Re: [PATCH 6/8] blk-mq: don't check queue mapped in __blk_mq_delay_run_hw_queue()

[Sagi Grimberg]

Looks good,

Reviewed-by: Sagi Grimberg 

Re: [PATCH 6/8] blk-mq: don't check queue mapped in __blk_mq_delay_run_hw_queue()

[Christoph Hellwig]

On Sun, Apr 08, 2018 at 05:48:12PM +0800, Ming Lei wrote:
> There are several reasons for removing the check:
> 
> 1) blk_mq_hw_queue_mapped() returns true always now since each hctx
> may be mapped by one CPU at least

Sounds like we should remove it, then..

The patch looks good:

Reviewed-by: Christoph Hellwig 

[PATCH 6/8] blk-mq: don't check queue mapped in __blk_mq_delay_run_hw_queue()

[Ming Lei]

There are several reasons for removing the check:

1) blk_mq_hw_queue_mapped() returns true always now since each hctx
may be mapped by one CPU at least

2) when there isn't any online CPU mapped to this hctx, there won't
be any IO queued to this CPU, blk_mq_run_hw_queue() only runs queue
if there is IO queued to this hctx

3) If __blk_mq_delay_run_hw_queue() is called by blk_mq_delay_run_hw_queue(),
which is run from blk_mq_dispatch_rq_list() or scsi_mq_get_budget(), and
the hctx to be handled has to be mapped.

Cc: Christian Borntraeger 
Cc: Christoph Hellwig 
Cc: Stefan Haberland 
Signed-off-by: Ming Lei 
---
 block/blk-mq.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8743e9105612..3b4ce83a0ba2 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1394,9 +1394,6 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx 
*hctx)
 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
unsigned long msecs)
 {
-   if (WARN_ON_ONCE(!blk_mq_hw_queue_mapped(hctx)))
-   return;
-
if (unlikely(blk_mq_hctx_stopped(hctx)))
return;
 
-- 
2.9.5