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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>
This commit is contained in:
Tejun Heo 2015-08-18 14:55:02 -07:00 committed by Jens Axboe
parent d93a11f1cd
commit 2da8de0bb7
1 changed files with 10 additions and 35 deletions
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45
block/cfq-iosched.c
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@ -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 {
/*