From 51defeada069c0e33b03b96be962f155ce3df295 Mon Sep 17 00:00:00 2001
From: Jason Dillaman <dillaman@redhat.com>
Date: Wed, 22 Jun 2016 18:19:52 -0400
Subject: [PATCH] librbd: fix crash while using advisory locks with R/O image

Fixes: http://tracker.ceph.com/issues/16364
Signed-off-by: Jason Dillaman <dillaman@redhat.com>
(cherry picked from commit 1007aea3d78ca5aead8a11f932da0c1d9d67259e)
---
 src/librbd/ImageCtx.cc     | 5 +----
 src/librbd/ImageWatcher.cc | 8 ++++++++
 src/librbd/ImageWatcher.h  | 2 ++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/librbd/ImageCtx.cc b/src/librbd/ImageCtx.cc
index 564996985f9c6..87c710e9be447 100644
--- a/src/librbd/ImageCtx.cc
+++ b/src/librbd/ImageCtx.cc
@@ -1019,10 +1019,7 @@ struct C_InvalidateCache : public Context {
 
   void ImageCtx::notify_update() {
     state->handle_update_notification();
-
-    C_SaferCond ctx;
-    image_watcher->notify_header_update(&ctx);
-    ctx.wait();
+    ImageWatcher::notify_header_update(md_ctx, header_oid);
   }
 
   void ImageCtx::notify_update(Context *on_finish) {
diff --git a/src/librbd/ImageWatcher.cc b/src/librbd/ImageWatcher.cc
index d3d4e701a736e..d9c6bfe6e3f9b 100644
--- a/src/librbd/ImageWatcher.cc
+++ b/src/librbd/ImageWatcher.cc
@@ -317,6 +317,14 @@ void ImageWatcher::notify_header_update(Context *on_finish) {
   m_notifier.notify(bl, nullptr, on_finish);
 }
 
+void ImageWatcher::notify_header_update(librados::IoCtx &io_ctx,
+				        const std::string &oid) {
+  // supports legacy (empty buffer) clients
+  bufferlist bl;
+  ::encode(NotifyMessage(HeaderUpdatePayload()), bl);
+  io_ctx.notify2(oid, bl, image_watcher::Notifier::NOTIFY_TIMEOUT, nullptr);
+}
+
 void ImageWatcher::schedule_cancel_async_requests() {
   FunctionContext *ctx = new FunctionContext(
     boost::bind(&ImageWatcher::cancel_async_requests, this));
diff --git a/src/librbd/ImageWatcher.h b/src/librbd/ImageWatcher.h
index da1c11b332b5b..0ae5245a23908 100644
--- a/src/librbd/ImageWatcher.h
+++ b/src/librbd/ImageWatcher.h
@@ -54,6 +54,8 @@ class ImageWatcher {
   void notify_request_lock();
 
   void notify_header_update(Context *on_finish);
+  static void notify_header_update(librados::IoCtx &io_ctx,
+                                   const std::string &oid);
 
   uint64_t get_watch_handle() const {
     RWLock::RLocker watch_locker(m_watch_lock);