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Commit 49f4c2dc authored by Dennis Zhou (Facebook)'s avatar Dennis Zhou (Facebook) Committed by Jens Axboe
Browse files

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: default avatarDennis Zhou <dennisszhou@gmail.com>
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarLiu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 27e6fa99

block/blk-cgroup.c

+28 −3
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 
}



/**

 * blkg_lookup_create - lookup blkg, try to create one if not there

 * __blkg_lookup_create - lookup blkg, try to create one if not there

 * @blkcg: blkcg of interest

 * @q: request_queue of interest

 *
@@ -272,7 +272,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, 
 * value on error.  If @q is dead, returns ERR_PTR(-EINVAL).  If @q is not

 * dead and bypassing, returns ERR_PTR(-EBUSY).

 */

struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,

struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,

				      struct request_queue *q)

{

	struct blkcg_gq *blkg;
@@ -310,6 +310,31 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, 
	}

}



/**

 * blkg_lookup_create - find or create a blkg

 * @blkcg: target block cgroup

 * @q: target request_queue

 *

 * This looks up or creates the blkg representing the unique pair

 * of the blkcg and the request_queue.

 */

struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,

				    struct request_queue *q)

{

	struct blkcg_gq *blkg = blkg_lookup(blkcg, q);

	unsigned long flags;



	if (unlikely(!blkg)) {

		spin_lock_irqsave(q->queue_lock, flags);



		blkg = __blkg_lookup_create(blkcg, q);



		spin_unlock_irqrestore(q->queue_lock, flags);

	}



	return blkg;

}



static void blkg_destroy(struct blkcg_gq *blkg)

{

	struct blkcg *blkcg = blkg->blkcg;

block/blk-iolatency.c

+1 −1
Original line number Diff line number Diff line
@@ -407,7 +407,7 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio, 
	if (unlikely(!blkg)) {

		if (!lock)

			spin_lock_irq(q->queue_lock);

		blkg = blkg_lookup_create(blkcg, q);

		blkg = __blkg_lookup_create(blkcg, q);

		if (IS_ERR(blkg))

			blkg = NULL;

		if (!lock)

include/linux/blk-cgroup.h

+3 −1
Original line number Diff line number Diff line
@@ -184,6 +184,8 @@ extern struct cgroup_subsys_state * const blkcg_root_css; 


struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,

				      struct request_queue *q, bool update_hint);

struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,

				      struct request_queue *q);

struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,

				    struct request_queue *q);

int blkcg_init_queue(struct request_queue *q);
@@ -897,7 +899,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q, 
	blkg = blkg_lookup(blkcg, q);

	if (unlikely(!blkg)) {

		spin_lock_irq(q->queue_lock);

		blkg = blkg_lookup_create(blkcg, q);

		blkg = __blkg_lookup_create(blkcg, q);

		if (IS_ERR(blkg))

			blkg = NULL;

		spin_unlock_irq(q->queue_lock);