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authorTejun Heo <tj@kernel.org>2015-08-18 14:55:12 -0700
committerJens Axboe <axboe@fb.com>2015-08-18 15:49:16 -0700
commit4fb72036fbf9c28de7a64b1d3f19b4ce9da1c6bf (patch)
treeec418021883beb54038b9a2c3f9aaaf3c858c171 /block/blk-throttle.c
parent001bea73e70efdf48a9e00188cf302f6b6aed2bf (diff)
downloadlwn-4fb72036fbf9c28de7a64b1d3f19b4ce9da1c6bf.tar.gz
lwn-4fb72036fbf9c28de7a64b1d3f19b4ce9da1c6bf.zip
blk-throttle: remove asynchrnous percpu stats allocation mechanism
Because percpu allocator couldn't do non-blocking allocations, blk-throttle was forced to implement an ad-hoc asynchronous allocation mechanism for its percpu stats for cases where blkg's (blkcg_gq's) are allocated from an IO path without sleepable context. Now that percpu allocator can handle gfp_mask and blkg_policy_data alloc / free are handled by policy methods, the ad-hoc asynchronous allocation mechanism can be replaced with direct allocation from tg_stats_alloc_fn(). Rit it out. This ensures that an active throtl_grp always has valid non-NULL ->stats_cpu. Remove checks on it. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c112
1 files changed, 25 insertions, 87 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f1dd691c5359..3c869768cfdd 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -144,9 +144,6 @@ struct throtl_grp {
/* Per cpu stats pointer */
struct tg_stats_cpu __percpu *stats_cpu;
-
- /* List of tgs waiting for per cpu stats memory to be allocated */
- struct list_head stats_alloc_node;
};
struct throtl_data
@@ -168,13 +165,6 @@ struct throtl_data
struct work_struct dispatch_work;
};
-/* list and work item to allocate percpu group stats */
-static DEFINE_SPINLOCK(tg_stats_alloc_lock);
-static LIST_HEAD(tg_stats_alloc_list);
-
-static void tg_stats_alloc_fn(struct work_struct *);
-static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn);
-
static void throtl_pending_timer_fn(unsigned long arg);
static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd)
@@ -256,53 +246,6 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
} \
} while (0)
-static void tg_stats_init(struct tg_stats_cpu *tg_stats)
-{
- blkg_rwstat_init(&tg_stats->service_bytes);
- blkg_rwstat_init(&tg_stats->serviced);
-}
-
-/*
- * Worker for allocating per cpu stat for tgs. This is scheduled on the
- * system_wq once there are some groups on the alloc_list waiting for
- * allocation.
- */
-static void tg_stats_alloc_fn(struct work_struct *work)
-{
- static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */
- struct delayed_work *dwork = to_delayed_work(work);
- bool empty = false;
-
-alloc_stats:
- if (!stats_cpu) {
- int cpu;
-
- stats_cpu = alloc_percpu(struct tg_stats_cpu);
- if (!stats_cpu) {
- /* allocation failed, try again after some time */
- schedule_delayed_work(dwork, msecs_to_jiffies(10));
- return;
- }
- for_each_possible_cpu(cpu)
- tg_stats_init(per_cpu_ptr(stats_cpu, cpu));
- }
-
- spin_lock_irq(&tg_stats_alloc_lock);
-
- if (!list_empty(&tg_stats_alloc_list)) {
- struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list,
- struct throtl_grp,
- stats_alloc_node);
- swap(tg->stats_cpu, stats_cpu);
- list_del_init(&tg->stats_alloc_node);
- }
-
- empty = list_empty(&tg_stats_alloc_list);
- spin_unlock_irq(&tg_stats_alloc_lock);
- if (!empty)
- goto alloc_stats;
-}
-
static void throtl_qnode_init(struct throtl_qnode *qn, struct throtl_grp *tg)
{
INIT_LIST_HEAD(&qn->node);
@@ -405,7 +348,27 @@ static void throtl_service_queue_exit(struct throtl_service_queue *sq)
static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node)
{
- return kzalloc_node(sizeof(struct throtl_grp), gfp, node);
+ struct throtl_grp *tg;
+ int cpu;
+
+ tg = kzalloc_node(sizeof(*tg), gfp, node);
+ if (!tg)
+ return NULL;
+
+ tg->stats_cpu = alloc_percpu_gfp(struct tg_stats_cpu, gfp);
+ if (!tg->stats_cpu) {
+ kfree(tg);
+ return NULL;
+ }
+
+ for_each_possible_cpu(cpu) {
+ struct tg_stats_cpu *stats_cpu = per_cpu_ptr(tg->stats_cpu, cpu);
+
+ blkg_rwstat_init(&stats_cpu->service_bytes);
+ blkg_rwstat_init(&stats_cpu->serviced);
+ }
+
+ return &tg->pd;
}
static void throtl_pd_init(struct blkcg_gq *blkg)
@@ -413,7 +376,6 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_data *td = blkg->q->td;
struct throtl_service_queue *parent_sq;
- unsigned long flags;
int rw;
/*
@@ -448,16 +410,6 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
tg->bps[WRITE] = -1;
tg->iops[READ] = -1;
tg->iops[WRITE] = -1;
-
- /*
- * Ugh... We need to perform per-cpu allocation for tg->stats_cpu
- * but percpu allocator can't be called from IO path. Queue tg on
- * tg_stats_alloc_list and allocate from work item.
- */
- spin_lock_irqsave(&tg_stats_alloc_lock, flags);
- list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
- schedule_delayed_work(&tg_stats_alloc_work, 0);
- spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
}
/*
@@ -487,20 +439,16 @@ static void throtl_pd_online(struct blkcg_gq *blkg)
static void throtl_pd_exit(struct blkcg_gq *blkg)
{
struct throtl_grp *tg = blkg_to_tg(blkg);
- unsigned long flags;
-
- spin_lock_irqsave(&tg_stats_alloc_lock, flags);
- list_del_init(&tg->stats_alloc_node);
- spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
-
- free_percpu(tg->stats_cpu);
throtl_service_queue_exit(&tg->service_queue);
}
static void throtl_pd_free(struct blkg_policy_data *pd)
{
- kfree(pd);
+ struct throtl_grp *tg = pd_to_tg(pd);
+
+ free_percpu(tg->stats_cpu);
+ kfree(tg);
}
static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
@@ -508,9 +456,6 @@ static void throtl_pd_reset_stats(struct blkcg_gq *blkg)
struct throtl_grp *tg = blkg_to_tg(blkg);
int cpu;
- if (tg->stats_cpu == NULL)
- return;
-
for_each_possible_cpu(cpu) {
struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
@@ -973,10 +918,6 @@ static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes,
struct tg_stats_cpu *stats_cpu;
unsigned long flags;
- /* If per cpu stats are not allocated yet, don't do any accounting. */
- if (tg->stats_cpu == NULL)
- return;
-
/*
* Disabling interrupts to provide mutual exclusion between two
* writes on same cpu. It probably is not needed for 64bit. Not
@@ -1302,9 +1243,6 @@ static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
struct blkg_rwstat rwstat = { }, tmp;
int i, cpu;
- if (tg->stats_cpu == NULL)
- return 0;
-
for_each_possible_cpu(cpu) {
struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);