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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Anders Blomdell <anders.blomdell@control.lth.se>
CC:     Jeff Layton <jlayton@kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH 1/1] Make nfsd_splice_actor work with reads with a
 non-zero offset that doesn't end on a page boundary
Thread-Topic: [PATCH 1/1] Make nfsd_splice_actor work with reads with a
 non-zero offset that doesn't end on a page boundary
Thread-Index: AQHY/2QsqGGpH6E0p0+3XcdGTC+ryq5MyoWA
Date:   Wed, 23 Nov 2022 17:54:37 +0000
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> On Nov 23, 2022, at 12:50 PM, Anders Blomdell <anders.blomdell@control.lt=
h.se> wrote:
>=20
> Make nfsd_splice_actor work with reads with a non-zero offset that doesn'=
t end on a page boundary.
>=20
> This was found when virtual machines with nfs-mounted qcow2 disks failed =
to boot properly (originally found
> on v6.0.5, fix also needed and tested on v6.0.9 and v6.1-rc6).
>=20
> Signed-off-by: Anders Blomdell <anders.blomdell@control.lth.se>
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=3D2142132
> Fixes: bfbfb6182ad1 "nfsd_splice_actor(): handle compound pages"
> Cc: stable@vger.kernel.org # v6.0+
>=20
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -873,7 +873,7 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struc=
t pipe_buffer *buf,
>        unsigned offset =3D buf->offset;
>         page +=3D offset / PAGE_SIZE;
> -       for (int i =3D sd->len; i > 0; i -=3D PAGE_SIZE)
> +       for (int i =3D sd->len + offset % PAGE_SIZE; i > 0; i -=3D PAGE_S=
IZE)
>                svc_rqst_replace_page(rqstp, page++);
>        if (rqstp->rq_res.page_len =3D=3D 0)        // first call
>                rqstp->rq_res.page_base =3D offset % PAGE_SIZE;

Thanks. I actually find Al's suggestion (posted in the other thread)
preferable. Can you test that and repost? I will then apply the fix
immediately to nfsd's for-rc tree.


--
Chuck Lever