[PATCH 1/3] rbd: support timeout in rbd_wait_state_locked

[Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>]

currently, the rbd_wait_state_locked() will wait forever if we
can't get our state locked. Example:

rbd map --exclusive test1  --> /dev/rbd0
rbd map test1  --> /dev/rbd1
dd if=/dev/zero of=/dev/rbd1 bs=1M count=1 --> IO blocked

To avoid this problem, this patch introduce a timeout design
in rbd_wait_state_locked(). Then rbd_wait_state_locked() will
return error when we reach a timeout.

Signed-off-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
---
 drivers/block/rbd.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 96657ad..199819d 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -761,6 +761,7 @@ struct rbd_options {
 #define RBD_READ_ONLY_DEFAULT	false
 #define RBD_LOCK_ON_READ_DEFAULT false
 #define RBD_EXCLUSIVE_DEFAULT	false
+#define RBD_WAIT_LOCK_TIMEOUT_DEFAULT	MAX_SCHEDULE_TIMEOUT
 
 static int parse_rbd_opts_token(char *c, void *private)
 {
@@ -3494,8 +3495,9 @@ static int rbd_obj_method_sync(struct rbd_device *rbd_dev,
 /*
  * lock_rwsem must be held for read
  */
-static void rbd_wait_state_locked(struct rbd_device *rbd_dev)
+static int rbd_wait_state_locked(struct rbd_device *rbd_dev)
 {
+	long timeo = RBD_WAIT_LOCK_TIMEOUT_DEFAULT;
 	DEFINE_WAIT(wait);
 
 	do {
@@ -3508,12 +3510,18 @@ static void rbd_wait_state_locked(struct rbd_device *rbd_dev)
 		prepare_to_wait_exclusive(&rbd_dev->lock_waitq, &wait,
 					  TASK_UNINTERRUPTIBLE);
 		up_read(&rbd_dev->lock_rwsem);
-		schedule();
+		timeo = schedule_timeout(timeo);
 		down_read(&rbd_dev->lock_rwsem);
+		if (!timeo) {
+			finish_wait(&rbd_dev->lock_waitq, &wait);
+			rbd_warn(rbd_dev, "timed out in waiting state locked");
+			return -ETIMEDOUT;
+		}
 	} while (rbd_dev->lock_state != RBD_LOCK_STATE_LOCKED &&
 		 !test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags));
 
 	finish_wait(&rbd_dev->lock_waitq, &wait);
+	return 0;
 }
 
 static void rbd_queue_workfn(struct work_struct *work)
@@ -3606,7 +3614,9 @@ static void rbd_queue_workfn(struct work_struct *work)
 				result = -EROFS;
 				goto err_unlock;
 			}
-			rbd_wait_state_locked(rbd_dev);
+			result = rbd_wait_state_locked(rbd_dev);
+			if (result)
+				goto err_unlock;
 		}
 		if (test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags)) {
 			result = -EBLACKLISTED;
@@ -5261,6 +5271,8 @@ static void rbd_dev_image_unlock(struct rbd_device *rbd_dev)
 
 static int rbd_add_acquire_lock(struct rbd_device *rbd_dev)
 {
+	int ret = 0;
+
 	if (!(rbd_dev->header.features & RBD_FEATURE_EXCLUSIVE_LOCK)) {
 		rbd_warn(rbd_dev, "exclusive-lock feature is not enabled");
 		return -EINVAL;
@@ -5268,8 +5280,11 @@ static int rbd_add_acquire_lock(struct rbd_device *rbd_dev)
 
 	/* FIXME: "rbd map --exclusive" should be in interruptible */
 	down_read(&rbd_dev->lock_rwsem);
-	rbd_wait_state_locked(rbd_dev);
+	ret = rbd_wait_state_locked(rbd_dev);
 	up_read(&rbd_dev->lock_rwsem);
+	if (ret) {
+		return ret;
+	}
 	if (test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags)) {
 		rbd_warn(rbd_dev, "failed to acquire exclusive lock");
 		return -EROFS;
-- 
1.8.3.1


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