blk-mq: Remove 'running from the wrong CPU' warning

It's guaranteed that no request is in flight when a hctx is going
offline. This warning is only triggered when the wq's CPU is hot
plugged and the blk-mq is not synced up yet.

As this state is temporary and the request is still processed
correctly, better remove the warning as this is the fast path.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index b09ce00..a428798 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1495,31 +1495,6 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
        int srcu_idx;
 
-       /*
-        * We should be running this queue from one of the CPUs that
-        * are mapped to it.
-        *
-        * There are at least two related races now between setting
-        * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
-        * __blk_mq_run_hw_queue():
-        *
-        * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
-        *   but later it becomes online, then this warning is harmless
-        *   at all
-        *
-        * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
-        *   but later it becomes offline, then the warning can't be
-        *   triggered, and we depend on blk-mq timeout handler to
-        *   handle dispatched requests to this hctx
-        */
-       if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
-               cpu_online(hctx->next_cpu)) {
-               printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
-                       raw_smp_processor_id(),
-                       cpumask_empty(hctx->cpumask) ? "inactive": "active");
-               dump_stack();
-       }
-
        /*
         * We can't run the queue inline with ints disabled. Ensure that
         * we catch bad users of this early.