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>

1 files changed, 17 insertions, 1 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();