From: Christoph Hellwig <hch@infradead.org>
To: Ameer Hamza <ameer.hamza@truenas.com>
Cc: cel@kernel.org, jlayton@kernel.org, neil@brown.name,
okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com,
trondmy@kernel.org, anna@kernel.org, linux-nfs@vger.kernel.org,
linux-kernel@vger.kernel.org, alexander.motin@truenas.com,
caleb.stjohn@truenas.com
Subject: Re: [PATCH 1/2] NFSD: Use nfsd_iter_read() when ->splice_read is not zero-copy
Date: Tue, 18 Aug 2026 07:42:01 -0700 [thread overview]
Message-ID: <aoRvOZTxA1kxBO9x@infradead.org> (raw)
In-Reply-To: <20260817210811.3984663-2-ameer.hamza@truenas.com>
On Tue, Aug 18, 2026 at 02:08:10AM +0500, Ameer Hamza wrote:
> For some files splicing a READ cannot avoid a copy: gfs2, kernfs
> and the cifs direct-I/O modes use copy_splice_read() as their
> ->splice_read, and the VFS substitutes it for DAX files.
> copy_splice_read() allocates a fresh page for every page of
> payload and reads into it; nfsd_splice_actor() then installs
> those pages in rq_respages, displacing Reply pages the thread
> already owns. Both sets of pages are then freed.
>
> Route these READs through nfsd_iter_read() instead. It performs
No. None of the above are sensible use cases for NFSD exports.
There is no good reason to add a barely maintained special code path
thae pokes into internals for this.
next prev parent reply other threads:[~2026-08-18 14:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-17 21:08 [PATCH 0/2] SUNRPC: Recycle sent Reply pages instead of freeing them Ameer Hamza
2026-08-17 21:08 ` [PATCH 1/2] NFSD: Use nfsd_iter_read() when ->splice_read is not zero-copy Ameer Hamza
2026-08-18 13:55 ` Chuck Lever
2026-08-18 23:12 ` Ameer Hamza
2026-08-18 14:42 ` Christoph Hellwig [this message]
2026-08-18 23:44 ` Ameer Hamza
2026-08-18 22:54 ` NeilBrown
2026-08-18 23:22 ` Ameer Hamza
2026-08-19 5:59 ` Christoph Hellwig
2026-08-17 21:08 ` [PATCH 2/2] SUNRPC: Recycle sent Reply pages instead of freeing them Ameer Hamza
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