From: "Darrick J. Wong" <djwong@kernel.org>
To: Dai Ngo <dai.ngo@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Dave Chinner <dgc@kernel.org>,
cem@kernel.org, linux-xfs@vger.kernel.org,
linux-nfs@vger.kernel.org,
Sergey Bashirov <sergeybashirov@gmail.com>
Subject: Re: [PATCH 1/1] xfs: fix overlapping extents returned for pNFS LAYOUTGET
Date: Wed, 20 May 2026 09:48:56 -0700 [thread overview]
Message-ID: <20260520164856.GI9555@frogsfrogsfrogs> (raw)
In-Reply-To: <e55a29a9-ed18-4e3a-8378-f712bcbc940f@oracle.com>
On Wed, May 20, 2026 at 08:09:29AM -0700, Dai Ngo wrote:
>
> On 5/20/26 1:24 AM, Christoph Hellwig wrote:
> > [adding Sergey, who wrote the code to allow multiple mappings]
> >
> > On Tue, May 19, 2026 at 07:59:49AM -0700, Darrick J. Wong wrote:
> > > 1) xfs_fs_map_blocks only takes i_rwsem and XFS_ILOCK; it doesn't take
> > > the mmap invalidation lock. Does that mean that pagefaults could wander
> > > in and mess with the layout?
> > Looks like it.
>
> I already described the scenario in which the file mapping can change
> between successive calls from nfsd—triggered by a single LAYOUTGET
> request—to xfs_fs_map_blocks().
>
> I also don't see how page faults are relevant in the context of pNFS
> layouts. The server is not servicing actual data accesses through page
> faults when constructing a LAYOUTGET response
Some other process on the nfs server mmaps the file and generates
faults.
> >
> > > 2) Now that NFS apparently can serve up multiple mappings at once,
> > > should ->map_blocks pass in an array element count so that we can do
> > > multiple iomaps in a single lock cycle?
> > I guess we need to do that, or revert the code to provide multiple maps
> > for now.
>
> I think we should address the immediate problem first by replacing XFS_BMAPI_ENTIRE
> with 0, and handle support for returning multiple map entries from a single
> call to xfs_fs_map_blocks() in follow-up patches. That work is more involved,
> as it requires coordinated changes in both the nfsd and XFS code.
Agreed.
> >
> > > 3) Do the reflink and realtime inode checks need to be re-assessed after
> > > grabbing the ilock since they can change?
> > Yes.
>
> I can move the check for reflink and realtime inode inside the ilock in v2
> of this patch series.
Yeah, that probably needs to be made too. :)
--D
> -Dai
>
>
next prev parent reply other threads:[~2026-05-20 16:48 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 17:21 [PATCH 1/1] xfs: fix overlapping extents returned for pNFS LAYOUTGET Dai Ngo
2026-05-12 17:34 ` Darrick J. Wong
2026-05-12 19:21 ` Dai Ngo
2026-05-13 7:01 ` Christoph Hellwig
2026-05-13 15:50 ` Dai Ngo
2026-05-13 17:28 ` Dai Ngo
2026-05-14 0:25 ` Darrick J. Wong
2026-05-14 17:19 ` Dai Ngo
2026-05-14 17:49 ` Darrick J. Wong
2026-05-15 21:39 ` Dave Chinner
2026-05-16 2:14 ` Dai Ngo
2026-05-18 5:09 ` Christoph Hellwig
2026-05-18 19:55 ` Dai Ngo
2026-05-19 6:30 ` Christoph Hellwig
2026-05-19 13:44 ` Dai Ngo
2026-05-19 14:59 ` Darrick J. Wong
2026-05-19 17:34 ` Dai Ngo
2026-05-20 8:24 ` Christoph Hellwig
2026-05-20 15:09 ` Dai Ngo
2026-05-20 16:48 ` Darrick J. Wong [this message]
2026-05-20 17:32 ` Dai Ngo
2026-05-20 22:08 ` Sergey Bashirov
2026-05-15 11:50 ` Christoph Hellwig
2026-05-15 11:49 ` Christoph Hellwig
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=20260520164856.GI9555@frogsfrogsfrogs \
--to=djwong@kernel.org \
--cc=cem@kernel.org \
--cc=dai.ngo@oracle.com \
--cc=dgc@kernel.org \
--cc=hch@infradead.org \
--cc=linux-nfs@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
--cc=sergeybashirov@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;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).