blkcg: introduce common blkg association logic

There are 3 ways blkg association can happen: association with the
current css, with the page css (swap), or from the wbc css (writeback).

This patch handles how association is done for the first case where we
are associating bsaed on the current css. If there is already a blkg
associated, the css will be reused and association will be redone as the
request_queue may have changed.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bio.c b/block/bio.c
index 5c9828524adc476d10fa339fc366fcd1e2b05972..452b8e79b998b1bb17cb8aadc1e74e679cdfefce 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -2009,7 +2009,21 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
 EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
- * bio_associate_blkg - associate a bio with the a blkg
+ * bio_disassociate_blkg - puts back the blkg reference if associated
+ * @bio: target bio
+ *
+ * Helper to disassociate the blkg from @bio if a blkg is associated.
+ */
+void bio_disassociate_blkg(struct bio *bio)
+{
+       if (bio->bi_blkg) {
+               blkg_put(bio->bi_blkg);
+               bio->bi_blkg = NULL;
+       }
+}
+
+/**
+ * __bio_associate_blkg - associate a bio with the a blkg
  * @bio: target bio
  * @blkg: the blkg to associate
  *
@@ -2022,12 +2036,42 @@ EXPORT_SYMBOL_GPL(bio_associate_blkcg);
  * A reference will be taken on the @blkg and will be released when @bio is
  * freed.
  */
-int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
+static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg)
 {
-       if (unlikely(bio->bi_blkg))
-               return -EBUSY;
+       bio_disassociate_blkg(bio);
+
        bio->bi_blkg = blkg_try_get_closest(blkg);
-       return 0;
+}
+
+/**
+ * bio_associate_blkg - associate a bio with a blkg
+ * @bio: target bio
+ *
+ * Associate @bio with the blkg found from the bio's css and request_queue.
+ * If one is not found, bio_lookup_blkg() creates the blkg.  If a blkg is
+ * already associated, the css is reused and association redone as the
+ * request_queue may have changed.
+ */
+void bio_associate_blkg(struct bio *bio)
+{
+       struct request_queue *q = bio->bi_disk->queue;
+       struct blkcg *blkcg;
+       struct blkcg_gq *blkg;
+
+       rcu_read_lock();
+
+       bio_associate_blkcg(bio, NULL);
+       blkcg = bio_blkcg(bio);
+
+       if (!blkcg->css.parent) {
+               __bio_associate_blkg(bio, q->root_blkg);
+       } else {
+               blkg = blkg_lookup_create(blkcg, q);
+
+               __bio_associate_blkg(bio, blkg);
+       }
+
+       rcu_read_unlock();
 }
 
 /**
@@ -2040,10 +2084,7 @@ void bio_disassociate_task(struct bio *bio)
                css_put(bio->bi_css);
                bio->bi_css = NULL;
        }
-       if (bio->bi_blkg) {
-               blkg_put(bio->bi_blkg);
-               bio->bi_blkg = NULL;
-       }
+       bio_disassociate_blkg(bio);
 }
 
 /**
@@ -2055,6 +2096,9 @@ void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
 {
        if (src->bi_css)
                WARN_ON(bio_associate_blkcg(dst, src->bi_css));
+
+       if (src->bi_blkg)
+               __bio_associate_blkg(dst, src->bi_blkg);
 }
 EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);
 #endif /* CONFIG_BLK_CGROUP */

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 46e86c34cf790cc7eaa58ebb60a76cd6c956ea9f..cdbd10564e666b5fb94894f9ee7f8d0949702ad1 100644 (file)
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -472,21 +472,15 @@ static void check_scale_change(struct iolatency_grp *iolat)
 static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
 {
        struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
-       struct blkcg *blkcg;
        struct blkcg_gq *blkg;
-       struct request_queue *q = rqos->q;
        bool issue_as_root = bio_issue_as_root_blkg(bio);
 
        if (!blk_iolatency_enabled(blkiolat))
                return;
 
-       rcu_read_lock();
-       bio_associate_blkcg(bio, NULL);
-       blkcg = bio_blkcg(bio);
-       blkg = blkg_lookup_create(blkcg, q);
+       bio_associate_blkg(bio);
+       blkg = bio->bi_blkg;
        bio_issue_init(&bio->bi_issue, bio_sectors(bio));
-       bio_associate_blkg(bio, blkg);
-       rcu_read_unlock();
 
        while (blkg && blkg->parent) {
                struct iolatency_grp *iolat = blkg_to_lat(blkg);

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index d648d6720f4691c69adddbbb0c934e01702fa0aa..228c3a007ebc4f1ad787ca222abf60fff01d2cde 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2115,10 +2115,10 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
 }
 #endif
 
-static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
+static void blk_throtl_assoc_bio(struct bio *bio)
 {
 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
-       bio_associate_blkg(bio, tg_to_blkg(tg));
+       bio_associate_blkg(bio);
        bio_issue_init(&bio->bi_issue, bio_sectors(bio));
 #endif
 }
@@ -2143,7 +2143,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,
 
        throtl_update_latency_buckets(td);
 
-       blk_throtl_assoc_bio(tg, bio);
+       blk_throtl_assoc_bio(bio);
        blk_throtl_update_idletime(tg);
 
        sq = &tg->service_queue;

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 056fb627edb3e82779d0d4f92b27be43a423ce15..62715a5a4f326146fde85053bd13f9b21642eb36 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -511,12 +511,15 @@ static inline int bio_associate_blkcg_from_page(struct bio *bio,
 
 #ifdef CONFIG_BLK_CGROUP
 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);
-int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg);
+void bio_disassociate_blkg(struct bio *bio);
+void bio_associate_blkg(struct bio *bio);
 void bio_disassociate_task(struct bio *bio);
 void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
 #else  /* CONFIG_BLK_CGROUP */
 static inline int bio_associate_blkcg(struct bio *bio,
                        struct cgroup_subsys_state *blkcg_css) { return 0; }
+static inline void bio_disassociate_blkg(struct bio *bio) { }
+static inline void bio_associate_blkg(struct bio *bio) { }
 static inline void bio_disassociate_task(struct bio *bio) { }
 static inline void bio_clone_blkcg_association(struct bio *dst,
                        struct bio *src) { }