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: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 1655ff1..3027fa6 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -555,8 +555,23 @@
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;
/*