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blkcg: remove bio->bi_css and instead use bio->bi_blkg
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Prior patches ensured that all bios are now associated with some blkg.
This now makes bio->bi_css unnecessary as blkg maintains a reference to
the blkcg already.

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

Signed-off-by: Dennis Zhou <[email protected]>
Reviewed-by: Josef Bacik <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
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@dennisszhou @axboe
dennisszhou authored and axboe committed Sep 22, 2018
1 parent bdc2491 commit c839e7a
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Showing 8 changed files with 25 additions and 62 deletions.
56 changes: 11 additions & 45 deletions block/bio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}
Expand Down Expand Up @@ -1956,34 +1956,6 @@ 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
Expand Down Expand Up @@ -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);
Expand All @@ -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);
}
Expand All @@ -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);
Expand All @@ -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)
Expand Down
2 changes: 1 addition & 1 deletion block/bounce.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down
5 changes: 3 additions & 2 deletions drivers/block/loop.c
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,7 @@
#include <linux/falloc.h>
#include <linux/uio.h>
#include <linux/ioprio.h>
#include <linux/blk-cgroup.h>

#include "loop.h"

Expand Down Expand Up @@ -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
Expand Down
2 changes: 1 addition & 1 deletion drivers/md/raid0.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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),
Expand Down
9 changes: 3 additions & 6 deletions include/linux/bio.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down
8 changes: 4 additions & 4 deletions include/linux/blk-cgroup.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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());
}

Expand All @@ -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;
}

Expand Down
1 change: 0 additions & 1 deletion include/linux/blk_types.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down
4 changes: 2 additions & 2 deletions kernel/trace/blktrace.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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 *
Expand Down

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