From: sashiko-bot@kernel.org
To: "Christian Göttsche" <cgoettsche@seltendoof.de>
Cc: tytso@mit.edu, linux-ext4@vger.kernel.org
Subject: Re: [PATCH] jbd2: set JBD2_LOADED under j_state_lock
Date: Mon, 28 Sep 2026 20:29:33 +0000 [thread overview]
Message-ID: <20260928202934.1B3831F000FF@smtp.kernel.org> (raw)
In-Reply-To: <20260928202159.2463182-1-cgoettsche@seltendoof.de>
> From: Christian Göttsche <cgzones@googlemail.com>
>
> j_flags is protected by j_state_lock, with only quick racy checks done
> without it. jbd2_journal_load() however sets JBD2_LOADED with a plain
> read-modify-write after journal_reset() has already started kjournald2,
> which tests and may update j_flags under the lock. KCSAN reports this
> while mounting the root file system:
>
> BUG: KCSAN: data-race in jbd2_journal_load / kjournald2
>
> write to 0xffff9c6b012c6000 of 8 bytes by task 1 on cpu 3:
> jbd2_journal_load+0x279/0x3c0
> ext4_fill_super+0x34dc/0x5740
> get_tree_bdev_flags+0x21d/0x340
> ...
> read to 0xffff9c6b012c6000 of 8 bytes by task 77 on cpu 0:
> kjournald2+0xc8/0x3e0
> kthread+0x1bd/0x200
> ...
>
> value changed: 0x00000000000000a8 -> 0x00000000000000b8
>
> A concurrent update of another flag, e.g. JBD2_ABORT, could be lost.
> Take j_state_lock when setting JBD2_LOADED, like the other writers of
> j_flags do.
>
> Fixes: 470decc613ab ("[PATCH] jbd2: initial copy of files from jbd")
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260928202159.2463182-1-cgoettsche@seltendoof.de?part=1
next prev parent reply other threads:[~2026-09-28 20:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-28 20:21 [PATCH] jbd2: set JBD2_LOADED under j_state_lock Christian Göttsche
2026-09-28 20:29 ` sashiko-bot [this message]
2026-09-30 11:34 ` Jan Kara
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