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block: trace all devices plug operation 

In func blk_queue_bio, if list of plug is empty,it will call
blk_trace_plug.
If process deal with a single device,it't ok.But if process deal with
multi devices,it only trace the first device.
Using request_count to judge, it can soleve this problem.

In addition, i modify the comment.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jianpeng Ma 2013-09-11 13:21:07 -06:00 committed by Jens Axboe
parent 6e4664525b
commit 7aef2e780b
1 changed files with 2 additions and 4 deletions
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6
block/blk-core.c
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@ -1549,11 +1549,9 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio)
if (plug) { if (plug) {
/* /*
* If this is the first request added after a plug, fire * If this is the first request added after a plug, fire
* of a plug trace. If others have been added before, check * of a plug trace.
* if we have multiple devices in this plug. If so, make a
* note to sort the list before dispatch.
*/ */
if (list_empty(&plug->list)) if (!request_count)
trace_block_plug(q); trace_block_plug(q);
else { else {
if (request_count >= BLK_MAX_REQUEST_COUNT) { if (request_count >= BLK_MAX_REQUEST_COUNT) {