linux-kernel - [PATCH] block:Remove extra condition in end of disk check

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Message-Id: <20130623171711.7127.16248.sendpatchset@codeblue.in.ibm.com>
Date:	Sun, 23 Jun 2013 22:47:11 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Jens Axboe <axboe@...nel.dk>, LKML <linux-kernel@...r.kernel.org>
Cc:	<raghavendra.kt@...ux.vnet.ibm.com>
Subject: [PATCH] block:Remove extra condition in end of disk check

From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>

Since #sector is always positive the reduced condition check
encompasses maxsector < nr_sectors check.

Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
An userspace program looping with:
maxsector - 0-9999
nr_sector - 0-999
sector - 0-999 gave 6.4% improvement with new condition though I agree that
it is not the best way to test it perhaps :)

diff --git a/block/blk-core.c b/block/blk-core.c
index 33c33bc..4a78583 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1656,7 +1656,7 @@ static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
 	if (maxsector) {
 		sector_t sector = bio->bi_sector;
 
-		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
+		if (maxsector - nr_sectors < sector) {
 			/*
 			 * This may well happen - the kernel calls bread()
 			 * without checking the size of the device, e.g., when

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