linux-kernel - [PATCH] staging/lustre: avoid zero buf for the first time

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Date:   Mon, 22 Aug 2016 16:46:04 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Oleg Drokin <oleg.drokin@...el.com>,
        Andreas Dilger <andreas.dilger@...el.com>,
        lustre-devel@...ts.lustre.org, devel@...verdev.osuosl.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Shawn Lin <shawn.lin@...k-chips.com>
Subject: [PATCH] staging/lustre: avoid zero buf for the first time

We only need to zero it when repeating in order to
avoid old garbage. Let's improve it by moving this
before we repeat the calculation to save some cpu
cycle.

Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
---

 drivers/staging/lustre/lustre/obdclass/llog.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/lustre/lustre/obdclass/llog.c b/drivers/staging/lustre/lustre/obdclass/llog.c
index 1784ca0..923061f 100644
--- a/drivers/staging/lustre/lustre/obdclass/llog.c
+++ b/drivers/staging/lustre/lustre/obdclass/llog.c
@@ -248,8 +248,6 @@ repeat:
 		CDEBUG(D_OTHER, "index: %d last_index %d\n",
 		       index, last_index);
 
-		/* get the buf with our target record; avoid old garbage */
-		memset(buf, 0, LLOG_CHUNK_SIZE);
 		last_offset = cur_offset;
 		rc = llog_next_block(lpi->lpi_env, loghandle, &saved_index,
 				     index, &cur_offset, buf, LLOG_CHUNK_SIZE);
@@ -275,8 +273,11 @@ repeat:
 			if (rec->lrh_index == 0) {
 				/* probably another rec just got added? */
 				rc = 0;
-				if (index <= loghandle->lgh_last_idx)
+				if (index <= loghandle->lgh_last_idx) {
+					/* avoid old garbage */
+					memset(buf, 0, LLOG_CHUNK_SIZE);
 					goto repeat;
+				}
 				goto out; /* no more records */
 			}
 			if (rec->lrh_len == 0 ||
-- 
2.3.7