From: Christoph Hellwig <hch@infradead.org>
To: Cen Zhang <zzzccc427@gmail.com>
Cc: cem@kernel.org, linux-xfs@vger.kernel.org,
linux-kernel@vger.kernel.org, baijiaju1990@gmail.com,
stable@vger.kernel.org
Subject: Re: [PATCH] xfs: annotate data race on li_lsn in CIL formatting vs AIL insertion
Date: Sun, 22 Mar 2026 23:14:27 -0700 [thread overview]
Message-ID: <acDaQ6DQ7ehMji4r@infradead.org> (raw)
In-Reply-To: <20260320025507.3331221-1-zzzccc427@gmail.com>
On Fri, Mar 20, 2026 at 10:55:07AM +0800, Cen Zhang wrote:
> Under simple interleaving on 64-bit architectures this is benign since
> li_lsn monotonically increases and both old/new values are valid
> checkpoint LSNs. However, on 32-bit architectures the 64-bit xfs_lsn_t
> can be torn into two 32-bit loads, producing a bogus LSN that could
> cause log recovery to make incorrect replay decisions. XFS already
> acknowledges this concern via the xfs_trans_ail_copy_lsn() helper which
> takes ail_lock on 32-bit.
Yes.
> Annotate with READ_ONCE()/WRITE_ONCE() to prevent compiler-level
> tearing on all architectures.
Well, xfs_trans_ail_copy_lsn pretty clearly documents that we actually
need a locak for the 32-bit case. Assuming we don't have lock ordering
issues, using xfs_trans_ail_copy_lsn would be the right thing here.
> - xfs_inode_to_log_dinode(ip, dic, ip->i_itemp->ili_item.li_lsn);
> + xfs_inode_to_log_dinode(ip, dic, READ_ONCE(ip->i_itemp->ili_item.li_lsn));
.. and either way please avoid the overly long lines.
next prev parent reply other threads:[~2026-03-23 6:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 2:55 [PATCH] xfs: annotate data race on li_lsn in CIL formatting vs AIL insertion Cen Zhang
2026-03-23 6:14 ` Christoph Hellwig [this message]
2026-03-23 7:28 ` Cen Zhang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=acDaQ6DQ7ehMji4r@infradead.org \
--to=hch@infradead.org \
--cc=baijiaju1990@gmail.com \
--cc=cem@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=zzzccc427@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox