blk-mq: add helper to insert requests from irq context
Both the cache flush state machine and the SCSI midlayer want to submit
requests from irq context, and the current per-request requeue_work
unfortunately causes corruption due to sharing with the csd field for
flushes. Replace them with a per-request_queue list of requests to
be requeued.
Based on an earlier test by Ming Lei.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Ming Lei <tom.leiming@gmail.com>
Tested-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 010b878..67066ecc 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -516,10 +516,68 @@
blk_clear_rq_complete(rq);
BUG_ON(blk_queued_rq(rq));
- blk_mq_insert_request(rq, true, true, false);
+ blk_mq_add_to_requeue_list(rq, true);
}
EXPORT_SYMBOL(blk_mq_requeue_request);
+static void blk_mq_requeue_work(struct work_struct *work)
+{
+ struct request_queue *q =
+ container_of(work, struct request_queue, requeue_work);
+ LIST_HEAD(rq_list);
+ struct request *rq, *next;
+ unsigned long flags;
+
+ spin_lock_irqsave(&q->requeue_lock, flags);
+ list_splice_init(&q->requeue_list, &rq_list);
+ spin_unlock_irqrestore(&q->requeue_lock, flags);
+
+ list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
+ if (!(rq->cmd_flags & REQ_SOFTBARRIER))
+ continue;
+
+ rq->cmd_flags &= ~REQ_SOFTBARRIER;
+ list_del_init(&rq->queuelist);
+ blk_mq_insert_request(rq, true, false, false);
+ }
+
+ while (!list_empty(&rq_list)) {
+ rq = list_entry(rq_list.next, struct request, queuelist);
+ list_del_init(&rq->queuelist);
+ blk_mq_insert_request(rq, false, false, false);
+ }
+
+ blk_mq_run_queues(q, false);
+}
+
+void blk_mq_add_to_requeue_list(struct request *rq, bool at_head)
+{
+ struct request_queue *q = rq->q;
+ unsigned long flags;
+
+ /*
+ * We abuse this flag that is otherwise used by the I/O scheduler to
+ * request head insertation from the workqueue.
+ */
+ BUG_ON(rq->cmd_flags & REQ_SOFTBARRIER);
+
+ spin_lock_irqsave(&q->requeue_lock, flags);
+ if (at_head) {
+ rq->cmd_flags |= REQ_SOFTBARRIER;
+ list_add(&rq->queuelist, &q->requeue_list);
+ } else {
+ list_add_tail(&rq->queuelist, &q->requeue_list);
+ }
+ spin_unlock_irqrestore(&q->requeue_lock, flags);
+}
+EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
+
+void blk_mq_kick_requeue_list(struct request_queue *q)
+{
+ kblockd_schedule_work(&q->requeue_work);
+}
+EXPORT_SYMBOL(blk_mq_kick_requeue_list);
+
struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
return tags->rqs[tag];
@@ -1812,6 +1870,10 @@
q->sg_reserved_size = INT_MAX;
+ INIT_WORK(&q->requeue_work, blk_mq_requeue_work);
+ INIT_LIST_HEAD(&q->requeue_list);
+ spin_lock_init(&q->requeue_lock);
+
if (q->nr_hw_queues > 1)
blk_queue_make_request(q, blk_mq_make_request);
else
