From: David Zafman <david.zafman@inktank.com>
Date: Mon, 5 Nov 2012 19:26:56 +0000 (-0800)
Subject: Improve performance of __writeback_single_inode() for nfs server
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=cb9e39d1f783b107477145880193a8004089db51;p=ceph-client.git

Improve performance of __writeback_single_inode() for nfs server

Don't need to call filemap_fdatawait() if do_writepages() didn't do anything

This fixes http://tracker.newdream.net/issues/3430

Signed-off-by: David Zafman <david.zafman@inktank.com>
---

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index be3efc4f64f4..a53079879799 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -455,7 +455,7 @@ __writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 	 * This is important for filesystems that modify metadata on data
 	 * I/O completion.
 	 */
-	if (wbc->sync_mode == WB_SYNC_ALL) {
+	if (wbc->sync_mode == WB_SYNC_ALL && nr_to_write > 0) {
 		int err = filemap_fdatawait(mapping);
 		if (ret == 0)
 			ret = err;