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Subject[PATCH 03/11] block: Stop abusing rq->csd.list in blk-softirq
Date
From: Jan Kara <jack@suse.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@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.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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