nfsd4: fix xdr decoding of large non-write compounds

commit 365da4adebb1c012febf81019ad3dc5bb52e2a13 upstream.

This fixes a regression from 247500820ebd02ad87525db5d9b199e5b66f6636
"nfsd4: fix decoding of compounds across page boundaries".  The previous
code was correct: argp->pagelist is initialized in
nfs4svc_deocde_compoundargs to rqstp->rq_arg.pages, and is therefore a
pointer to the page *after* the page we are currently decoding.

The reason that patch nevertheless fixed a problem with decoding
compounds containing write was a bug in the write decoding introduced by
5a80a54d21c96590d013378d8c5f65f879451ab4 "nfsd4: reorganize write
decoding", after which write decoding no longer adhered to the rule that
argp->pagelist point to the next page.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
[bwh: Backported to 3.2: adjust context; there is only one instance to fix]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 99625b8192ff01c85bae7f928c75271834c6c09b..ade5316d0cf54373c99d5f6ee21dcd0bb6f2d62a 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -177,8 +177,8 @@ static __be32 *read_buf(struct nfsd4_compoundargs *argp, u32 nbytes)
         */
        memcpy(p, argp->p, avail);
        /* step to next page */
-       argp->pagelist++;
        argp->p = page_address(argp->pagelist[0]);
+       argp->pagelist++;
        if (argp->pagelen < PAGE_SIZE) {
                argp->end = argp->p + (argp->pagelen>>2);
                argp->pagelen = 0;