From: Mr NeilBrown <neilb@suse.de>
Date: Tue, 21 Jul 2020 01:09:37 +0000 (+1000)
Subject: LU-12275 sec: use memchr_inv() to check if page is zero.
X-Git-Tag: 2.13.56~113
X-Git-Url: https://git.whamcloud.com/?a=commitdiff_plain;h=afee2380c105c37e440aaa9ec588cd27189bc18e;p=fs%2Flustre-release.git

LU-12275 sec: use memchr_inv() to check if page is zero.

memchr_inv() is the preferred way to check if a memory region is all
zeros.  It is likely fast that memcmp() is it doesn't need to read the
ZERO_PAGE into cache, or into the CPU.  It was introduced in Linux
3.2.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I0a5c3d30d5db43a3f5ebb270ea66b9db2b200a9a
Reviewed-on: https://review.whamcloud.com/39459
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
---

diff --git a/lustre/osc/osc_request.c b/lustre/osc/osc_request.c
index e190f74..bef2b26 100644
--- a/lustre/osc/osc_request.c
+++ b/lustre/osc/osc_request.c
@@ -2058,9 +2058,8 @@ static int osc_brw_fini_request(struct ptlrpc_request *req, int rc)
 			struct brw_page *pg = aa->aa_ppga[idx];
 
 			/* do not decrypt if page is all 0s */
-			if (memcmp(page_address(pg->pg),
-				   page_address(ZERO_PAGE(0)),
-				   PAGE_SIZE) == 0) {
+			if (memchr_inv(page_address(pg->pg), 0,
+				       PAGE_SIZE) == NULL) {
 				/* if page is empty forward info to upper layers
 				 * (ll_io_zero_page) by clearing PagePrivate2
 				 */