blkcg: remove bio->bi_css and instead use bio->bi_blkg

Prior patches ensured that any bio that interacts with a request_queue
is properly associated with a blkg. This makes bio->bi_css unnecessary
as blkg maintains a reference to blkcg already.

This removes the bio field bi_css and transfers corresponding uses to
access via bi_blkg.

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 b42477b..2b6bc7b 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -610,7 +610,7 @@ 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);
 }
 EXPORT_SYMBOL(__bio_clone_fast);
@@ -1958,34 +1958,6 @@ 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_disassociate_blkg - puts back the blkg reference if associated
  * @bio: target bio
  *
@@ -1994,6 +1966,8 @@ EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 void bio_disassociate_blkg(struct bio *bio)
 {
        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;
        }
@@ -2047,7 +2021,6 @@ void bio_associate_blkg_from_css(struct bio *bio,
                                 struct cgroup_subsys_state *css)
 {
        css_get(css);
-       bio->bi_css = css;
        __bio_associate_blkg_from_css(bio, css);
 }
 EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);
@@ -2066,13 +2039,10 @@ void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
 {
        struct cgroup_subsys_state *css;
 
-       if (unlikely(bio->bi_css))
-               return;
        if (!page->mem_cgroup)
                return;
 
        css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
-       bio->bi_css = css;
        __bio_associate_blkg_from_css(bio, css);
 }
 #endif /* CONFIG_MEMCG */
@@ -2094,8 +2064,10 @@ void bio_associate_blkg(struct bio *bio)
 
        rcu_read_lock();
 
-       bio_associate_blkcg(bio, NULL);
-       blkcg = bio_blkcg(bio);
+       if (bio->bi_blkg)
+               blkcg = bio->bi_blkg->blkcg;
+       else
+               blkcg = css_to_blkcg(blkcg_get_css());
 
        if (!blkcg->css.parent) {
                __bio_associate_blkg(bio, q->root_blkg);
@@ -2115,27 +2087,22 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg);
  */
 void bio_disassociate_task(struct bio *bio)
 {
-       if (bio->bi_css) {
-               css_put(bio->bi_css);
-               bio->bi_css = NULL;
-       }
        bio_disassociate_blkg(bio);
 }
 
 /**
- * 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 cfb96d5..ffb9e9e 100644 (file)
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -277,7 +277,7 @@ 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);
 
        return bio;

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 176ab1f..0770004 100644 (file)
--- 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"
 
@@ -1820,8 +1821,8 @@ 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 ac1cffd..f3fb5bb 100644 (file)
--- 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 f043806..84e1c4d 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -498,7 +498,7 @@ do {                                                \
 do {                                           \
        (dst)->bi_disk = (src)->bi_disk;        \
        (dst)->bi_partno = (src)->bi_partno;    \
-       bio_clone_blkcg_association(dst, src);  \
+       bio_clone_blkg_association(dst, src);   \
 } while (0)
 
 #define bio_dev(bio) \
@@ -512,24 +512,21 @@ static inline void 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);
 void bio_disassociate_blkg(struct bio *bio);
 void bio_associate_blkg(struct bio *bio);
 void bio_associate_blkg_from_css(struct bio *bio,
                                 struct cgroup_subsys_state *css);
 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 void bio_disassociate_blkg(struct bio *bio) { }
 static inline void bio_associate_blkg(struct bio *bio) { }
 static inline void bio_associate_blkg_from_css(struct bio *bio,
                                               struct cgroup_subsys_state *css)
 { }
 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 8b069c3..f11c37f 100644 (file)
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -309,8 +309,8 @@ 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());
 }
 
@@ -324,8 +324,8 @@ 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 c0ba1a0..46c005d 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -174,10 +174,11 @@ struct bio {
        void                    *bi_private;
 #ifdef CONFIG_BLK_CGROUP
        /*
-        * Optional css associated with this bio.  Put on bio
-        * release.  Read comment on top of bio_associate_current().
+        * Represents the association of the css and request_queue for the bio.
+        * If a bio goes direct to device, it will not have a blkg as it will
+        * not have a request_queue associated with it.  The reference is put
+        * on release of the bio.
         */
-       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 2868d85..fac0ddf 100644 (file)
--- 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 *