Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-22 12:11:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

blkcg: let blkcg core manage per-queue blkg list and counter

Browse Source 
With the previous patch to move blkg list heads and counters to
request_queue and blkg, logic to manage them in both policies are
almost identical and can be moved to blkcg core.

This patch moves blkg link logic into blkg_lookup_create(), implements
common blkg unlink code in blkg_destroy(), and updates
blkg_destory_all() so that it's policy specific and can skip root
group.  The updated blkg_destroy_all() is now used to both clear queue
for bypassing and elv switching, and release all blkgs on q exit.

This patch introduces a race window where policy [de]registration may
race against queue blkg clearing.  This can only be a problem on cfq
unload and shouldn't be a real problem in practice (and we have many
other places where this race already exists).  Future patches will
remove these unlikely races.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2012-03-05 13:15:19 -08:00 committed by Jens Axboe
parent 4eef304998
commit 03aa264ac1
6 changed files with 74 additions and 221 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
block/blk-cgroup.c
View File

@ -596,8 +596,11 @@ struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
/* insert */
spin_lock(&blkcg->lock);
swap(blkg, new_blkg);
hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
pol->ops.blkio_link_group_fn(q, blkg);
list_add(&blkg->q_node[plid], &q->blkg_list[plid]);
q->nr_blkgs[plid]++;
spin_unlock(&blkcg->lock);
out:
blkg_free(new_blkg);
@ -646,36 +649,69 @@ struct blkio_group *blkg_lookup(struct blkio_cgroup *blkcg,
}
EXPORT_SYMBOL_GPL(blkg_lookup);
void blkg_destroy_all(struct request_queue *q)
static void blkg_destroy(struct blkio_group *blkg, enum blkio_policy_id plid)
{
struct blkio_policy_type *pol;
struct request_queue *q = blkg->q;
lockdep_assert_held(q->queue_lock);
/* Something wrong if we are trying to remove same group twice */
WARN_ON_ONCE(list_empty(&blkg->q_node[plid]));
list_del_init(&blkg->q_node[plid]);
WARN_ON_ONCE(q->nr_blkgs[plid] <= 0);
q->nr_blkgs[plid]--;
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
blkg_put(blkg);
}
void blkg_destroy_all(struct request_queue *q, enum blkio_policy_id plid,
bool destroy_root)
{
struct blkio_group *blkg, *n;
while (true) {
bool done = true;
spin_lock(&blkio_list_lock);
spin_lock_irq(q->queue_lock);
/*
* clear_queue_fn() might return with non-empty group list
* if it raced cgroup removal and lost. cgroup removal is
* guaranteed to make forward progress and retrying after a
* while is enough. This ugliness is scheduled to be
* removed after locking update.
*/
list_for_each_entry(pol, &blkio_list, list)
if (!pol->ops.blkio_clear_queue_fn(q))
list_for_each_entry_safe(blkg, n, &q->blkg_list[plid],
q_node[plid]) {
/* skip root? */
if (!destroy_root && blkg->blkcg == &blkio_root_cgroup)
continue;
/*
* If cgroup removal path got to blk_group first
* and removed it from cgroup list, then it will
* take care of destroying cfqg also.
*/
if (!blkiocg_del_blkio_group(blkg))
blkg_destroy(blkg, plid);
else
done = false;
}
spin_unlock_irq(q->queue_lock);
spin_unlock(&blkio_list_lock);
/*
* Group list may not be empty if we raced cgroup removal
* and lost. cgroup removal is guaranteed to make forward
* progress and retrying after a while is enough. This
* ugliness is scheduled to be removed after locking
* update.
*/
if (done)
break;
msleep(10); /* just some random duration I like */
}
}
EXPORT_SYMBOL_GPL(blkg_destroy_all);
static void blkg_rcu_free(struct rcu_head *rcu_head)
{
@ -1549,11 +1585,13 @@ static int blkiocg_pre_destroy(struct cgroup_subsys *subsys,
* this event.
*/
spin_lock(&blkio_list_lock);
spin_lock_irqsave(q->queue_lock, flags);
list_for_each_entry(blkiop, &blkio_list, list) {
if (blkiop->plid != blkg->plid)
continue;
blkiop->ops.blkio_unlink_group_fn(q, blkg);
blkg_destroy(blkg, blkiop->plid);
}
spin_unlock_irqrestore(q->queue_lock, flags);
spin_unlock(&blkio_list_lock);
} while (1);
@ -1695,12 +1733,14 @@ static void blkcg_bypass_start(void)
__acquires(&all_q_mutex)
{
struct request_queue *q;
int i;
mutex_lock(&all_q_mutex);
list_for_each_entry(q, &all_q_list, all_q_node) {
blk_queue_bypass_start(q);
blkg_destroy_all(q);
for (i = 0; i < BLKIO_NR_POLICIES; i++)
blkg_destroy_all(q, i, false);
}
}

15
block/blk-cgroup.h
View File

@ -196,11 +196,6 @@ struct blkio_group {
};
typedef void (blkio_init_group_fn)(struct blkio_group *blkg);
typedef void (blkio_link_group_fn)(struct request_queue *q,
struct blkio_group *blkg);
typedef void (blkio_unlink_group_fn)(struct request_queue *q,
struct blkio_group *blkg);
typedef bool (blkio_clear_queue_fn)(struct request_queue *q);
typedef void (blkio_update_group_weight_fn)(struct request_queue *q,
struct blkio_group *blkg, unsigned int weight);
typedef void (blkio_update_group_read_bps_fn)(struct request_queue *q,
@ -214,9 +209,6 @@ typedef void (blkio_update_group_write_iops_fn)(struct request_queue *q,
struct blkio_policy_ops {
blkio_init_group_fn *blkio_init_group_fn;
blkio_link_group_fn *blkio_link_group_fn;
blkio_unlink_group_fn *blkio_unlink_group_fn;
blkio_clear_queue_fn *blkio_clear_queue_fn;
blkio_update_group_weight_fn *blkio_update_group_weight_fn;
blkio_update_group_read_bps_fn *blkio_update_group_read_bps_fn;
blkio_update_group_write_bps_fn *blkio_update_group_write_bps_fn;
@ -238,7 +230,8 @@ extern void blkcg_exit_queue(struct request_queue *q);
/* Blkio controller policy registration */
extern void blkio_policy_register(struct blkio_policy_type *);
extern void blkio_policy_unregister(struct blkio_policy_type *);
extern void blkg_destroy_all(struct request_queue *q);
extern void blkg_destroy_all(struct request_queue *q,
enum blkio_policy_id plid, bool destroy_root);
/**
* blkg_to_pdata - get policy private data
@ -319,7 +312,9 @@ static inline void blkcg_drain_queue(struct request_queue *q) { }
static inline void blkcg_exit_queue(struct request_queue *q) { }
static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { }
static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
static inline void blkg_destroy_all(struct request_queue *q) { }
static inline void blkg_destroy_all(struct request_queue *q,
enum blkio_policy_id plid,
bool destory_root) { }
static inline void *blkg_to_pdata(struct blkio_group *blkg,
struct blkio_policy_type *pol) { return NULL; }

99
block/blk-throttle.c
View File

@ -157,14 +157,6 @@ static void throtl_init_blkio_group(struct blkio_group *blkg)
tg->iops[WRITE] = -1;
}
static void throtl_link_blkio_group(struct request_queue *q,
struct blkio_group *blkg)
{
list_add(&blkg->q_node[BLKIO_POLICY_THROTL],
&q->blkg_list[BLKIO_POLICY_THROTL]);
q->nr_blkgs[BLKIO_POLICY_THROTL]++;
}
static struct
throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
{
@ -813,89 +805,6 @@ throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
}
}
static void
throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
{
struct blkio_group *blkg = tg_to_blkg(tg);
/* Something wrong if we are trying to remove same group twice */
WARN_ON_ONCE(list_empty(&blkg->q_node[BLKIO_POLICY_THROTL]));
list_del_init(&blkg->q_node[BLKIO_POLICY_THROTL]);
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
blkg_put(tg_to_blkg(tg));
td->queue->nr_blkgs[BLKIO_POLICY_THROTL]--;
}
static bool throtl_release_tgs(struct throtl_data *td, bool release_root)
{
struct request_queue *q = td->queue;
struct blkio_group *blkg, *n;
bool empty = true;
list_for_each_entry_safe(blkg, n, &q->blkg_list[BLKIO_POLICY_THROTL],
q_node[BLKIO_POLICY_THROTL]) {
struct throtl_grp *tg = blkg_to_tg(blkg);
/* skip root? */
if (!release_root && tg == td->root_tg)
continue;
/*
* If cgroup removal path got to blk_group first and removed
* it from cgroup list, then it will take care of destroying
* cfqg also.
*/
if (!blkiocg_del_blkio_group(blkg))
throtl_destroy_tg(td, tg);
else
empty = false;
}
return empty;
}
/*
* Blk cgroup controller notification saying that blkio_group object is being
* delinked as associated cgroup object is going away. That also means that
* no new IO will come in this group. So get rid of this group as soon as
* any pending IO in the group is finished.
*
* This function is called under rcu_read_lock(). @q is the rcu protected
* pointer. That means @q is a valid request_queue pointer as long as we
* are rcu read lock.
*
* @q was fetched from blkio_group under blkio_cgroup->lock. That means
* it should not be NULL as even if queue was going away, cgroup deltion
* path got to it first.
*/
void throtl_unlink_blkio_group(struct request_queue *q,
struct blkio_group *blkg)
{
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
throtl_destroy_tg(q->td, blkg_to_tg(blkg));
spin_unlock_irqrestore(q->queue_lock, flags);
}
static bool throtl_clear_queue(struct request_queue *q)
{
lockdep_assert_held(q->queue_lock);
/*
* Clear tgs but leave the root one alone. This is necessary
* because root_tg is expected to be persistent and safe because
* blk-throtl can never be disabled while @q is alive. This is a
* kludge to prepare for unified blkg. This whole function will be
* removed soon.
*/
return throtl_release_tgs(q->td, false);
}
static void throtl_update_blkio_group_common(struct throtl_data *td,
struct throtl_grp *tg)
{
@ -960,9 +869,6 @@ static void throtl_shutdown_wq(struct request_queue *q)
static struct blkio_policy_type blkio_policy_throtl = {
.ops = {
.blkio_init_group_fn = throtl_init_blkio_group,
.blkio_link_group_fn = throtl_link_blkio_group,
.blkio_unlink_group_fn = throtl_unlink_blkio_group,
.blkio_clear_queue_fn = throtl_clear_queue,
.blkio_update_group_read_bps_fn =
throtl_update_blkio_group_read_bps,
.blkio_update_group_write_bps_fn =
@ -1148,12 +1054,11 @@ void blk_throtl_exit(struct request_queue *q)
throtl_shutdown_wq(q);
spin_lock_irq(q->queue_lock);
throtl_release_tgs(td, true);
blkg_destroy_all(q, BLKIO_POLICY_THROTL, true);
/* If there are other groups */
spin_lock_irq(q->queue_lock);
wait = q->nr_blkgs[BLKIO_POLICY_THROTL];
spin_unlock_irq(q->queue_lock);
/*

100
block/cfq-iosched.c
View File

@ -1045,14 +1045,6 @@ static void cfq_update_blkio_group_weight(struct request_queue *q,
cfqg->needs_update = true;
}
static void cfq_link_blkio_group(struct request_queue *q,
struct blkio_group *blkg)
{
list_add(&blkg->q_node[BLKIO_POLICY_PROP],
&q->blkg_list[BLKIO_POLICY_PROP]);
q->nr_blkgs[BLKIO_POLICY_PROP]++;
}
static void cfq_init_blkio_group(struct blkio_group *blkg)
{
struct cfq_group *cfqg = blkg_to_cfqg(blkg);
@ -1096,84 +1088,6 @@ static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
blkg_get(cfqg_to_blkg(cfqg));
}
static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct blkio_group *blkg = cfqg_to_blkg(cfqg);
/* Something wrong if we are trying to remove same group twice */
BUG_ON(list_empty(&blkg->q_node[BLKIO_POLICY_PROP]));
list_del_init(&blkg->q_node[BLKIO_POLICY_PROP]);
BUG_ON(cfqd->queue->nr_blkgs[BLKIO_POLICY_PROP] <= 0);
cfqd->queue->nr_blkgs[BLKIO_POLICY_PROP]--;
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
blkg_put(cfqg_to_blkg(cfqg));
}
static bool cfq_release_cfq_groups(struct cfq_data *cfqd)
{
struct request_queue *q = cfqd->queue;
struct blkio_group *blkg, *n;
bool empty = true;
list_for_each_entry_safe(blkg, n, &q->blkg_list[BLKIO_POLICY_PROP],
q_node[BLKIO_POLICY_PROP]) {
/*
* If cgroup removal path got to blk_group first and removed
* it from cgroup list, then it will take care of destroying
* cfqg also.
*/
if (!cfq_blkiocg_del_blkio_group(blkg))
cfq_destroy_cfqg(cfqd, blkg_to_cfqg(blkg));
else
empty = false;
}
return empty;
}
/*
* Blk cgroup controller notification saying that blkio_group object is being
* delinked as associated cgroup object is going away. That also means that
* no new IO will come in this group. So get rid of this group as soon as
* any pending IO in the group is finished.
*
* This function is called under rcu_read_lock(). key is the rcu protected
* pointer. That means @q is a valid request_queue pointer as long as we
* are rcu read lock.
*
* @q was fetched from blkio_group under blkio_cgroup->lock. That means
* it should not be NULL as even if elevator was exiting, cgroup deltion
* path got to it first.
*/
static void cfq_unlink_blkio_group(struct request_queue *q,
struct blkio_group *blkg)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
cfq_destroy_cfqg(cfqd, blkg_to_cfqg(blkg));
spin_unlock_irqrestore(q->queue_lock, flags);
}
static struct elevator_type iosched_cfq;
static bool cfq_clear_queue(struct request_queue *q)
{
lockdep_assert_held(q->queue_lock);
/* shoot down blkgs iff the current elevator is cfq */
if (!q->elevator || q->elevator->type != &iosched_cfq)
return true;
return cfq_release_cfq_groups(q->elevator->elevator_data);
}
#else /* GROUP_IOSCHED */
static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
struct blkio_cgroup *blkcg)
@ -1186,8 +1100,6 @@ cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
cfqq->cfqg = cfqg;
}
static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
#endif /* GROUP_IOSCHED */
/*
@ -3547,17 +3459,20 @@ static void cfq_exit_queue(struct elevator_queue *e)
__cfq_slice_expired(cfqd, cfqd->active_queue, 0);
cfq_put_async_queues(cfqd);
cfq_release_cfq_groups(cfqd);
spin_unlock_irq(q->queue_lock);
blkg_destroy_all(q, BLKIO_POLICY_PROP, true);
#ifdef CONFIG_BLK_CGROUP
/*
* If there are groups which we could not unlink from blkcg list,
* wait for a rcu period for them to be freed.
*/
spin_lock_irq(q->queue_lock);
wait = q->nr_blkgs[BLKIO_POLICY_PROP];
#endif
spin_unlock_irq(q->queue_lock);
#endif
cfq_shutdown_timer_wq(cfqd);
/*
@ -3794,9 +3709,6 @@ static struct elevator_type iosched_cfq = {
static struct blkio_policy_type blkio_policy_cfq = {
.ops = {
.blkio_init_group_fn = cfq_init_blkio_group,
.blkio_link_group_fn = cfq_link_blkio_group,
.blkio_unlink_group_fn = cfq_unlink_blkio_group,
.blkio_clear_queue_fn = cfq_clear_queue,
.blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
},
.plid = BLKIO_POLICY_PROP,

5
block/elevator.c
View File

@ -876,7 +876,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
{
struct elevator_queue *old = q->elevator;
bool registered = old->registered;
int err;
int i, err;
/*
* Turn on BYPASS and drain all requests w/ elevator private data.
@ -895,7 +895,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
ioc_clear_queue(q);
spin_unlock_irq(q->queue_lock);
blkg_destroy_all(q);
for (i = 0; i < BLKIO_NR_POLICIES; i++)
blkg_destroy_all(q, i, false);
/* allocate, init and register new elevator */
err = -ENOMEM;

4
include/linux/blkdev.h
View File

@ -364,8 +364,8 @@ struct request_queue {
struct list_head icq_list;
#ifdef CONFIG_BLK_CGROUP
/* XXX: array size hardcoded to avoid include dependency (temporary) */
struct list_head blkg_list[2];
int nr_blkgs[2];
struct list_head blkg_list;
int nr_blkgs;
#endif
struct queue_limits limits;