rbd: exclusive map option

Support disabling automatic exclusive lock transfers to allow users
to be in charge of which node should own the lock while being able to
reuse exclusive lock's built-in blacklist/break-lock functionality.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jason Dillaman <dillaman@redhat.com>

drivers/block/rbd.c

@@ -798,6 +798,7 @@ enum {
 	Opt_read_only,
 	Opt_read_write,
 	Opt_lock_on_read,
+	Opt_exclusive,
 	Opt_err
 };
 
@@ -810,6 +811,7 @@ static match_table_t rbd_opts_tokens = {
 	{Opt_read_write, "read_write"},
 	{Opt_read_write, "rw"},		/* Alternate spelling */
 	{Opt_lock_on_read, "lock_on_read"},
+	{Opt_exclusive, "exclusive"},
 	{Opt_err, NULL}
 };
 
@@ -817,11 +819,13 @@ struct rbd_options {
 	int	queue_depth;
 	bool	read_only;
 	bool	lock_on_read;
+	bool	exclusive;
 };
 
 #define RBD_QUEUE_DEPTH_DEFAULT	BLKDEV_MAX_RQ
 #define RBD_READ_ONLY_DEFAULT	false
 #define RBD_LOCK_ON_READ_DEFAULT false
+#define RBD_EXCLUSIVE_DEFAULT	false
 
 static int parse_rbd_opts_token(char *c, void *private)
 {
@@ -860,6 +864,9 @@ static int parse_rbd_opts_token(char *c, void *private)
 	case Opt_lock_on_read:
 		rbd_opts->lock_on_read = true;
 		break;
+	case Opt_exclusive:
+		rbd_opts->exclusive = true;
+		break;
 	default:
 		/* libceph prints "bad option" msg */
 		return -EINVAL;
@@ -3440,6 +3447,18 @@ again:
 	ret = rbd_request_lock(rbd_dev);
 	if (ret == -ETIMEDOUT) {
 		goto again; /* treat this as a dead client */
+	} else if (ret == -EROFS) {
+		rbd_warn(rbd_dev, "peer will not release lock");
+		/*
+		 * If this is rbd_add_acquire_lock(), we want to fail
+		 * immediately -- reuse BLACKLISTED flag.  Otherwise we
+		 * want to block.
+		 */
+		if (!(rbd_dev->disk->flags & GENHD_FL_UP)) {
+			set_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags);
+			/* wake "rbd map --exclusive" process */
+			wake_requests(rbd_dev, false);
+		}
 	} else if (ret < 0) {
 		rbd_warn(rbd_dev, "error requesting lock: %d", ret);
 		mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_dwork,
@@ -3606,9 +3625,15 @@ static int rbd_handle_request_lock(struct rbd_device *rbd_dev, u8 struct_v,
 		result = 0;
 
 		if (rbd_dev->lock_state == RBD_LOCK_STATE_LOCKED) {
-			dout("%s rbd_dev %p queueing unlock_work\n", __func__,
-			     rbd_dev);
-			queue_work(rbd_dev->task_wq, &rbd_dev->unlock_work);
+			if (!rbd_dev->opts->exclusive) {
+				dout("%s rbd_dev %p queueing unlock_work\n",
+				     __func__, rbd_dev);
+				queue_work(rbd_dev->task_wq,
+					   &rbd_dev->unlock_work);
+			} else {
+				/* refuse to release the lock */
+				result = -EROFS;
+			}
 		}
 	}
 
@@ -4073,8 +4098,14 @@ static void rbd_queue_workfn(struct work_struct *work)
 	if (must_be_locked) {
 		down_read(&rbd_dev->lock_rwsem);
 		if (rbd_dev->lock_state != RBD_LOCK_STATE_LOCKED &&
-		    !test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags))
+		    !test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags)) {
+			if (rbd_dev->opts->exclusive) {
+				rbd_warn(rbd_dev, "exclusive lock required");
+				result = -EROFS;
+				goto err_unlock;
+			}
 			rbd_wait_state_locked(rbd_dev);
+		}
 		if (test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags)) {
 			result = -EBLACKLISTED;
 			goto err_unlock;
@@ -5640,6 +5671,7 @@ static int rbd_add_parse_args(const char *buf,
 	rbd_opts->read_only = RBD_READ_ONLY_DEFAULT;
 	rbd_opts->queue_depth = RBD_QUEUE_DEPTH_DEFAULT;
 	rbd_opts->lock_on_read = RBD_LOCK_ON_READ_DEFAULT;
+	rbd_opts->exclusive = RBD_EXCLUSIVE_DEFAULT;
 
 	copts = ceph_parse_options(options, mon_addrs,
 					mon_addrs + mon_addrs_size - 1,
@@ -5698,6 +5730,33 @@ again:
 	return ret;
 }
 
+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);
+	up_write(&rbd_dev->lock_rwsem);
+}
+
+static int rbd_add_acquire_lock(struct rbd_device *rbd_dev)
+{
+	if (!(rbd_dev->header.features & RBD_FEATURE_EXCLUSIVE_LOCK)) {
+		rbd_warn(rbd_dev, "exclusive-lock feature is not enabled");
+		return -EINVAL;
+	}
+
+	/* FIXME: "rbd map --exclusive" should be in interruptible */
+	down_read(&rbd_dev->lock_rwsem);
+	rbd_wait_state_locked(rbd_dev);
+	up_read(&rbd_dev->lock_rwsem);
+	if (test_bit(RBD_DEV_FLAG_BLACKLISTED, &rbd_dev->flags)) {
+		rbd_warn(rbd_dev, "failed to acquire exclusive lock");
+		return -EROFS;
+	}
+
+	return 0;
+}
+
 /*
  * An rbd format 2 image has a unique identifier, distinct from the
  * name given to it by the user.  Internally, that identifier is
@@ -6141,11 +6200,17 @@ static ssize_t do_rbd_add(struct bus_type *bus,
 	if (rc)
 		goto err_out_image_probe;
 
+	if (rbd_dev->opts->exclusive) {
+		rc = rbd_add_acquire_lock(rbd_dev);
+		if (rc)
+			goto err_out_device_setup;
+	}
+
 	/* Everything's ready.  Announce the disk to the world. */
 
 	rc = device_add(&rbd_dev->dev);
 	if (rc)
-		goto err_out_device_setup;
+		goto err_out_image_lock;
 
 	add_disk(rbd_dev->disk);
 	/* see rbd_init_disk() */
@@ -6163,6 +6228,8 @@ out:
 	module_put(THIS_MODULE);
 	return rc;
 
+err_out_image_lock:
+	rbd_dev_image_unlock(rbd_dev);
 err_out_device_setup:
 	rbd_dev_device_release(rbd_dev);
 err_out_image_probe:
@@ -6286,11 +6353,7 @@ static ssize_t do_rbd_remove(struct bus_type *bus,
 	spin_unlock(&rbd_dev_list_lock);
 	device_del(&rbd_dev->dev);
 
-	down_write(&rbd_dev->lock_rwsem);
-	if (__rbd_is_lock_owner(rbd_dev))
-		rbd_unlock(rbd_dev);
-	up_write(&rbd_dev->lock_rwsem);
-
+	rbd_dev_image_unlock(rbd_dev);
 	rbd_dev_device_release(rbd_dev);
 	rbd_dev_image_release(rbd_dev);
 	rbd_dev_destroy(rbd_dev);