linux-ext4 - Re: [PATCH v2] ext4: truncate during setxattr leads to kernel panic

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Date:   Thu, 31 Mar 2022 11:02:51 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     linux-ext4@...r.kernel.org,
        Artem Blagodarenko <artem.blagodarenko@...il.com>
Cc:     adilger.kernel@...ger.ca,
        Andrew Perepechko <andrew.perepechko@....com>
Subject: Re: [PATCH v2] ext4: truncate during setxattr leads to kernel panic

On Fri, Mar 25, 2022 at 02:49:50PM -0400, Theodore Ts'o wrote:
> On Sat, 12 Mar 2022 18:18:30 -0500, Artem Blagodarenko wrote:
> > From: Andrew Perepechko <andrew.perepechko@....com>
> > 
> > When changing a large xattr value to a different large xattr value,
> > the old xattr inode is freed. Truncate during the final iput causes
> > current transaction restart. Eventually, parent inode bh is marked
> > dirty and kernel panic happens when jbd2 figures out that this bh
> > belongs to the committed transaction.
> > 
> > [...]
> 
> Applied, thanks!
> 
> [1/1] ext4: truncate during setxattr leads to kernel panic
>       commit: c7cded845fc192cc35a1ca37c0cd957ee35abdf8

I'm going to drop this patch from the dev branch for now, due to the
issue pointed out here[1].  The solution, as suggested in [2], is we
need to use our own subsystem workqueue.  Perhaps we can reuse
rsv_conversion_wq for that purpose (after renaming it, of course).

[1] https://lore.kernel.org/all/385ce718-f965-4005-56b6-34922c4533b8@I-love.SAKURA.ne.jp/
[2] https://lore.kernel.org/all/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp/T/#u

						- Ted