[PATCH 2/3] block: make blkcg aware of kthread stored original cgroup info

[Shaohua Li <shli@kernel.org>]

From: Shaohua Li <shli@fb.com>

Several blkcg APIs are deprecated. After removing them, bio_blkcg is the
only API to get cgroup info for a bio. If bio_blkcg finds current task
is a kthread and has original css recorded, it will use the css instead
of associating the bio to current task.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 block/bio.c                | 31 -------------------------------
 include/linux/bio.h        |  2 --
 include/linux/blk-cgroup.h | 25 +++++++------------------
 3 files changed, 7 insertions(+), 51 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 6745759..9271fa3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2033,37 +2033,6 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
 EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
- * bio_associate_current - associate a bio with %current
- * @bio: target bio
- *
- * Associate @bio with %current if it hasn't been associated yet.  Block
- * layer will treat @bio as if it were issued by %current no matter which
- * task actually issues it.
- *
- * This function takes an extra reference of @task's io_context and blkcg
- * which will be put when @bio is released.  The caller must own @bio,
- * ensure %current->io_context exists, and is responsible for synchronizing
- * calls to this function.
- */
-int bio_associate_current(struct bio *bio)
-{
-	struct io_context *ioc;
-
-	if (bio->bi_css)
-		return -EBUSY;
-
-	ioc = current->io_context;
-	if (!ioc)
-		return -ENOENT;
-
-	get_io_context_active(ioc);
-	bio->bi_ioc = ioc;
-	bio->bi_css = task_get_css(current, io_cgrp_id);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(bio_associate_current);
-
-/**
  * bio_disassociate_task - undo bio_associate_current()
  * @bio: target bio
  */
diff --git a/include/linux/bio.h b/include/linux/bio.h
index a8fe793..d795cdd 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -514,13 +514,11 @@ do {						\
 
 #ifdef CONFIG_BLK_CGROUP
 int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css);
-int bio_associate_current(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 int bio_associate_current(struct bio *bio) { return -ENOENT; }
 static inline void bio_disassociate_task(struct bio *bio) { }
 static inline void bio_clone_blkcg_association(struct bio *dst,
 			struct bio *src) { }
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 9d92153..0cdcf6b 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -19,6 +19,7 @@
 #include <linux/radix-tree.h>
 #include <linux/blkdev.h>
 #include <linux/atomic.h>
+#include <linux/kthread.h>
 
 /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
 #define BLKG_STAT_CPU_BATCH	(INT_MAX / 2)
@@ -223,22 +224,16 @@ static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 	return css ? container_of(css, struct blkcg, css) : NULL;
 }
 
-static inline struct blkcg *task_blkcg(struct task_struct *tsk)
-{
-	return css_to_blkcg(task_css(tsk, io_cgrp_id));
-}
-
 static inline struct blkcg *bio_blkcg(struct bio *bio)
 {
+	struct cgroup_subsys_state *css;
+
 	if (bio && bio->bi_css)
 		return css_to_blkcg(bio->bi_css);
-	return task_blkcg(current);
-}
-
-static inline struct cgroup_subsys_state *
-task_get_blkcg_css(struct task_struct *task)
-{
-	return task_get_css(task, io_cgrp_id);
+	css = kthread_get_orig_css();
+	if (css)
+		return css_to_blkcg(css);
+	return css_to_blkcg(task_css(current, io_cgrp_id));
 }
 
 /**
@@ -735,12 +730,6 @@ struct blkcg_policy {
 
 #define blkcg_root_css	((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))
 
-static inline struct cgroup_subsys_state *
-task_get_blkcg_css(struct task_struct *task)
-{
-	return NULL;
-}
-
 #ifdef CONFIG_BLOCK
 
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
-- 
2.9.5