Commits
Jiufei Xue committed 742b06b5628
jbd2: check superblock mapped prior to committing
We hit a BUG at fs/buffer.c:3057 if we detached the nbd device
before unmounting ext4 filesystem.
The typical chain of events leading to the BUG:
jbd2_write_superblock
submit_bh
submit_bh_wbc
BUG_ON(!buffer_mapped(bh));
The block device is removed and all the pages are invalidated. JBD2
was trying to write journal superblock to the block device which is
no longer present.
Fix this by checking the journal superblock's buffer head prior to
submitting.
Reported-by: Eric Ren <renzhen@linux.alibaba.com>
Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org