blkcg_bio_issue_check() open codes blkcg_gq lookup and creation using
blkg_lookup() and blkg_lookup_create(). Refactor the code so that
* blkg_lookup_create() is renamed to blkcg_lookup_create_locked().
* blkg_lookup_create() is now a new function which encapsulates the
RCU protected lookup and queue_locked protected creation.
* blkg_lookup_create() is guaranteed to return a non-NULL blkcg_gq.
The NULL checks are removed from the users.
This is pure refactoring and doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
block/blk-cgroup.c | 6 +++---
block/blk-throttle.c | 2 +-
include/linux/blk-cgroup.h | 32 +++++++++++++++++++++-----------
3 files changed, 25 insertions(+), 15 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 60a4486..490b0a6 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -290,7 +290,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
}
/**
- * blkg_lookup_create - lookup blkg, try to create one if not there
+ * blkg_lookup_create_locked - lookup blkg, try to create one if not there
* @blkcg: blkcg of interest
* @q: request_queue of interest
*
@@ -303,8 +303,8 @@ 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_locked(struct blkcg *blkcg,
+ struct request_queue *q)
{
struct blkcg_gq *blkg;
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8631763..1e6916b 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2123,7 +2123,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
struct bio *bio)
{
struct throtl_qnode *qn = NULL;
- struct throtl_grp *tg = blkg_to_tg(blkg ?: q->root_blkg);
+ struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq;
bool rw = bio_data_dir(bio);
bool throttled = false;
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index b5721d32..1de5158 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -172,8 +172,8 @@ 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_locked(struct blkcg *blkcg,
+ struct request_queue *q);
int blkcg_init_queue(struct request_queue *q);
void blkcg_drain_queue(struct request_queue *q);
void blkcg_exit_queue(struct request_queue *q);
@@ -680,6 +680,24 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg
struct bio *bio) { return false; }
#endif
+static inline struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+ struct request_queue *q)
+{
+ struct blkcg_gq *blkg;
+
+ blkg = blkg_lookup(blkcg, q);
+ if (likely(blkg))
+ return blkg;
+
+ spin_lock_irq(q->queue_lock);
+ blkg = blkg_lookup_create_locked(blkcg, q);
+ spin_unlock_irq(q->queue_lock);
+ if (likely(!IS_ERR(blkg)))
+ return blkg;
+ else
+ return q->root_blkg;
+}
+
static inline bool blkcg_bio_issue_check(struct request_queue *q,
struct bio *bio)
{
@@ -693,19 +711,11 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,
/* associate blkcg if bio hasn't attached one */
bio_associate_blkcg(bio, &blkcg->css);
- blkg = blkg_lookup(blkcg, q);
- if (unlikely(!blkg)) {
- spin_lock_irq(q->queue_lock);
- blkg = blkg_lookup_create(blkcg, q);
- if (IS_ERR(blkg))
- blkg = NULL;
- spin_unlock_irq(q->queue_lock);
- }
+ blkg = blkg_lookup_create(blkcg, q);
throtl = blk_throtl_bio(q, blkg, bio);
if (!throtl) {
- blkg = blkg ?: q->root_blkg;
blkg_rwstat_add(&blkg->stat_bytes, bio->bi_opf,
bio->bi_iter.bi_size);
blkg_rwstat_add(&blkg->stat_ios, bio->bi_opf, 1);
--
2.9.5
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