block: Stop abusing rq->csd.list in blk-softirq

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 <axboe@fb.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 57790c1a97eb..b5c37d96cf0e 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;