From: Jason Dillaman <dillaman@redhat.com>
Date: Thu, 28 May 2020 13:17:04 +0000 (-0400)
Subject: librbd: drop exclusive-lock image dispatch lock before acquiring lock
X-Git-Tag: v17.0.0~2184^2~3
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=3457f0bf280231a46d87e2f0adf96ecad6c60a79;p=ceph.git

librbd: drop exclusive-lock image dispatch lock before acquiring lock

This avoids a potential race with the exclusive lock being acquired by
another thread while the image dispatch layer attempts to acquire it.

Signed-off-by: Jason Dillaman <dillaman@redhat.com>
---

diff --git a/src/librbd/exclusive_lock/ImageDispatch.cc b/src/librbd/exclusive_lock/ImageDispatch.cc
index dccb340a95446..ec76e25f25544 100644
--- a/src/librbd/exclusive_lock/ImageDispatch.cc
+++ b/src/librbd/exclusive_lock/ImageDispatch.cc
@@ -286,6 +286,7 @@ bool ImageDispatch<I>::needs_exclusive_lock(bool read_op, uint64_t tid,
 
     ceph_assert(m_on_dispatches.empty() || retesting_lock);
     m_on_dispatches.push_back(on_dispatched);
+    locker.unlock();
 
     *dispatch_result = io::DISPATCH_RESULT_RESTART;
     auto ctx = create_context_callback<