blkcg: move blkio_group_stats_cpu and friends to blk-throttle.c
blkio_group_stats_cpu is used only by blk-throtl and has no reason to
be defined in blkcg core.
* Move blkio_group_stats_cpu to blk-throttle.c and rename it to
tg_stats_cpu.
* blkg_policy_data->stats_cpu is replaced with throtl_grp->stats_cpu.
prfill functions updated accordingly.
* All related macros / functions are renamed so that they have tg_
prefix and the unnecessary @pol arguments are dropped.
* Per-cpu stats allocation code is also moved from blk-cgroup.c to
blk-throttle.c and gets simplified to only deal with
BLKIO_POLICY_THROTL. percpu stat free is performed by the exit
method throtl_exit_blkio_group().
* throtl_reset_group_stats() implemented for
blkio_reset_group_stats_fn method so that tg->stats_cpu can be
reset.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index cb259bc4..27f7960 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -40,6 +40,14 @@
#define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node)
+/* Per-cpu group stats */
+struct tg_stats_cpu {
+ /* total bytes transferred */
+ struct blkg_rwstat service_bytes;
+ /* total IOs serviced, post merge */
+ struct blkg_rwstat serviced;
+};
+
struct throtl_grp {
/* active throtl group service_tree member */
struct rb_node rb_node;
@@ -76,6 +84,12 @@
/* Some throttle limits got updated for the group */
int limits_changed;
+
+ /* 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
@@ -100,6 +114,13 @@
int limits_changed;
};
+/* 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 inline struct throtl_grp *blkg_to_tg(struct blkio_group *blkg)
{
return blkg_to_pdata(blkg, &blkio_policy_throtl);
@@ -142,6 +163,44 @@
return td->nr_queued[0] + td->nr_queued[1];
}
+/*
+ * Worker for allocating per cpu stat for tgs. This is scheduled on the
+ * system_nrt_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) {
+ stats_cpu = alloc_percpu(struct tg_stats_cpu);
+ if (!stats_cpu) {
+ /* allocation failed, try again after some time */
+ queue_delayed_work(system_nrt_wq, dwork,
+ msecs_to_jiffies(10));
+ return;
+ }
+ }
+
+ 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_init_blkio_group(struct blkio_group *blkg)
{
struct throtl_grp *tg = blkg_to_tg(blkg);
@@ -155,6 +214,43 @@
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(&tg_stats_alloc_lock);
+ list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
+ queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0);
+ spin_unlock(&tg_stats_alloc_lock);
+}
+
+static void throtl_exit_blkio_group(struct blkio_group *blkg)
+{
+ struct throtl_grp *tg = blkg_to_tg(blkg);
+
+ spin_lock(&tg_stats_alloc_lock);
+ list_del_init(&tg->stats_alloc_node);
+ spin_unlock(&tg_stats_alloc_lock);
+
+ free_percpu(tg->stats_cpu);
+}
+
+static void throtl_reset_group_stats(struct blkio_group *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);
+
+ blkg_rwstat_reset(&sc->service_bytes);
+ blkg_rwstat_reset(&sc->serviced);
+ }
}
static struct
@@ -565,12 +661,12 @@
static void throtl_update_dispatch_stats(struct blkio_group *blkg, u64 bytes,
int rw)
{
- struct blkg_policy_data *pd = blkg->pd[BLKIO_POLICY_THROTL];
- struct blkio_group_stats_cpu *stats_cpu;
+ struct throtl_grp *tg = blkg_to_tg(blkg);
+ struct tg_stats_cpu *stats_cpu;
unsigned long flags;
/* If per cpu stats are not allocated yet, don't do any accounting. */
- if (pd->stats_cpu == NULL)
+ if (tg->stats_cpu == NULL)
return;
/*
@@ -580,7 +676,7 @@
*/
local_irq_save(flags);
- stats_cpu = this_cpu_ptr(pd->stats_cpu);
+ stats_cpu = this_cpu_ptr(tg->stats_cpu);
blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
@@ -842,15 +938,15 @@
throtl_schedule_delayed_work(td, 0);
}
-static u64 blkg_prfill_cpu_rwstat(struct seq_file *sf,
- struct blkg_policy_data *pd, int off)
+static u64 tg_prfill_cpu_rwstat(struct seq_file *sf,
+ struct blkg_policy_data *pd, int off)
{
+ struct throtl_grp *tg = (void *)pd->pdata;
struct blkg_rwstat rwstat = { }, tmp;
int i, cpu;
for_each_possible_cpu(cpu) {
- struct blkio_group_stats_cpu *sc =
- per_cpu_ptr(pd->stats_cpu, cpu);
+ struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu);
tmp = blkg_rwstat_read((void *)sc + off);
for (i = 0; i < BLKG_RWSTAT_NR; i++)
@@ -861,12 +957,12 @@
}
/* print per-cpu blkg_rwstat specified by BLKCG_STAT_PRIV() */
-static int blkcg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
- struct seq_file *sf)
+static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
+ struct seq_file *sf)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
- blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_rwstat,
+ blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat,
BLKCG_STAT_POL(cft->private),
BLKCG_STAT_OFF(cft->private), true);
return 0;
@@ -1012,14 +1108,14 @@
{
.name = "throttle.io_service_bytes",
.private = BLKCG_STAT_PRIV(BLKIO_POLICY_THROTL,
- offsetof(struct blkio_group_stats_cpu, service_bytes)),
- .read_seq_string = blkcg_print_cpu_rwstat,
+ offsetof(struct tg_stats_cpu, service_bytes)),
+ .read_seq_string = tg_print_cpu_rwstat,
},
{
.name = "throttle.io_serviced",
.private = BLKCG_STAT_PRIV(BLKIO_POLICY_THROTL,
- offsetof(struct blkio_group_stats_cpu, serviced)),
- .read_seq_string = blkcg_print_cpu_rwstat,
+ offsetof(struct tg_stats_cpu, serviced)),
+ .read_seq_string = tg_print_cpu_rwstat,
},
{ } /* terminate */
};
@@ -1034,6 +1130,8 @@
static struct blkio_policy_type blkio_policy_throtl = {
.ops = {
.blkio_init_group_fn = throtl_init_blkio_group,
+ .blkio_exit_group_fn = throtl_exit_blkio_group,
+ .blkio_reset_group_stats_fn = throtl_reset_group_stats,
},
.plid = BLKIO_POLICY_THROTL,
.pdata_size = sizeof(struct throtl_grp),