On 09/27/16 06:22, Ming Lei wrote:

On Tue, Sep 27, 2016 at 2:27 AM, Bart Van Assche
[off-list ref] wrote:

quoted

Signed-off-by: Bart Van Assche <redacted>
---
 block/blk-core.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 8cc8006..5ecc7ab 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c

@@ -689,7 +689,10 @@ void blk_freeze_queue_start(struct request_queue *q)
        freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
        if (freeze_depth == 1) {
                percpu_ref_kill(&q->q_usage_counter);
-               blk_mq_run_hw_queues(q, false);
+               if (q->mq_ops)
+                       blk_mq_run_hw_queues(q, false);
+               else if (q->request_fn)
+                       blk_run_queue(q);

Just wondering if you have a non-blk-mq drivers which need this change,
cause we only hold .q_usage_counter for sync bio.

Hello Ming Lei,

Patch 8/9 calls blk_quiesce_queue() and blk_resume_queue() from a code 
path that is used in both blk-mq and non-blk-mq mode. Although it 
wouldn't be hard to modify that patch such that it only uses these two 
functions in blk-mq mode, that wouldn't be very elegant.

Jens, regarding non-blk-mq mode and q_usage_counter: do you prefer that 
I rework patch 8/9 such that blk_quiesce_queue() and blk_resume_queue() 
are only used in blk-mq mode or are you OK with adding a 
blk_queue_enter() call in get_request() and a blk_queue_exit() call to 
__blk_put_request()?

Bart.