ext4: fix unjournaled inode bitmap modification
authorEric Sandeen <sandeen@redhat.com>
Mon, 29 Oct 2012 02:24:57 +0000 (22:24 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 5 Nov 2012 08:50:41 +0000 (09:50 +0100)
commit0d819068496793d2f8ef48a6fcec4c7d329d8b8a
tree4c99864fbba503190f68fc918ab1d7efc7422de9
parent5390967b2f98e6aa46f20eae09580e7db73826b9
ext4: fix unjournaled inode bitmap modification

commit ffb5387e85d528fb6d0d924abfa3fbf0fc484071 upstream.

commit 119c0d4460b001e44b41dcf73dc6ee794b98bd31 changed
ext4_new_inode() such that the inode bitmap was being modified
outside a transaction, which could lead to corruption, and was
discovered when journal_checksum found a bad checksum in the
journal during log replay.

Nix ran into this when using the journal_async_commit mount
option, which enables journal checksumming.  The ensuing
journal replay failures due to the bad checksums led to
filesystem corruption reported as the now infamous
"Apparent serious progressive ext4 data corruption bug"

[ Changed by tytso to only call ext4_journal_get_write_access() only
  when we're fairly certain that we're going to allocate the inode. ]

I've tested this by mounting with journal_checksum and
running fsstress then dropping power; I've also tested by
hacking DM to create snapshots w/o first quiescing, which
allows me to test journal replay repeatedly w/o actually
power-cycling the box.  Without the patch I hit a journal
checksum error every time.  With this fix it survives
many iterations.

Reported-by: Nix <nix@esperi.org.uk>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/ialloc.c