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

[Anders Blomdell]

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@xxxxxxxxxxxxxx>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2142132
Fixes: bfbfb6182ad1 "nfsd_splice_actor(): handle compound pages"
Cc: stable@xxxxxxxxxxxxxxx # 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;


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