blk-mq-sched: bypass the scheduler for flushes entirely

There's a weird inconsistency that flushes are mostly hidden from the
scheduler, but it needs to be aware of them in ->insert_requests().
Instead of having every scheduler call blk_mq_sched_bypass_insert(),
let's do it in the common framework.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 114814ec3d49f4cd17ebd006adffcec4151cbb99..3ec52f4940944afa0ebb41cb87e35c1631008379 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -289,7 +289,8 @@ void blk_mq_sched_request_inserted(struct request *rq)
 }
 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
 
-bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
+static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
+                                      struct request *rq)
 {
        if (rq->tag == -1) {
                rq->rq_flags |= RQF_SORTED;
@@ -305,7 +306,6 @@ bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
        spin_unlock(&hctx->lock);
        return true;
 }
-EXPORT_SYMBOL_GPL(blk_mq_sched_bypass_insert);
 
 static void blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
 {
@@ -363,6 +363,9 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head,
                return;
        }
 
+       if (e && blk_mq_sched_bypass_insert(hctx, rq))
+               goto run;
+
        if (e && e->type->ops.mq.insert_requests) {
                LIST_HEAD(list);
 
@@ -374,6 +377,7 @@ void blk_mq_sched_insert_request(struct request *rq, bool at_head,
                spin_unlock(&ctx->lock);
        }
 
+run:
        if (run_queue)
                blk_mq_run_hw_queue(hctx, async);
 }
@@ -385,6 +389,23 @@ void blk_mq_sched_insert_requests(struct request_queue *q,
        struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
        struct elevator_queue *e = hctx->queue->elevator;
 
+       if (e) {
+               struct request *rq, *next;
+
+               /*
+                * We bypass requests that already have a driver tag assigned,
+                * which should only be flushes. Flushes are only ever inserted
+                * as single requests, so we shouldn't ever hit the
+                * WARN_ON_ONCE() below (but let's handle it just in case).
+                */
+               list_for_each_entry_safe(rq, next, list, queuelist) {
+                       if (WARN_ON_ONCE(rq->tag != -1)) {
+                               list_del_init(&rq->queuelist);
+                               blk_mq_sched_bypass_insert(hctx, rq);
+                       }
+               }
+       }
+
        if (e && e->type->ops.mq.insert_requests)
                e->type->ops.mq.insert_requests(hctx, list, false);
        else

diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 9478aaeb48c59b9a72e40e9e465e39f0e24df437..add5f090a8cd6907e65f35889ad94bf3d7230a9b 100644 (file)
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -15,7 +15,6 @@ struct request *blk_mq_sched_get_request(struct request_queue *q, struct bio *bi
 void blk_mq_sched_put_request(struct request *rq);
 
 void blk_mq_sched_request_inserted(struct request *rq);
-bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq);
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio);
 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio);
 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq);

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index 49583536698c49eae1912a70c8acd24bcce54981..8f91f21e866323095fbd252dec05e54f8127bfa9 100644 (file)
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -395,9 +395,6 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 
        blk_mq_sched_request_inserted(rq);
 
-       if (blk_mq_sched_bypass_insert(hctx, rq))
-               return;
-
        if (at_head || blk_rq_is_passthrough(rq)) {
                if (at_head)
                        list_add(&rq->queuelist, &dd->dispatch);