linux-kernel - [PATCH 03/11] block: Stop abusing rq->csd.list in blk-softirq

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Date:	Sat,  8 Feb 2014 17:18:32 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 03/11] block: Stop abusing rq->csd.list in blk-softirq

From: Jan Kara <jack@...e.cz>

Abusing rq->csd.list for a list of requests to complete is rather ugly.
We use rq->queuelist instead which is much cleaner. It is safe because
queuelist is used by the block layer only for requests waiting to be
submitted to a device. Thus it is unused when irq reports the request IO
is finished.

Signed-off-by: Jan Kara <jack@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jens Axboe <jens.axboe@...cle.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 block/blk-softirq.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 57790c1..b5c37d9 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -30,8 +30,8 @@ static void blk_done_softirq(struct softirq_action *h)
 	while (!list_empty(&local_list)) {
 		struct request *rq;
 
-		rq = list_entry(local_list.next, struct request, csd.list);
-		list_del_init(&rq->csd.list);
+		rq = list_entry(local_list.next, struct request, queuelist);
+		list_del_init(&rq->queuelist);
 		rq->q->softirq_done_fn(rq);
 	}
 }
@@ -45,9 +45,14 @@ static void trigger_softirq(void *data)
 
 	local_irq_save(flags);
 	list = this_cpu_ptr(&blk_cpu_done);
-	list_add_tail(&rq->csd.list, list);
+	/*
+	 * We reuse queuelist for a list of requests to process. Since the
+	 * queuelist is used by the block layer only for requests waiting to be
+	 * submitted to the device it is unused now.
+	 */
+	list_add_tail(&rq->queuelist, list);
 
-	if (list->next == &rq->csd.list)
+	if (list->next == &rq->queuelist)
 		raise_softirq_irqoff(BLOCK_SOFTIRQ);
 
 	local_irq_restore(flags);
@@ -136,7 +141,7 @@ void __blk_complete_request(struct request *req)
 		struct list_head *list;
 do_local:
 		list = this_cpu_ptr(&blk_cpu_done);
-		list_add_tail(&req->csd.list, list);
+		list_add_tail(&req->queuelist, list);
 
 		/*
 		 * if the list only contains our just added request,
@@ -144,7 +149,7 @@ do_local:
 		 * entries there, someone already raised the irq but it
 		 * hasn't run yet.
 		 */
-		if (list->next == &req->csd.list)
+		if (list->next == &req->queuelist)
 			raise_softirq_irqoff(BLOCK_SOFTIRQ);
 	} else if (raise_blk_irq(ccpu, req))
 		goto do_local;
-- 
1.8.3.1

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