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

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
......@@ -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
*
......@@ -272,8 +272,8 @@ 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 request_queue *q)
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;
......
......@@ -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)
......
......@@ -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);
......
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