commit c99d1e6e83 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: 86f0afd463
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ccdbe7da07