
  			ret = -EACCES;
  	}
  	return ret;
  }
  
  /*
   * Here we use ext4_map_blocks() to get a block mapping for a extent-based
   * file rather than ext4_ext_walk_space() because we can introduce
   * SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
   * function.  When extent status tree has been fully implemented, it will
   * track all extent status for a file and we can directly use it to
   * retrieve the offset for SEEK_DATA/SEEK_HOLE.
   */
  
  /*
   * When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
   * lookup page cache to check whether or not there has some data between
   * [startoff, endoff] because, if this range contains an unwritten extent,
   * we determine this extent as a data or a hole according to whether the
   * page cache has data or not.
   */
  static int ext4_find_unwritten_pgoff(struct inode *inode,
  				     int whence,
  				     struct ext4_map_blocks *map,
  				     loff_t *offset)
  {
  	struct pagevec pvec;
  	unsigned int blkbits;
  	pgoff_t index;
  	pgoff_t end;
  	loff_t endoff;
  	loff_t startoff;
  	loff_t lastoff;
  	int found = 0;
  
  	blkbits = inode->i_sb->s_blocksize_bits;
  	startoff = *offset;
  	lastoff = startoff;
  	endoff = (loff_t)(map->m_lblk + map->m_len) << blkbits;
  
  	index = startoff >> PAGE_CACHE_SHIFT;
  	end = endoff >> PAGE_CACHE_SHIFT;
  
  	pagevec_init(&pvec, 0);
  	do {
  		int i, num;
  		unsigned long nr_pages;
  
  		num = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
  		nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
  					  (pgoff_t)num);
  		if (nr_pages == 0) {
  			if (whence == SEEK_DATA)
  				break;
  
  			BUG_ON(whence != SEEK_HOLE);
  			/*
  			 * If this is the first time to go into the loop and
  			 * offset is not beyond the end offset, it will be a
  			 * hole at this offset
  			 */
  			if (lastoff == startoff || lastoff < endoff)
  				found = 1;
  			break;
  		}
  
  		/*
  		 * If this is the first time to go into the loop and
  		 * offset is smaller than the first page offset, it will be a
  		 * hole at this offset.
  		 */
  		if (lastoff == startoff && whence == SEEK_HOLE &&
  		    lastoff < page_offset(pvec.pages[0])) {
  			found = 1;
  			break;
  		}
  
  		for (i = 0; i < nr_pages; i++) {
  			struct page *page = pvec.pages[i];
  			struct buffer_head *bh, *head;
  
  			/*
  			 * If the current offset is not beyond the end of given
  			 * range, it will be a hole.
  			 */
  			if (lastoff < endoff && whence == SEEK_HOLE &&
  			    page->index > end) {
  				found = 1;
  				*offset = lastoff;
  				goto out;
  			}
  
  			lock_page(page);
  
  			if (unlikely(page->mapping != inode->i_mapping)) {
  				unlock_page(page);
  				continue;
  			}
  
  			if (!page_has_buffers(page)) {
  				unlock_page(page);
  				continue;
  			}
  
  			if (page_has_buffers(page)) {
  				lastoff = page_offset(page);
  				bh = head = page_buffers(page);
  				do {
  					if (buffer_uptodate(bh) ||
  					    buffer_unwritten(bh)) {
  						if (whence == SEEK_DATA)
  							found = 1;
  					} else {
  						if (whence == SEEK_HOLE)
  							found = 1;
  					}
  					if (found) {
  						*offset = max_t(loff_t,
  							startoff, lastoff);
  						unlock_page(page);
  						goto out;
  					}
  					lastoff += bh->b_size;
  					bh = bh->b_this_page;
  				} while (bh != head);
  			}
  
  			lastoff = page_offset(page) + PAGE_SIZE;
  			unlock_page(page);
  		}
  
  		/*
  		 * The no. of pages is less than our desired, that would be a
  		 * hole in there.
  		 */
  		if (nr_pages < num && whence == SEEK_HOLE) {
  			found = 1;
  			*offset = lastoff;
  			break;
  		}
  
  		index = pvec.pages[i - 1]->index + 1;
  		pagevec_release(&pvec);
  	} while (index <= end);
  
  out:
  	pagevec_release(&pvec);
  	return found;
  }
  
  /*
   * ext4_seek_data() retrieves the offset for SEEK_DATA.
   */
  static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
  {
  	struct inode *inode = file->f_mapping->host;
  	struct ext4_map_blocks map;
  	struct extent_status es;
  	ext4_lblk_t start, last, end;
  	loff_t dataoff, isize;
  	int blkbits;
  	int ret = 0;
  
  	mutex_lock(&inode->i_mutex);
  
  	isize = i_size_read(inode);
  	if (offset >= isize) {
  		mutex_unlock(&inode->i_mutex);
  		return -ENXIO;
  	}
  
  	blkbits = inode->i_sb->s_blocksize_bits;
  	start = offset >> blkbits;
  	last = start;
  	end = isize >> blkbits;
  	dataoff = offset;
  
  	do {
  		map.m_lblk = last;
  		map.m_len = end - last + 1;
  		ret = ext4_map_blocks(NULL, inode, &map, 0);
  		if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
  			if (last != start)
  				dataoff = (loff_t)last << blkbits;
  			break;
  		}
  
  		/*
  		 * If there is a delay extent at this offset,
  		 * it will be as a data.
  		 */
  		ext4_es_find_delayed_extent_range(inode, last, last, &es);
  		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
  			if (last != start)
  				dataoff = (loff_t)last << blkbits;
  			break;
  		}
  
  		/*
  		 * If there is a unwritten extent at this offset,
  		 * it will be as a data or a hole according to page
  		 * cache that has data or not.
  		 */
  		if (map.m_flags & EXT4_MAP_UNWRITTEN) {
  			int unwritten;
  			unwritten = ext4_find_unwritten_pgoff(inode, SEEK_DATA,
  							      &map, &dataoff);
  			if (unwritten)
  				break;
  		}
  
  		last++;
  		dataoff = (loff_t)last << blkbits;
  	} while (last <= end);
  
  	mutex_unlock(&inode->i_mutex);
  
  	if (dataoff > isize)
  		return -ENXIO;
  
  	return vfs_setpos(file, dataoff, maxsize);
  }
  
  /*
   * ext4_seek_hole() retrieves the offset for SEEK_HOLE.
   */
  static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
  {
  	struct inode *inode = file->f_mapping->host;
  	struct ext4_map_blocks map;
  	struct extent_status es;
  	ext4_lblk_t start, last, end;
  	loff_t holeoff, isize;
  	int blkbits;
  	int ret = 0;
  
  	mutex_lock(&inode->i_mutex);
  
  	isize = i_size_read(inode);
  	if (offset >= isize) {
  		mutex_unlock(&inode->i_mutex);
  		return -ENXIO;
  	}
  
  	blkbits = inode->i_sb->s_blocksize_bits;
  	start = offset >> blkbits;
  	last = start;
  	end = isize >> blkbits;
  	holeoff = offset;
  
  	do {
  		map.m_lblk = last;
  		map.m_len = end - last + 1;
  		ret = ext4_map_blocks(NULL, inode, &map, 0);
  		if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
  			last += ret;
  			holeoff = (loff_t)last << blkbits;
  			continue;
  		}
  
  		/*
  		 * If there is a delay extent at this offset,
  		 * we will skip this extent.
  		 */
  		ext4_es_find_delayed_extent_range(inode, last, last, &es);
  		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
  			last = es.es_lblk + es.es_len;
  			holeoff = (loff_t)last << blkbits;
  			continue;
  		}
  
  		/*
  		 * If there is a unwritten extent at this offset,
  		 * it will be as a data or a hole according to page
  		 * cache that has data or not.
  		 */
  		if (map.m_flags & EXT4_MAP_UNWRITTEN) {
  			int unwritten;
  			unwritten = ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
  							      &map, &holeoff);
  			if (!unwritten) {
  				last += ret;
  				holeoff = (loff_t)last << blkbits;
  				continue;
  			}
  		}
  
  		/* find a hole */
  		break;
  	} while (last <= end);
  
  	mutex_unlock(&inode->i_mutex);
  
  	if (holeoff > isize)
  		holeoff = isize;
  
  	return vfs_setpos(file, holeoff, maxsize);
  }
  
  /*
   * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
   * by calling generic_file_llseek_size() with the appropriate maxbytes
   * value for each.
   */
  loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
  {
  	struct inode *inode = file->f_mapping->host;
  	loff_t maxbytes;
  
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
  		maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
  	else
  		maxbytes = inode->i_sb->s_maxbytes;
  
  	switch (whence) {
  	case SEEK_SET:
  	case SEEK_CUR:
  	case SEEK_END:
  		return generic_file_llseek_size(file, offset, whence,
  						maxbytes, i_size_read(inode));
  	case SEEK_DATA:
  		return ext4_seek_data(file, offset, maxbytes);
  	case SEEK_HOLE:
  		return ext4_seek_hole(file, offset, maxbytes);
  	}
  
  	return -EINVAL;
  }
  
  const struct file_operations ext4_file_operations = {
  	.llseek		= ext4_llseek,
  	.read_iter	= generic_file_read_iter,
  	.write_iter	= ext4_file_write_iter,
  	.unlocked_ioctl = ext4_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= ext4_compat_ioctl,
  #endif
  	.mmap		= ext4_file_mmap,
  	.open		= ext4_file_open,
  	.release	= ext4_release_file,
  	.fsync		= ext4_sync_file,
  	.splice_read	= generic_file_splice_read,
  	.splice_write	= iter_file_splice_write,
  	.fallocate	= ext4_fallocate,
  };
  
  const struct inode_operations ext4_file_inode_operations = {
  	.setattr	= ext4_setattr,
  	.getattr	= ext4_getattr,
  	.setxattr	= generic_setxattr,
  	.getxattr	= generic_getxattr,
  	.listxattr	= ext4_listxattr,
  	.removexattr	= generic_removexattr,
  	.get_acl	= ext4_get_acl,
  	.set_acl	= ext4_set_acl,
  	.fiemap		= ext4_fiemap,
  };
  
  