From: Dai Ngo <dai.ngo@oracle.com>
To: Christoph Hellwig <hch@infradead.org>,
"Darrick J. Wong" <djwong@kernel.org>
Cc: 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 08:09:29 -0700 [thread overview]
Message-ID: <e55a29a9-ed18-4e3a-8378-f712bcbc940f@oracle.com> (raw)
In-Reply-To: <ag1vwFHoYatausLK@infradead.org>
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
>
>> 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.
>
>> 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.
-Dai
next prev parent reply other threads:[~2026-05-20 15:10 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 [this message]
2026-05-20 16:48 ` Darrick J. Wong
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
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