NFSv4: pnfs_roc() must use cred_fscmp() to compare creds

When comparing two 'struct cred' for equality w.r.t. behaviour under
filesystem access, we need to use cred_fscmp().

Fixes: a52458b4 ("NFS/NFSD/SUNRPC: replace generic creds with 'struct cred'.")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/pnfs.c

@@ -1425,7 +1425,7 @@ bool pnfs_roc(struct inode *ino,
 	/* lo ref dropped in pnfs_roc_release() */
 	layoutreturn = pnfs_prepare_layoutreturn(lo, &stateid, &iomode);
 	/* If the creds don't match, we can't compound the layoutreturn */
-	if (!layoutreturn || cred != lo->plh_lc_cred)
+	if (!layoutreturn || cred_fscmp(cred, lo->plh_lc_cred) != 0)
 		goto out_noroc;
 
 	roc = layoutreturn;