We can retrieve any workers via xarray, so not add it into idle list.
Meantime reduce .lo_work_lock coverage, especially we don't need that
in IO path except for adding/deleting worker into xarray.
Also simplify code a bit.
Cc: Michal Koutný <mkoutny@xxxxxxxx>
Cc: Dan Schatzberg <schatzberg.dan@xxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
drivers/block/loop.c | 138 ++++++++++++++++++++++++++-----------------
1 file changed, 84 insertions(+), 54 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 6e9725521330..146eaa03629b 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -920,10 +920,11 @@ static void loop_config_discard(struct loop_device *lo)
struct loop_worker {
struct work_struct work;
struct list_head cmd_list;
- struct list_head idle_list;
struct loop_device *lo;
struct cgroup_subsys_state *blkcg_css;
unsigned long last_ran_at;
+ spinlock_t lock;
+ refcount_t refcnt;
};
static void loop_workfn(struct work_struct *work);
@@ -941,13 +942,56 @@ static inline int queue_on_root_worker(struct cgroup_subsys_state *css)
}
#endif
+static struct loop_worker *loop_alloc_or_get_worker(struct loop_device *lo,
+ struct cgroup_subsys_state *blkcg_css)
+{
+ gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;
+ struct loop_worker *worker = kzalloc(sizeof(*worker), gfp);
+ struct loop_worker *worker_old;
+
+ if (!worker)
+ return NULL;
+
+ worker->blkcg_css = blkcg_css;
+ INIT_WORK(&worker->work, loop_workfn);
+ INIT_LIST_HEAD(&worker->cmd_list);
+ worker->lo = lo;
+ spin_lock_init(&worker->lock);
+ refcount_set(&worker->refcnt, 2); /* INIT + INC */
+
+ spin_lock(&lo->lo_work_lock);
+ /* maybe someone is storing a new worker */
+ worker_old = xa_load(&lo->workers, blkcg_css->id);
+ if (!worker_old || !refcount_inc_not_zero(&worker_old->refcnt)) {
+ if (xa_err(xa_store(&lo->workers, blkcg_css->id, worker, gfp))) {
+ kfree(worker);
+ worker = NULL;
+ } else {
+ css_get(worker->blkcg_css);
+ }
+ } else {
+ kfree(worker);
+ worker = worker_old;
+ }
+ spin_unlock(&lo->lo_work_lock);
+
+ return worker;
+}
+
+static void loop_release_worker(struct loop_worker *worker)
+{
+ xa_erase(&worker->lo->workers, worker->blkcg_css->id);
+ css_put(worker->blkcg_css);
+ kfree(worker);
+}
+
static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
{
struct loop_worker *worker = NULL;
struct work_struct *work;
struct list_head *cmd_list;
struct cgroup_subsys_state *blkcg_css = NULL;
- gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;
+ spinlock_t *lock;
#ifdef CONFIG_BLK_CGROUP
struct request *rq = blk_mq_rq_from_pdu(cmd);
@@ -955,54 +999,38 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
blkcg_css = &bio_blkcg(rq->bio)->css;
#endif
- spin_lock(&lo->lo_work_lock);
-
- if (queue_on_root_worker(blkcg_css))
- goto queue_work;
-
- /* css->id is unique in each cgroup subsystem */
- worker = xa_load(&lo->workers, blkcg_css->id);
- if (worker)
- goto queue_work;
-
- worker = kzalloc(sizeof(*worker), gfp);
- /*
- * In the event we cannot allocate a worker, just queue on the
- * rootcg worker and issue the I/O as the rootcg
- */
- if (!worker)
- goto queue_work;
+ if (!queue_on_root_worker(blkcg_css)) {
+ int ret = 0;
- worker->blkcg_css = blkcg_css;
- css_get(worker->blkcg_css);
- INIT_WORK(&worker->work, loop_workfn);
- INIT_LIST_HEAD(&worker->cmd_list);
- INIT_LIST_HEAD(&worker->idle_list);
- worker->lo = lo;
+ rcu_read_lock();
+ /* css->id is unique in each cgroup subsystem */
+ worker = xa_load(&lo->workers, blkcg_css->id);
+ if (worker)
+ ret = refcount_inc_not_zero(&worker->refcnt);
+ rcu_read_unlock();
- if (xa_err(xa_store(&lo->workers, blkcg_css->id, worker, gfp))) {
- kfree(worker);
- worker = NULL;
+ if (!worker || !ret)
+ worker = loop_alloc_or_get_worker(lo, blkcg_css);
+ /*
+ * In the event we cannot allocate a worker, just queue on the
+ * rootcg worker and issue the I/O as the rootcg
+ */
}
-queue_work:
if (worker) {
- /*
- * We need to remove from the idle list here while
- * holding the lock so that the idle timer doesn't
- * free the worker
- */
- if (!list_empty(&worker->idle_list))
- list_del_init(&worker->idle_list);
work = &worker->work;
cmd_list = &worker->cmd_list;
+ lock = &worker->lock;
} else {
work = &lo->rootcg_work;
cmd_list = &lo->rootcg_cmd_list;
+ lock = &lo->lo_work_lock;
}
+
+ spin_lock(lock);
list_add_tail(&cmd->list_entry, cmd_list);
+ spin_unlock(lock);
queue_work(lo->workqueue, work);
- spin_unlock(&lo->lo_work_lock);
}
static void loop_update_rotational(struct loop_device *lo)
@@ -1131,20 +1159,18 @@ static void loop_set_timer(struct loop_device *lo)
static void __loop_free_idle_workers(struct loop_device *lo, bool force)
{
- struct loop_worker *pos, *worker;
+ struct loop_worker *worker;
+ unsigned long id;
spin_lock(&lo->lo_work_lock);
- list_for_each_entry_safe(worker, pos, &lo->idle_worker_list,
- idle_list) {
+ xa_for_each(&lo->workers, id, worker) {
if (!force && time_is_after_jiffies(worker->last_ran_at +
LOOP_IDLE_WORKER_TIMEOUT))
break;
- list_del(&worker->idle_list);
- xa_erase(&lo->workers, worker->blkcg_css->id);
- css_put(worker->blkcg_css);
- kfree(worker);
+ if (refcount_dec_and_test(&worker->refcnt))
+ loop_release_worker(worker);
}
- if (!list_empty(&lo->idle_worker_list))
+ if (!xa_empty(&lo->workers))
loop_set_timer(lo);
spin_unlock(&lo->lo_work_lock);
}
@@ -2148,27 +2174,29 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
}
static void loop_process_work(struct loop_worker *worker,
- struct list_head *cmd_list, struct loop_device *lo)
+ struct list_head *cmd_list, spinlock_t *lock)
{
int orig_flags = current->flags;
struct loop_cmd *cmd;
LIST_HEAD(list);
+ int cnt = 0;
current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
- spin_lock(&lo->lo_work_lock);
+ spin_lock(lock);
again:
list_splice_init(cmd_list, &list);
- spin_unlock(&lo->lo_work_lock);
+ spin_unlock(lock);
while (!list_empty(&list)) {
cmd = list_first_entry(&list, struct loop_cmd, list_entry);
list_del_init(&cmd->list_entry);
loop_handle_cmd(cmd);
+ cnt++;
}
- spin_lock(&lo->lo_work_lock);
+ spin_lock(lock);
if (!list_empty(cmd_list))
goto again;
@@ -2179,11 +2207,13 @@ static void loop_process_work(struct loop_worker *worker,
*/
if (worker && !work_pending(&worker->work)) {
worker->last_ran_at = jiffies;
- list_add_tail(&worker->idle_list, &lo->idle_worker_list);
- loop_set_timer(lo);
+ loop_set_timer(worker->lo);
}
- spin_unlock(&lo->lo_work_lock);
+ spin_unlock(lock);
current->flags = orig_flags;
+
+ if (worker && refcount_sub_and_test(cnt, &worker->refcnt))
+ loop_release_worker(worker);
}
static void loop_workfn(struct work_struct *work)
@@ -2202,7 +2232,7 @@ static void loop_workfn(struct work_struct *work)
old_memcg = set_active_memcg(
mem_cgroup_from_css(memcg_css));
- loop_process_work(worker, &worker->cmd_list, worker->lo);
+ loop_process_work(worker, &worker->cmd_list, &worker->lock);
kthread_associate_blkcg(NULL);
if (memcg_css) {
@@ -2215,7 +2245,7 @@ static void loop_rootcg_workfn(struct work_struct *work)
{
struct loop_device *lo =
container_of(work, struct loop_device, rootcg_work);
- loop_process_work(NULL, &lo->rootcg_cmd_list, lo);
+ loop_process_work(NULL, &lo->rootcg_cmd_list, &lo->lo_work_lock);
}
static const struct blk_mq_ops loop_mq_ops = {
--
2.31.1
