On Nov 23, 2022, at 2:00 PM, Anders Blomdell anders.blomdell@control.lth.se wrote:

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@control.lth.se Link: https://bugzilla.redhat.com/show_bug.cgi?id=2142132 Fixes: bfbfb6182ad1 "nfsd_splice_actor(): handle compound pages" Cc: stable@vger.kernel.org # v6.0+

"b4 am" and other tooling failed to recognize the diff content in this email, so I've applied Al's version to nfsd's for-rc, after running some regression tests. See:

https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git/log/?h=for-rc

I will see that a pull request is sent to Linus before 6.1-rc7.

Thanks for reporting and chasing this down.

-- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -869,12 +869,13 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf, struct splice_desc *sd) { struct svc_rqst *rqstp = sd->u.data;

• struct page *page = buf->page; // may be a compound one

• // buf->page may be a compound one unsigned offset = buf->offset;
• struct page *first = buf->page + offset / PAGE_SIZE;
• struct page *last = buf->page + (offset + sd->len - 1) / PAGE_SIZE;

• page += offset / PAGE_SIZE;
• for (int i = sd->len; i > 0; i -= PAGE_SIZE)

• svc_rqst_replace_page(rqstp, page++);
  

• for (struct page *page = first; page <= last; page++)

• svc_rqst_replace_page(rqstp, page);
  

  if (rqstp->rq_res.page_len == 0) // first call rqstp->rq_res.page_base = offset % PAGE_SIZE; rqstp->rq_res.page_len += sd->len;

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

-- Chuck Lever