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Subject[PATCH] block: Remove should_sort judgement when flush blk_plug.
In commit 975927b942c932,it add blk_rq_pos to sort rq when flushing.
Although this commit was used for the situation which blk_plug handled
multi devices on the same time like md device.
I think there must be some situations like this but only single
device.
So remove the should_sort judgement.
Because the parameter should_sort is only for this purpose,it can delete
should_sort from blk_plug.

CC: Shaohua Li <shli@kernel.org>
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
block/blk-core.c | 13 +------------
include/linux/blkdev.h | 1 -
2 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index c973249..aca5d82 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1548,13 +1548,6 @@ get_rq:
if (list_empty(&plug->list))
trace_block_plug(q);
else {
- if (!plug->should_sort) {
- struct request *__rq;
-
- __rq = list_entry_rq(plug->list.prev);
- if (__rq->q != q)
- plug->should_sort = 1;
- }
if (request_count >= BLK_MAX_REQUEST_COUNT) {
blk_flush_plug_list(plug, false);
trace_block_plug(q);
@@ -2888,7 +2881,6 @@ void blk_start_plug(struct blk_plug *plug)
plug->magic = PLUG_MAGIC;
INIT_LIST_HEAD(&plug->list);
INIT_LIST_HEAD(&plug->cb_list);
- plug->should_sort = 0;

/*
* If this is a nested plug, don't actually assign it. It will be
@@ -2990,10 +2982,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)

list_splice_init(&plug->list, &list);

- if (plug->should_sort) {
- list_sort(NULL, &list, plug_rq_cmp);
- plug->should_sort = 0;
- }
+ list_sort(NULL, &list, plug_rq_cmp);

q = NULL;
depth = 0;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f94bc83..dbe7427 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -974,7 +974,6 @@ struct blk_plug {
unsigned long magic; /* detect uninitialized use-cases */
struct list_head list; /* requests */
struct list_head cb_list; /* md requires an unplug callback */
- unsigned int should_sort; /* list to be sorted before flushing? */
};
#define BLK_MAX_REQUEST_COUNT 16

--
1.7.9.5
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