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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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19
fs/ext4/indirect.c
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@@ -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;
/*