[PATCH V6 2/6] block: tracking request allocation with q_usage_counter

[Ming Lei]

This usage is basically same with blk-mq, so that we can
support to freeze legacy queue easily.

Also 'wake_up_all(&q->mq_freeze_wq)' has to be moved
into blk_set_queue_dying() since both legacy and blk-mq
may wait on the wait queue of .mq_freeze_wq.

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 block/blk-core.c | 14 ++++++++++++++
 block/blk-mq.c   |  7 -------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index aebe676225e6..abfba798ee03 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -610,6 +610,12 @@ void blk_set_queue_dying(struct request_queue *q)
                }
                spin_unlock_irq(q->queue_lock);
        }
+
+       /*
+        * We need to ensure that processes currently waiting on
+        * the queue are notified as well.
+        */
+       wake_up_all(&q->mq_freeze_wq);
 }
 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
 
@@ -1392,16 +1398,21 @@ static struct request *blk_old_get_request(struct 
request_queue *q,
                                           unsigned int op, gfp_t gfp_mask)
 {
        struct request *rq;
+       int ret = 0;
 
        WARN_ON_ONCE(q->mq_ops);
 
        /* create ioc upfront */
        create_io_context(gfp_mask, q->node);
 
+       ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM));
+       if (ret)
+               return ERR_PTR(ret);
        spin_lock_irq(q->queue_lock);
        rq = get_request(q, op, NULL, gfp_mask);
        if (IS_ERR(rq)) {
                spin_unlock_irq(q->queue_lock);
+               blk_queue_exit(q);
                return rq;
        }
 
@@ -1573,6 +1584,7 @@ void __blk_put_request(struct request_queue *q, struct 
request *req)
                blk_free_request(rl, req);
                freed_request(rl, sync, rq_flags);
                blk_put_rl(rl);
+               blk_queue_exit(q);
        }
 }
 EXPORT_SYMBOL_GPL(__blk_put_request);
@@ -1854,8 +1866,10 @@ static blk_qc_t blk_queue_bio(struct request_queue *q, 
struct bio *bio)
         * Grab a free request. This is might sleep but can not fail.
         * Returns with the queue unlocked.
         */
+       blk_queue_enter_live(q);
        req = get_request(q, bio->bi_opf, bio, GFP_NOIO);
        if (IS_ERR(req)) {
+               blk_queue_exit(q);
                __wbt_done(q->rq_wb, wb_acct);
                if (PTR_ERR(req) == -ENOMEM)
                        bio->bi_status = BLK_STS_RESOURCE;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6fd9f86fc86d..10c1f49f663d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -256,13 +256,6 @@ void blk_mq_wake_waiters(struct request_queue *q)
        queue_for_each_hw_ctx(q, hctx, i)
                if (blk_mq_hw_queue_mapped(hctx))
                        blk_mq_tag_wakeup_all(hctx->tags, true);
-
-       /*
-        * If we are called because the queue has now been marked as
-        * dying, we need to ensure that processes currently waiting on
-        * the queue are notified as well.
-        */
-       wake_up_all(&q->mq_freeze_wq);
 }
 
 bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
-- 
2.9.5