diff --git a/block/blk-core.c b/block/blk-core.c
index 5d0d7441a44387c4164cc92b3841e8fa7066ac58..77807a5d7f9e3ee8e8d42e8c8811f0f9caff34b1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -520,6 +520,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
mutex_init(&q->blk_trace_mutex);
#endif
mutex_init(&q->sysfs_lock);
+ mutex_init(&q->sysfs_dir_lock);
spin_lock_init(&q->queue_lock);
init_waitqueue_head(&q->mq_freeze_wq);
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 6ddde3774ebe871d2e8e2d2be9dbecb2618d612c..a0d3ce30fa0893e6d854e4097bc627685d97cc7a 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -270,7 +270,7 @@ void blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
struct blk_mq_hw_ctx *hctx;
int i;
- lockdep_assert_held(&q->sysfs_lock);
+ lockdep_assert_held(&q->sysfs_dir_lock);
queue_for_each_hw_ctx(q, hctx, i)
blk_mq_unregister_hctx(hctx);
@@ -320,7 +320,7 @@ int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
int ret, i;
WARN_ON_ONCE(!q->kobj.parent);
- lockdep_assert_held(&q->sysfs_lock);
+ lockdep_assert_held(&q->sysfs_dir_lock);
ret = kobject_add(q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq");
if (ret < 0)
@@ -354,7 +354,7 @@ void blk_mq_sysfs_unregister(struct request_queue *q)
struct blk_mq_hw_ctx *hctx;
int i;
- mutex_lock(&q->sysfs_lock);
+ mutex_lock(&q->sysfs_dir_lock);
if (!q->mq_sysfs_init_done)
goto unlock;
@@ -362,7 +362,7 @@ void blk_mq_sysfs_unregister(struct request_queue *q)
blk_mq_unregister_hctx(hctx);
unlock:
- mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
}
int blk_mq_sysfs_register(struct request_queue *q)
@@ -370,7 +370,7 @@ int blk_mq_sysfs_register(struct request_queue *q)
struct blk_mq_hw_ctx *hctx;
int i, ret = 0;
- mutex_lock(&q->sysfs_lock);
+ mutex_lock(&q->sysfs_dir_lock);
if (!q->mq_sysfs_init_done)
goto unlock;
@@ -381,7 +381,7 @@ int blk_mq_sysfs_register(struct request_queue *q)
}
unlock:
- mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
return ret;
}
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 5b0b5224cfd45e039ce18fbd2bebcc0810963fde..1075134952205a560559a7bdba8cc433b50fd840 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -938,6 +938,7 @@ int blk_register_queue(struct gendisk *disk)
int ret;
struct device *dev = disk_to_dev(disk);
struct request_queue *q = disk->queue;
+ bool has_elevator = false;
if (WARN_ON(!q))
return -ENXIO;
@@ -945,7 +946,6 @@ int blk_register_queue(struct gendisk *disk)
WARN_ONCE(blk_queue_registered(q),
"%s is registering an already registered queue\n",
kobject_name(&dev->kobj));
- blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);
/*
* SCSI probing may synchronously create and destroy a lot of
@@ -965,8 +965,7 @@ int blk_register_queue(struct gendisk *disk)
if (ret)
return ret;
- /* Prevent changes through sysfs until registration is completed. */
- mutex_lock(&q->sysfs_lock);
+ mutex_lock(&q->sysfs_dir_lock);
ret = kobject_add(&q->kobj, kobject_get(&dev->kobj), "%s", "queue");
if (ret < 0) {
@@ -987,26 +986,36 @@ int blk_register_queue(struct gendisk *disk)
blk_mq_debugfs_register(q);
}
- kobject_uevent(&q->kobj, KOBJ_ADD);
-
- wbt_enable_default(q);
-
- blk_throtl_register_queue(q);
-
+ /*
+ * The flag of QUEUE_FLAG_REGISTERED isn't set yet, so elevator
+ * switch won't happen at all.
+ */
if (q->elevator) {
- ret = elv_register_queue(q);
+ ret = elv_register_queue(q, false);
if (ret) {
- mutex_unlock(&q->sysfs_lock);
- kobject_uevent(&q->kobj, KOBJ_REMOVE);
+ mutex_unlock(&q->sysfs_dir_lock);
kobject_del(&q->kobj);
blk_trace_remove_sysfs(dev);
kobject_put(&dev->kobj);
return ret;
}
+ has_elevator = true;
}
+
+ mutex_lock(&q->sysfs_lock);
+ blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);
+ wbt_enable_default(q);
+ blk_throtl_register_queue(q);
+
+ /* Now everything is ready and send out KOBJ_ADD uevent */
+ kobject_uevent(&q->kobj, KOBJ_ADD);
+ if (has_elevator)
+ kobject_uevent(&q->elevator->kobj, KOBJ_ADD);
+ mutex_unlock(&q->sysfs_lock);
+
ret = 0;
unlock:
- mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
return ret;
}
EXPORT_SYMBOL_GPL(blk_register_queue);
@@ -1021,6 +1030,7 @@ EXPORT_SYMBOL_GPL(blk_register_queue);
void blk_unregister_queue(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
+ bool has_elevator;
if (WARN_ON(!q))
return;
@@ -1035,25 +1045,25 @@ void blk_unregister_queue(struct gendisk *disk)
* concurrent elv_iosched_store() calls.
*/
mutex_lock(&q->sysfs_lock);
-
blk_queue_flag_clear(QUEUE_FLAG_REGISTERED, q);
+ has_elevator = !!q->elevator;
+ mutex_unlock(&q->sysfs_lock);
+ mutex_lock(&q->sysfs_dir_lock);
/*
* Remove the sysfs attributes before unregistering the queue data
* structures that can be modified through sysfs.
*/
if (queue_is_mq(q))
blk_mq_unregister_dev(disk_to_dev(disk), q);
- mutex_unlock(&q->sysfs_lock);
kobject_uevent(&q->kobj, KOBJ_REMOVE);
kobject_del(&q->kobj);
blk_trace_remove_sysfs(disk_to_dev(disk));
- mutex_lock(&q->sysfs_lock);
- if (q->elevator)
+ if (has_elevator)
elv_unregister_queue(q);
- mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
kobject_put(&disk_to_dev(disk)->kobj);
}
diff --git a/block/blk.h b/block/blk.h
index de6b2e146d6eb64c0be5e9f0cdb80777897c179b..e4619fc5c99aa13bce2d017948438f9e443d8f25 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -188,7 +188,7 @@ int elevator_init_mq(struct request_queue *q);
int elevator_switch_mq(struct request_queue *q,
struct elevator_type *new_e);
void __elevator_exit(struct request_queue *, struct elevator_queue *);
-int elv_register_queue(struct request_queue *q);
+int elv_register_queue(struct request_queue *q, bool uevent);
void elv_unregister_queue(struct request_queue *q);
static inline void elevator_exit(struct request_queue *q,
diff --git a/block/elevator.c b/block/elevator.c
index 03d9231965691a56e6aabb31ca6d27687c158ef8..4781c4205a5d4ba19deb5a1ac2755711748d14ab 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -470,13 +470,16 @@ static struct kobj_type elv_ktype = {
.release = elevator_release,
};
-int elv_register_queue(struct request_queue *q)
+/*
+ * elv_register_queue is called from either blk_register_queue or
+ * elevator_switch, elevator switch is prevented from being happen
+ * in the two paths, so it is safe to not hold q->sysfs_lock.
+ */
+int elv_register_queue(struct request_queue *q, bool uevent)
{
struct elevator_queue *e = q->elevator;
int error;
- lockdep_assert_held(&q->sysfs_lock);
-
error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
if (!error) {
struct elv_fs_entry *attr = e->type->elevator_attrs;
@@ -487,24 +490,34 @@ int elv_register_queue(struct request_queue *q)
attr++;
}
}
- kobject_uevent(&e->kobj, KOBJ_ADD);
+ if (uevent)
+ kobject_uevent(&e->kobj, KOBJ_ADD);
+
+ mutex_lock(&q->sysfs_lock);
e->registered = 1;
+ mutex_unlock(&q->sysfs_lock);
}
return error;
}
+/*
+ * elv_unregister_queue is called from either blk_unregister_queue or
+ * elevator_switch, elevator switch is prevented from being happen
+ * in the two paths, so it is safe to not hold q->sysfs_lock.
+ */
void elv_unregister_queue(struct request_queue *q)
{
- lockdep_assert_held(&q->sysfs_lock);
-
if (q) {
struct elevator_queue *e = q->elevator;
kobject_uevent(&e->kobj, KOBJ_REMOVE);
kobject_del(&e->kobj);
+
+ mutex_lock(&q->sysfs_lock);
e->registered = 0;
/* Re-enable throttling in case elevator disabled it */
wbt_enable_default(q);
+ mutex_unlock(&q->sysfs_lock);
}
}
@@ -567,10 +580,32 @@ int elevator_switch_mq(struct request_queue *q,
lockdep_assert_held(&q->sysfs_lock);
if (q->elevator) {
- if (q->elevator->registered)
+ if (q->elevator->registered) {
+ mutex_unlock(&q->sysfs_lock);
+
+ /*
+ * Concurrent elevator switch can't happen becasue
+ * sysfs write is always exclusively on same file.
+ *
+ * Also the elevator queue won't be freed after
+ * sysfs_lock is released becasue kobject_del() in
+ * blk_unregister_queue() waits for completion of
+ * .store & .show on its attributes.
+ */
elv_unregister_queue(q);
+
+ mutex_lock(&q->sysfs_lock);
+ }
ioc_clear_queue(q);
elevator_exit(q, q->elevator);
+
+ /*
+ * sysfs_lock may be dropped, so re-check if queue is
+ * unregistered. If yes, don't switch to new elevator
+ * any more
+ */
+ if (!blk_queue_registered(q))
+ return 0;
}
ret = blk_mq_init_sched(q, new_e);
@@ -578,7 +613,11 @@ int elevator_switch_mq(struct request_queue *q,
goto out;
if (new_e) {
- ret = elv_register_queue(q);
+ mutex_unlock(&q->sysfs_lock);
+
+ ret = elv_register_queue(q, true);
+
+ mutex_lock(&q->sysfs_lock);
if (ret) {
elevator_exit(q, q->elevator);
goto out;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d5077f3fdfd6e10a4f5b8c7223a8b6362d2c3907..1ac790178787e3e9109937686993d610c4bbd3cb 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -535,6 +535,7 @@ struct request_queue {
struct delayed_work requeue_work;
struct mutex sysfs_lock;
+ struct mutex sysfs_dir_lock;
/*
* for reusing dead hctx instance in case of updating