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Commit facab4d9 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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ext4: return hole from ext4_map_blocks() 



Currently, ext4_map_blocks() just returns 0 when it finds a hole and
allocation is not requested. However we have all the information
available to tell how large the hole actually is and there are callers
of ext4_map_blocks() which would save some block-by-block hole iteration
if they knew this information. So fill in struct ext4_map_blocks even
for holes with the information we have. We keep returning 0 for holes to
maintain backward compatibility of the function.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 140a5250

fs/ext4/extents.c

+9 −2
Original line number Diff line number Diff line
@@ -4374,13 +4374,20 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, 
	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {

		ext4_lblk_t hole_start, hole_len;



		hole_start = map->m_lblk;

		hole_len = ext4_ext_determine_hole(inode, path, &hole_start);

		/*

		 * put just found gap into cache to speed up

		 * subsequent requests

		 */

		hole_start = map->m_lblk;

		hole_len = ext4_ext_determine_hole(inode, path, &hole_start);

		ext4_ext_put_gap_in_cache(inode, hole_start, hole_len);



		/* Update hole_len to reflect hole size after map->m_lblk */

		if (hole_start != map->m_lblk)

			hole_len -= map->m_lblk - hole_start;

		map->m_pblk = 0;

		map->m_len = min_t(unsigned int, map->m_len, hole_len);



		goto out2;

	}

fs/ext4/indirect.c

+17 −2
Original line number Diff line number Diff line
@@ -555,8 +555,23 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode, 
		goto got_it;

	}



	/* Next simple case - plain lookup or failed read of indirect block */

	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)

	/* Next simple case - plain lookup failed */

	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {

		unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);

		int i;



		/* Count number blocks in a subtree under 'partial' */

		count = 1;

		for (i = 0; partial + i != chain + depth - 1; i++)

			count *= epb;

		/* Fill in size of a hole we found */

		map->m_pblk = 0;

		map->m_len = min_t(unsigned int, map->m_len, count);

		goto cleanup;

	}



	/* Failed read of indirect block */

	if (err == -EIO)

		goto cleanup;



	/*

fs/ext4/inode.c

+10 −5
Original line number Diff line number Diff line
@@ -455,13 +455,13 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, 
 * 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 block,

 * the result buffer head is unmapped. If the create ==1, it will make sure

 * the buffer head is mapped.

 * 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, buffer head is unmapped

 * 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.

 */
@@ -504,6 +504,11 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
				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_ON(1);