block: always associate blkg and refcount cleanup
Subsystems (13)
v6 cover block: always associate blkg and refcount cleanup
Hi everyone,
This is a minor update addressing the feedback from Mike and Josef.
v6:
0005: Address Mike's feedback for the flush bio comment. 0006: Add a WARN_ONCE() for blkg fallback suggested by Josef.
From v5:
A special case with dm is the flush bio which is statically initialized before the block device is opened and associated with a disk. This caused blkg association to throw a NPE. 0005 addresses this case by moving association to be on the flush path.
With v4 moving association to piggyback off of bio_set_dev(), this caused a NPE to be thrown by the special case above. I was overly cautious with v4 and added the bio_has_queue() check which is now removed in v5.
Also, the addition of bio_set_dev_only() wasn't quite right due to writeback and swap sharing the same bio init paths in many places. The safer thing to do is double association for those paths and in a follow up series split out the bio init paths.
Changes in v5:
All: Fixed minor grammar and syntactic issues.
0004: Removed bio_has_queue() for being overly cautious. 0005: New, properly addressed the static flush_bio in md. 0006: Removed the rcu lock in blkcg_bio_issue_check() as the bio will
own a ref on the blkg so it is unnecessary.
0011: Consolidated bio_associate_blkg_from_css() (removed __ version).
From v4:
This is respin of v3 [1] with fixes for the errors reported in [2] and [3]. v3 was reverted in [4].
The issue in [3] was that bio->bi_disk->queue and blkg->q were out of sync. So when I changed blk_get_rl() to use blkg->q, the wrong queue was returned and elevator from q->elevator->type threw a NPE. Note, with v4.21, the old block stack was removed and so this patch was dropped. I did backport this to v4.20 and verified this series does not encounter the error.
The biggest changes in v4 are when association occurs and clearly defining the cases where association should happen.
1. Association is now done when the device is set to keep blkg->q and
bio->bi_disk->queue in sync.
2. When a bio is submitted directly to the device, it will not be associated with a blkg. This is because a blkg represents the relationship between a blkcg and a request_queue. Going directly to the device means the request_queue may not exist meaning no blkg will exist.
The patch updating blk_get_rl() was dropped (v3 10/12). The patch to always associate a blkg from v3 (v3 04/12) was fixed and split into patches 0004 and 0005. 0011 is new removing bio_disassociate_task().
Summarizing the ideas of this series:
1. Gracefully handle blkg failure to create by walking up the blkg tree rather than fall through to root.
2. Associate a bio with a blkg in core logic rather than per controller logic.
3. Rather than have a css and blkg reference, hold just a blkg ref as it also holds a css ref.
4. Switch to percpu ref counting for blkg.
[1] https://lore.kernel.org/lkml/[email protected]/
[2] https://lore.kernel.org/lkml/[email protected]/
[3] https://marc.info/?l=linux-cgroups&m=154110436103723
[4] https://lore.kernel.org/lkml/[email protected]/
This patchset contains the following 14 patches:
0001-blkcg-fix-ref-count-issue-with-bio_blkcg-using-task_.patch 0002-blkcg-update-blkg_lookup_create-to-do-locking.patch 0003-blkcg-convert-blkg_lookup_create-to-find-closest-blk.patch 0004-blkcg-introduce-common-blkg-association-logic.patch 0005-dm-set-flush-bio-device-on-demand.patch 0006-blkcg-associate-blkg-when-associating-a-device.patch 0007-blkcg-consolidate-bio_issue_init-to-be-a-part-of-cor.patch 0008-blkcg-associate-a-blkg-for-pages-being-evicted-by-sw.patch 0009-blkcg-associate-writeback-bios-with-a-blkg.patch 0010-blkcg-remove-bio-bi_css-and-instead-use-bio-bi_blkg.patch 0011-blkcg-remove-additional-reference-to-the-css.patch 0012-blkcg-remove-bio_disassociate_task.patch 0013-blkcg-change-blkg-reference-counting-to-use-percpu_r.patch 0014-blkcg-rename-blkg_try_get-to-blkg_tryget.patch
This patchset is on top of linux-block#for-4.21/block 154989e45fd8.
diffstats below:
Dennis Zhou (14):
blkcg: fix ref count issue with bio_blkcg() using task_css
blkcg: update blkg_lookup_create() to do locking
blkcg: convert blkg_lookup_create() to find closest blkg
blkcg: introduce common blkg association logic
dm: set the static flush bio device on demand
blkcg: associate blkg when associating a device
blkcg: consolidate bio_issue_init() to be a part of core
blkcg: associate a blkg for pages being evicted by swap
blkcg: associate writeback bios with a blkg
blkcg: remove bio->bi_css and instead use bio->bi_blkg
blkcg: remove additional reference to the css
blkcg: remove bio_disassociate_task()
blkcg: change blkg reference counting to use percpu_ref
blkcg: rename blkg_try_get() to blkg_tryget()
Documentation/admin-guide/cgroup-v2.rst | 8 +- block/bfq-cgroup.c | 4 +- block/bfq-iosched.c | 2 +- block/bio.c | 156 +++++++++++++++--------- block/blk-cgroup.c | 95 ++++++++++++--- block/blk-iolatency.c | 24 +--- block/blk-throttle.c | 11 -- block/bounce.c | 3 +- drivers/block/loop.c | 5 +- drivers/md/dm.c | 12 +- drivers/md/raid0.c | 2 +- fs/buffer.c | 10 +- fs/ext4/page-io.c | 2 +- include/linux/bio.h | 29 +++-- include/linux/blk-cgroup.h | 125 +++++++++++++------ include/linux/blk_types.h | 7 +- include/linux/cgroup.h | 2 + include/linux/writeback.h | 5 +- kernel/cgroup/cgroup.c | 48 ++++++-- kernel/trace/blktrace.c | 4 +- mm/page_io.c | 2 +- 21 files changed, 367 insertions(+), 189 deletions(-)
Thanks,
Dennis
PATCH v6 1/14 blkcg: fix ref count issue with bio_blkcg() using task_css
The bio_blkcg() function turns out to be inconsistent and consequently dangerous to use. The first part returns a blkcg where a reference is owned by the bio meaning it does not need to be rcu protected. However, the third case, the last line, is problematic:
return css_to_blkcg(task_css(current, io_cgrp_id));
This can race against task migration and the cgroup dying. It is also semantically different as it must be called rcu protected and is susceptible to failure when trying to get a reference to it.
This patch adds association ahead of calling bio_blkcg() rather than after. This makes association a required and explicit step along the code paths for calling bio_blkcg(). In blk-iolatency, association is moved above the bio_blkcg() call to ensure it will not return %NULL.
BFQ uses the old bio_blkcg() function, but I do not want to address it in this series due to the complexity. I have created a private version documenting the inconsistency and noting not to use it.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bfq-cgroup.c | 4 +- block/bfq-iosched.c | 2 +- block/bio.c | 10 +++- block/blk-iolatency.c | 2 +- include/linux/blk-cgroup.h | 98 ++++++++++++++++++++++++++++++++++---- 5 files changed, 102 insertions(+), 14 deletions(-)
block/bfq-cgroup.c +2 -2
@@ -642,7 +642,7 @@ void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)uint64_t serial_nr;rcu_read_lock (); - serial_nr =bio_blkcg (bio)->css.serial_nr; + serial_nr =__bio_blkcg (bio)->css.serial_nr;/* * Check whether blkcg has changed. The condition may trigger
@@ -651,7 +651,7 @@ void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)if (unlikely (!bfqd) ||likely (bic->blkcg_serial_nr == serial_nr)) goto out; - bfqg =__bfq_bic_change_cgroup (bfqd, bic,bio_blkcg (bio)); + bfqg =__bfq_bic_change_cgroup (bfqd, bic,__bio_blkcg (bio));/* * Update blkg_path for bfq_log_* functions. We cache this * path, and update it here, for the following
block/bfq-iosched.c +1 -1
@@ -4384,7 +4384,7 @@ static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,rcu_read_lock (); - bfqg =bfq_find_set_group (bfqd,bio_blkcg (bio)); + bfqg =bfq_find_set_group (bfqd,__bio_blkcg (bio));if (!bfqg) { bfqq = &bfqd->oom_bfqq; goto out;
block/bio.c +8 -2
@@ -1990,13 +1990,19 @@ int bio_associate_blkcg_from_page(struct bio *bio, struct page *page)* * 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. +* 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 ; -css_get (blkcg_css); + +if (blkcg_css) +css_get (blkcg_css); +else + blkcg_css =blkcg_get_css (); + bio->bi_css = blkcg_css;return 0 ; }
block/blk-iolatency.c +1 -1
@@ -481,8 +481,8 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)return ;rcu_read_lock (); +bio_associate_blkcg (bio,NULL ); blkcg =bio_blkcg (bio); -bio_associate_blkcg (bio, &blkcg->css); blkg =blkg_lookup (blkcg, q);if (unlikely (!blkg)) {spin_lock_irq (&q->queue_lock);
include/linux/blk-cgroup.h +90 -8
128 lines not on this page · raw message
Signature · 1 line
2.17.1
PATCH v6 2/14 blkcg: update blkg_lookup_create() to do locking
In reply to Dennis ZhouTo know when to create a blkg, the general pattern is to do a blkg_lookup() and if that fails, lock and do the lookup again, and if that fails finally create. It doesn't make much sense for everyone who wants to do creation to write this themselves.
This changes blkg_lookup_create() to do locking and implement this pattern. The old blkg_lookup_create() is renamed to __blkg_lookup_create(). If a call site wants to do its own error handling or already owns the queue lock, they can use __blkg_lookup_create(). This will be used in upcoming patches.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Liu Bo <[email protected]>
--- block/blk-cgroup.c | 28 +++++++++++++++++++++++++--- block/blk-iolatency.c | 2 +- include/linux/blk-cgroup.h | 4 +++- 3 files changed, 29 insertions(+), 5 deletions(-)
block/blk-cgroup.c +25 -3
@@ -249,7 +249,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, }/** -* blkg_lookup_create - lookup blkg, try to create one if not there +* __blkg_lookup_create - lookup blkg, try to create one if not there * @blkcg: blkcg of interest * @q: request_queue of interest *
@@ -262,8 +262,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,* value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not * dead and bypassing, returns ERR_PTR(-EBUSY). */ -struct blkcg_gq *blkg_lookup_create (struct blkcg *blkcg, -struct request_queue *q) +struct blkcg_gq *__blkg_lookup_create (struct blkcg *blkcg, +struct request_queue *q) {struct blkcg_gq *blkg;
@@ -293,6 +293,28 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, } } +/** +* blkg_lookup_create - find or create a blkg +* @blkcg: target block cgroup +* @q: target request_queue +* +* This looks up or creates the blkg representing the unique pair +* of the blkcg and the request_queue. +*/ +struct blkcg_gq *blkg_lookup_create (struct blkcg *blkcg, +struct request_queue *q) +{ +struct blkcg_gq *blkg =blkg_lookup (blkcg, q); + +if (unlikely (!blkg)) { +spin_lock_irq (&q->queue_lock); + blkg =__blkg_lookup_create (blkcg, q); +spin_unlock_irq (&q->queue_lock); + } + +return blkg; +} +static void blkg_destroy (struct blkcg_gq *blkg) {struct blkcg *blkcg = blkg->blkcg;
block/blk-iolatency.c +1 -1
@@ -486,7 +486,7 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) blkg =blkg_lookup (blkcg, q);if (unlikely (!blkg)) {spin_lock_irq (&q->queue_lock); - blkg =blkg_lookup_create (blkcg, q); + blkg =__blkg_lookup_create (blkcg, q);if (IS_ERR (blkg)) blkg =NULL ;spin_unlock_irq (&q->queue_lock);
include/linux/blk-cgroup.h +3 -1
@@ -181,6 +181,8 @@ extern struct cgroup_subsys_state * const blkcg_root_css;struct blkcg_gq *blkg_lookup_slowpath (struct blkcg *blkcg,struct request_queue *q,bool update_hint); +struct blkcg_gq *__blkg_lookup_create (struct blkcg *blkcg, +struct request_queue *q);struct blkcg_gq *blkg_lookup_create (struct blkcg *blkcg,struct request_queue *q);int blkcg_init_queue (struct request_queue *q);
@@ -799,7 +801,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q, blkg =blkg_lookup (blkcg, q);if (unlikely (!blkg)) {spin_lock_irq (&q->queue_lock); - blkg =blkg_lookup_create (blkcg, q); + blkg =__blkg_lookup_create (blkcg, q);if (IS_ERR (blkg)) blkg =NULL ;spin_unlock_irq (&q->queue_lock);
Signature · 1 line
2.17.1
PATCH v6 3/14 blkcg: convert blkg_lookup_create() to find closest blkg
In reply to Dennis ZhouThere are several scenarios where blkg_lookup_create() can fail such as the blkcg dying, request_queue is dying, or simply being OOM. Most handle this by simply falling back to the q->root_blkg and calling it a day.
This patch implements the notion of closest blkg. During blkg_lookup_create(), if it fails to create, return the closest blkg found or the q->root_blkg. blkg_try_get_closest() is introduced and used during association so a bio is always attached to a blkg.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bio.c | 17 ++++++++++------- block/blk-cgroup.c | 23 ++++++++++++++++------- block/blk-iolatency.c | 14 ++------------ block/blk-throttle.c | 4 +--- include/linux/blk-cgroup.h | 24 +++++++++++++++--------- 5 files changed, 44 insertions(+), 38 deletions(-)
block/bio.c +10 -7
@@ -2009,21 +2009,24 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)EXPORT_SYMBOL_GPL (bio_associate_blkcg);/** -* bio_associate_blkg - associate a bio with the specified blkg +* bio_associate_blkg - associate a bio with the a blkg * @bio: target bio * @blkg: the blkg to associate * -* Associate @bio with the blkg specified by @blkg. This is the queue specific -* blkcg information associated with the @bio, a reference will be taken on the -* @blkg and will be freed when the bio is freed. +* This tries to associate @bio with the specified @blkg. Association failure +* is handled by walking up the blkg tree. Therefore, the blkg associated can +* be anything between @blkg and the root_blkg. This situation only happens +* when a cgroup is dying and then the remaining bios will spill to the closest +* alive blkg. +* +* A reference will be taken on the @blkg and will be released when @bio is +* freed. */ int bio_associate_blkg (struct bio *bio,struct blkcg_gq *blkg) {if (unlikely (bio->bi_blkg))return -EBUSY ; -if (!blkg_try_get (blkg)) -return -ENODEV ; - bio->bi_blkg = blkg; + bio->bi_blkg =blkg_try_get_closest (blkg);return 0 ; }
block/blk-cgroup.c +16 -7
@@ -258,9 +258,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,* that all non-root blkg's have access to the parent blkg. This function * should be called under RCU read lock and @q->queue_lock. * -* Returns pointer to the looked up or created blkg on success, ERR_PTR() -* value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not -* dead and bypassing, returns ERR_PTR(-EBUSY). +* Returns the blkg or the closest blkg if blkg_create() fails as it walks +* down from root. */ struct blkcg_gq *__blkg_lookup_create (struct blkcg *blkcg,struct request_queue *q)
@@ -276,19 +275,29 @@ struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,/* * Create blkgs walking down from blkcg_root to @blkcg, so that all -* non-root blkgs have access to their parents. +* non-root blkgs have access to their parents. Returns the closest +* blkg to the intended blkg should blkg_create() fail. */ while (true) {struct blkcg *pos = blkcg;struct blkcg *parent =blkcg_parent (blkcg); - -while (parent && !__blkg_lookup (parent, q, false)) { +struct blkcg_gq *ret_blkg = q->root_blkg; + +while (parent) { + blkg =__blkg_lookup (parent, q, false); +if (blkg) { +/* remember closest blkg */ + ret_blkg = blkg; +break ; + } pos = parent; parent =blkcg_parent (parent); } blkg =blkg_create (pos, q,NULL ); -if (pos == blkcg ||IS_ERR (blkg)) +if (IS_ERR (blkg)) +return ret_blkg; +if (pos == blkcg)return blkg; } }
block/blk-iolatency.c +2 -12
@@ -483,21 +483,11 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)rcu_read_lock ();bio_associate_blkcg (bio,NULL ); blkcg =bio_blkcg (bio); - blkg =blkg_lookup (blkcg, q); -if (unlikely (!blkg)) { -spin_lock_irq (&q->queue_lock); - blkg =__blkg_lookup_create (blkcg, q); -if (IS_ERR (blkg)) - blkg =NULL ; -spin_unlock_irq (&q->queue_lock); - } -if (!blkg) - goto out; - + blkg =blkg_lookup_create (blkcg, q);bio_issue_init (&bio->bi_issue,bio_sectors (bio));bio_associate_blkg (bio, blkg); -out:rcu_read_unlock (); +while (blkg && blkg->parent) {struct iolatency_grp *iolat =blkg_to_lat (blkg);if (!iolat) {
block/blk-throttle.c +1 -3
@@ -2118,9 +2118,7 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)static void blk_throtl_assoc_bio (struct throtl_grp *tg,struct bio *bio) {#ifdef CONFIG_BLK_DEV_THROTTLING_LOW -/* fallback to root_blkg if we fail to get a blkg ref */ -if (bio->bi_css && (bio_associate_blkg (bio,tg_to_blkg (tg)) == -ENODEV )) -bio_associate_blkg (bio, bio->bi_disk->queue->root_blkg); +bio_associate_blkg (bio,tg_to_blkg (tg));bio_issue_init (&bio->bi_issue,bio_sectors (bio));#endif }
include/linux/blk-cgroup.h +15 -9
@@ -545,6 +545,20 @@ static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg)return NULL ; } +/** +* blkg_try_get_closest - try and get a blkg ref on the closet blkg +* @blkg: blkg to get +* +* This walks up the blkg tree to find the closest non-dying blkg and returns +* the blkg that it did association with as it may not be the passed in blkg. +*/ +static inline struct blkcg_gq *blkg_try_get_closest (struct blkcg_gq *blkg) +{ +while (!atomic_inc_not_zero (&blkg->refcnt)) + blkg = blkg->parent; + +return blkg; +}void __blkg_release_rcu (struct rcu_head *rcu);
@@ -797,15 +811,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,/* associate blkcg if bio hasn't attached one */ bio_associate_blkcg (bio,NULL ); blkcg =bio_blkcg (bio); - - blkg =blkg_lookup (blkcg, q); -if (unlikely (!blkg)) { -spin_lock_irq (&q->queue_lock); - blkg =__blkg_lookup_create (blkcg, q); -if (IS_ERR (blkg)) - blkg =NULL ; -spin_unlock_irq (&q->queue_lock); - } + blkg =blkg_lookup_create (blkcg, q); throtl =blk_throtl_bio (q, blkg, bio);
Signature · 1 line
2.17.1
PATCH v6 4/14 blkcg: introduce common blkg association logic
In reply to Dennis ZhouThere are 3 ways blkg association can happen: association with the current css, with the page css (swap), or from the wbc css (writeback).
This patch handles how association is done for the first case where we are associating bsaed on the current css. If there is already a blkg associated, the css will be reused and association will be redone as the request_queue may have changed.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
--- block/bio.c | 62 ++++++++++++++++++++++++++++++++++++------- block/blk-iolatency.c | 10 ++----- block/blk-throttle.c | 6 ++--- include/linux/bio.h | 5 +++- 4 files changed, 62 insertions(+), 21 deletions(-)
block/bio.c +53 -9
@@ -2009,7 +2009,21 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)EXPORT_SYMBOL_GPL (bio_associate_blkcg);/** -* bio_associate_blkg - associate a bio with the a blkg +* bio_disassociate_blkg - puts back the blkg reference if associated +* @bio: target bio +* +* Helper to disassociate the blkg from @bio if a blkg is associated. +*/ +void bio_disassociate_blkg (struct bio *bio) +{ +if (bio->bi_blkg) { +blkg_put (bio->bi_blkg); + bio->bi_blkg =NULL ; + } +} + +/** +* __bio_associate_blkg - associate a bio with the a blkg * @bio: target bio * @blkg: the blkg to associate *
@@ -2022,12 +2036,42 @@ EXPORT_SYMBOL_GPL(bio_associate_blkcg);* A reference will be taken on the @blkg and will be released when @bio is * freed. */ -int bio_associate_blkg (struct bio *bio,struct blkcg_gq *blkg) +static void __bio_associate_blkg (struct bio *bio,struct blkcg_gq *blkg) { -if (unlikely (bio->bi_blkg)) -return -EBUSY ; +bio_disassociate_blkg (bio); + bio->bi_blkg =blkg_try_get_closest (blkg); -return 0 ; +} + +/** +* bio_associate_blkg - associate a bio with a blkg +* @bio: target bio +* +* Associate @bio with the blkg found from the bio's css and request_queue. +* If one is not found, bio_lookup_blkg() creates the blkg. If a blkg is +* already associated, the css is reused and association redone as the +* request_queue may have changed. +*/ +void bio_associate_blkg (struct bio *bio) +{ +struct request_queue *q = bio->bi_disk->queue; +struct blkcg *blkcg; +struct blkcg_gq *blkg; + +rcu_read_lock (); + +bio_associate_blkcg (bio,NULL ); + blkcg =bio_blkcg (bio); + +if (!blkcg->css.parent) { +__bio_associate_blkg (bio, q->root_blkg); + }else { + blkg =blkg_lookup_create (blkcg, q); + +__bio_associate_blkg (bio, blkg); + } + +rcu_read_unlock (); }/**
@@ -2040,10 +2084,7 @@ void bio_disassociate_task(struct bio *bio)css_put (bio->bi_css); bio->bi_css =NULL ; } -if (bio->bi_blkg) { -blkg_put (bio->bi_blkg); - bio->bi_blkg =NULL ; - } +bio_disassociate_blkg (bio); }/**
@@ -2055,6 +2096,9 @@ void bio_clone_blkcg_association(struct bio *dst, struct bio *src) {if (src->bi_css)WARN_ON (bio_associate_blkcg (dst, src->bi_css)); + +if (src->bi_blkg) +__bio_associate_blkg (dst, src->bi_blkg); }EXPORT_SYMBOL_GPL (bio_clone_blkcg_association);#endif /* CONFIG_BLK_CGROUP */
block/blk-iolatency.c +2 -8
@@ -472,21 +472,15 @@ static void check_scale_change(struct iolatency_grp *iolat)static void blkcg_iolatency_throttle (struct rq_qos *rqos,struct bio *bio) {struct blk_iolatency *blkiolat =BLKIOLATENCY (rqos); -struct blkcg *blkcg;struct blkcg_gq *blkg; -struct request_queue *q = rqos->q;bool issue_as_root =bio_issue_as_root_blkg (bio);if (!blk_iolatency_enabled (blkiolat))return ; -rcu_read_lock (); -bio_associate_blkcg (bio,NULL ); - blkcg =bio_blkcg (bio); - blkg =blkg_lookup_create (blkcg, q); +bio_associate_blkg (bio); + blkg = bio->bi_blkg;bio_issue_init (&bio->bi_issue,bio_sectors (bio)); -bio_associate_blkg (bio, blkg); -rcu_read_unlock ();while (blkg && blkg->parent) {struct iolatency_grp *iolat =blkg_to_lat (blkg);
block/blk-throttle.c +3 -3
@@ -2115,10 +2115,10 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td) }#endif -static void blk_throtl_assoc_bio (struct throtl_grp *tg,struct bio *bio) +static void blk_throtl_assoc_bio (struct bio *bio) {#ifdef CONFIG_BLK_DEV_THROTTLING_LOW -bio_associate_blkg (bio,tg_to_blkg (tg)); +bio_associate_blkg (bio);bio_issue_init (&bio->bi_issue,bio_sectors (bio));#endif }
@@ -2143,7 +2143,7 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,throtl_update_latency_buckets (td); -blk_throtl_assoc_bio (tg, bio); +blk_throtl_assoc_bio (bio);blk_throtl_update_idletime (tg); sq = &tg->service_queue;
include/linux/bio.h +4 -1
@@ -511,12 +511,15 @@ static inline int bio_associate_blkcg_from_page(struct bio *bio,#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); +void bio_disassociate_blkg (struct bio *bio); +void bio_associate_blkg (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 void bio_disassociate_blkg (struct bio *bio) { } +static inline void bio_associate_blkg (struct bio *bio) { }static inline void bio_disassociate_task (struct bio *bio) { }static inline void bio_clone_blkcg_association (struct bio *dst,struct bio *src) { }
Signature · 1 line
2.17.1
PATCH v6 5/14 dm: set the static flush bio device on demand
In reply to Dennis ZhouThe next patch changes the macro bio_set_dev() to associate a bio with a blkg based on the device set. However, dm creates a static bio to be used as the basis for cloning empty flush bios on creation. The bio_set_dev() call in alloc_dev() will cause problems with the next patch adding association to bio_set_dev() because the call is before the bdev is associated with a gendisk (bd_disk is %NULL). To get around this, set the device on the static bio every time and use that to clone to the other bios.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Mike Snitzer <[email protected]>
Cc Alasdair Kergon <[email protected]>
--- block/bio.c | 1 + drivers/md/dm.c | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-)
block/bio.c +1 -0
@@ -2021,6 +2021,7 @@ void bio_disassociate_blkg(struct bio *bio) bio->bi_blkg =NULL ; } } +EXPORT_SYMBOL_GPL (bio_disassociate_blkg);/** * __bio_associate_blkg - associate a bio with the a blkg
drivers/md/dm.c +11 -1
@@ -1417,10 +1417,21 @@ static int __send_empty_flush(struct clone_info *ci)unsigned target_nr =0 ;struct dm_target *ti; +/* +* Empty flush uses a statically initialized bio, &md->flush_bio, as +* the base for cloning. However, blkg association requires that a +* bdev is associated with a gendisk, which doesn't happen until the +* bdev is opened. So, blkg association is done at issue time of the +* flush rather than when the device is created in alloc_dev(). +*/ +bio_set_dev (ci->bio, ci->io->md->bdev); +BUG_ON (bio_has_data (ci->bio));while ((ti =dm_table_get_target (ci->map, target_nr++)))__send_duplicate_bios (ci, ti, ti->num_flush_bios,NULL ); +bio_disassociate_blkg (ci->bio); +return 0 ; }
@@ -1939,7 +1950,6 @@ static struct mapped_device *alloc_dev(int minor) goto bad;bio_init (&md->flush_bio,NULL ,0 ); -bio_set_dev (&md->flush_bio, md->bdev); md->flush_bio.bi_opf =REQ_OP_WRITE |REQ_PREFLUSH |REQ_SYNC ;dm_stats_init (&md->stats);
Signature · 1 line
2.17.1
PATCH v6 6/14 blkcg: associate blkg when associating a device
In reply to Dennis ZhouPreviously, blkg association was handled by controller specific code in blk-throttle and blk-iolatency. However, because a blkg represents a relationship between a blkcg and a request_queue, it makes sense to keep the blkg->q and bio->bi_disk->queue consistent.
This patch moves association into the bio_set_dev macro(). This should cover the majority of cases where the device is set/changed keeping the two pointers consistent. Fallback code is added to blkcg_bio_issue_check() to catch any missing paths.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bio.c | 1 + block/blk-iolatency.c | 4 +--- block/blk-throttle.c | 1 - include/linux/bio.h | 2 ++ include/linux/blk-cgroup.h | 18 ++++++++++-------- 5 files changed, 14 insertions(+), 12 deletions(-)
block/bio.c +1 -0
@@ -2074,6 +2074,7 @@ void bio_associate_blkg(struct bio *bio)rcu_read_unlock (); } +EXPORT_SYMBOL_GPL (bio_associate_blkg);/** * bio_disassociate_task - undo bio_associate_current()
block/blk-iolatency.c +1 -3
@@ -472,14 +472,12 @@ static void check_scale_change(struct iolatency_grp *iolat)static void blkcg_iolatency_throttle (struct rq_qos *rqos,struct bio *bio) {struct blk_iolatency *blkiolat =BLKIOLATENCY (rqos); -struct blkcg_gq *blkg; +struct blkcg_gq *blkg = bio->bi_blkg;bool issue_as_root =bio_issue_as_root_blkg (bio);if (!blk_iolatency_enabled (blkiolat))return ; -bio_associate_blkg (bio); - blkg = bio->bi_blkg;bio_issue_init (&bio->bi_issue,bio_sectors (bio));while (blkg && blkg->parent) {
block/blk-throttle.c +0 -1
@@ -2118,7 +2118,6 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)static void blk_throtl_assoc_bio (struct bio *bio) {#ifdef CONFIG_BLK_DEV_THROTTLING_LOW -bio_associate_blkg (bio);bio_issue_init (&bio->bi_issue,bio_sectors (bio));#endif }
include/linux/bio.h +2 -0
@@ -491,12 +491,14 @@ do { \bio_clear_flag (bio,BIO_THROTTLED );\ (bio)->bi_disk = (bdev)->bd_disk; \ (bio)->bi_partno = (bdev)->bd_partno; \ +bio_associate_blkg (bio); \ } while (0)#define bio_copy_dev (dst, src) \ do { \ (dst)->bi_disk = (src)->bi_disk; \ (dst)->bi_partno = (src)->bi_partno; \ + bio_clone_blkcg_association(dst, src); \ } while (0)#define bio_dev (bio) \
include/linux/blk-cgroup.h +10 -8
@@ -21,6 +21,7 @@#include <linux/blkdev.h> #include <linux/atomic.h> #include <linux/kthread.h> +#include <linux/fs.h> /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */ #define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
@@ -802,21 +803,23 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkgstatic inline bool blkcg_bio_issue_check (struct request_queue *q,struct bio *bio) { -struct blkcg *blkcg;struct blkcg_gq *blkg;bool throtl = false; -rcu_read_lock (); +if (!bio->bi_blkg) { +char b[BDEVNAME_SIZE ]; + +WARN_ONCE (1 , +"no blkg associated for bio on block-device: %s\n" , +bio_devname (bio, b)); +bio_associate_blkg (bio); + } -/* associate blkcg if bio hasn't attached one */ -bio_associate_blkcg (bio,NULL ); - blkcg =bio_blkcg (bio); - blkg =blkg_lookup_create (blkcg, q); + blkg = bio->bi_blkg; throtl =blk_throtl_bio (q, blkg, bio);if (!throtl) { - blkg = blkg ?: q->root_blkg;/* * If the bio is flagged with BIO_QUEUE_ENTERED it means this * is a split bio and we would have already accounted for the
@@ -828,7 +831,6 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,blkg_rwstat_add (&blkg->stat_ios, bio->bi_opf,1 ); } -rcu_read_unlock ();return !throtl; }
Signature · 1 line
2.17.1
PATCH v6 7/14 blkcg: consolidate bio_issue_init() to be a part of core
In reply to Dennis Zhoubio_issue_init among other things initializes the timestamp for an IO. Rather than have this logic handled by policies, this consolidates it to be on the init paths (normal, clone, bounce clone).
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Liu Bo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bio.c | 1 + block/blk-iolatency.c | 2 -- block/blk-throttle.c | 8 -------- block/bounce.c | 1 + include/linux/blk-cgroup.h | 9 +++++++++ 5 files changed, 11 insertions(+), 10 deletions(-)
block/bio.c +1 -0
@@ -611,6 +611,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src) bio->bi_io_vec = bio_src->bi_io_vec;bio_clone_blkcg_association (bio, bio_src); +blkcg_bio_issue_init (bio); }EXPORT_SYMBOL (__bio_clone_fast);
block/blk-iolatency.c +0 -2
@@ -478,8 +478,6 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)if (!blk_iolatency_enabled (blkiolat))return ; -bio_issue_init (&bio->bi_issue,bio_sectors (bio)); -while (blkg && blkg->parent) {struct iolatency_grp *iolat =blkg_to_lat (blkg);if (!iolat) {
block/blk-throttle.c +0 -8
@@ -2115,13 +2115,6 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td) }#endif -static void blk_throtl_assoc_bio (struct bio *bio) -{ -#ifdef CONFIG_BLK_DEV_THROTTLING_LOW -bio_issue_init (&bio->bi_issue,bio_sectors (bio)); -#endif -} -bool blk_throtl_bio (struct request_queue *q,struct blkcg_gq *blkg,struct bio *bio) {
@@ -2142,7 +2135,6 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg,throtl_update_latency_buckets (td); -blk_throtl_assoc_bio (bio);blk_throtl_update_idletime (tg); sq = &tg->service_queue;
block/bounce.c +1 -0
@@ -278,6 +278,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask, }bio_clone_blkcg_association (bio, bio_src); +blkcg_bio_issue_init (bio);return bio; }
include/linux/blk-cgroup.h +9 -0
@@ -800,6 +800,12 @@ static inline bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg struct bio *bio) { return false; }#endif + +static inline void blkcg_bio_issue_init (struct bio *bio) +{ +bio_issue_init (&bio->bi_issue,bio_sectors (bio)); +} +static inline bool blkcg_bio_issue_check (struct request_queue *q,struct bio *bio) {
@@ -831,6 +837,8 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q,blkg_rwstat_add (&blkg->stat_ios, bio->bi_opf,1 ); } +blkcg_bio_issue_init (bio); +return !throtl; }
@@ -936,6 +944,7 @@ static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }static inline void blkg_get (struct blkcg_gq *blkg) { }static inline void blkg_put (struct blkcg_gq *blkg) { } +static inline void blkcg_bio_issue_init (struct bio *bio) { }static inline bool blkcg_bio_issue_check (struct request_queue *q,struct bio *bio) {return true; }
Signature · 1 line
2.17.1
PATCH v6 8/14 blkcg: associate a blkg for pages being evicted by swap
In reply to Dennis ZhouA prior patch in this series added blkg association to bios issued by cgroups. There are two other paths that we want to attribute work back to the appropriate cgroup: swap and writeback. Here we modify the way swap tags bios to include the blkg. Writeback will be tackle in the next patch.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
--- block/bio.c | 62 +++++++++++++++++++++++++++------------------ include/linux/bio.h | 6 ++--- mm/page_io.c | 2 +- 3 files changed, 42 insertions(+), 28 deletions(-)
block/bio.c +38 -24
@@ -1957,30 +1957,6 @@ EXPORT_SYMBOL(bioset_init_from_src);#ifdef CONFIG_BLK_CGROUP -#ifdef CONFIG_MEMCG -/** -* bio_associate_blkcg_from_page - associate a bio with the page's blkcg -* @bio: target bio -* @page: the page to lookup the blkcg from -* -* Associate @bio with the blkcg from @page's owning memcg. This works like -* every other associate function wrt references. -*/ -int bio_associate_blkcg_from_page (struct bio *bio,struct page *page) -{ -struct cgroup_subsys_state *blkcg_css; - -if (unlikely (bio->bi_css)) -return -EBUSY ; -if (!page->mem_cgroup) -return 0 ; - blkcg_css =cgroup_get_e_css (page->mem_cgroup->css.cgroup, - &io_cgrp_subsys); - bio->bi_css = blkcg_css; -return 0 ; -} -#endif /* CONFIG_MEMCG */ -/** * bio_associate_blkcg - associate a bio with the specified blkcg * @bio: target bio
@@ -2045,6 +2021,44 @@ static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) bio->bi_blkg =blkg_try_get_closest (blkg); } +static void __bio_associate_blkg_from_css (struct bio *bio, +struct cgroup_subsys_state *css) +{ +struct blkcg_gq *blkg; + +rcu_read_lock (); + + blkg =blkg_lookup_create (css_to_blkcg (css), bio->bi_disk->queue); +__bio_associate_blkg (bio, blkg); + +rcu_read_unlock (); +} + +#ifdef CONFIG_MEMCG +/** +* bio_associate_blkg_from_page - associate a bio with the page's blkg +* @bio: target bio +* @page: the page to lookup the blkcg from +* +* Associate @bio with the blkg from @page's owning memcg and the respective +* request_queue. This works like every other associate function wrt +* references. +*/ +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 */ +/** * bio_associate_blkg - associate a bio with a blkg * @bio: target bio
include/linux/bio.h +3 -3
@@ -505,10 +505,10 @@ do { \ disk_devt((bio)->bi_disk)#if defined(CONFIG_MEMCG ) && defined(CONFIG_BLK_CGROUP ) -int bio_associate_blkcg_from_page (struct bio *bio,struct page *page); +void bio_associate_blkg_from_page (struct bio *bio,struct page *page);#else -static inline int bio_associate_blkcg_from_page (struct bio *bio, -struct page *page) {return 0 ; } +static inline void bio_associate_blkg_from_page (struct bio *bio, +struct page *page) { }#endif #ifdef CONFIG_BLK_CGROUP
mm/page_io.c +1 -1
@@ -339,7 +339,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, goto out; } bio->bi_opf =REQ_OP_WRITE |REQ_SWAP |wbc_to_write_flags (wbc); -bio_associate_blkcg_from_page (bio, page); +bio_associate_blkg_from_page (bio, page);count_swpout_vm_event (page);set_page_writeback (page);unlock_page (page);
Signature · 1 line
2.17.1
PATCH v6 9/14 blkcg: associate writeback bios with a blkg
In reply to Dennis ZhouOne of the goals of this series is to remove a separate reference to the css of the bio. This can and should be accessed via bio_blkcg(). In this patch, wbc_init_bio() now requires a bio to have a device associated with it.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
--- Documentation/admin-guide/cgroup-v2.rst | 8 +++++--- block/bio.c | 18 ++++++++++++++++++ fs/buffer.c | 10 +++++----- fs/ext4/page-io.c | 2 +- include/linux/bio.h | 5 +++++ include/linux/writeback.h | 5 +++-- 6 files changed, 37 insertions(+), 11 deletions(-)
Documentation/admin-guide/cgroup-v2.rst +5 -3
@@ -1879,8 +1879,10 @@ following two functions. wbc_init_bio(@wbc, @bio) Should be called for each bio carrying writeback data and - associates the bio with the inode's owner cgroup. Can be - called anytime between bio allocation and submission. + associates the bio with the inode's owner cgroup and the + corresponding request queue. This must be called after + a queue (device) has been associated with the bio and + before submission. wbc_account_io(@wbc, @page, @bytes) Should be called for each data segment being written out.
@@ -1899,7 +1901,7 @@ the configuration, the bio may be executed at a lower priority and if the writeback session is holding shared resources, e.g. a journal entry, may lead to priority inversion. There is no one easy solution for the problem. Filesystems can try to work around specific problem -cases by skipping wbc_init_bio() or using bio_associate_blkcg() +cases by skipping wbc_init_bio() and using bio_associate_blkg() directly.
block/bio.c +18 -0
@@ -2034,6 +2034,24 @@ static void __bio_associate_blkg_from_css(struct bio *bio,rcu_read_unlock (); } +/** +* bio_associate_blkg_from_css - associate a bio with a specified css +* @bio: target bio +* @css: target css +* +* Associate @bio with the blkg found by combining the css's blkg and the +* request_queue of the @bio. This takes a reference on the css that will +* be put upon freeing of @bio. +*/ +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); +#ifdef CONFIG_MEMCG /** * bio_associate_blkg_from_page - associate a bio with the page's blkg
fs/buffer.c +5 -5
@@ -3060,11 +3060,6 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,*/ bio =bio_alloc (GFP_NOIO ,1 ); -if (wbc) { -wbc_init_bio (wbc, bio); -wbc_account_io (wbc, bh->b_page, bh->b_size); - } - bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >>9 );bio_set_dev (bio, bh->b_bdev); bio->bi_write_hint = write_hint;
@@ -3084,6 +3079,11 @@ static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh, op_flags |=REQ_PRIO ;bio_set_op_attrs (bio, op, op_flags); +if (wbc) { +wbc_init_bio (wbc, bio); +wbc_account_io (wbc, bh->b_page, bh->b_size); + } +submit_bio (bio);return 0 ; }
fs/ext4/page-io.c +1 -1
@@ -374,13 +374,13 @@ static int io_submit_init_bio(struct ext4_io_submit *io, bio =bio_alloc (GFP_NOIO ,BIO_MAX_PAGES );if (!bio)return -ENOMEM ; -wbc_init_bio (io->io_wbc, bio); bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >>9 );bio_set_dev (bio, bh->b_bdev); bio->bi_end_io = ext4_end_bio; bio->bi_private =ext4_get_io_end (io->io_end); io->io_bio = bio; io->io_next_block = bh->b_blocknr; +wbc_init_bio (io->io_wbc, bio);return 0 ; }
include/linux/bio.h +5 -0
@@ -515,6 +515,8 @@ static inline void bio_associate_blkg_from_page(struct bio *bio,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);#else /* CONFIG_BLK_CGROUP */
@@ -522,6 +524,9 @@ 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) { }
include/linux/writeback.h +3 -2
@@ -246,7 +246,8 @@ static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,* * @bio is a part of the writeback in progress controlled by @wbc. Perform * writeback specific initialization. This is used to apply the cgroup -* writeback context. +* writeback context. Must be called after the bio has been associated with +* a device. */ static inline void wbc_init_bio (struct writeback_control *wbc,struct bio *bio) {
@@ -257,7 +258,7 @@ static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)* regular writeback instead of writing things out itself. */ if (wbc->wb) - bio_associate_blkcg(bio, wbc->wb->blkcg_css); + bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css); }#else /* CONFIG_CGROUP_WRITEBACK */
Signature · 1 line
2.17.1
PATCH v6 10/14 blkcg: remove bio->bi_css and instead use bio->bi_blkg
In reply to Dennis ZhouPrior 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 <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
--- block/bio.c | 59 +++++++++----------------------------- block/bounce.c | 2 +- drivers/block/loop.c | 5 ++-- drivers/md/raid0.c | 2 +- include/linux/bio.h | 11 +++---- include/linux/blk-cgroup.h | 8 +++--- include/linux/blk_types.h | 7 +++-- kernel/trace/blktrace.c | 4 +-- 8 files changed, 32 insertions(+), 66 deletions(-)
block/bio.c +13 -46
@@ -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);
@@ -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_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 )
block/bounce.c +1 -1
@@ -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;
drivers/block/loop.c +3 -2
@@ -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
drivers/md/raid0.c +1 -1
@@ -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),
include/linux/bio.h +4 -7
@@ -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
include/linux/blk-cgroup.h +4 -4
@@ -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 ; }
include/linux/blk_types.h +4 -3
@@ -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
kernel/trace/blktrace.c +2 -2
@@ -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 *
Signature · 1 line
2.17.1
PATCH v6 11/14 blkcg: remove additional reference to the css
In reply to Dennis ZhouThe previous patch in this series removed carrying around a pointer to the css in blkg. However, the blkg association logic still relied on taking a reference on the css to ensure we wouldn't fail in getting a reference for the blkg.
Here the implicit dependency on the css is removed. The association continues to rely on the tryget logic walking up the blkg tree. This streamlines the three ways that association can happen: normal, swap, and writeback.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bio.c | 66 ++++++++++++++++---------------------- include/linux/blk-cgroup.h | 41 ----------------------- include/linux/cgroup.h | 2 ++ kernel/cgroup/cgroup.c | 48 +++++++++++++++++++++------ 4 files changed, 69 insertions(+), 88 deletions(-)
block/bio.c +28 -38
@@ -1966,8 +1966,6 @@ EXPORT_SYMBOL(bioset_init_from_src);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 ; }
@@ -1995,33 +1993,31 @@ static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) bio->bi_blkg =blkg_try_get_closest (blkg); } -static void __bio_associate_blkg_from_css (struct bio *bio, -struct cgroup_subsys_state *css) -{ -struct blkcg_gq *blkg; - -rcu_read_lock (); - - blkg =blkg_lookup_create (css_to_blkcg (css), bio->bi_disk->queue); -__bio_associate_blkg (bio, blkg); - -rcu_read_unlock (); -} -/** * bio_associate_blkg_from_css - associate a bio with a specified css * @bio: target bio * @css: target css * * Associate @bio with the blkg found by combining the css's blkg and the -* request_queue of the @bio. This takes a reference on the css that will -* be put upon freeing of @bio. +* request_queue of the @bio. This falls back to the queue's root_blkg if +* the association fails with the css. */ void bio_associate_blkg_from_css (struct bio *bio,struct cgroup_subsys_state *css) { -css_get (css); -__bio_associate_blkg_from_css (bio, css); +struct request_queue *q = bio->bi_disk->queue; +struct blkcg_gq *blkg; + +rcu_read_lock (); + +if (!css || !css->parent) + blkg = q->root_blkg; +else + blkg =blkg_lookup_create (css_to_blkcg (css), q); + +__bio_associate_blkg (bio, blkg); + +rcu_read_unlock (); }EXPORT_SYMBOL_GPL (bio_associate_blkg_from_css);
@@ -2032,8 +2028,8 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css);* @page: the page to lookup the blkcg from * * Associate @bio with the blkg from @page's owning memcg and the respective -* request_queue. This works like every other associate function wrt -* references. +* request_queue. If cgroup_e_css returns %NULL, fall back to the queue's +* root_blkg. */ void bio_associate_blkg_from_page (struct bio *bio,struct page *page) {
@@ -2042,8 +2038,12 @@ void bio_associate_blkg_from_page(struct bio *bio, struct page *page)if (!page->mem_cgroup)return ; - css =cgroup_get_e_css (page->mem_cgroup->css.cgroup, &io_cgrp_subsys); - __bio_associate_blkg_from_css(bio, css); +rcu_read_lock (); + + css =cgroup_e_css (page->mem_cgroup->css.cgroup, &io_cgrp_subsys); +bio_associate_blkg_from_css (bio, css); + + rcu_read_unlock(); }#endif /* CONFIG_MEMCG */
@@ -2058,24 +2058,16 @@ void bio_associate_blkg_from_page(struct bio *bio, struct page *page)*/ void bio_associate_blkg (struct bio *bio) { -struct request_queue *q = bio->bi_disk->queue; -struct blkcg *blkcg; -struct blkcg_gq *blkg; +struct cgroup_subsys_state *css;rcu_read_lock ();if (bio->bi_blkg) - blkcg = bio->bi_blkg->blkcg; + css = &bio_blkcg (bio)->css;else - blkcg =css_to_blkcg (blkcg_get_css ()); + css =blkcg_css (); -if (!blkcg->css.parent) { -__bio_associate_blkg (bio, q->root_blkg); - }else { - blkg =blkg_lookup_create (blkcg, q); - -__bio_associate_blkg (bio, blkg); - } +bio_associate_blkg_from_css (bio, css);rcu_read_unlock (); }
@@ -2097,10 +2089,8 @@ void bio_disassociate_task(struct bio *bio)*/ void bio_clone_blkg_association (struct bio *dst,struct bio *src) { -if (src->bi_blkg) { -css_get (&bio_blkcg (src)->css); +if (src->bi_blkg)__bio_associate_blkg (dst, src->bi_blkg); - } }EXPORT_SYMBOL_GPL (bio_clone_blkg_association);#endif /* CONFIG_BLK_CGROUP */
include/linux/blk-cgroup.h +0 -41
47 lines not on this page · raw message
include/linux/cgroup.h +2 -0
@@ -93,6 +93,8 @@ extern struct css_set init_css_set;bool css_has_online_children (struct cgroup_subsys_state *css);struct cgroup_subsys_state *css_from_id (int id,struct cgroup_subsys *ss); +struct cgroup_subsys_state *cgroup_e_css (struct cgroup *cgroup, +struct cgroup_subsys *ss);struct cgroup_subsys_state *cgroup_get_e_css (struct cgroup *cgroup,struct cgroup_subsys *ss); struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
kernel/cgroup/cgroup.c +39 -9
84 lines not on this page · raw message
Signature · 1 line
2.17.1
PATCH v6 12/14 blkcg: remove bio_disassociate_task()
In reply to Dennis ZhouNow that a bio only holds a blkg reference, so clean up is simply putting back that reference. Remove bio_disassociate_task() as it just calls bio_disassociate_blkg() and call the latter directly.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/bio.c | 11 +---------- include/linux/bio.h | 2 -- 2 files changed, 1 insertion(+), 12 deletions(-)
block/bio.c +1 -10
@@ -244,7 +244,7 @@ struct bio_vec *bvec_alloc(gfp_t gfp_mask, int nr, unsigned long *idx,void bio_uninit (struct bio *bio) { -bio_disassociate_task (bio); +bio_disassociate_blkg (bio); }EXPORT_SYMBOL (bio_uninit);
@@ -2073,15 +2073,6 @@ void bio_associate_blkg(struct bio *bio) }EXPORT_SYMBOL_GPL (bio_associate_blkg); -/** -* bio_disassociate_task - undo bio_associate_current() -* @bio: target bio -*/ -void bio_disassociate_task (struct bio *bio) -{ -bio_disassociate_blkg (bio); -} -/** * bio_clone_blkg_association - clone blkg association from src to dst bio * @dst: destination bio
include/linux/bio.h +0 -2
@@ -516,7 +516,6 @@ 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_blkg_association (struct bio *dst,struct bio *src);#else /* CONFIG_BLK_CGROUP */ static inline void bio_disassociate_blkg (struct bio *bio) { }
@@ -524,7 +523,6 @@ 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_blkg_association (struct bio *dst,struct bio *src) { }#endif /* CONFIG_BLK_CGROUP */
Signature · 1 line
2.17.1
PATCH v6 13/14 blkcg: change blkg reference counting to use percpu_ref
In reply to Dennis ZhouEvery bio is now associated with a blkg putting blkg_get, blkg_try_get, and blkg_put on the hot path. Switch over the refcnt in blkg to use percpu_ref.
Signed-off-by Dennis Zhou <[email protected]>
Acked-by Tejun Heo <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
--- block/blk-cgroup.c | 41 ++++++++++++++++++++++++++++++++++++-- include/linux/blk-cgroup.h | 15 +++++--------- 2 files changed, 44 insertions(+), 12 deletions(-)
block/blk-cgroup.c +39 -2
@@ -81,6 +81,37 @@ static void blkg_free(struct blkcg_gq *blkg)kfree (blkg); } +static void __blkg_release (struct rcu_head *rcu) +{ + struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head); + +percpu_ref_exit (&blkg->refcnt); + +/* release the blkcg and parent blkg refs this blkg has been holding */ +css_put (&blkg->blkcg->css); +if (blkg->parent) +blkg_put (blkg->parent); + +wb_congested_put (blkg->wb_congested); + +blkg_free (blkg); +} + +/* +* A group is RCU protected, but having an rcu lock does not mean that one +* can access all the fields of blkg and assume these are valid. For +* example, don't try to follow throtl_data and request queue links. +* +* Having a reference to blkg under an rcu allows accesses to only values +* local to groups like group stats and group rate limits. +*/ +static void blkg_release (struct percpu_ref *ref) +{ + struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt); + +call_rcu (&blkg->rcu_head, __blkg_release); +} +/** * blkg_alloc - allocate a blkg * @blkcg: block cgroup the new blkg is associated with
@@ -107,7 +138,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q, blkg->q = q;INIT_LIST_HEAD (&blkg->q_node); blkg->blkcg = blkcg; -atomic_set (&blkg->refcnt,1 );for (i =0 ; i <BLKCG_MAX_POLS ; i++) {struct blkcg_policy *pol = blkcg_policy[i];
@@ -207,6 +237,11 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,blkg_get (blkg->parent); } + ret =percpu_ref_init (&blkg->refcnt, blkg_release,0 , +GFP_NOWAIT | __GFP_NOWARN); +if (ret) + goto err_cancel_ref; +/* invoke per-policy init */ for (i =0 ; i <BLKCG_MAX_POLS ; i++) {struct blkcg_policy *pol = blkcg_policy[i];
@@ -239,6 +274,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,blkg_put (blkg);return ERR_PTR (ret); +err_cancel_ref: +percpu_ref_exit (&blkg->refcnt); err_put_congested:wb_congested_put (wb_congested); err_put_css:
@@ -367,7 +404,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)* Put the reference taken at the time of creation so that when all * queues are gone, group can be destroyed. */ -blkg_put (blkg); +percpu_ref_kill (&blkg->refcnt); }/**
include/linux/blk-cgroup.h +5 -10
@@ -124,7 +124,7 @@ struct blkcg_gq {struct blkcg_gq *parent;/* reference count */ -atomic_t refcnt; +struct percpu_ref refcnt;/* is this blkg online? protected by both blkcg and q locks */ bool online;
@@ -487,8 +487,7 @@ static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)*/ static inline void blkg_get (struct blkcg_gq *blkg) { -WARN_ON_ONCE (atomic_read (&blkg->refcnt) <=0 ); -atomic_inc (&blkg->refcnt); +percpu_ref_get (&blkg->refcnt); }/**
@@ -500,7 +499,7 @@ static inline void blkg_get(struct blkcg_gq *blkg)*/ static inline struct blkcg_gq *blkg_try_get (struct blkcg_gq *blkg) { -if (atomic_inc_not_zero (&blkg->refcnt)) +if (percpu_ref_tryget (&blkg->refcnt))return blkg;return NULL ; }
@@ -514,23 +513,19 @@ static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg)*/ static inline struct blkcg_gq *blkg_try_get_closest (struct blkcg_gq *blkg) { -while (!atomic_inc_not_zero (&blkg->refcnt)) +while (!percpu_ref_tryget (&blkg->refcnt)) blkg = blkg->parent;return blkg; } -void __blkg_release_rcu (struct rcu_head *rcu); -/** * blkg_put - put a blkg reference * @blkg: blkg to put */ static inline void blkg_put (struct blkcg_gq *blkg) { -WARN_ON_ONCE (atomic_read (&blkg->refcnt) <=0 ); -if (atomic_dec_and_test (&blkg->refcnt)) -call_rcu (&blkg->rcu_head, __blkg_release_rcu); +percpu_ref_put (&blkg->refcnt); }/**
Signature · 1 line
2.17.1
PATCH v6 14/14 blkcg: rename blkg_try_get() to blkg_tryget()
In reply to Dennis Zhoublkg reference counting now uses percpu_ref rather than atomic_t. Let's make this consistent with css_tryget. This renames blkg_try_get to blkg_tryget and now returns a bool rather than the blkg or %NULL.
Signed-off-by Dennis Zhou <[email protected]>
Reviewed-by Josef Bacik <[email protected]>
Acked-by Tejun Heo <[email protected]>
--- block/bio.c | 2 +- block/blk-cgroup.c | 3 +-- block/blk-iolatency.c | 2 +- include/linux/blk-cgroup.h | 12 +++++------- 4 files changed, 8 insertions(+), 11 deletions(-)
block/bio.c +1 -1
@@ -1990,7 +1990,7 @@ static void __bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) {bio_disassociate_blkg (bio); - bio->bi_blkg =blkg_try_get_closest (blkg); + bio->bi_blkg =blkg_tryget_closest (blkg); }/**
block/blk-cgroup.c +1 -2
@@ -1736,8 +1736,7 @@ void blkcg_maybe_throttle_current(void) blkg =blkg_lookup (blkcg, q);if (!blkg) goto out; - blkg =blkg_try_get (blkg); -if (!blkg) +if (!blkg_tryget (blkg)) goto out;rcu_read_unlock ();
block/blk-iolatency.c +1 -1
@@ -698,7 +698,7 @@ static void blkiolatency_timer_fn(struct timer_list *t)* We could be exiting, don't access the pd unless we have a * ref on the blkg. */ -if (!blkg_try_get (blkg)) +if (!blkg_tryget (blkg))continue ; iolat =blkg_to_lat (blkg);
include/linux/blk-cgroup.h +5 -7
@@ -491,27 +491,25 @@ static inline void blkg_get(struct blkcg_gq *blkg) }/** -* blkg_try_get - try and get a blkg reference +* blkg_tryget - try and get a blkg reference * @blkg: blkg to get * * This is for use when doing an RCU lookup of the blkg. We may be in the midst * of freeing this blkg, so we can only use it if the refcnt is not zero. */ -static inline struct blkcg_gq *blkg_try_get (struct blkcg_gq *blkg) +static inline bool blkg_tryget (struct blkcg_gq *blkg) { -if (percpu_ref_tryget (&blkg->refcnt)) -return blkg; -return NULL ; +return percpu_ref_tryget (&blkg->refcnt); }/** -* blkg_try_get_closest - try and get a blkg ref on the closet blkg +* blkg_tryget_closest - try and get a blkg ref on the closet blkg * @blkg: blkg to get * * This walks up the blkg tree to find the closest non-dying blkg and returns * the blkg that it did association with as it may not be the passed in blkg. */ -static inline struct blkcg_gq *blkg_try_get_closest (struct blkcg_gq *blkg) +static inline struct blkcg_gq *blkg_tryget_closest (struct blkcg_gq *blkg) {while (!percpu_ref_tryget (&blkg->refcnt)) blkg = blkg->parent;
Signature · 1 line
2.17.1
Jens Axboe
maintainerQuoted 7 lines · Dennis Zhou
Hi everyone,
This is a minor update addressing the feedback from Mike and Josef.
v6:
0005: Address Mike's feedback for the flush bio comment. 0006: Add aWARN_ONCE()for blkg fallback suggested by Josef.
Thanks Dennis, applied for 4.21.
Signature · 1 line
Jens Axboe