client: fix segment fault in Client::_invalidate_kernel_dcache().

when umounting, root can be NULL

Fixes: http://tracker.ceph.com/issues/17253
Signed-off-by: Yan, Zheng <zyan@redhat.com>
(cherry picked from commit ddea9a5b78151c0abe834e4a9872f7cf5f918ebc)

diff --git a/src/client/Client.cc b/src/client/Client.cc
index b465cadec55f2f337b6e74fce0b0d411f0cbe7b9..189fc265bb0d96c337966f45234793216d450c6e 100644 (file)
--- a/src/client/Client.cc
+++ b/src/client/Client.cc
@@ -3923,6 +3923,8 @@ public:
 
 void Client::_invalidate_kernel_dcache()
 {
+  if (unmounting)
+    return;
   if (can_invalidate_dentries && dentry_invalidate_cb && root->dir) {
     for (ceph::unordered_map<string, Dentry*>::iterator p = root->dir->dentries.begin();
         p != root->dir->dentries.end();