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blkcg: Introduce blkg_root_lookup()

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This new function will be used in a later patch to verify whether a
queue has been dissociated from the cgroup controller before being
released.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Alexandru Moise <00moses.alexander00@gmail.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2018-08-09 07:53:36 -07:00 committed by Jens Axboe
parent b1f4267cc5
commit 6bad9b210a
1 changed files with 18 additions and 0 deletions
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18
include/linux/blk-cgroup.h
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@ -341,6 +341,23 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
return __blkg_lookup(blkcg, q, false);
}
/**
* blkg_lookup - look up blkg for the specified request queue
* @q: request_queue of interest
*
* Lookup blkg for @q at the root level. See also blkg_lookup().
*/
static inline struct blkcg_gq *blkg_root_lookup(struct request_queue *q)
{
struct blkcg_gq *blkg;
rcu_read_lock();
blkg = blkg_lookup(&blkcg_root, q);
rcu_read_unlock();
return blkg;
}
/**
* blkg_to_pdata - get policy private data
* @blkg: blkg of interest
@ -864,6 +881,7 @@ static inline bool blk_cgroup_congested(void) { return false; }
static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }
static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
static inline struct blkcg_gq *blkg_root_lookup(struct request_queue *q) { return NULL; }
static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
static inline void blkcg_drain_queue(struct request_queue *q) { }
static inline void blkcg_exit_queue(struct request_queue *q) { }