NFSv4/pnfs: Fix a page lock leak in nfs_pageio_resend()

If the attempt to resend the pages fails, we need to ensure that we
clean up those pages that were not transmitted.

Fixes: d600ad1f ("NFS41: pop some layoutget errors to application")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Cc: stable@vger.kernel.org # v4.5+

fs/nfs/pagelist.c

@@ -1251,20 +1251,22 @@ static void nfs_pageio_complete_mirror(struct nfs_pageio_descriptor *desc,
 int nfs_pageio_resend(struct nfs_pageio_descriptor *desc,
 		      struct nfs_pgio_header *hdr)
 {
-	LIST_HEAD(failed);
+	LIST_HEAD(pages);
 
 	desc->pg_io_completion = hdr->io_completion;
 	desc->pg_dreq = hdr->dreq;
-	while (!list_empty(&hdr->pages)) {
-		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
+	list_splice_init(&hdr->pages, &pages);
+	while (!list_empty(&pages)) {
+		struct nfs_page *req = nfs_list_entry(pages.next);
 
 		if (!nfs_pageio_add_request(desc, req))
-			nfs_list_move_request(req, &failed);
+			break;
 	}
 	nfs_pageio_complete(desc);
-	if (!list_empty(&failed)) {
-		list_move(&failed, &hdr->pages);
-		return desc->pg_error < 0 ? desc->pg_error : -EIO;
+	if (!list_empty(&pages)) {
+		int err = desc->pg_error < 0 ? desc->pg_error : -EIO;
+		hdr->completion_ops->error_cleanup(&pages, err);
+		return err;
 	}
 	return 0;
 }