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Subject[PATCH v2 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@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+

-- 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

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