Commit 9d01e07f authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

rbd: prevent busy loop when requesting exclusive lock 



Due to rbd_try_acquire_lock() effectively swallowing all but
EBLOCKLISTED error from rbd_try_lock() ("request lock anyway") and
rbd_request_lock() returning ETIMEDOUT error not only for an actual
notify timeout but also when the lock owner doesn't respond, a busy
loop inside of rbd_acquire_lock() between rbd_try_acquire_lock() and
rbd_request_lock() is possible.

Requesting the lock on EBUSY error (returned by get_lock_owner_info()
if an incompatible lock or invalid lock owner is detected) makes very
little sense.  The same goes for ETIMEDOUT error (might pop up pretty
much anywhere if osd_request_timeout option is set) and many others.

Just fail I/O requests on rbd_dev->acquiring_list immediately on any
error from rbd_try_lock().

Cc: stable@vger.kernel.org # 58815900: rbd: retrieve and check lock owner twice before blocklisting
Cc: stable@vger.kernel.org
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
Reviewed-by: default avatarDongsheng Yang <dongsheng.yang@easystack.cn>
parent e7e607bd

drivers/block/rbd.c

+15 −13
Original line number Diff line number Diff line
@@ -3675,7 +3675,7 @@ static int rbd_lock(struct rbd_device *rbd_dev) 
	ret = ceph_cls_lock(osdc, &rbd_dev->header_oid, &rbd_dev->header_oloc,

			    RBD_LOCK_NAME, CEPH_CLS_LOCK_EXCLUSIVE, cookie,

			    RBD_LOCK_TAG, "", 0);

	if (ret)

	if (ret && ret != -EEXIST)

		return ret;



	__rbd_lock(rbd_dev, cookie);
@@ -3878,7 +3878,7 @@ static struct ceph_locker *get_lock_owner_info(struct rbd_device *rbd_dev) 
				 &rbd_dev->header_oloc, RBD_LOCK_NAME,

				 &lock_type, &lock_tag, &lockers, &num_lockers);

	if (ret) {

		rbd_warn(rbd_dev, "failed to retrieve lockers: %d", ret);

		rbd_warn(rbd_dev, "failed to get header lockers: %d", ret);

		return ERR_PTR(ret);

	}
@@ -3940,8 +3940,10 @@ static int find_watcher(struct rbd_device *rbd_dev, 
	ret = ceph_osdc_list_watchers(osdc, &rbd_dev->header_oid,

				      &rbd_dev->header_oloc, &watchers,

				      &num_watchers);

	if (ret)

	if (ret) {

		rbd_warn(rbd_dev, "failed to get watchers: %d", ret);

		return ret;

	}



	sscanf(locker->id.cookie, RBD_LOCK_COOKIE_PREFIX " %llu", &cookie);

	for (i = 0; i < num_watchers; i++) {
@@ -3985,8 +3987,12 @@ static int rbd_try_lock(struct rbd_device *rbd_dev) 
		locker = refreshed_locker = NULL;



		ret = rbd_lock(rbd_dev);

		if (ret != -EBUSY)

		if (!ret)

			goto out;

		if (ret != -EBUSY) {

			rbd_warn(rbd_dev, "failed to lock header: %d", ret);

			goto out;

		}



		/* determine if the current lock holder is still alive */

		locker = get_lock_owner_info(rbd_dev);
@@ -4089,11 +4095,8 @@ static int rbd_try_acquire_lock(struct rbd_device *rbd_dev) 


	ret = rbd_try_lock(rbd_dev);

	if (ret < 0) {

		rbd_warn(rbd_dev, "failed to lock header: %d", ret);

		if (ret == -EBLOCKLISTED)

		rbd_warn(rbd_dev, "failed to acquire lock: %d", ret);

		goto out;



		ret = 1; /* request lock anyway */

	}

	if (ret > 0) {

		up_write(&rbd_dev->lock_rwsem);
@@ -6627,12 +6630,11 @@ static int rbd_add_acquire_lock(struct rbd_device *rbd_dev) 
		cancel_delayed_work_sync(&rbd_dev->lock_dwork);

		if (!ret)

			ret = -ETIMEDOUT;

	}



	if (ret) {

		rbd_warn(rbd_dev, "failed to acquire exclusive lock: %ld", ret);

		return ret;

		rbd_warn(rbd_dev, "failed to acquire lock: %ld", ret);

	}

	if (ret)

		return ret;



	/*

	 * The lock may have been released by now, unless automatic lock