From: "Theodore Ts'o" <tytso@mit.edu>
To: Nix <nix@esperi.org.uk>
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
"J. Bruce Fields" <bfields@fieldses.org>,
"Bryan Schumaker" <bjschuma@netapp.com>,
"Peng Tao" <bergwolf@gmail.com>,
Trond.Myklebust@netapp.com, gregkh@linuxfoundation.org,
"Toralf Förster" <toralf.foerster@gmx.de>,
"Eric Sandeen" <sandeen@redhat.com>,
stable@vger.kernel.org, "Jan Kara" <jack@suse.cz>
Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)
Date: Tue, 23 Oct 2012 19:16:07 -0400 [thread overview]
Message-ID: <20121023231607.GE28626@thunk.org> (raw)
In-Reply-To: <87k3ugn6v4.fsf@spindle.srvr.nix>
Just to follow up (mostly for ext4 developers). After talking to Eric
via irc, it appears he thought it was sufficient to check (s_start ==
0) from commit 24bcc89c7e, which was authored by Jan Kara. (Which we
now need to audit very carefully, although it's been in the upstream
kernel since 3.4, so it's obviously not causing failures as
spectacularly or as easily as eeecef0af5e.)
And I suspect the reason why Jan thought this was OK is because of the
following totally bogus comment at fs/jbd2/recovery.c:259:
/*
* The journal superblock's s_start field (the current log head)
* is always zero if, and only if, the journal was cleanly
* unmounted.
*/
After doing some code archeology, I've found that this comment dates
back to the very first commit in the historic git tree when the fs/jbd
code was added to the 2.4.14 tree. I suspect that s_start was
originally a physical block number (in the very early days when sct
was initially developing ext3, before it was submitted to the kernel),
but then when Stephen added the ability to store the journal in an
inode, it became a logical block number, and this comment became
incorrect, but no one noticed and/or decided to fix the comment in the
last ten years. :-(
So now we know the root cause of the thought processes that lead to
the bug, and now we need to double check the changes in commits
24bcc89c7e for jbd2, and 9754e39c7b for jbd (a similar change was also
added to ext3 in v3.5).
- Ted
next prev parent reply other threads:[~2012-10-23 23:16 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-22 16:17 Heads-up: 3.6.2 / 3.6.3 NFS server panic: 3.6.2+ regression? Nix
2012-10-23 1:33 ` J. Bruce Fields
2012-10-23 14:07 ` Nix
2012-10-23 14:30 ` J. Bruce Fields
2012-10-23 16:32 ` Heads-up: 3.6.2 / 3.6.3 NFS server oops: 3.6.2+ regression? (also an unrelated ext4 data loss bug) Nix
2012-10-23 16:46 ` J. Bruce Fields
2012-10-23 16:54 ` J. Bruce Fields
2012-10-23 16:56 ` Myklebust, Trond
2012-10-23 17:05 ` Nix
2012-10-23 17:36 ` Nix
2012-10-23 17:43 ` J. Bruce Fields
2012-10-23 17:44 ` Myklebust, Trond
2012-10-23 17:57 ` Myklebust, Trond
[not found] ` <1351015039.4622.23.camel@lade.trondhjem.org>
2012-10-23 18:23 ` Myklebust, Trond
2012-10-23 19:49 ` Nix
2012-10-24 10:18 ` [PATCH] lockd: fix races in per-net NSM client handling Stanislav Kinsbursky
2012-10-23 20:57 ` Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?) Nix
2012-10-23 22:19 ` Theodore Ts'o
2012-10-23 22:47 ` Nix
2012-10-23 23:16 ` Theodore Ts'o [this message]
2012-10-23 23:06 ` Nix
2012-10-23 23:28 ` Theodore Ts'o
2012-10-23 23:34 ` Nix
2012-10-24 0:57 ` Eric Sandeen
2012-10-24 20:17 ` Jan Kara
2012-10-26 15:25 ` Eric Sandeen
2012-10-24 19:13 ` Jannis Achstetter
2012-10-24 21:31 ` Theodore Ts'o
2012-10-24 22:05 ` Jannis Achstetter
2012-10-24 23:47 ` Nix
2012-10-25 17:02 ` Felipe Contreras
2012-10-24 21:04 ` Jannis Achstetter
2012-10-24 1:13 ` Eric Sandeen
2012-10-24 4:15 ` Nix
2012-10-24 4:27 ` Eric Sandeen
2012-10-24 5:23 ` Theodore Ts'o
2012-10-24 7:00 ` Hugh Dickins
2012-10-24 11:46 ` Nix
2012-10-24 11:45 ` Nix
2012-10-24 17:22 ` Eric Sandeen
2012-10-24 19:49 ` Nix
2012-10-24 19:54 ` Nix
2012-10-24 20:30 ` Eric Sandeen
2012-10-24 20:34 ` Nix
2012-10-24 20:45 ` Nix
2012-10-24 21:08 ` Theodore Ts'o
2012-10-24 23:27 ` Apparent serious progressive ext4 data corruption bug in 3.6 (when rebooting during umount) Nix
2012-10-24 23:42 ` Nix
2012-10-25 1:10 ` Theodore Ts'o
2012-10-25 1:45 ` Nix
2012-10-25 14:12 ` Theodore Ts'o
2012-10-25 14:15 ` Nix
2012-10-25 17:39 ` Nix
2012-10-25 11:06 ` Nix
2012-10-26 0:22 ` Apparent serious progressive ext4 data corruption bug in 3.6 (when rebooting during umount) (possibly blockdev / arcmsr at fault??) Nix
2012-10-26 0:11 ` Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?) Ric Wheeler
2012-10-26 0:43 ` Theodore Ts'o
2012-10-26 12:12 ` Nix
2012-10-26 20:35 ` Eric Sandeen
2012-10-26 20:37 ` Nix
2012-10-26 20:56 ` Theodore Ts'o
2012-10-26 20:59 ` Nix
2012-10-26 21:15 ` Theodore Ts'o
2012-10-26 21:19 ` Nix
2012-10-27 0:22 ` Theodore Ts'o
2012-10-27 12:45 ` Nix
2012-10-27 17:55 ` Theodore Ts'o
2012-10-27 18:47 ` Nix
2012-10-27 21:19 ` Eric Sandeen
2012-10-27 22:42 ` Eric Sandeen
2012-10-29 1:00 ` Theodore Ts'o
2012-10-29 1:04 ` Nix
2012-10-29 2:24 ` Eric Sandeen
2012-10-29 2:34 ` Theodore Ts'o
2012-10-29 2:35 ` Eric Sandeen
2012-10-29 2:42 ` Theodore Ts'o
2012-10-27 18:30 ` Eric Sandeen
2012-10-27 3:11 ` Jim Rees
2012-10-28 4:23 ` [PATCH] ext4: fix unjournaled inode bitmap modification Eric Sandeen
2012-10-28 13:59 ` Nix
2012-10-29 2:30 ` [PATCH -v3] " Theodore Ts'o
2012-10-29 3:24 ` Eric Sandeen
2012-10-29 17:08 ` Darrick J. Wong
[not found] <jXsTo-5lW-13@gated-at.bofh.it>
[not found] ` <jXBDk-7vn-13@gated-at.bofh.it>
[not found] ` <jXNl8-5m5-13@gated-at.bofh.it>
[not found] ` <jXNOa-5MR-23@gated-at.bofh.it>
[not found] ` <jXPGh-87s-5@gated-at.bofh.it>
[not found] ` <jXTJW-4CH-55@gated-at.bofh.it>
[not found] ` <jXUZj-6mo-13@gated-at.bofh.it>
[not found] ` <jXVLH-7kO-5@gated-at.bofh.it>
[not found] ` <jXW53-7CC-5@gated-at.bofh.it>
[not found] ` <jXWeJ-7Lk-1@gated-at.bofh.it>
2012-10-24 17:38 ` Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?) Martin
2012-10-26 20:13 ` Martin
2012-10-26 20:24 ` Nix
2012-10-26 20:44 ` Martin
2012-10-26 20:47 ` Nix
2012-10-26 21:10 ` Theodore Ts'o
2012-10-26 23:15 ` Martin
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