NFS: Fix I/O request leakages

When we fail to add the request to the I/O queue, we currently leave it
to the caller to free the failed request. However since some of the
requests that fail are actually created by nfs_pageio_add_request()
itself, and are not passed back the caller, this leads to a leakage
issue, which can again cause page locks to leak.

This commit addresses the leakage by freeing the created requests on
error, using desc->pg_completion_ops->error_cleanup()

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Fixes: a7d42dd ("nfs: add mirroring support to pgio layer")
Cc: stable@vger.kernel.org # v4.0: c18b96a: nfs: clean up rest of reqs
Cc: stable@vger.kernel.org # v4.0: d600ad1: NFS41: pop some layoutget
Cc: stable@vger.kernel.org # v4.0+

fs/nfs/pagelist.c

@@ -988,6 +988,17 @@ static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
 	}
 }
 
+static void
+nfs_pageio_cleanup_request(struct nfs_pageio_descriptor *desc,
+		struct nfs_page *req)
+{
+	LIST_HEAD(head);
+
+	nfs_list_remove_request(req);
+	nfs_list_add_request(req, &head);
+	desc->pg_completion_ops->error_cleanup(&head);
+}
+
 /**
  * nfs_pageio_add_request - Attempt to coalesce a request into a page list.
  * @desc: destination io descriptor
@@ -1025,10 +1036,8 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 			nfs_page_group_unlock(req);
 			desc->pg_moreio = 1;
 			nfs_pageio_doio(desc);
-			if (desc->pg_error < 0)
-				return 0;
-			if (mirror->pg_recoalesce)
-				return 0;
+			if (desc->pg_error < 0 || mirror->pg_recoalesce)
+				goto out_cleanup_subreq;
 			/* retry add_request for this subreq */
 			nfs_page_group_lock(req);
 			continue;
@@ -1061,6 +1070,10 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 	desc->pg_error = PTR_ERR(subreq);
 	nfs_page_group_unlock(req);
 	return 0;
+out_cleanup_subreq:
+	if (req != subreq)
+		nfs_pageio_cleanup_request(desc, subreq);
+	return 0;
 }
 
 static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
@@ -1168,11 +1181,14 @@ int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 		if (nfs_pgio_has_mirroring(desc))
 			desc->pg_mirror_idx = midx;
 		if (!nfs_pageio_add_request_mirror(desc, dupreq))
-			goto out_failed;
+			goto out_cleanup_subreq;
 	}
 
 	return 1;
 
+out_cleanup_subreq:
+	if (req != dupreq)
+		nfs_pageio_cleanup_request(desc, dupreq);
 out_failed:
 	nfs_pageio_error_cleanup(desc);
 	return 0;