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bdi: Do not wait for cgwbs release in bdi_unregister()

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Currently we wait for all cgwbs to get released in cgwb_bdi_destroy()
(called from bdi_unregister()). That is however unnecessary now when
cgwb->bdi is a proper refcounted reference (thus bdi cannot get
released before all cgwbs are released) and when cgwb_bdi_destroy()
shuts down writeback directly.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jan Kara 2017-03-23 01:36:58 +01:00 committed by Jens Axboe
parent 5318ce7d46
commit 4514451e79
2 changed files with 1 additions and 22 deletions
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1
include/linux/backing-dev-defs.h
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@ -164,7 +164,6 @@ struct backing_dev_info {
#ifdef CONFIG_CGROUP_WRITEBACK #ifdef CONFIG_CGROUP_WRITEBACK
struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */ struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
struct rb_root cgwb_congested_tree; /* their congested states */ struct rb_root cgwb_congested_tree; /* their congested states */
atomic_t usage_cnt; /* counts both cgwbs and cgwb_contested's */
#else #else
struct bdi_writeback_congested *wb_congested; struct bdi_writeback_congested *wb_congested;
#endif #endif

22
mm/backing-dev.c
View File

@ -406,11 +406,9 @@ static void wb_exit(struct bdi_writeback *wb)
/* /*
* cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree, * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
* blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
* protected. cgwb_release_wait is used to wait for the completion of cgwb * protected.
* releases from bdi destruction path.
*/ */
static DEFINE_SPINLOCK(cgwb_lock); static DEFINE_SPINLOCK(cgwb_lock);
static DECLARE_WAIT_QUEUE_HEAD(cgwb_release_wait);
/** /**
* wb_congested_get_create - get or create a wb_congested * wb_congested_get_create - get or create a wb_congested
@ -505,7 +503,6 @@ static void cgwb_release_workfn(struct work_struct *work)
{ {
struct bdi_writeback *wb = container_of(work, struct bdi_writeback, struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
release_work); release_work);
struct backing_dev_info *bdi = wb->bdi;
wb_shutdown(wb); wb_shutdown(wb);
@ -516,9 +513,6 @@ static void cgwb_release_workfn(struct work_struct *work)
percpu_ref_exit(&wb->refcnt); percpu_ref_exit(&wb->refcnt);
wb_exit(wb); wb_exit(wb);
kfree_rcu(wb, rcu); kfree_rcu(wb, rcu);
if (atomic_dec_and_test(&bdi->usage_cnt))
wake_up_all(&cgwb_release_wait);
} }
static void cgwb_release(struct percpu_ref *refcnt) static void cgwb_release(struct percpu_ref *refcnt)
@ -608,7 +602,6 @@ static int cgwb_create(struct backing_dev_info *bdi,
/* we might have raced another instance of this function */ /* we might have raced another instance of this function */
ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb); ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
if (!ret) { if (!ret) {
atomic_inc(&bdi->usage_cnt);
list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list); list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
list_add(&wb->memcg_node, memcg_cgwb_list); list_add(&wb->memcg_node, memcg_cgwb_list);
list_add(&wb->blkcg_node, blkcg_cgwb_list); list_add(&wb->blkcg_node, blkcg_cgwb_list);
@ -698,7 +691,6 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC); INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
bdi->cgwb_congested_tree = RB_ROOT; bdi->cgwb_congested_tree = RB_ROOT;
atomic_set(&bdi->usage_cnt, 1);
ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL); ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (!ret) { if (!ret) {
@ -728,18 +720,6 @@ static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
spin_lock_irq(&cgwb_lock); spin_lock_irq(&cgwb_lock);
} }
spin_unlock_irq(&cgwb_lock); spin_unlock_irq(&cgwb_lock);
/*
* All cgwb's must be shutdown and released before returning. Drain
* the usage counter to wait for all cgwb's ever created on @bdi.
*/
atomic_dec(&bdi->usage_cnt);
wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
/*
* Grab back our reference so that we hold it when @bdi gets
* re-registered.
*/
atomic_inc(&bdi->usage_cnt);
} }
/** /**