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ext4: return hole from ext4_map_blocks()

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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: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara
2016-03-09 22:54:00 -05:00
committed by Theodore Ts'o
parent 140a52508a
commit facab4d971
3 changed files with 36 additions and 9 deletions
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11
fs/ext4/extents.c
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@@ -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;
}