blk-cgroup: replace bio_blkcg with bio_blkcg_css

All callers of bio_blkcg actually want the CSS, so replace it with an
interface that does return the CSS.  This now allows to move
struct blkcg_gq to block/blk-cgroup.h instead of exposing it in a
public header.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220420042723.1010598-10-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 81 insertions, 4 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bb52797c02bd..8e32cc494808 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -156,6 +156,22 @@ static void blkg_async_bio_workfn(struct work_struct *work)
 }
 
 /**
+ * bio_blkcg_css - return the blkcg CSS associated with a bio
+ * @bio: target bio
+ *
+ * This returns the CSS for the blkcg associated with a bio, or %NULL if not
+ * associated. Callers are expected to either handle %NULL or know association
+ * has been done prior to calling this.
+ */
+struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
+{
+	if (!bio || !bio->bi_blkg)
+		return NULL;
+	return &bio->bi_blkg->blkcg->css;
+}
+EXPORT_SYMBOL_GPL(bio_blkcg_css);
+
+/**
  * blkcg_parent - get the parent of a blkcg
  * @blkcg: blkcg of interest
  *
@@ -1938,7 +1954,7 @@ void bio_associate_blkg(struct bio *bio)
 	rcu_read_lock();
 
 	if (bio->bi_blkg)
-		css = &bio_blkcg(bio)->css;
+		css = bio_blkcg_css(bio);
 	else
 		css = blkcg_css();
 
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index b00fb1169e7c..03405ddf2a7b 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -25,6 +25,64 @@ struct blkg_policy_data;
 #define BLKG_STAT_CPU_BATCH	(INT_MAX / 2)
 
 #ifdef CONFIG_BLK_CGROUP
+
+enum blkg_iostat_type {
+	BLKG_IOSTAT_READ,
+	BLKG_IOSTAT_WRITE,
+	BLKG_IOSTAT_DISCARD,
+
+	BLKG_IOSTAT_NR,
+};
+
+struct blkg_iostat {
+	u64				bytes[BLKG_IOSTAT_NR];
+	u64				ios[BLKG_IOSTAT_NR];
+};
+
+struct blkg_iostat_set {
+	struct u64_stats_sync		sync;
+	struct blkg_iostat		cur;
+	struct blkg_iostat		last;
+};
+
+/* association between a blk cgroup and a request queue */
+struct blkcg_gq {
+	/* Pointer to the associated request_queue */
+	struct request_queue		*q;
+	struct list_head		q_node;
+	struct hlist_node		blkcg_node;
+	struct blkcg			*blkcg;
+
+	/* all non-root blkcg_gq's are guaranteed to have access to parent */
+	struct blkcg_gq			*parent;
+
+	/* reference count */
+	struct percpu_ref		refcnt;
+
+	/* is this blkg online? protected by both blkcg and q locks */
+	bool				online;
+
+	struct blkg_iostat_set __percpu	*iostat_cpu;
+	struct blkg_iostat_set		iostat;
+
+	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
+
+	spinlock_t			async_bio_lock;
+	struct bio_list			async_bios;
+	union {
+		struct work_struct	async_bio_work;
+		struct work_struct	free_work;
+	};
+
+	atomic_t			use_delay;
+	atomic64_t			delay_nsec;
+	atomic64_t			delay_start;
+	u64				last_delay;
+	int				last_use;
+
+	struct rcu_head			rcu_head;
+};
+
 struct blkcg {
 	struct cgroup_subsys_state	css;
 	spinlock_t			lock;
@@ -173,9 +231,9 @@ static inline struct cgroup_subsys_state *blkcg_css(void)
  *
  * In order to avoid priority inversions we sometimes need to issue a bio as if
  * it were attached to the root blkg, and then backcharge to the actual owning
- * blkg.  The idea is we do bio_blkcg() to look up the actual context for the
- * bio and attach the appropriate blkg to the bio.  Then we call this helper and
- * if it is true run with the root blkg for that queue and then do any
+ * blkg.  The idea is we do bio_blkcg_css() to look up the actual context for
+ * the bio and attach the appropriate blkg to the bio.  Then we call this helper
+ * and if it is true run with the root blkg for that queue and then do any
  * backcharging to the originating cgroup once the io is complete.
  */
 static inline bool bio_issue_as_root_blkg(struct bio *bio)
@@ -464,6 +522,9 @@ struct blkcg_policy_data {
 struct blkcg_policy {
 };
 
+struct blkcg {
+};
+
 #ifdef CONFIG_BLOCK
 
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }