8 files changed, 25 insertions, 62 deletions

diff --git a/block/bio.c b/block/bio.c
index 387480de6992..71cfe3720ea7 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -609,7 +609,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
         bio->bi_iter = bio_src->bi_iter;
         bio->bi_io_vec = bio_src->bi_io_vec;
 
-        bio_clone_blkcg_association(bio, bio_src);
+        bio_clone_blkg_association(bio, bio_src);
 
         blkcg_bio_issue_init(bio);
 }
@@ -1957,34 +1957,6 @@ EXPORT_SYMBOL(bioset_init_from_src);
 #ifdef CONFIG_BLK_CGROUP
 
 /**
- * bio_associate_blkcg - associate a bio with the specified blkcg
- * @bio: target bio
- * @blkcg_css: css of the blkcg to associate
- *
- * Associate @bio with the blkcg specified by @blkcg_css.  Block layer will
- * treat @bio as if it were issued by a task which belongs to the blkcg.
- *
- * This function takes an extra reference of @blkcg_css which will be put
- * when @bio is released.  The caller must own @bio and is responsible for
- * synchronizing calls to this function.  If @blkcg_css is NULL, a call to
- * blkcg_get_css finds the current css from the kthread or task.
- */
-int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
-{
-        if (unlikely(bio->bi_css))
-                return -EBUSY;
-
-        if (blkcg_css)
-                css_get(blkcg_css);
-        else
-                blkcg_css = blkcg_get_css();
-
-        bio->bi_css = blkcg_css;
-        return 0;
-}
-EXPORT_SYMBOL_GPL(bio_associate_blkcg);
-
-/**
  * bio_associate_blkg - associate a bio with the a blkg
  * @bio: target bio
  * @blkg: the blkg to associate
@@ -2033,7 +2005,6 @@ int bio_associate_blkg_from_css(struct bio *bio,
                                 struct cgroup_subsys_state *css)
 {
         css_get(css);
-        bio->bi_css = css;
         return __bio_associate_blkg_from_css(bio, css);
 }
 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
@@ -2054,12 +2025,11 @@ int bio_associate_blkg_from_page(struct bio *bio, struct page *page)
 {
         struct cgroup_subsys_state *css;
 
-        if (unlikely(bio->bi_css))
+        if (unlikely(bio->bi_blkg))
                 return -EBUSY;
         if (!page->mem_cgroup)
                 return 0;
         css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
-        bio->bi_css = css;
 
         return __bio_associate_blkg_from_css(bio, css);
 }
@@ -2085,8 +2055,7 @@ int bio_associate_create_blkg(struct request_queue *q, struct bio *bio)
 
         rcu_read_lock();
 
-        bio_associate_blkcg(bio, NULL);
-        blkcg = bio_blkcg(bio);
+        blkcg = css_to_blkcg(blkcg_get_css());
 
         if (!blkcg->css.parent) {
                 ret = bio_associate_blkg(bio, q->root_blkg);
@@ -2110,30 +2079,27 @@ void bio_disassociate_task(struct bio *bio)
                 put_io_context(bio->bi_ioc);
                 bio->bi_ioc = NULL;
         }
-        if (bio->bi_css) {
-                css_put(bio->bi_css);
-                bio->bi_css = NULL;
-        }
         if (bio->bi_blkg) {
+                /* a ref is always taken on css */
+                css_put(&bio_blkcg(bio)->css);
                 blkg_put(bio->bi_blkg);
                 bio->bi_blkg = NULL;
         }
 }
 
 /**
- * bio_clone_blkcg_association - clone blkcg association from src to dst bio
+ * bio_clone_blkg_association - clone blkg association from src to dst bio
  * @dst: destination bio
  * @src: source bio
  */
-void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
+void bio_clone_blkg_association(struct bio *dst, struct bio *src)
 {
-        if (src->bi_css)
-                WARN_ON(bio_associate_blkcg(dst, src->bi_css));
-
-        if (src->bi_blkg)
+        if (src->bi_blkg) {
+                css_get(&bio_blkcg(src)->css);
                 bio_associate_blkg(dst, src->bi_blkg);
+        }
 }
-EXPORT_SYMBOL_GPL(bio_clone_blkcg_association);
+EXPORT_SYMBOL_GPL(bio_clone_blkg_association);
 #endif /* CONFIG_BLK_CGROUP */
 
 static void __init biovec_init_slabs(void)
diff --git a/block/bounce.c b/block/bounce.c
index 7a08703b1204..b30071ac4ec6 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -257,7 +257,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
                 }
         }
 
-        bio_clone_blkcg_association(bio, bio_src);
+        bio_clone_blkg_association(bio, bio_src);
 
         blkcg_bio_issue_init(bio);
 
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ea9debf59b22..abad6d15f956 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -77,6 +77,7 @@
 #include <linux/falloc.h>
 #include <linux/uio.h>
 #include <linux/ioprio.h>
+#include <linux/blk-cgroup.h>
 
 #include "loop.h"
 
@@ -1760,8 +1761,8 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
 
         /* always use the first bio's css */
 #ifdef CONFIG_BLK_CGROUP
-        if (cmd->use_aio && rq->bio && rq->bio->bi_css) {
-                cmd->css = rq->bio->bi_css;
+        if (cmd->use_aio && rq->bio && rq->bio->bi_blkg) {
+                cmd->css = &bio_blkcg(rq->bio)->css;
                 css_get(cmd->css);
         } else
 #endif
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index ac1cffd2a09b..f3fb5bb8c82a 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -542,7 +542,7 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
                     !discard_bio)
                         continue;
                 bio_chain(discard_bio, bio);
-                bio_clone_blkcg_association(discard_bio, bio);
+                bio_clone_blkg_association(discard_bio, bio);
                 if (mddev->gendisk)
                         trace_block_bio_remap(bdev_get_queue(rdev->bdev),
                                 discard_bio, disk_devt(mddev->gendisk),
diff --git a/include/linux/bio.h b/include/linux/bio.h
index c73a870ebc0e..e973876625a8 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -540,24 +540,21 @@ static inline int bio_associate_blkg_from_page(struct bio *bio,
 #endif
 
 #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);
 int bio_associate_blkg_from_css(struct bio *bio,
                                 struct cgroup_subsys_state *css);
 int bio_associate_create_blkg(struct request_queue *q, struct bio *bio);
 void bio_disassociate_task(struct bio *bio);
-void bio_clone_blkcg_association(struct bio *dst, struct bio *src);
+void bio_clone_blkg_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_blkg_from_css(struct bio *bio,
                                               struct cgroup_subsys_state *css)
 { return 0; }
 static inline int bio_associate_create_blkg(struct request_queue *q,
                                             struct bio *bio) { return 0; }
 static inline void bio_disassociate_task(struct bio *bio) { }
-static inline void bio_clone_blkcg_association(struct bio *dst,
-                        struct bio *src) { }
+static inline void bio_clone_blkg_association(struct bio *dst,
+                                              struct bio *src) { }
 #endif  /* CONFIG_BLK_CGROUP */
 
 #ifdef CONFIG_HIGHMEM
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index a6b6e741a75e..c41cfcc2b4d8 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -308,8 +308,8 @@ static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
  */
 static inline struct blkcg *__bio_blkcg(struct bio *bio)
 {
-        if (bio && bio->bi_css)
-                return css_to_blkcg(bio->bi_css);
+        if (bio && bio->bi_blkg)
+                return bio->bi_blkg->blkcg;
         return css_to_blkcg(blkcg_css());
 }
 
@@ -323,8 +323,8 @@ static inline struct blkcg *__bio_blkcg(struct bio *bio)
  */
 static inline struct blkcg *bio_blkcg(struct bio *bio)
 {
-        if (bio && bio->bi_css)
-                return css_to_blkcg(bio->bi_css);
+        if (bio && bio->bi_blkg)
+                return bio->bi_blkg->blkcg;
         return NULL;
 }
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index f6dfb30737d8..9578c7ab1eb6 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -178,7 +178,6 @@ struct bio {
          * release.  Read comment on top of bio_associate_current().
          */
         struct io_context       *bi_ioc;
-        struct cgroup_subsys_state *bi_css;
         struct blkcg_gq         *bi_blkg;
         struct bio_issue        bi_issue;
 #endif
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 2868d85f1fb1..fac0ddf8a8e2 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -764,9 +764,9 @@ blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
         if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
                 return NULL;
 
-        if (!bio->bi_css)
+        if (!bio->bi_blkg)
                 return NULL;
-        return cgroup_get_kernfs_id(bio->bi_css->cgroup);
+        return cgroup_get_kernfs_id(bio_blkcg(bio)->css.cgroup);
 }
 #else
 static union kernfs_node_id *