From: Li Dongyang <dongyangli@ddn.com>
Date: Fri, 14 Dec 2018 01:36:22 +0000 (+1100)
Subject: LU-11775 osc: check if opg is in lru list without locking
X-Git-Tag: 2.12.52~28
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=b3af0798682b24d0f39424a7db12c9710a0e64b4

LU-11775 osc: check if opg is in lru list without locking

osc_lru_use is called for every page queued for io,
we can just check if the osc_page is in the lru list
without taking the cl_lru_list_lock and return if not
as a fast path.
Note we still need to do the check again after locking
as it could be removed from the lru list by another thread.

Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: I1587b6b5547ae5a7a8bfe32a78361bb888c85d5b
Reviewed-on: https://review.whamcloud.com/33860
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lustre/osc/osc_page.c b/lustre/osc/osc_page.c
index ff64374..cd4107b 100644
--- a/lustre/osc/osc_page.c
+++ b/lustre/osc/osc_page.c
@@ -516,6 +516,8 @@ static void osc_lru_use(struct client_obd *cli, struct osc_page *opg)
 	/* If page is being transferred for the first time,
 	 * ops_lru should be empty */
 	if (opg->ops_in_lru) {
+		if (list_empty(&opg->ops_lru))
+			return;
 		spin_lock(&cli->cl_lru_list_lock);
 		if (!list_empty(&opg->ops_lru)) {
 			__osc_lru_del(cli, opg);