blk-mq: don't check queue mapped in __blk_mq_delay_run_hw_queue()

BugLink: http://bugs.launchpad.net/bugs/1759723
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: Stefan Haberland <sth@linux.vnet.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit efea8450c3d2d3918029b36f59ef612be57d91ae)
Signed-off-by: Jose Ricardo Ziviani <joserz@linux.ibm.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3362f274d0861dfaf7e68013c6461f5e818c5db8..107993dbb377ea3757245e08d777d0a17122725d 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1306,9 +1306,6 @@ select_cpu:
 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;