blkcg: update blkg_lookup_create to do locking
To know when to create a blkg, the general pattern is to do a blkg_lookup and if that fails, lock and then do a lookup again and if that fails finally create. It doesn't make much sense for everyone who wants to do creation to write this themselves. This changes blkg_lookup_create to do locking and implement this pattern. The old blkg_lookup_create is renamed to __blkg_lookup_create. If a call site wants to do its own error handling or already owns the queue lock, they can use __blkg_lookup_create. This will be used in upcoming patches. Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -259,7 +259,7 @@ err_free_blkg:
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}
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}
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/**
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/**
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* blkg_lookup_create - lookup blkg, try to create one if not there
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* __blkg_lookup_create - lookup blkg, try to create one if not there
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* @blkcg: blkcg of interest
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* @blkcg: blkcg of interest
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* @q: request_queue of interest
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* @q: request_queue of interest
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*
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*
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@ -272,8 +272,8 @@ err_free_blkg:
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* value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
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* value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not
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* dead and bypassing, returns ERR_PTR(-EBUSY).
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* dead and bypassing, returns ERR_PTR(-EBUSY).
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*/
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*/
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struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
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struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
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struct request_queue *q)
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struct request_queue *q)
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{
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{
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struct blkcg_gq *blkg;
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struct blkcg_gq *blkg;
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@ -310,6 +310,31 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
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}
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}
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}
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}
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/**
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* blkg_lookup_create - find or create a blkg
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* @blkcg: target block cgroup
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* @q: target request_queue
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*
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* This looks up or creates the blkg representing the unique pair
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* of the blkcg and the request_queue.
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*/
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struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
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struct request_queue *q)
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{
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struct blkcg_gq *blkg = blkg_lookup(blkcg, q);
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unsigned long flags;
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if (unlikely(!blkg)) {
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spin_lock_irqsave(q->queue_lock, flags);
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blkg = __blkg_lookup_create(blkcg, q);
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spin_unlock_irqrestore(q->queue_lock, flags);
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}
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return blkg;
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}
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static void blkg_destroy(struct blkcg_gq *blkg)
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static void blkg_destroy(struct blkcg_gq *blkg)
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{
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{
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struct blkcg *blkcg = blkg->blkcg;
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struct blkcg *blkcg = blkg->blkcg;
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@ -407,7 +407,7 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio,
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if (unlikely(!blkg)) {
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if (unlikely(!blkg)) {
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if (!lock)
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if (!lock)
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spin_lock_irq(q->queue_lock);
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spin_lock_irq(q->queue_lock);
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blkg = blkg_lookup_create(blkcg, q);
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blkg = __blkg_lookup_create(blkcg, q);
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if (IS_ERR(blkg))
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if (IS_ERR(blkg))
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blkg = NULL;
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blkg = NULL;
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if (!lock)
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if (!lock)
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@ -184,6 +184,8 @@ extern struct cgroup_subsys_state * const blkcg_root_css;
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struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
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struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
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struct request_queue *q, bool update_hint);
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struct request_queue *q, bool update_hint);
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struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
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struct request_queue *q);
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struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
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struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
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struct request_queue *q);
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struct request_queue *q);
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int blkcg_init_queue(struct request_queue *q);
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int blkcg_init_queue(struct request_queue *q);
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@ -897,7 +899,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
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blkg = blkg_lookup(blkcg, q);
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blkg = blkg_lookup(blkcg, q);
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if (unlikely(!blkg)) {
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if (unlikely(!blkg)) {
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spin_lock_irq(q->queue_lock);
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spin_lock_irq(q->queue_lock);
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blkg = blkg_lookup_create(blkcg, q);
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blkg = __blkg_lookup_create(blkcg, q);
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if (IS_ERR(blkg))
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if (IS_ERR(blkg))
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blkg = NULL;
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blkg = NULL;
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spin_unlock_irq(q->queue_lock);
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spin_unlock_irq(q->queue_lock);
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