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

[Tejun Heo]

Hello,

On Wed, Sep 06, 2017 at 07:00:52PM -0700, Shaohua Li wrote:
> From: Shaohua Li 
> 
> 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.

Can you please separate out removal of unused APIs from modifications
of existing ones?  The patch is a bit confusing to follow.

Thanks.

-- 
tejun

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

[Shaohua Li]

From: Shaohua Li 

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 
---
 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 
 #include 
 #include 
+#include 
 
 /* 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