Re: [PATCH 13/20] rbd: quiescing lock should wait for image requests

[Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>]

On 06/25/2019 10:41 PM, Ilya Dryomov wrote:
> Syncing OSD requests doesn't really work.  A single image request may
> be comprised of multiple object requests, each of which can go through
> a series of OSD requests (original, copyups, etc).  On top of that, the
> OSD cliest may be shared with other rbd devices.
>
> What we want is to ensure that all in-flight image requests complete.
> Introduce rbd_dev->running_list and block in RBD_LOCK_STATE_RELEASING
> until that happens.  New OSD requests may be started during this time.
>
> Note that __rbd_img_handle_request() acquires rbd_dev->lock_rwsem only
> if need_exclusive_lock() returns true.  This avoids a deadlock similar
> to the one outlined in the previous commit between unlock and I/O that
> doesn't require lock, such as a read with object-map feature disabled.
>
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>

Reviewed-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
> ---
>   drivers/block/rbd.c | 104 ++++++++++++++++++++++++++++++++++++++------
>   1 file changed, 90 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 5fcb4ebd981a..59d1fef35663 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -331,6 +331,7 @@ struct rbd_img_request {
>   		struct rbd_obj_request	*obj_request;	/* obj req initiator */
>   	};
>   
> +	struct list_head	lock_item;
>   	struct list_head	object_extents;	/* obj_req.ex structs */
>   
>   	struct mutex		state_mutex;
> @@ -410,6 +411,9 @@ struct rbd_device {
>   	struct work_struct	released_lock_work;
>   	struct delayed_work	lock_dwork;
>   	struct work_struct	unlock_work;
> +	spinlock_t		lock_lists_lock;
> +	struct list_head	running_list;
> +	struct completion	releasing_wait;
>   	wait_queue_head_t	lock_waitq;
>   
>   	struct workqueue_struct	*task_wq;
> @@ -1726,6 +1730,7 @@ static struct rbd_img_request *rbd_img_request_create(
>   	if (rbd_dev_parent_get(rbd_dev))
>   		img_request_layered_set(img_request);
>   
> +	INIT_LIST_HEAD(&img_request->lock_item);
>   	INIT_LIST_HEAD(&img_request->object_extents);
>   	mutex_init(&img_request->state_mutex);
>   	kref_init(&img_request->kref);
> @@ -1745,6 +1750,7 @@ static void rbd_img_request_destroy(struct kref *kref)
>   
>   	dout("%s: img %p\n", __func__, img_request);
>   
> +	WARN_ON(!list_empty(&img_request->lock_item));
>   	for_each_obj_request_safe(img_request, obj_request, next_obj_request)
>   		rbd_img_obj_request_del(img_request, obj_request);
>   
> @@ -2872,6 +2878,50 @@ static void rbd_obj_handle_request(struct rbd_obj_request *obj_req, int result)
>   		rbd_img_handle_request(obj_req->img_request, result);
>   }
>   
> +static bool need_exclusive_lock(struct rbd_img_request *img_req)
> +{
> +	struct rbd_device *rbd_dev = img_req->rbd_dev;
> +
> +	if (!(rbd_dev->header.features & RBD_FEATURE_EXCLUSIVE_LOCK))
> +		return false;
> +
> +	if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
> +		return false;
> +
> +	rbd_assert(!test_bit(IMG_REQ_CHILD, &img_req->flags));
> +	if (rbd_dev->opts->lock_on_read)
> +		return true;
> +
> +	return rbd_img_is_write(img_req);
> +}
> +
> +static void rbd_lock_add_request(struct rbd_img_request *img_req)
> +{
> +	struct rbd_device *rbd_dev = img_req->rbd_dev;
> +
> +	lockdep_assert_held(&rbd_dev->lock_rwsem);
> +	spin_lock(&rbd_dev->lock_lists_lock);
> +	rbd_assert(list_empty(&img_req->lock_item));
> +	list_add_tail(&img_req->lock_item, &rbd_dev->running_list);
> +	spin_unlock(&rbd_dev->lock_lists_lock);
> +}
> +
> +static void rbd_lock_del_request(struct rbd_img_request *img_req)
> +{
> +	struct rbd_device *rbd_dev = img_req->rbd_dev;
> +	bool need_wakeup;
> +
> +	lockdep_assert_held(&rbd_dev->lock_rwsem);
> +	spin_lock(&rbd_dev->lock_lists_lock);
> +	rbd_assert(!list_empty(&img_req->lock_item));
> +	list_del_init(&img_req->lock_item);
> +	need_wakeup = (rbd_dev->lock_state == RBD_LOCK_STATE_RELEASING &&
> +		       list_empty(&rbd_dev->running_list));
> +	spin_unlock(&rbd_dev->lock_lists_lock);
> +	if (need_wakeup)
> +		complete(&rbd_dev->releasing_wait);
> +}
> +
>   static void rbd_img_object_requests(struct rbd_img_request *img_req)
>   {
>   	struct rbd_obj_request *obj_req;
> @@ -2927,9 +2977,19 @@ static bool __rbd_img_handle_request(struct rbd_img_request *img_req,
>   	struct rbd_device *rbd_dev = img_req->rbd_dev;
>   	bool done;
>   
> -	mutex_lock(&img_req->state_mutex);
> -	done = rbd_img_advance(img_req, result);
> -	mutex_unlock(&img_req->state_mutex);
> +	if (need_exclusive_lock(img_req)) {
> +		down_read(&rbd_dev->lock_rwsem);
> +		mutex_lock(&img_req->state_mutex);
> +		done = rbd_img_advance(img_req, result);
> +		if (done)
> +			rbd_lock_del_request(img_req);
> +		mutex_unlock(&img_req->state_mutex);
> +		up_read(&rbd_dev->lock_rwsem);
> +	} else {
> +		mutex_lock(&img_req->state_mutex);
> +		done = rbd_img_advance(img_req, result);
> +		mutex_unlock(&img_req->state_mutex);
> +	}
>   
>   	if (done && *result) {
>   		rbd_assert(*result < 0);
> @@ -3413,30 +3473,40 @@ static void rbd_acquire_lock(struct work_struct *work)
>   
>   static bool rbd_quiesce_lock(struct rbd_device *rbd_dev)
>   {
> +	bool need_wait;
> +
>   	dout("%s rbd_dev %p\n", __func__, rbd_dev);
>   	lockdep_assert_held_exclusive(&rbd_dev->lock_rwsem);
>   
>   	if (rbd_dev->lock_state != RBD_LOCK_STATE_LOCKED)
>   		return false;
>   
> -	rbd_dev->lock_state = RBD_LOCK_STATE_RELEASING;
> -	downgrade_write(&rbd_dev->lock_rwsem);
>   	/*
>   	 * Ensure that all in-flight IO is flushed.
> -	 *
> -	 * FIXME: ceph_osdc_sync() flushes the entire OSD client, which
> -	 * may be shared with other devices.
>   	 */
> -	ceph_osdc_sync(&rbd_dev->rbd_client->client->osdc);
> +	rbd_dev->lock_state = RBD_LOCK_STATE_RELEASING;
> +	rbd_assert(!completion_done(&rbd_dev->releasing_wait));
> +	need_wait = !list_empty(&rbd_dev->running_list);
> +	downgrade_write(&rbd_dev->lock_rwsem);
> +	if (need_wait)
> +		wait_for_completion(&rbd_dev->releasing_wait);
>   	up_read(&rbd_dev->lock_rwsem);
>   
>   	down_write(&rbd_dev->lock_rwsem);
>   	if (rbd_dev->lock_state != RBD_LOCK_STATE_RELEASING)
>   		return false;
>   
> +	rbd_assert(list_empty(&rbd_dev->running_list));
>   	return true;
>   }
>   
> +static void __rbd_release_lock(struct rbd_device *rbd_dev)
> +{
> +	rbd_assert(list_empty(&rbd_dev->running_list));
> +
> +	rbd_unlock(rbd_dev);
> +}
> +
>   /*
>    * lock_rwsem must be held for write
>    */
> @@ -3445,7 +3515,7 @@ static void rbd_release_lock(struct rbd_device *rbd_dev)
>   	if (!rbd_quiesce_lock(rbd_dev))
>   		return;
>   
> -	rbd_unlock(rbd_dev);
> +	__rbd_release_lock(rbd_dev);
>   
>   	/*
>   	 * Give others a chance to grab the lock - we would re-acquire
> @@ -3819,7 +3889,7 @@ static void rbd_reacquire_lock(struct rbd_device *rbd_dev)
>   		 * Lock cookie cannot be updated on older OSDs, so do
>   		 * a manual release and queue an acquire.
>   		 */
> -		rbd_unlock(rbd_dev);
> +		__rbd_release_lock(rbd_dev);
>   		queue_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork, 0);
>   	} else {
>   		__rbd_lock(rbd_dev, cookie);
> @@ -4085,9 +4155,12 @@ static void rbd_queue_workfn(struct work_struct *work)
>   	if (result)
>   		goto err_img_request;
>   
> -	rbd_img_handle_request(img_request, 0);
> -	if (must_be_locked)
> +	if (must_be_locked) {
> +		rbd_lock_add_request(img_request);
>   		up_read(&rbd_dev->lock_rwsem);
> +	}
> +
> +	rbd_img_handle_request(img_request, 0);
>   	return;
>   
>   err_img_request:
> @@ -4761,6 +4834,9 @@ static struct rbd_device *__rbd_dev_create(struct rbd_client *rbdc,
>   	INIT_WORK(&rbd_dev->released_lock_work, rbd_notify_released_lock);
>   	INIT_DELAYED_WORK(&rbd_dev->lock_dwork, rbd_acquire_lock);
>   	INIT_WORK(&rbd_dev->unlock_work, rbd_release_lock_work);
> +	spin_lock_init(&rbd_dev->lock_lists_lock);
> +	INIT_LIST_HEAD(&rbd_dev->running_list);
> +	init_completion(&rbd_dev->releasing_wait);
>   	init_waitqueue_head(&rbd_dev->lock_waitq);
>   
>   	rbd_dev->dev.bus = &rbd_bus_type;
> @@ -5777,7 +5853,7 @@ static void rbd_dev_image_unlock(struct rbd_device *rbd_dev)
>   {
>   	down_write(&rbd_dev->lock_rwsem);
>   	if (__rbd_is_lock_owner(rbd_dev))
> -		rbd_unlock(rbd_dev);
> +		__rbd_release_lock(rbd_dev);
>   	up_write(&rbd_dev->lock_rwsem);
>   }
>