blk-mq: remove blk_mq_put_ctx()

No code that occurs between blk_mq_get_ctx() and blk_mq_put_ctx() depends
on preemption being disabled for its correctness. Since removing the CPU
preemption calls does not measurably affect performance, simplify the
blk-mq code by removing the blk_mq_put_ctx() function and also by not
disabling preemption in blk_mq_get_ctx().

Cc: Hannes Reinecke <hare@suse.com>
Cc: Omar Sandoval <osandov@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 956a7aa..c9d183d 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -330,10 +330,8 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
        bool ret = false;
        enum hctx_type type;
 
-       if (e && e->type->ops.bio_merge) {
-               blk_mq_put_ctx(ctx);
+       if (e && e->type->ops.bio_merge)
                return e->type->ops.bio_merge(hctx, bio, nr_segs);
-       }
 
        type = hctx->type;
        if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
@@ -344,7 +342,6 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
                spin_unlock(&ctx->lock);
        }
 
-       blk_mq_put_ctx(ctx);
        return ret;
 }
 

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 7513c8e..da19f0b 100644 (file)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -113,7 +113,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
        struct sbq_wait_state *ws;
        DEFINE_SBQ_WAIT(wait);
        unsigned int tag_offset;
-       bool drop_ctx;
        int tag;
 
        if (data->flags & BLK_MQ_REQ_RESERVED) {
@@ -136,7 +135,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
                return BLK_MQ_TAG_FAIL;
 
        ws = bt_wait_ptr(bt, data->hctx);
-       drop_ctx = data->ctx == NULL;
        do {
                struct sbitmap_queue *bt_prev;
 
@@ -161,9 +159,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
                if (tag != -1)
                        break;
 
-               if (data->ctx)
-                       blk_mq_put_ctx(data->ctx);
-
                bt_prev = bt;
                io_schedule();
 
@@ -189,9 +184,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
                ws = bt_wait_ptr(bt, data->hctx);
        } while (1);
 
-       if (drop_ctx && data->ctx)
-               blk_mq_put_ctx(data->ctx);
-
        sbitmap_finish_wait(bt, ws, &wait);
 
 found_tag:

diff --git a/block/blk-mq.c b/block/blk-mq.c
index d893838..0cb1b15 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -355,13 +355,13 @@ static struct request *blk_mq_get_request(struct request_queue *q,
        struct elevator_queue *e = q->elevator;
        struct request *rq;
        unsigned int tag;
-       bool put_ctx_on_error = false;
+       bool clear_ctx_on_error = false;
 
        blk_queue_enter_live(q);
        data->q = q;
        if (likely(!data->ctx)) {
                data->ctx = blk_mq_get_ctx(q);
-               put_ctx_on_error = true;
+               clear_ctx_on_error = true;
        }
        if (likely(!data->hctx))
                data->hctx = blk_mq_map_queue(q, data->cmd_flags,
@@ -387,10 +387,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
 
        tag = blk_mq_get_tag(data);
        if (tag == BLK_MQ_TAG_FAIL) {
-               if (put_ctx_on_error) {
-                       blk_mq_put_ctx(data->ctx);
+               if (clear_ctx_on_error)
                        data->ctx = NULL;
-               }
                blk_queue_exit(q);
                return NULL;
        }
@@ -427,8 +425,6 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
        if (!rq)
                return ERR_PTR(-EWOULDBLOCK);
 
-       blk_mq_put_ctx(alloc_data.ctx);
-
        rq->__data_len = 0;
        rq->__sector = (sector_t) -1;
        rq->bio = rq->biotail = NULL;
@@ -1977,7 +1973,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
        plug = current->plug;
        if (unlikely(is_flush_fua)) {
-               blk_mq_put_ctx(data.ctx);
                blk_mq_bio_to_request(rq, bio, nr_segs);
 
                /* bypass scheduler for flush rq */
@@ -1991,7 +1986,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
                unsigned int request_count = plug->rq_count;
                struct request *last = NULL;
 
-               blk_mq_put_ctx(data.ctx);
                blk_mq_bio_to_request(rq, bio, nr_segs);
 
                if (!request_count)
@@ -2025,8 +2019,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
                blk_add_rq_to_plug(plug, rq);
                trace_block_plug(q);
 
-               blk_mq_put_ctx(data.ctx);
-
                if (same_queue_rq) {
                        data.hctx = same_queue_rq->mq_hctx;
                        trace_block_unplug(q, 1, true);
@@ -2035,11 +2027,9 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
                }
        } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
                        !data.hctx->dispatch_busy)) {
-               blk_mq_put_ctx(data.ctx);
                blk_mq_bio_to_request(rq, bio, nr_segs);
                blk_mq_try_issue_directly(data.hctx, rq, &cookie);
        } else {
-               blk_mq_put_ctx(data.ctx);
                blk_mq_bio_to_request(rq, bio, nr_segs);
                blk_mq_sched_insert_request(rq, false, true, true);
        }

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 633a5a7..f4bf516 100644 (file)
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -151,12 +151,7 @@ static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
  */
 static inline struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
 {
-       return __blk_mq_get_ctx(q, get_cpu());
-}
-
-static inline void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
-{
-       put_cpu();
+       return __blk_mq_get_ctx(q, raw_smp_processor_id());
 }
 
 struct blk_mq_alloc_data {

diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
index 3c26026..34dcea0 100644 (file)
--- a/block/kyber-iosched.c
+++ b/block/kyber-iosched.c
@@ -575,7 +575,6 @@ static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
        spin_lock(&kcq->lock);
        merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
        spin_unlock(&kcq->lock);
-       blk_mq_put_ctx(ctx);
 
        return merged;
 }