Use prepare_to_wait() and finish_wait() instead of open-coding these
functions. Reduce the number of if-statements to make
blk_mq_mark_tag_wait() easier to read. Both add_wait_queue() and
blk_mq_dispatch_wake() protect wait queue manipulations with the wait
queue lock. Hence also protect the !list_empty(&wait->entry) test with
the wait queue lock instead of the hctx lock.
Note: a side effect of this patch is that the task state is changed
for shared queues before and after the blk_mq_get_driver_tag().
Since blk_mq_dispatch_wake() ignores the task state these task state
changes do not affect which task gets woken up.
See also commit f906a6a0f426 ("blk-mq: improve tag waiting setup for
non-shared tags").
Signed-off-by: Bart Van Assche <bart.vanass...@wdc.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Omar Sandoval <osan...@fb.com>
Cc: Hannes Reinecke <h...@suse.de>
Cc: Johannes Thumshirn <jthumsh...@suse.de>
---
block/blk-mq.c | 49 +++++++++++++++++--------------------------------
1 file changed, 17 insertions(+), 32 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 61bdbf45c3be..29f140b4dbf7 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1121,50 +1121,35 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx
**hctx,
if (!shared_tags) {
if (!test_bit(BLK_MQ_S_SCHED_RESTART, &this_hctx->state))
set_bit(BLK_MQ_S_SCHED_RESTART, &this_hctx->state);
+ ret = blk_mq_get_driver_tag(rq, hctx, false);
+ /*
+ * Don't clear RESTART here, someone else could have set it.
+ * At most this will cost an extra queue run.
+ */
} else {
wait = &this_hctx->dispatch_wait;
if (!list_empty_careful(&wait->entry))
return false;
- spin_lock(&this_hctx->lock);
- if (!list_empty(&wait->entry)) {
- spin_unlock(&this_hctx->lock);
- return false;
- }
-
ws = bt_wait_ptr(&this_hctx->tags->bitmap_tags, this_hctx);
- add_wait_queue(&ws->wait, wait);
- }
-
- /*
- * It's possible that a tag was freed in the window between the
- * allocation failure and adding the hardware queue to the wait
- * queue.
- */
- ret = blk_mq_get_driver_tag(rq, hctx, false);
+ prepare_to_wait(&ws->wait, wait, TASK_UNINTERRUPTIBLE);
- if (!shared_tags) {
/*
- * Don't clear RESTART here, someone else could have set it.
- * At most this will cost an extra queue run.
+ * It's possible that a tag was freed in the window between the
+ * allocation failure and adding the hardware queue to the wait
+ * queue.
*/
- return ret;
- } else {
- if (!ret) {
- spin_unlock(&this_hctx->lock);
- return false;
- }
-
+ ret = blk_mq_get_driver_tag(rq, hctx, false);
/*
- * We got a tag, remove ourselves from the wait queue to ensure
- * someone else gets the wakeup.
+ * If we got a tag, remove ourselves from the wait queue to
+ * ensure someone else gets the wakeup.
*/
- spin_lock_irq(&ws->wait.lock);
- list_del_init(&wait->entry);
- spin_unlock_irq(&ws->wait.lock);
- spin_unlock(&this_hctx->lock);
- return true;
+ if (ret)
+ finish_wait(&ws->wait, wait);
+ else
+ __set_current_state(TASK_RUNNING);
}
+ return ret;
}
bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
--
2.15.1
