librbd: bail from schedule_request_lock() if already lock owner

Race condition may be hit if there are multiple pending locks for the
same image and pending callbacks. Abort exclusive lock process if
already exclusive lock owner.

Fixes: https://tracker.ceph.com/issues/56549
Signed-off-by: Christopher Hoffman <choffman@redhat.com>
(cherry picked from commit 3527d2c764626c09c5ede80ae844551fd8845756)

diff --git a/src/librbd/ImageWatcher.cc b/src/librbd/ImageWatcher.cc
index f4fdc54b90d116196bbd20932c7aba21dc712abc..f5a27e0c2bbafc6496f80940e63d130e99f98578 100644 (file)
--- a/src/librbd/ImageWatcher.cc
+++ b/src/librbd/ImageWatcher.cc
@@ -572,12 +572,11 @@ template <typename I>
 void ImageWatcher<I>::schedule_request_lock(bool use_timer, int timer_delay) {
   ceph_assert(ceph_mutex_is_locked(m_image_ctx.owner_lock));
 
-  if (m_image_ctx.exclusive_lock == nullptr) {
-    // exclusive lock dynamically disabled via image refresh
+  // see notify_request_lock()
+  if (m_image_ctx.exclusive_lock == nullptr ||
+      m_image_ctx.exclusive_lock->is_lock_owner()) {
     return;
   }
-  ceph_assert(m_image_ctx.exclusive_lock &&
-              !m_image_ctx.exclusive_lock->is_lock_owner());
 
   std::shared_lock watch_locker{this->m_watch_lock};
   if (this->is_registered(this->m_watch_lock)) {