Message-ID: <c40c8cb067f0d33d0eb5cb70c236ec5402535990.camel@kernel.org>
Subject: Re: [PATCH 1/2] nfsd: don't replace page in rq_pages if it's a
 continuation of last page
From:   Jeff Layton <jlayton@kernel.org>
To:     Chuck Lever III <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        "dcritch@redhat.com" <dcritch@redhat.com>,
        "d.lesca@solinos.it" <d.lesca@solinos.it>
Date:   Fri, 17 Mar 2023 13:23:55 -0400
In-Reply-To: <9EAA4947-0139-481D-8D0A-6DF30444342D@oracle.com>
References: <20230317105608.19393-1-jlayton@kernel.org>
         <c57b48f500b859a3daf6f95ccefdfbec72e1c9de.camel@kernel.org>
         <65C84563-6BCD-41CE-AF68-80E1869D217F@oracle.com>
         <c1d4fbaf83c6e1e41e31f77d58d889adaecb6d35.camel@kernel.org>
         <9EAA4947-0139-481D-8D0A-6DF30444342D@oracle.com>
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On Fri, 2023-03-17 at 15:04 +0000, Chuck Lever III wrote:
>=20
> > On Mar 17, 2023, at 10:59 AM, Jeff Layton <jlayton@kernel.org> wrote:
> >=20
> > On Fri, 2023-03-17 at 14:16 +0000, Chuck Lever III wrote:
> >=20
> > > In the patch description, would you mention that this case
> > > arises if the READ request is not page-aligned?
> >=20
> > Does it though? I'm not sure that page alignment has that much to do
> > with it. I imagine you can hit this even with aligned I/Os.
>=20
> Maybe, but no-one has actually seen that. The vast majority of
> reports of this problem are with unaligned I/O, which POSIX OS
> NFS clients (like the Linux NFS client) usually avoid.
>=20
> I didn't mean to exclude the possibility of hitting this issue
> in other ways, but simply observing a common way it is hit.
>=20

An unaligned read will consume an extra page, so maybe it just makes it
more likely to overrun the array in that case?
--=20
Jeff Layton <jlayton@kernel.org>