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-rw-r--r--block/blk-ioc.c135
1 files changed, 88 insertions, 47 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 8b782a63c297..fb95dd2f889a 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -36,11 +36,23 @@ static void icq_free_icq_rcu(struct rcu_head *head)
kmem_cache_free(icq->__rcu_icq_cache, icq);
}
-/*
- * Exit and free an icq. Called with both ioc and q locked.
- */
+/* Exit an icq. Called with both ioc and q locked. */
static void ioc_exit_icq(struct io_cq *icq)
{
+ struct elevator_type *et = icq->q->elevator->type;
+
+ if (icq->flags & ICQ_EXITED)
+ return;
+
+ if (et->ops.elevator_exit_icq_fn)
+ et->ops.elevator_exit_icq_fn(icq);
+
+ icq->flags |= ICQ_EXITED;
+}
+
+/* Release an icq. Called with both ioc and q locked. */
+static void ioc_destroy_icq(struct io_cq *icq)
+{
struct io_context *ioc = icq->ioc;
struct request_queue *q = icq->q;
struct elevator_type *et = q->elevator->type;
@@ -60,8 +72,7 @@ static void ioc_exit_icq(struct io_cq *icq)
if (rcu_dereference_raw(ioc->icq_hint) == icq)
rcu_assign_pointer(ioc->icq_hint, NULL);
- if (et->ops.elevator_exit_icq_fn)
- et->ops.elevator_exit_icq_fn(icq);
+ ioc_exit_icq(icq);
/*
* @icq->q might have gone away by the time RCU callback runs
@@ -79,7 +90,6 @@ static void ioc_release_fn(struct work_struct *work)
{
struct io_context *ioc = container_of(work, struct io_context,
release_work);
- struct request_queue *last_q = NULL;
unsigned long flags;
/*
@@ -93,44 +103,19 @@ static void ioc_release_fn(struct work_struct *work)
while (!hlist_empty(&ioc->icq_list)) {
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
struct io_cq, ioc_node);
- struct request_queue *this_q = icq->q;
-
- if (this_q != last_q) {
- /*
- * Need to switch to @this_q. Once we release
- * @ioc->lock, it can go away along with @cic.
- * Hold on to it.
- */
- __blk_get_queue(this_q);
-
- /*
- * blk_put_queue() might sleep thanks to kobject
- * idiocy. Always release both locks, put and
- * restart.
- */
- if (last_q) {
- spin_unlock(last_q->queue_lock);
- spin_unlock_irqrestore(&ioc->lock, flags);
- blk_put_queue(last_q);
- } else {
- spin_unlock_irqrestore(&ioc->lock, flags);
- }
-
- last_q = this_q;
- spin_lock_irqsave(this_q->queue_lock, flags);
- spin_lock_nested(&ioc->lock, 1);
- continue;
+ struct request_queue *q = icq->q;
+
+ if (spin_trylock(q->queue_lock)) {
+ ioc_destroy_icq(icq);
+ spin_unlock(q->queue_lock);
+ } else {
+ spin_unlock_irqrestore(&ioc->lock, flags);
+ cpu_relax();
+ spin_lock_irqsave_nested(&ioc->lock, flags, 1);
}
- ioc_exit_icq(icq);
}
- if (last_q) {
- spin_unlock(last_q->queue_lock);
- spin_unlock_irqrestore(&ioc->lock, flags);
- blk_put_queue(last_q);
- } else {
- spin_unlock_irqrestore(&ioc->lock, flags);
- }
+ spin_unlock_irqrestore(&ioc->lock, flags);
kmem_cache_free(iocontext_cachep, ioc);
}
@@ -145,6 +130,7 @@ static void ioc_release_fn(struct work_struct *work)
void put_io_context(struct io_context *ioc)
{
unsigned long flags;
+ bool free_ioc = false;
if (ioc == NULL)
return;
@@ -159,8 +145,13 @@ void put_io_context(struct io_context *ioc)
spin_lock_irqsave(&ioc->lock, flags);
if (!hlist_empty(&ioc->icq_list))
schedule_work(&ioc->release_work);
+ else
+ free_ioc = true;
spin_unlock_irqrestore(&ioc->lock, flags);
}
+
+ if (free_ioc)
+ kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL(put_io_context);
@@ -168,13 +159,41 @@ EXPORT_SYMBOL(put_io_context);
void exit_io_context(struct task_struct *task)
{
struct io_context *ioc;
+ struct io_cq *icq;
+ struct hlist_node *n;
+ unsigned long flags;
task_lock(task);
ioc = task->io_context;
task->io_context = NULL;
task_unlock(task);
- atomic_dec(&ioc->nr_tasks);
+ if (!atomic_dec_and_test(&ioc->nr_tasks)) {
+ put_io_context(ioc);
+ return;
+ }
+
+ /*
+ * Need ioc lock to walk icq_list and q lock to exit icq. Perform
+ * reverse double locking. Read comment in ioc_release_fn() for
+ * explanation on the nested locking annotation.
+ */
+retry:
+ spin_lock_irqsave_nested(&ioc->lock, flags, 1);
+ hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) {
+ if (icq->flags & ICQ_EXITED)
+ continue;
+ if (spin_trylock(icq->q->queue_lock)) {
+ ioc_exit_icq(icq);
+ spin_unlock(icq->q->queue_lock);
+ } else {
+ spin_unlock_irqrestore(&ioc->lock, flags);
+ cpu_relax();
+ goto retry;
+ }
+ }
+ spin_unlock_irqrestore(&ioc->lock, flags);
+
put_io_context(ioc);
}
@@ -194,7 +213,7 @@ void ioc_clear_queue(struct request_queue *q)
struct io_context *ioc = icq->ioc;
spin_lock(&ioc->lock);
- ioc_exit_icq(icq);
+ ioc_destroy_icq(icq);
spin_unlock(&ioc->lock);
}
}
@@ -363,13 +382,13 @@ struct io_cq *ioc_create_icq(struct request_queue *q, gfp_t gfp_mask)
return icq;
}
-void ioc_set_changed(struct io_context *ioc, int which)
+void ioc_set_icq_flags(struct io_context *ioc, unsigned int flags)
{
struct io_cq *icq;
struct hlist_node *n;
hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node)
- set_bit(which, &icq->changed);
+ icq->flags |= flags;
}
/**
@@ -387,7 +406,7 @@ void ioc_ioprio_changed(struct io_context *ioc, int ioprio)
spin_lock_irqsave(&ioc->lock, flags);
ioc->ioprio = ioprio;
- ioc_set_changed(ioc, ICQ_IOPRIO_CHANGED);
+ ioc_set_icq_flags(ioc, ICQ_IOPRIO_CHANGED);
spin_unlock_irqrestore(&ioc->lock, flags);
}
@@ -404,11 +423,33 @@ void ioc_cgroup_changed(struct io_context *ioc)
unsigned long flags;
spin_lock_irqsave(&ioc->lock, flags);
- ioc_set_changed(ioc, ICQ_CGROUP_CHANGED);
+ ioc_set_icq_flags(ioc, ICQ_CGROUP_CHANGED);
spin_unlock_irqrestore(&ioc->lock, flags);
}
EXPORT_SYMBOL(ioc_cgroup_changed);
+/**
+ * icq_get_changed - fetch and clear icq changed mask
+ * @icq: icq of interest
+ *
+ * Fetch and clear ICQ_*_CHANGED bits from @icq. Grabs and releases
+ * @icq->ioc->lock.
+ */
+unsigned icq_get_changed(struct io_cq *icq)
+{
+ unsigned int changed = 0;
+ unsigned long flags;
+
+ if (unlikely(icq->flags & ICQ_CHANGED_MASK)) {
+ spin_lock_irqsave(&icq->ioc->lock, flags);
+ changed = icq->flags & ICQ_CHANGED_MASK;
+ icq->flags &= ~ICQ_CHANGED_MASK;
+ spin_unlock_irqrestore(&icq->ioc->lock, flags);
+ }
+ return changed;
+}
+EXPORT_SYMBOL(icq_get_changed);
+
static int __init blk_ioc_init(void)
{
iocontext_cachep = kmem_cache_create("blkdev_ioc",
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-21 21:36:07 +0000