linux-kernel - [patch]blk: use correct sectors limitation for discard request

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Date:	Fri, 16 Mar 2012 15:40:06 +0800
From:	Shaohua Li <shli@...nel.org>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"axboe@...nel.dk" <axboe@...nel.dk>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: [patch]blk: use correct sectors limitation for discard request


Subject: blk: use correct sectors limitation for discard request

max_discard_sectors doesn't equal to max_sectors/max_hw_sectors. Without 
this,
discard request merge might be ignored.

Signed-off-by: Shaohua Li <shli@...ionio.com>
---
  block/blk-merge.c      |   13 ++++++++-----
  include/linux/blkdev.h |    5 +++++
  2 files changed, 13 insertions(+), 5 deletions(-)

Index: linux/block/blk-merge.c
===================================================================
--- linux.orig/block/blk-merge.c	2012-03-14 09:53:15.574255985 +0800
+++ linux/block/blk-merge.c	2012-03-14 11:06:01.504462095 +0800
@@ -228,9 +228,11 @@ no_merge:
  int ll_back_merge_fn(struct request_queue *q, struct request *req,
  		     struct bio *bio)
  {
-	unsigned short max_sectors;
+	unsigned int max_sectors;

-	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
+	if (unlikely(req->cmd_flags & REQ_DISCARD))
+		max_sectors = queue_max_discard_sectors(q);
+	else if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
  		max_sectors = queue_max_hw_sectors(q);
  	else
  		max_sectors = queue_max_sectors(q);
@@ -252,14 +254,15 @@ int ll_back_merge_fn(struct request_queu
  int ll_front_merge_fn(struct request_queue *q, struct request *req,
  		      struct bio *bio)
  {
-	unsigned short max_sectors;
+	unsigned int max_sectors;

-	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
+	if (unlikely(req->cmd_flags & REQ_DISCARD))
+		max_sectors = queue_max_discard_sectors(q);
+	else if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
  		max_sectors = queue_max_hw_sectors(q);
  	else
  		max_sectors = queue_max_sectors(q);

-
  	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
  		req->cmd_flags |= REQ_NOMERGE;
  		if (req == q->last_merge)
Index: linux/include/linux/blkdev.h
===================================================================
--- linux.orig/include/linux/blkdev.h	2012-03-14 10:17:19.523960440 +0800
+++ linux/include/linux/blkdev.h	2012-03-14 10:57:22.324465357 +0800
@@ -1006,6 +1006,11 @@ static inline unsigned int queue_max_hw_
  	return q->limits.max_hw_sectors;
  }

+static inline unsigned int queue_max_discard_sectors(struct 
request_queue *q)
+{
+	return q->limits.max_discard_sectors;
+}
+
  static inline unsigned short queue_max_segments(struct request_queue *q)
  {
  	return q->limits.max_segments;
--
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