1 files changed, 43 insertions, 3 deletions

diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c
index 1566163c6d85..7359e1a3bd84 100644
--- a/fs/nfs/nfs3proc.c
+++ b/fs/nfs/nfs3proc.c
@@ -844,6 +844,41 @@ nfs3_proc_pathconf(struct nfs_server *server, struct nfs_fh *fhandle,
 	return status;
 }
 
+#if IS_ENABLED(CONFIG_NFS_LOCALIO)
+
+static unsigned nfs3_localio_probe_throttle __read_mostly = 0;
+module_param(nfs3_localio_probe_throttle, uint, 0644);
+MODULE_PARM_DESC(nfs3_localio_probe_throttle,
+		 "Probe for NFSv3 LOCALIO every N IO requests. Must be power-of-2, defaults to 0 (probing disabled).");
+
+static void nfs3_localio_probe(struct nfs_server *server)
+{
+	struct nfs_client *clp = server->nfs_client;
+
+	/* Throttled to reduce nfs_local_probe_async() frequency */
+	if (!nfs3_localio_probe_throttle || nfs_server_is_local(clp))
+		return;
+
+	/*
+	 * Try (re)enabling LOCALIO if isn't enabled -- admin deems
+	 * it worthwhile to periodically check if LOCALIO possible by
+	 * setting the 'nfs3_localio_probe_throttle' module parameter.
+	 *
+	 * This is useful if LOCALIO was previously enabled, but was
+	 * disabled due to server restart, and IO has successfully
+	 * completed in terms of normal RPC.
+	 */
+	if ((clp->cl_uuid.nfs3_localio_probe_count++ &
+	     (nfs3_localio_probe_throttle - 1)) == 0) {
+		if (!nfs_server_is_local(clp))
+			nfs_local_probe_async(clp);
+	}
+}
+
+#else
+static void nfs3_localio_probe(struct nfs_server *server) {}
+#endif
+
 static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 {
 	struct inode *inode = hdr->inode;
@@ -855,8 +890,11 @@ static int nfs3_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 	if (nfs3_async_handle_jukebox(task, inode))
 		return -EAGAIN;
 
-	if (task->tk_status >= 0 && !server->read_hdrsize)
-		cmpxchg(&server->read_hdrsize, 0, hdr->res.replen);
+	if (task->tk_status >= 0) {
+		if (!server->read_hdrsize)
+			cmpxchg(&server->read_hdrsize, 0, hdr->res.replen);
+		nfs3_localio_probe(server);
+	}
 
 	nfs_invalidate_atime(inode);
 	nfs_refresh_inode(inode, &hdr->fattr);
@@ -886,8 +924,10 @@ static int nfs3_write_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 
 	if (nfs3_async_handle_jukebox(task, inode))
 		return -EAGAIN;
-	if (task->tk_status >= 0)
+	if (task->tk_status >= 0) {
 		nfs_writeback_update_inode(hdr);
+		nfs3_localio_probe(NFS_SERVER(inode));
+	}
 	return 0;
 }