cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue()

Even when allocations fail, cfq_find_alloc_queue() always returns a
valid cfq_queue by falling back to the oom cfq_queue.  As such, there
isn't much point in taking @gfp_mask and trying "harder" if __GFP_WAIT
is set.  GFP_NOWAIT allocations don't fail often and even when they do
the degraded behavior is acceptable and temporary.

After all, the only reason get_request(), which ultimately determines
the gfp_mask, cares about __GFP_WAIT is to guarantee request
allocation, assuming IO forward progress, for callers which are
willing to wait.  There's no reason for cfq_find_alloc_queue() to
behave differently on __GFP_WAIT when it already has a fallback
mechanism.

Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes
to its callers.  This simplifies the function quite a bit and will
help making async queues per-cfq_group.

v2: Updated to reflect GFP_ATOMIC -> GPF_NOWAIT.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5f119292a254abf6bb4cde3722768a2f2fa63140..146b03d64b7e5f2d3309a11489a6e086c5f2ae6f 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -883,8 +883,7 @@ static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
-                                      struct cfq_io_cq *cic, struct bio *bio,
-                                      gfp_t gfp_mask);
+                                      struct cfq_io_cq *cic, struct bio *bio);
 
 static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
 {
@@ -3575,7 +3574,7 @@ static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
        cfqq = cic_to_cfqq(cic, false);
        if (cfqq) {
                cfq_put_queue(cfqq);
-               cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio, GFP_NOWAIT);
+               cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio);
                cic_set_cfqq(cic, cfqq, false);
        }
 
@@ -3643,13 +3642,12 @@ static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) {
 
 static struct cfq_queue *
 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
-                    struct bio *bio, gfp_t gfp_mask)
+                    struct bio *bio)
 {
        struct blkcg *blkcg;
-       struct cfq_queue *cfqq, *new_cfqq = NULL;
+       struct cfq_queue *cfqq;
        struct cfq_group *cfqg;
 
-retry:
        rcu_read_lock();
 
        blkcg = bio_blkcg(bio);
@@ -3666,27 +3664,9 @@ retry:
         * originally, since it should just be a temporary situation.
         */
        if (!cfqq || cfqq == &cfqd->oom_cfqq) {
-               cfqq = NULL;
-               if (new_cfqq) {
-                       cfqq = new_cfqq;
-                       new_cfqq = NULL;
-               } else if (gfp_mask & __GFP_WAIT) {
-                       rcu_read_unlock();
-                       spin_unlock_irq(cfqd->queue->queue_lock);
-                       new_cfqq = kmem_cache_alloc_node(cfq_pool,
-                                       gfp_mask | __GFP_ZERO,
-                                       cfqd->queue->node);
-                       spin_lock_irq(cfqd->queue->queue_lock);
-                       if (new_cfqq)
-                               goto retry;
-                       else
-                               return &cfqd->oom_cfqq;
-               } else {
-                       cfqq = kmem_cache_alloc_node(cfq_pool,
-                                       gfp_mask | __GFP_ZERO,
-                                       cfqd->queue->node);
-               }
-
+               cfqq = kmem_cache_alloc_node(cfq_pool,
+                                            GFP_NOWAIT | __GFP_ZERO,
+                                            cfqd->queue->node);
                if (cfqq) {
                        cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
                        cfq_init_prio_data(cfqq, cic);
@@ -3696,9 +3676,6 @@ retry:
                        cfqq = &cfqd->oom_cfqq;
        }
 out:
-       if (new_cfqq)
-               kmem_cache_free(cfq_pool, new_cfqq);
-
        rcu_read_unlock();
        return cfqq;
 }
@@ -3723,7 +3700,7 @@ cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
 
 static struct cfq_queue *
 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
-             struct bio *bio, gfp_t gfp_mask)
+             struct bio *bio)
 {
        int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
        int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
@@ -3742,7 +3719,7 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
                        goto out;
        }
 
-       cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
+       cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio);
 
        /*
         * pin the queue now that it's allocated, scheduler exit will prune it
@@ -4286,8 +4263,6 @@ cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
        const bool is_sync = rq_is_sync(rq);
        struct cfq_queue *cfqq;
 
-       might_sleep_if(gfp_mask & __GFP_WAIT);
-
        spin_lock_irq(q->queue_lock);
 
        check_ioprio_changed(cic, bio);
@@ -4297,7 +4272,7 @@ new_queue:
        if (!cfqq || cfqq == &cfqd->oom_cfqq) {
                if (cfqq)
                        cfq_put_queue(cfqq);
-               cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);
+               cfqq = cfq_get_queue(cfqd, is_sync, cic, bio);
                cic_set_cfqq(cic, cfqq, is_sync);
        } else {
                /*