linux-kernel - [PATCH 1/1] Make nfsd_splice_actor work with reads with a non-zero offset that doesn't end on a page boundary

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Date:   Wed, 23 Nov 2022 18:50:10 +0100
From:   Anders Blomdell <anders.blomdell@...trol.lth.se>
To:     Jeff Layton <jlayton@...nel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        "Al Viro" <viro@...iv.linux.org.uk>
CC:     <linux-nfs@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: [PATCH 1/1] Make nfsd_splice_actor work with reads with a non-zero
 offset that doesn't end on a page boundary

Make nfsd_splice_actor work with reads with a non-zero offset that doesn't end on a page boundary.

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).

Signed-off-by: Anders Blomdell <anders.blomdell@...trol.lth.se>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2142132
Fixes: bfbfb6182ad1 "nfsd_splice_actor(): handle compound pages"
Cc: stable@...r.kernel.org # v6.0+

--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -873,7 +873,7 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
         unsigned offset = buf->offset;
  
         page += offset / PAGE_SIZE;
-       for (int i = sd->len; i > 0; i -= PAGE_SIZE)
+       for (int i = sd->len + offset % PAGE_SIZE; i > 0; i -= PAGE_SIZE)
                 svc_rqst_replace_page(rqstp, page++);
         if (rqstp->rq_res.page_len == 0)        // first call
                 rqstp->rq_res.page_base = offset % PAGE_SIZE;


-- 
Anders Blomdell                  Email: anders.blomdell@...trol.lth.se
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118
SE-221 00 Lund, Sweden