[PATCH 6.1 087/127] rbd: prevent busy loop when requesting exclusive lock

Greg Kroah-Hartman
2023-08-09T10:55:16Z

From: Ilya Dryomov <idryomov@gmail.com>

commit 9d01e07fd1bfb4daae156ab528aa196f5ac2b2bc upstream.

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 # 588159009d5b: rbd: retrieve and check lock owner twice before blocklisting
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/block/rbd.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3676,7 +3676,7 @@ static int rbd_lock(struct rbd_device *r
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);
@@ -3879,7 +3879,7 @@ static struct ceph_locker *get_lock_owne
&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);
}

@@ -3941,8 +3941,10 @@ static int find_watcher(struct rbd_devic
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++) {
@@ -3986,8 +3988,12 @@ static int rbd_try_lock(struct rbd_devic
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);
@@ -4090,11 +4096,8 @@ static int rbd_try_acquire_lock(struct r

ret = rbd_try_lock(rbd_dev);
if (ret < 0) {
- rbd_warn(rbd_dev, "failed to lock header: %d", ret);
- if (ret == -EBLOCKLISTED)
- goto out;
-
- ret = 1; /* request lock anyway */
+ rbd_warn(rbd_dev, "failed to acquire lock: %d", ret);
+ goto out;
}
if (ret > 0) {
up_write(&rbd_dev->lock_rwsem);
@@ -6628,12 +6631,11 @@ static int rbd_add_acquire_lock(struct r
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