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Commit dd6cf3e1 authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

blk: clean up plug 



Current code looks like inner plug gets flushed with a
blk_finish_plug(). Actually it's a nop. All requests/callbacks are added
to current->plug, while only outmost plug is assigned to current->plug.
So inner plug always has empty request/callback list, which makes
blk_flush_plug_list() a nop. This tries to make the code more clear.

Signed-off-by: default avatarShaohua Li <shli@fb.com>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 9dc6c806

block/blk-core.c

+12 −12
Original line number Original line Diff line number Diff line
@@ -3032,22 +3032,21 @@ void blk_start_plug(struct blk_plug *plug) 
{

{

	struct task_struct *tsk = current;

	struct task_struct *tsk = current;





	/*

	 * If this is a nested plug, don't actually assign it.

	 */

	if (tsk->plug)

		return;



	INIT_LIST_HEAD(&plug->list);

	INIT_LIST_HEAD(&plug->list);

	INIT_LIST_HEAD(&plug->mq_list);

	INIT_LIST_HEAD(&plug->mq_list);

	INIT_LIST_HEAD(&plug->cb_list);

	INIT_LIST_HEAD(&plug->cb_list);



	/*

	 * If this is a nested plug, don't actually assign it. It will be

	 * flushed on its own.

	 */

	if (!tsk->plug) {

	/*

	/*

	 * Store ordering should not be needed here, since a potential

	 * Store ordering should not be needed here, since a potential

	 * preempt will imply a full memory barrier

	 * preempt will imply a full memory barrier

	 */

	 */

	tsk->plug = plug;

	tsk->plug = plug;

}

}

}

EXPORT_SYMBOL(blk_start_plug);

EXPORT_SYMBOL(blk_start_plug);





static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)

static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
@@ -3193,9 +3192,10 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) 




void blk_finish_plug(struct blk_plug *plug)

void blk_finish_plug(struct blk_plug *plug)

{

{

	if (plug != current->plug)

		return;

	blk_flush_plug_list(plug, false);

	blk_flush_plug_list(plug, false);





	if (plug == current->plug)

	current->plug = NULL;

	current->plug = NULL;

}

}

EXPORT_SYMBOL(blk_finish_plug);

EXPORT_SYMBOL(blk_finish_plug);