linux-kernel - [RFC] block: change blk_check_merge

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Date:	Fri, 20 Nov 2015 18:55:25 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	axboe@...com, snitzer@...hat.com, tj@...nel.org, jack@...e.cz,
	shli@...com, ross.zwisler@...ux.intel.com,
	matthew.r.wilcox@...el.com, rafael.j.wysocki@...el.com,
	yalin.wang2010@...il.com, linux-kernel@...r.kernel.org
Subject: [RFC] block: change blk_check_merge_flags() implementation

Use XOR to chenk some flags in flags1 and flags2 if the same,
much faster on some platforms.

Signed-off-by: yalin wang <yalin.wang2010@...il.com>
---
 include/linux/blkdev.h | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c401ecd..3d0f053 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -655,16 +655,7 @@ static inline bool rq_mergeable(struct request *rq)
 static inline bool blk_check_merge_flags(unsigned int flags1,
 					 unsigned int flags2)
 {
-	if ((flags1 & REQ_DISCARD) != (flags2 & REQ_DISCARD))
-		return false;
-
-	if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
-		return false;
-
-	if ((flags1 & REQ_WRITE_SAME) != (flags2 & REQ_WRITE_SAME))
-		return false;
-
-	return true;
+	return !((flags1 ^ flags2) & (REQ_DISCARD | REQ_SECURE | REQ_WRITE_SAME));
 }
 
 static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
-- 
1.9.1

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