text: /*
   *  linux/fs/ext4/indirect.c
   *
   *  from
   *
   *  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
   *
   *  Goal-directed block allocation by Stephen Tweedie
   *	(sct@redhat.com), 1993, 1998
   */
  
  #include "ext4_jbd2.h"
  #include "truncate.h"
  #include <linux/dax.h>
  #include <linux/uio.h>
  
  #include <trace/events/ext4.h>
  
  typedef struct {
  	__le32	*p;
  	__le32	key;
  	struct buffer_head *bh;
  } Indirect;
  
  static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
  {
  	p->key = *(p->p = v);
  	p->bh = bh;
  }
  
  /**
   *	ext4_block_to_path - parse the block number into array of offsets
   *	@inode: inode in question (we are only interested in its superblock)
   *	@i_block: block number to be parsed
   *	@offsets: array to store the offsets in
   *	@boundary: set this non-zero if the referred-to block is likely to be
   *	       followed (on disk) by an indirect block.
   *
   *	To store the locations of file's data ext4 uses a data structure common
   *	for UNIX filesystems - tree of pointers anchored in the inode, with
   *	data blocks at leaves and indirect blocks in intermediate nodes.
   *	This function translates the block number into path in that tree -
   *	return value is the path length and @offsets[n] is the offset of
   *	pointer to (n+1)th node in the nth one. If @block is out of range
   *	(negative or too large) warning is printed and zero returned.
   *
   *	Note: function doesn't find node addresses, so no IO is needed. All
   *	we need to know is the capacity of indirect blocks (taken from the
   *	inode->i_sb).
   */
  
  /*
   * Portability note: the last comparison (check that we fit into triple
   * indirect block) is spelled differently, because otherwise on an
   * architecture with 32-bit longs and 8Kb pages we might get into trouble
   * if our filesystem had 8Kb blocks. We might use long long, but that would
   * kill us on x86. Oh, well, at least the sign propagation does not matter -
   * i_block would have to be negative in the very beginning, so we would not
   * get there at all.
   */
  
  static int ext4_block_to_path(struct inode *inode,
  			      ext4_lblk_t i_block,
  			      ext4_lblk_t offsets[4], int *boundary)
  {
  	int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  	int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
  	const long direct_blocks = EXT4_NDIR_BLOCKS,
  		indirect_blocks = ptrs,
  		double_blocks = (1 << (ptrs_bits * 2));
  	int n = 0;
  	int final = 0;
  
  	if (i_block < direct_blocks) {
  		offsets[n++] = i_block;
  		final = direct_blocks;
  	} else if ((i_block -= direct_blocks) < indirect_blocks) {
  		offsets[n++] = EXT4_IND_BLOCK;
  		offsets[n++] = i_block;
  		final = ptrs;
  	} else if ((i_block -= indirect_blocks) < double_blocks) {
  		offsets[n++] = EXT4_DIND_BLOCK;
  		offsets[n++] = i_block >> ptrs_bits;
  		offsets[n++] = i_block & (ptrs - 1);
  		final = ptrs;
  	} else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
  		offsets[n++] = EXT4_TIND_BLOCK;
  		offsets[n++] = i_block >> (ptrs_bits * 2);
  		offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
  		offsets[n++] = i_block & (ptrs - 1);
  		final = ptrs;
  	} else {
  		ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
  			     i_block + direct_blocks +
  			     indirect_blocks + double_blocks, inode->i_ino);
  	}
  	if (boundary)
  		*boundary = final - 1 - (i_block & (ptrs - 1));
  	return n;
  }
  
  /**
   *	ext4_get_branch - read the chain of indirect blocks leading to data
   *	@inode: inode in question
   *	@depth: depth of the chain (1 - direct pointer, etc.)
   *	@offsets: offsets of pointers in inode/indirect blocks
   *	@chain: place to store the result
   *	@err: here we store the error value
   *
   *	Function fills the array of triples <key, p, bh> and returns %NULL
   *	if everything went OK or the pointer to the last filled triple
   *	(incomplete one) otherwise. Upon the return chain[i].key contains
   *	the number of (i+1)-th block in the chain (as it is stored in memory,
   *	i.e. little-endian 32-bit), chain[i].p contains the address of that
   *	number (it points into struct inode for i==0 and into the bh->b_data
   *	for i>0) and chain[i].bh points to the buffer_head of i-th indirect
   *	block for i>0 and NULL for i==0. In other words, it holds the block
   *	numbers of the chain, addresses they were taken from (and where we can
   *	verify that chain did not change) and buffer_heads hosting these
   *	numbers.
   *
   *	Function stops when it stumbles upon zero pointer (absent block)
   *		(pointer to last triple returned, *@err == 0)
   *	or when it gets an IO error reading an indirect block
   *		(ditto, *@err == -EIO)
   *	or when it reads all @depth-1 indirect blocks successfully and finds
   *	the whole chain, all way to the data (returns %NULL, *err == 0).
   *
   *      Need to be called with
   *      down_read(&EXT4_I(inode)->i_data_sem)
   */
  static Indirect *ext4_get_branch(struct inode *inode, int depth,
  				 ext4_lblk_t  *offsets,
  				 Indirect chain[4], int *err)
  {
  	struct super_block *sb = inode->i_sb;
  	Indirect *p = chain;
  	struct buffer_head *bh;
  	int ret = -EIO;
  
  	*err = 0;
  	/* i_data is not going away, no lock needed */
  	add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
  	if (!p->key)
  		goto no_block;
  	while (--depth) {
  		bh = sb_getblk(sb, le32_to_cpu(p->key));
  		if (unlikely(!bh)) {
  			ret = -ENOMEM;
  			goto failure;
  		}
  
  		if (!bh_uptodate_or_lock(bh)) {
  			if (bh_submit_read(bh) < 0) {
  				put_bh(bh);
  				goto failure;
  			}
  			/* validate block references */
  			if (ext4_check_indirect_blockref(inode, bh)) {
  				put_bh(bh);
  				goto failure;
  			}
  		}
  
  		add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
  		/* Reader: end */
  		if (!p->key)
  			goto no_block;
  	}
  	return NULL;
  
  failure:
  	*err = ret;
  no_block:
  	return p;
  }
  
  /**
   *	ext4_find_near - find a place for allocation with sufficient locality
   *	@inode: owner
   *	@ind: descriptor of indirect block.
   *
   *	This function returns the preferred place for block allocation.
   *	It is used when heuristic for sequential allocation fails.
   *	Rules are:
   *	  + if there is a block to the left of our position - allocate near it.
   *	  + if pointer will live in indirect block - allocate near that block.
   *	  + if pointer will live in inode - allocate in the same
   *	    cylinder group.
   *
   * In the latter case we colour the starting block by the callers PID to
   * prevent it from clashing with concurrent allocations for a different inode
   * in the same block group.   The PID is used here so that functionally related
   * files will be close-by on-disk.
   *
   *	Caller must make sure that @ind is valid and will stay that way.
   */
  static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
  	__le32 *p;
  
  	/* Try to find previous block */
  	for (p = ind->p - 1; p >= start; p--) {
  		if (*p)
  			return le32_to_cpu(*p);
  	}
  
  	/* No such thing, so let's try location of indirect block */
  	if (ind->bh)
  		return ind->bh->b_blocknr;
  
  	/*
  	 * It is going to be referred to from the inode itself? OK, just put it
  	 * into the same cylinder group then.
  	 */
  	return ext4_inode_to_goal_block(inode);
  }
  
  /**
   *	ext4_find_goal - find a preferred place for allocation.
   *	@inode: owner
   *	@block:  block we want
   *	@partial: pointer to the last triple within a chain
   *
   *	Normally this function find the preferred place for block allocation,
   *	returns it.
   *	Because this is only used for non-extent files, we limit the block nr
   *	to 32 bits.
   */
  static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
  				   Indirect *partial)
  {
  	ext4_fsblk_t goal;
  
  	/*
  	 * XXX need to get goal block from mballoc's data structures
  	 */
  
  	goal = ext4_find_near(inode, partial);
  	goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
  	return goal;
  }
  
  /**
   *	ext4_blks_to_allocate - Look up the block map and count the number
   *	of direct blocks need to be allocated for the given branch.
   *
   *	@branch: chain of indirect blocks
   *	@k: number of blocks need for indirect blocks
   *	@blks: number of data blocks to be mapped.
   *	@blocks_to_boundary:  the offset in the indirect block
   *
   *	return the total number of blocks to be allocate, including the
   *	direct and indirect blocks.
   */
  static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
  				 int blocks_to_boundary)
  {
  	unsigned int count = 0;
  
  	/*
  	 * Simple case, [t,d]Indirect block(s) has not allocated yet
  	 * then it's clear blocks on that path have not allocated
  	 */
  	if (k > 0) {
  		/* right now we don't handle cross boundary allocation */
  		if (blks < blocks_to_boundary + 1)
  			count += blks;
  		else
  			count += blocks_to_boundary + 1;
  		return count;
  	}
  
  	count++;
  	while (count < blks && count <= blocks_to_boundary &&
  		le32_to_cpu(*(branch[0].p + count)) == 0) {
  		count++;
  	}
  	return count;
  }
  
  /**
   *	ext4_alloc_branch - allocate and set up a chain of blocks.
   *	@handle: handle for this transaction
   *	@inode: owner
   *	@indirect_blks: number of allocated indirect blocks
   *	@blks: number of allocated direct blocks
   *	@goal: preferred place for allocation
   *	@offsets: offsets (in the blocks) to store the pointers to next.
   *	@branch: place to store the chain in.
   *
   *	This function allocates blocks, zeroes out all but the last one,
   *	links them into chain and (if we are synchronous) writes them to disk.
   *	In other words, it prepares a branch that can be spliced onto the
   *	inode. It stores the information about that chain in the branch[], in
   *	the same format as ext4_get_branch() would do. We are calling it after
   *	we had read the existing part of chain and partial points to the last
   *	triple of that (one with zero ->key). Upon the exit we have the same
   *	picture as after the successful ext4_get_block(), except that in one
   *	place chain is disconnected - *branch->p is still zero (we did not
   *	set the last link), but branch->key contains the number that should
   *	be placed into *branch->p to fill that gap.
   *
   *	If allocation fails we free all blocks we've allocated (and forget
   *	their buffer_heads) and return the error value the from failed
   *	ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
   *	as described above and return 0.
   */
  static int ext4_alloc_branch(handle_t *handle,
  			     struct ext4_allocation_request *ar,
  			     int indirect_blks, ext4_lblk_t *offsets,
  			     Indirect *branch)
  {
  	struct buffer_head *		bh;
  	ext4_fsblk_t			b, new_blocks[4];
  	__le32				*p;
  	int				i, j, err, len = 1;
  
  	for (i = 0; i <= indirect_blks; i++) {
  		if (i == indirect_blks) {
  			new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
  		} else
  			ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
  					ar->inode, ar->goal,
  					ar->flags & EXT4_MB_DELALLOC_RESERVED,
  					NULL, &err);
  		if (err) {
  			i--;
  			goto failed;
  		}
  		branch[i].key = cpu_to_le32(new_blocks[i]);
  		if (i == 0)
  			continue;
  
  		bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
  		if (unlikely(!bh)) {
  			err = -ENOMEM;
  			goto failed;
  		}
  		lock_buffer(bh);
  		BUFFER_TRACE(bh, "call get_create_access");
  		err = ext4_journal_get_create_access(handle, bh);
  		if (err) {
  			unlock_buffer(bh);
  			goto failed;
  		}
  
  		memset(bh->b_data, 0, bh->b_size);
  		p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
  		b = new_blocks[i];
  
  		if (i == indirect_blks)
  			len = ar->len;
  		for (j = 0; j < len; j++)
  			*p++ = cpu_to_le32(b++);
  
  		BUFFER_TRACE(bh, "marking uptodate");
  		set_buffer_uptodate(bh);
  		unlock_buffer(bh);
  
  		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
  		err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
  		if (err)
  			goto failed;
  	}
  	return 0;
  failed:
  	for (; i >= 0; i--) {
  		/*
  		 * We want to ext4_forget() only freshly allocated indirect
  		 * blocks.  Buffer for new_blocks[i-1] is at branch[i].bh and
  		 * buffer at branch[0].bh is indirect block / inode already
  		 * existing before ext4_alloc_branch() was called.
  		 */
  		if (i > 0 && i != indirect_blks && branch[i].bh)
  			ext4_forget(handle, 1, ar->inode, branch[i].bh,
  				    branch[i].bh->b_blocknr);
  		ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
  				 (i == indirect_blks) ? ar->len : 1, 0);
  	}
  	return err;
  }
  
  /**
   * ext4_splice_branch - splice the allocated branch onto inode.
   * @handle: handle for this transaction
   * @inode: owner
   * @block: (logical) number of block we are adding
   * @chain: chain of indirect blocks (with a missing link - see
   *	ext4_alloc_branch)
   * @where: location of missing link
   * @num:   number of indirect blocks we are adding
   * @blks:  number of direct blocks we are adding
   *
   * This function fills the missing link and does all housekeeping needed in
   * inode (->i_blocks, etc.). In case of success we end up with the full
   * chain to new block and return 0.
   */
  static int ext4_splice_branch(handle_t *handle,
  			      struct ext4_allocation_request *ar,
  			      Indirect *where, int num)
  {
  	int i;
  	int err = 0;
  	ext4_fsblk_t current_block;
  
  	/*
  	 * If we're splicing into a [td]indirect block (as opposed to the
  	 * inode) then we need to get write access to the [td]indirect block
  	 * before the splice.
  	 */
  	if (where->bh) {
  		BUFFER_TRACE(where->bh, "get_write_access");
  		err = ext4_journal_get_write_access(handle, where->bh);
  		if (err)
  			goto err_out;
  	}
  	/* That's it */
  
  	*where->p = where->key;
  
  	/*
  	 * Update the host buffer_head or inode to point to more just allocated
  	 * direct blocks blocks
  	 */
  	if (num == 0 && ar->len > 1) {
  		current_block = le32_to_cpu(where->key) + 1;
  		for (i = 1; i < ar->len; i++)
  			*(where->p + i) = cpu_to_le32(current_block++);
  	}
  
  	/* We are done with atomic stuff, now do the rest of housekeeping */
  	/* had we spliced it onto indirect block? */
  	if (where->bh) {
  		/*
  		 * If we spliced it onto an indirect block, we haven't
  		 * altered the inode.  Note however that if it is being spliced
  		 * onto an indirect block at the very end of the file (the
  		 * file is growing) then we *will* alter the inode to reflect
  		 * the new i_size.  But that is not done here - it is done in
  		 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
  		 */
  		jbd_debug(5, "splicing indirect only\n");
  		BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
  		err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
  		if (err)
  			goto err_out;
  	} else {
  		/*
  		 * OK, we spliced it into the inode itself on a direct block.
  		 */
  		ext4_mark_inode_dirty(handle, ar->inode);
  		jbd_debug(5, "splicing direct\n");
  	}
  	return err;
  
  err_out:
  	for (i = 1; i <= num; i++) {
  		/*
  		 * branch[i].bh is newly allocated, so there is no
  		 * need to revoke the block, which is why we don't
  		 * need to set EXT4_FREE_BLOCKS_METADATA.
  		 */
  		ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
  				 EXT4_FREE_BLOCKS_FORGET);
  	}
  	ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
  			 ar->len, 0);
  
  	return err;
  }
  
  /*
   * The ext4_ind_map_blocks() function handles non-extents inodes
   * (i.e., using the traditional indirect/double-indirect i_blocks
   * scheme) for ext4_map_blocks().
   *
   * Allocation strategy is simple: if we have to allocate something, we will
   * have to go the whole way to leaf. So let's do it before attaching anything
   * to tree, set linkage between the newborn blocks, write them if sync is
   * required, recheck the path, free and repeat if check fails, otherwise
   * set the last missing link (that will protect us from any truncate-generated
   * removals - all blocks on the path are immune now) and possibly force the
   * write on the parent block.
   * That has a nice additional property: no special recovery from the failed
   * allocations is needed - we simply release blocks and do not touch anything
   * reachable from inode.
   *
   * `handle' can be NULL if create == 0.
   *
   * return > 0, # of blocks mapped or allocated.
   * return = 0, if plain lookup failed.
   * return < 0, error case.
   *
   * The ext4_ind_get_blocks() function should be called with
   * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
   * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
   * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
   * blocks.
   */
  int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
  			struct ext4_map_blocks *map,
  			int flags)
  {
  	struct ext4_allocation_request ar;
  	int err = -EIO;
  	ext4_lblk_t offsets[4];
  	Indirect chain[4];
  	Indirect *partial;
  	int indirect_blks;
  	int blocks_to_boundary = 0;
  	int depth;
  	int count = 0;
  	ext4_fsblk_t first_block = 0;
  
  	trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
  	J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
  	J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
  	depth = ext4_block_to_path(inode, map->m_lblk, offsets,
  				   &blocks_to_boundary);
  
  	if (depth == 0)
  		goto out;
  
  	partial = ext4_get_branch(inode, depth, offsets, chain, &err);
  
  	/* Simplest case - block found, no allocation needed */
  	if (!partial) {
  		first_block = le32_to_cpu(chain[depth - 1].key);
  		count++;
  		/*map more blocks*/
  		while (count < map->m_len && count <= blocks_to_boundary) {
  			ext4_fsblk_t blk;
  
  			blk = le32_to_cpu(*(chain[depth-1].p + count));
  
  			if (blk == first_block + count)
  				count++;
  			else
  				break;
  		}
  		goto got_it;
  	}
  
  	/* Next simple case - plain lookup or failed read of indirect block */
  	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
  		goto cleanup;
  
  	/*
  	 * Okay, we need to do block allocation.
  	*/
  	if (ext4_has_feature_bigalloc(inode->i_sb)) {
  		EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
  				 "non-extent mapped inodes with bigalloc");
  		return -EFSCORRUPTED;
  	}
  
  	/* Set up for the direct block allocation */
  	memset(&ar, 0, sizeof(ar));
  	ar.inode = inode;
  	ar.logical = map->m_lblk;
  	if (S_ISREG(inode->i_mode))
  		ar.flags = EXT4_MB_HINT_DATA;
  	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
  		ar.flags |= EXT4_MB_DELALLOC_RESERVED;
  	if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
  		ar.flags |= EXT4_MB_USE_RESERVED;
  
  	ar.goal = ext4_find_goal(inode, map->m_lblk, partial);
  
  	/* the number of blocks need to allocate for [d,t]indirect blocks */
  	indirect_blks = (chain + depth) - partial - 1;
  
  	/*
  	 * Next look up the indirect map to count the totoal number of
  	 * direct blocks to allocate for this branch.
  	 */
  	ar.len = ext4_blks_to_allocate(partial, indirect_blks,
  				       map->m_len, blocks_to_boundary);
  
  	/*
  	 * Block out ext4_truncate while we alter the tree
  	 */
  	err = ext4_alloc_branch(handle, &ar, indirect_blks,
  				offsets + (partial - chain), partial);
  
  	/*
  	 * The ext4_splice_branch call will free and forget any buffers
  	 * on the new chain if there is a failure, but that risks using
  	 * up transaction credits, especially for bitmaps where the
  	 * credits cannot be returned.  Can we handle this somehow?  We
  	 * may need to return -EAGAIN upwards in the worst case.  --sct
  	 */
  	if (!err)
  		err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
  	if (err)
  		goto cleanup;
  
  	map->m_flags |= EXT4_MAP_NEW;
  
  	ext4_update_inode_fsync_trans(handle, inode, 1);
  	count = ar.len;
  got_it:
  	map->m_flags |= EXT4_MAP_MAPPED;
  	map->m_pblk = le32_to_cpu(chain[depth-1].key);
  	map->m_len = count;
  	if (count > blocks_to_boundary)
  		map->m_flags |= EXT4_MAP_BOUNDARY;
  	err = count;
  	/* Clean up and exit */
  	partial = chain + depth - 1;	/* the whole chain */
  cleanup:
  	while (partial > chain) {
  		BUFFER_TRACE(partial->bh, "call brelse");
  		brelse(partial->bh);
  		partial--;
  	}
  out:
  	trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
  	return err;
  }
  
  /*
   * O_DIRECT for ext3 (or indirect map) based files
   *
   * If the O_DIRECT write will extend the file then add this inode to the
   * orphan list.  So recovery will truncate it back to the original size
   * if the machine crashes during the write.
   *
   * If the O_DIRECT write is intantiating holes inside i_size and the machine
   * crashes then stale disk data _may_ be exposed inside the file. But current
   * VFS code falls back into buffered path in that case so we are safe.
   */
  ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
  			   loff_t offset)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	handle_t *handle;
  	ssize_t ret;
  	int orphan = 0;
  	size_t count = iov_iter_count(iter);
  	int retries = 0;
  
  	if (iov_iter_rw(iter) == WRITE) {
  		loff_t final_size = offset + count;
  
  		if (final_size > inode->i_size) {
  			/* Credits for sb + inode write */
  			handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  			if (IS_ERR(handle)) {
  				ret = PTR_ERR(handle);
  				goto out;
  			}
  			ret = ext4_orphan_add(handle, inode);
  			if (ret) {
  				ext4_journal_stop(handle);
  				goto out;
  			}
  			orphan = 1;
  			ei->i_disksize = inode->i_size;
  			ext4_journal_stop(handle);
  		}
  	}
  
  retry:
  	if (iov_iter_rw(iter) == READ && ext4_should_dioread_nolock(inode)) {
  		/*
  		 * Nolock dioread optimization may be dynamically disabled
  		 * via ext4_inode_block_unlocked_dio(). Check inode's state
  		 * while holding extra i_dio_count ref.
  		 */
  		inode_dio_begin(inode);
  		smp_mb();
  		if (unlikely(ext4_test_inode_state(inode,
  						    EXT4_STATE_DIOREAD_LOCK))) {
  			inode_dio_end(inode);
  			goto locked;
  		}
  		if (IS_DAX(inode))
  			ret = dax_do_io(iocb, inode, iter, offset,
  					ext4_get_block, NULL, 0);
  		else
  			ret = __blockdev_direct_IO(iocb, inode,
  						   inode->i_sb->s_bdev, iter,
  						   offset, ext4_get_block, NULL,
  						   NULL, 0);
  		inode_dio_end(inode);
  	} else {
  locked:
  		if (IS_DAX(inode))
  			ret = dax_do_io(iocb, inode, iter, offset,
  					ext4_get_block, NULL, DIO_LOCKING);
  		else
  			ret = blockdev_direct_IO(iocb, inode, iter, offset,
  						 ext4_get_block);
  
  		if (unlikely(iov_iter_rw(iter) == WRITE && ret < 0)) {
  			loff_t isize = i_size_read(inode);
  			loff_t end = offset + count;
  
  			if (end > isize)
  				ext4_truncate_failed_write(inode);
  		}
  	}
  	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
  		goto retry;
  
  	if (orphan) {
  		int err;
  
  		/* Credits for sb + inode write */
  		handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  		if (IS_ERR(handle)) {
  			/* This is really bad luck. We've written the data
  			 * but cannot extend i_size. Bail out and pretend
  			 * the write failed... */
  			ret = PTR_ERR(handle);
  			if (inode->i_nlink)
  				ext4_orphan_del(NULL, inode);
  
  			goto out;
  		}
  		if (inode->i_nlink)
  			ext4_orphan_del(handle, inode);
  		if (ret > 0) {
  			loff_t end = offset + ret;
  			if (end > inode->i_size) {
  				ei->i_disksize = end;
  				i_size_write(inode, end);
  				/*
  				 * We're going to return a positive `ret'
  				 * here due to non-zero-length I/O, so there's
  				 * no way of reporting error returns from
  				 * ext4_mark_inode_dirty() to userspace.  So
  				 * ignore it.
  				 */
  				ext4_mark_inode_dirty(handle, inode);
  			}
  		}
  		err = ext4_journal_stop(handle);
  		if (ret == 0)
  			ret = err;
  	}
  out:
  	return ret;
  }
  
  /*
   * Calculate the number of metadata blocks need to reserve
   * to allocate a new block at @lblocks for non extent file based file
   */
  int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
  	int blk_bits;
  
  	if (lblock < EXT4_NDIR_BLOCKS)
  		return 0;
  
  	lblock -= EXT4_NDIR_BLOCKS;
  
  	if (ei->i_da_metadata_calc_len &&
  	    (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
  		ei->i_da_metadata_calc_len++;
  		return 0;
  	}
  	ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
  	ei->i_da_metadata_calc_len = 1;
  	blk_bits = order_base_2(lblock);
  	return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
  }
  
  /*
   * Calculate number of indirect blocks touched by mapping @nrblocks logically
   * contiguous blocks
   */
  int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
  {
  	/*
  	 * With N contiguous data blocks, we need at most
  	 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
  	 * 2 dindirect blocks, and 1 tindirect block
  	 */
  	return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
  }
  
  /*
   * Truncate transactions can be complex and absolutely huge.  So we need to
   * be able to restart the transaction at a conventient checkpoint to make
   * sure we don't overflow the journal.
   *
   * Try to extend this transaction for the purposes of truncation.  If
   * extend fails, we need to propagate the failure up and restart the
   * transaction in the top-level truncate loop. --sct
   *
   * Returns 0 if we managed to create more room.  If we can't create more
   * room, and the transaction must be restarted we return 1.
   */
  static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
  {
  	if (!ext4_handle_valid(handle))
  		return 0;
  	if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
  		return 0;
  	if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
  		return 0;
  	return 1;
  }
  
  /*
   * Probably it should be a library function... search for first non-zero word
   * or memcmp with zero_page, whatever is better for particular architecture.
   * Linus?
   */
  static inline int all_zeroes(__le32 *p, __le32 *q)
  {
  	while (p < q)
  		if (*p++)
  			return 0;
  	return 1;
  }
  
  /**
   *	ext4_find_shared - find the indirect blocks for partial truncation.
   *	@inode:	  inode in question
   *	@depth:	  depth of the affected branch
   *	@offsets: offsets of pointers in that branch (see ext4_block_to_path)
   *	@chain:	  place to store the pointers to partial indirect blocks
   *	@top:	  place to the (detached) top of branch
   *
   *	This is a helper function used by ext4_truncate().
   *
   *	When we do truncate() we may have to clean the ends of several
   *	indirect blocks but leave the blocks themselves alive. Block is
   *	partially truncated if some data below the new i_size is referred
   *	from it (and it is on the path to the first completely truncated
   *	data block, indeed).  We have to free the top of that path along
   *	with everything to the right of the path. Since no allocation
   *	past the truncation point is possible until ext4_truncate()
   *	finishes, we may safely do the latter, but top of branch may
   *	require special attention - pageout below the truncation point
   *	might try to populate it.
   *
   *	We atomically detach the top of branch from the tree, store the
   *	block number of its root in *@top, pointers to buffer_heads of
   *	partially truncated blocks - in @chain[].bh and pointers to
   *	their last elements that should not be removed - in
   *	@chain[].p. Return value is the pointer to last filled element
   *	of @chain.
   *
   *	The work left to caller to do the actual freeing of subtrees:
   *		a) free the subtree starting from *@top
   *		b) free the subtrees whose roots are stored in
   *			(@chain[i].p+1 .. end of @chain[i].bh->b_data)
   *		c) free the subtrees growing from the inode past the @chain[0].
   *			(no partially truncated stuff there).  */
  
  static Indirect *ext4_find_shared(struct inode *inode, int depth,
  				  ext4_lblk_t offsets[4], Indirect chain[4],
  				  __le32 *top)
  {
  	Indirect *partial, *p;
  	int k, err;
  
  	*top = 0;
  	/* Make k index the deepest non-null offset + 1 */
  	for (k = depth; k > 1 && !offsets[k-1]; k--)
  		;
  	partial = ext4_get_branch(inode, k, offsets, chain, &err);
  	/* Writer: pointers */
  	if (!partial)
  		partial = chain + k-1;
  	/*
  	 * If the branch acquired continuation since we've looked at it -
  	 * fine, it should all survive and (new) top doesn't belong to us.
  	 */
  	if (!partial->key && *partial->p)
  		/* Writer: end */
  		goto no_top;
  	for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
  		;
  	/*
  	 * OK, we've found the last block that must survive. The rest of our
  	 * branch should be detached before unlocking. However, if that rest
  	 * of branch is all ours and does not grow immediately from the inode
  	 * it's easier to cheat and just decrement partial->p.
  	 */
  	if (p == chain + k - 1 && p > chain) {
  		p->p--;
  	} else {
  		*top = *p->p;
  		/* Nope, don't do this in ext4.  Must leave the tree intact */
  #if 0
  		*p->p = 0;
  #endif
  	}
  	/* Writer: end */
  
  	while (partial > p) {
  		brelse(partial->bh);
  		partial--;
  	}
  no_top:
  	return partial;
  }
  
  /*
   * Zero a number of block pointers in either an inode or an indirect block.
   * If we restart the transaction we must again get write access to the
   * indirect block for further modification.
   *
   * We release `count' blocks on disk, but (last - first) may be greater
   * than `count' because there can be holes in there.
   *
   * Return 0 on success, 1 on invalid block range
   * and < 0 on fatal error.
   */
  static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
  			     struct buffer_head *bh,
  			     ext4_fsblk_t block_to_free,
  			     unsigned long count, __le32 *first,
  			     __le32 *last)
  {
  	__le32 *p;
  	int	flags = EXT4_FREE_BLOCKS_VALIDATED;
  	int	err;
  
  	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
  		flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
  	else if (ext4_should_journal_data(inode))
  		flags |= EXT4_FREE_BLOCKS_FORGET;
  
  	if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
  				   count)) {
  		EXT4_ERROR_INODE(inode, "attempt to clear invalid "
  				 "blocks %llu len %lu",
  				 (unsigned long long) block_to_free, count);
  		return 1;
  	}
  
  	if (try_to_extend_transaction(handle, inode)) {
  		if (bh) {
  			BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
  			err = ext4_handle_dirty_metadata(handle, inode, bh);
  			if (unlikely(err))
  				goto out_err;
  		}
  		err = ext4_mark_inode_dirty(handle, inode);
  		if (unlikely(err))
  			goto out_err;
  		err = ext4_truncate_restart_trans(handle, inode,
  					ext4_blocks_for_truncate(inode));
  		if (unlikely(err))
  			goto out_err;
  		if (bh) {
  			BUFFER_TRACE(bh, "retaking write access");
  			err = ext4_journal_get_write_access(handle, bh);
  			if (unlikely(err))
  				goto out_err;
  		}
  	}
  
  	for (p = first; p < last; p++)
  		*p = 0;
  
  	ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
  	return 0;
  out_err:
  	ext4_std_error(inode->i_sb, err);
  	return err;
  }
  
  /**
   * ext4_free_data - free a list of data blocks
   * @handle:	handle for this transaction
   * @inode:	inode we are dealing with
   * @this_bh:	indirect buffer_head which contains *@first and *@last
   * @first:	array of block numbers
   * @last:	points immediately past the end of array
   *
   * We are freeing all blocks referred from that array (numbers are stored as
   * little-endian 32-bit) and updating @inode->i_blocks appropriately.
   *
   * We accumulate contiguous runs of blocks to free.  Conveniently, if these
   * blocks are contiguous then releasing them at one time will only affect one
   * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
   * actually use a lot of journal space.
   *
   * @this_bh will be %NULL if @first and @last point into the inode's direct
   * block pointers.
   */
  static void ext4_free_data(handle_t *handle, struct inode *inode,
  			   struct buffer_head *this_bh,
  			   __le32 *first, __le32 *last)
  {
  	ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
  	unsigned long count = 0;	    /* Number of blocks in the run */
  	__le32 *block_to_free_p = NULL;	    /* Pointer into inode/ind
  					       corresponding to
  					       block_to_free */
  	ext4_fsblk_t nr;		    /* Current block # */
  	__le32 *p;			    /* Pointer into inode/ind
  					       for current block */
  	int err = 0;
  
  	if (this_bh) {				/* For indirect block */
  		BUFFER_TRACE(this_bh, "get_write_access");
  		err = ext4_journal_get_write_access(handle, this_bh);
  		/* Important: if we can't update the indirect pointers
  		 * to the blocks, we can't free them. */
  		if (err)
  			return;
  	}
  
  	for (p = first; p < last; p++) {
  		nr = le32_to_cpu(*p);
  		if (nr) {
  			/* accumulate blocks to free if they're contiguous */
  			if (count == 0) {
  				block_to_free = nr;
  				block_to_free_p = p;
  				count = 1;
  			} else if (nr == block_to_free + count) {
  				count++;
  			} else {
  				err = ext4_clear_blocks(handle, inode, this_bh,
  						        block_to_free, count,
  						        block_to_free_p, p);
  				if (err)
  					break;
  				block_to_free = nr;
  				block_to_free_p = p;
  				count = 1;
  			}
  		}
  	}
  
  	if (!err && count > 0)
  		err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
  					count, block_to_free_p, p);
  	if (err < 0)
  		/* fatal error */
  		return;
  
  	if (this_bh) {
  		BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
  
  		/*
  		 * The buffer head should have an attached journal head at this
  		 * point. However, if the data is corrupted and an indirect
  		 * block pointed to itself, it would have been detached when
  		 * the block was cleared. Check for this instead of OOPSing.
  		 */
  		if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
  			ext4_handle_dirty_metadata(handle, inode, this_bh);
  		else
  			EXT4_ERROR_INODE(inode,
  					 "circular indirect block detected at "
  					 "block %llu",
  				(unsigned long long) this_bh->b_blocknr);
  	}
  }
  
  /**
   *	ext4_free_branches - free an array of branches
   *	@handle: JBD handle for this transaction
   *	@inode:	inode we are dealing with
   *	@parent_bh: the buffer_head which contains *@first and *@last
   *	@first:	array of block numbers
   *	@last:	pointer immediately past the end of array
   *	@depth:	depth of the branches to free
   *
   *	We are freeing all blocks referred from these branches (numbers are
   *	stored as little-endian 32-bit) and updating @inode->i_blocks
   *	appropriately.
   */
  static void ext4_free_branches(handle_t *handle, struct inode *inode,
  			       struct buffer_head *parent_bh,
  			       __le32 *first, __le32 *last, int depth)
  {
  	ext4_fsblk_t nr;
  	__le32 *p;
  
  	if (ext4_handle_is_aborted(handle))
  		return;
  
  	if (depth--) {
  		struct buffer_head *bh;
  		int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  		p = last;
  		while (--p >= first) {
  			nr = le32_to_cpu(*p);
  			if (!nr)
  				continue;		/* A hole */
  
  			if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
  						   nr, 1)) {
  				EXT4_ERROR_INODE(inode,
  						 "invalid indirect mapped "
  						 "block %lu (level %d)",
  						 (unsigned long) nr, depth);
  				break;
  			}
  
  			/* Go read the buffer for the next level down */
  			bh = sb_bread(inode->i_sb, nr);
  
  			/*
  			 * A read failure? Report error and clear slot
  			 * (should be rare).
  			 */
  			if (!bh) {
  				EXT4_ERROR_INODE_BLOCK(inode, nr,
  						       "Read failure");
  				continue;
  			}
  
  			/* This zaps the entire block.  Bottom up. */
  			BUFFER_TRACE(bh, "free child branches");
  			ext4_free_branches(handle, inode, bh,
  					(__le32 *) bh->b_data,
  					(__le32 *) bh->b_data + addr_per_block,
  					depth);
  			brelse(bh);
  
  			/*
  			 * Everything below this this pointer has been
  			 * released.  Now let this top-of-subtree go.
  			 *
  			 * We want the freeing of this indirect block to be
  			 * atomic in the journal with the updating of the
  			 * bitmap block which owns it.  So make some room in
  			 * the journal.
  			 *
  			 * We zero the parent pointer *after* freeing its
  			 * pointee in the bitmaps, so if extend_transaction()
  			 * for some reason fails to put the bitmap changes and
  			 * the release into the same transaction, recovery
  			 * will merely complain about releasing a free block,
  			 * rather than leaking blocks.
  			 */
  			if (ext4_handle_is_aborted(handle))
  				return;
  			if (try_to_extend_transaction(handle, inode)) {
  				ext4_mark_inode_dirty(handle, inode);
  				ext4_truncate_restart_trans(handle, inode,
  					    ext4_blocks_for_truncate(inode));
  			}
  
  			/*
  			 * The forget flag here is critical because if
  			 * we are journaling (and not doing data
  			 * journaling), we have to make sure a revoke
  			 * record is written to prevent the journal
  			 * replay from overwriting the (former)
  			 * indirect block if it gets reallocated as a
  			 * data block.  This must happen in the same
  			 * transaction where the data blocks are
  			 * actually freed.
  			 */
  			ext4_free_blocks(handle, inode, NULL, nr, 1,
  					 EXT4_FREE_BLOCKS_METADATA|
  					 EXT4_FREE_BLOCKS_FORGET);
  
  			if (parent_bh) {
  				/*
  				 * The block which we have just freed is
  				 * pointed to by an indirect block: journal it
  				 */
  				BUFFER_TRACE(parent_bh, "get_write_access");
  				if (!ext4_journal_get_write_access(handle,
  								   parent_bh)){
  					*p = 0;
  					BUFFER_TRACE(parent_bh,
  					"call ext4_handle_dirty_metadata");
  					ext4_handle_dirty_metadata(handle,
  								   inode,
  								   parent_bh);
  				}
  			}
  		}
  	} else {
  		/* We have reached the bottom of the tree. */
  		BUFFER_TRACE(parent_bh, "free data blocks");
  		ext4_free_data(handle, inode, parent_bh, first, last);
  	}
  }
  
  void ext4_ind_truncate(handle_t *handle, struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	__le32 *i_data = ei->i_data;
  	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  	ext4_lblk_t offsets[4];
  	Indirect chain[4];
  	Indirect *partial;
  	__le32 nr = 0;
  	int n = 0;
  	ext4_lblk_t last_block, max_block;
  	unsigned blocksize = inode->i_sb->s_blocksize;
  
  	last_block = (inode->i_size + blocksize-1)
  					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
  	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
  					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
  
  	if (last_block != max_block) {
  		n = ext4_block_to_path(inode, last_block, offsets, NULL);
  		if (n == 0)
  			return;
  	}
  
  	ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block);
  
  	/*
  	 * The orphan list entry will now protect us from any crash which
  	 * occurs before the truncate completes, so it is now safe to propagate
  	 * the new, shorter inode size (held for now in i_size) into the
  	 * on-disk inode. We do this via i_disksize, which is the value which
  	 * ext4 *really* writes onto the disk inode.
  	 */
  	ei->i_disksize = inode->i_size;
  
  	if (last_block == max_block) {
  		/*
  		 * It is unnecessary to free any data blocks if last_block is
  		 * equal to the indirect block limit.
  		 */
  		return;
  	} else if (n == 1) {		/* direct blocks */
  		ext4_free_data(handle, inode, NULL, i_data+offsets[0],
  			       i_data + EXT4_NDIR_BLOCKS);
  		goto do_indirects;
  	}
  
  	partial = ext4_find_shared(inode, n, offsets, chain, &nr);
  	/* Kill the top of shared branch (not detached) */
  	if (nr) {
  		if (partial == chain) {
  			/* Shared branch grows from the inode */
  			ext4_free_branches(handle, inode, NULL,
  					   &nr, &nr+1, (chain+n-1) - partial);
  			*partial->p = 0;
  			/*
  			 * We mark the inode dirty prior to restart,
  			 * and prior to stop.  No need for it here.
  			 */
  		} else {
  			/* Shared branch grows from an indirect block */
  			BUFFER_TRACE(partial->bh, "get_write_access");
  			ext4_free_branches(handle, inode, partial->bh,
  					partial->p,
  					partial->p+1, (chain+n-1) - partial);
  		}
  	}
  	/* Clear the ends of indirect blocks on the shared branch */
  	while (partial > chain) {
  		ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
  				   (__le32*)partial->bh->b_data+addr_per_block,
  				   (chain+n-1) - partial);
  		BUFFER_TRACE(partial->bh, "call brelse");
  		brelse(partial->bh);
  		partial--;
  	}
  do_indirects:
  	/* Kill the remaining (whole) subtrees */
  	switch (offsets[0]) {
  	default:
  		nr = i_data[EXT4_IND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
  			i_data[EXT4_IND_BLOCK] = 0;
  		}
  	case EXT4_IND_BLOCK:
  		nr = i_data[EXT4_DIND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
  			i_data[EXT4_DIND_BLOCK] = 0;
  		}
  	case EXT4_DIND_BLOCK:
  		nr = i_data[EXT4_TIND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
  			i_data[EXT4_TIND_BLOCK] = 0;
  		}
  	case EXT4_TIND_BLOCK:
  		;
  	}
  }
  
  /**
   *	ext4_ind_remove_space - remove space from the range
   *	@handle: JBD handle for this transaction
   *	@inode:	inode we are dealing with
   *	@start:	First block to remove
   *	@end:	One block after the last block to remove (exclusive)
   *
   *	Free the blocks in the defined range (end is exclusive endpoint of
   *	range). This is used by ext4_punch_hole().
   */
  int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
  			  ext4_lblk_t start, ext4_lblk_t end)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	__le32 *i_data = ei->i_data;
  	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  	ext4_lblk_t offsets[4], offsets2[4];
  	Indirect chain[4], chain2[4];
  	Indirect *partial, *partial2;
  	ext4_lblk_t max_block;
  	__le32 nr = 0, nr2 = 0;
  	int n = 0, n2 = 0;
  	unsigned blocksize = inode->i_sb->s_blocksize;
  
  	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
  					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
  	if (end >= max_block)
  		end = max_block;
  	if ((start >= end) || (start > max_block))
  		return 0;
  
  	n = ext4_block_to_path(inode, start, offsets, NULL);
  	n2 = ext4_block_to_path(inode, end, offsets2, NULL);
  
  	BUG_ON(n > n2);
  
  	if ((n == 1) && (n == n2)) {
  		/* We're punching only within direct block range */
  		ext4_free_data(handle, inode, NULL, i_data + offsets[0],
  			       i_data + offsets2[0]);
  		return 0;
  	} else if (n2 > n) {
  		/*
  		 * Start and end are on a different levels so we're going to
  		 * free partial block at start, and partial block at end of
  		 * the range. If there are some levels in between then
  		 * do_indirects label will take care of that.
  		 */
  
  		if (n == 1) {
  			/*
  			 * Start is at the direct block level, free
  			 * everything to the end of the level.
  			 */
  			ext4_free_data(handle, inode, NULL, i_data + offsets[0],
  				       i_data + EXT4_NDIR_BLOCKS);
  			goto end_range;
  		}
  
  
  		partial = ext4_find_shared(inode, n, offsets, chain, &nr);
  		if (nr) {
  			if (partial == chain) {
  				/* Shared branch grows from the inode */
  				ext4_free_branches(handle, inode, NULL,
  					   &nr, &nr+1, (chain+n-1) - partial);
  				*partial->p = 0;
  			} else {
  				/* Shared branch grows from an indirect block */
  				BUFFER_TRACE(partial->bh, "get_write_access");
  				ext4_free_branches(handle, inode, partial->bh,
  					partial->p,
  					partial->p+1, (chain+n-1) - partial);
  			}
  		}
  
  		/*
  		 * Clear the ends of indirect blocks on the shared branch
  		 * at the start of the range
  		 */
  		while (partial > chain) {
  			ext4_free_branches(handle, inode, partial->bh,
  				partial->p + 1,
  				(__le32 *)partial->bh->b_data+addr_per_block,
  				(chain+n-1) - partial);
  			BUFFER_TRACE(partial->bh, "call brelse");
  			brelse(partial->bh);
  			partial--;
  		}
  
  end_range:
  		partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
  		if (nr2) {
  			if (partial2 == chain2) {
  				/*
  				 * Remember, end is exclusive so here we're at
  				 * the start of the next level we're not going
  				 * to free. Everything was covered by the start
  				 * of the range.
  				 */
  				goto do_indirects;
  			}
  		} else {
  			/*
  			 * ext4_find_shared returns Indirect structure which
  			 * points to the last element which should not be
  			 * removed by truncate. But this is end of the range
  			 * in punch_hole so we need to point to the next element
  			 */
  			partial2->p++;
  		}
  
  		/*
  		 * Clear the ends of indirect blocks on the shared branch
  		 * at the end of the range
  		 */
  		while (partial2 > chain2) {
  			ext4_free_branches(handle, inode, partial2->bh,
  					   (__le32 *)partial2->bh->b_data,
  					   partial2->p,
  					   (chain2+n2-1) - partial2);
  			BUFFER_TRACE(partial2->bh, "call brelse");
  			brelse(partial2->bh);
  			partial2--;
  		}
  		goto do_indirects;
  	}
  
  	/* Punch happened within the same level (n == n2) */
  	partial = ext4_find_shared(inode, n, offsets, chain, &nr);
  	partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
  
  	/* Free top, but only if partial2 isn't its subtree. */
  	if (nr) {
  		int level = min(partial - chain, partial2 - chain2);
  		int i;
  		int subtree = 1;
  
  		for (i = 0; i <= level; i++) {
  			if (offsets[i] != offsets2[i]) {
  				subtree = 0;
  				break;
  			}
  		}
  
  		if (!subtree) {
  			if (partial == chain) {
  				/* Shared branch grows from the inode */
  				ext4_free_branches(handle, inode, NULL,
  						   &nr, &nr+1,
  						   (chain+n-1) - partial);
  				*partial->p = 0;
  			} else {
  				/* Shared branch grows from an indirect block */
  				BUFFER_TRACE(partial->bh, "get_write_access");
  				ext4_free_branches(handle, inode, partial->bh,
  						   partial->p,
  						   partial->p+1,
  						   (chain+n-1) - partial);
  			}
  		}
  	}
  
  	if (!nr2) {
  		/*
  		 * ext4_find_shared returns Indirect structure which
  		 * points to the last element which should not be
  		 * removed by truncate. But this is end of the range
  		 * in punch_hole so we need to point to the next element
  		 */
  		partial2->p++;
  	}
  
  	while (partial > chain || partial2 > chain2) {
  		int depth = (chain+n-1) - partial;
  		int depth2 = (chain2+n2-1) - partial2;
  
  		if (partial > chain && partial2 > chain2 &&
  		    partial->bh->b_blocknr == partial2->bh->b_blocknr) {
  			/*
  			 * We've converged on the same block. Clear the range,
  			 * then we're done.
  			 */
  			ext4_free_branches(handle, inode, partial->bh,
  					   partial->p + 1,
  					   partial2->p,
  					   (chain+n-1) - partial);
  			BUFFER_TRACE(partial->bh, "call brelse");
  			brelse(partial->bh);
  			BUFFER_TRACE(partial2->bh, "call brelse");
  			brelse(partial2->bh);
  			return 0;
  		}
  
  		/*
  		 * The start and end partial branches may not be at the same
  		 * level even though the punch happened within one level. So, we
  		 * give them a chance to arrive at the same level, then walk
  		 * them in step with each other until we converge on the same
  		 * block.
  		 */
  		if (partial > chain && depth <= depth2) {
  			ext4_free_branches(handle, inode, partial->bh,
  					   partial->p + 1,
  					   (__le32 *)partial->bh->b_data+addr_per_block,
  					   (chain+n-1) - partial);
  			BUFFER_TRACE(partial->bh, "call brelse");
  			brelse(partial->bh);
  			partial--;
  		}
  		if (partial2 > chain2 && depth2 <= depth) {
  			ext4_free_branches(handle, inode, partial2->bh,
  					   (__le32 *)partial2->bh->b_data,
  					   partial2->p,
  					   (chain2+n2-1) - partial2);
  			BUFFER_TRACE(partial2->bh, "call brelse");
  			brelse(partial2->bh);
  			partial2--;
  		}
  	}
  	return 0;
  
  do_indirects:
  	/* Kill the remaining (whole) subtrees */
  	switch (offsets[0]) {
  	default:
  		if (++n >= n2)
  			return 0;
  		nr = i_data[EXT4_IND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
  			i_data[EXT4_IND_BLOCK] = 0;
  		}
  	case EXT4_IND_BLOCK:
  		if (++n >= n2)
  			return 0;
  		nr = i_data[EXT4_DIND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
  			i_data[EXT4_DIND_BLOCK] = 0;
  		}
  	case EXT4_DIND_BLOCK:
  		if (++n >= n2)
  			return 0;
  		nr = i_data[EXT4_TIND_BLOCK];
  		if (nr) {
  			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
  			i_data[EXT4_TIND_BLOCK] = 0;
  		}
  	case EXT4_TIND_BLOCK:
  		;
  	}
  	return 0;
  }
  