ext4: fix BUG_ON in mb_free_blocks()
authorTheodore Ts'o <tytso@mit.edu>
Sat, 23 Aug 2014 21:47:28 +0000 (17:47 -0400)
committerBen Hutchings <ben@decadent.org.uk>
Wed, 5 Nov 2014 20:27:47 +0000 (20:27 +0000)
commit4c84431245882b69537e78fea5f1686c35ddd9f9
tree4b8f4d3b07482ee6355a076a4ee5d29b96e33231
parenta0a8667a54a43250f962bf778c031c50c31e9142
ext4: fix BUG_ON in mb_free_blocks()

commit c99d1e6e83b06744c75d9f5e491ed495a7086b7b upstream.

If we suffer a block allocation failure (for example due to a memory
allocation failure), it's possible that we will call
ext4_discard_allocated_blocks() before we've actually allocated any
blocks.  In that case, fe_len and fe_start in ac->ac_f_ex will still
be zero, and this will result in mb_free_blocks(inode, e4b, 0, 0)
triggering the BUG_ON on mb_free_blocks():

BUG_ON(last >= (sb->s_blocksize << 3));

Fix this by bailing out of ext4_discard_allocated_blocks() if fs_len
is zero.

Also fix a missing ext4_mb_unload_buddy() call in
ext4_discard_allocated_blocks().

Google-Bug-Id: 16844242

Fixes: 86f0afd463215fc3e58020493482faa4ac3a4d69
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
fs/ext4/mballoc.c