mds: properly do null snapflush part2

previous commit 4b95fbe327 "mds: properly do null snapflush part2"
isn't complete. It doesn't properly handle case that snap get deleted
before receiving corresponding snapflush.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>

diff --git a/src/mds/Locker.cc b/src/mds/Locker.cc
index ab8e943acd2ae32492f8a2bf482bb4bd4957ebc4..6460972fe993b6e32df9e9ef7afcf5df4d2775e8 100644 (file)
--- a/src/mds/Locker.cc
+++ b/src/mds/Locker.cc
@@ -2710,6 +2710,7 @@ void Locker::handle_client_caps(MClientCaps *m)
     return;
   }
 
+  bool need_unpin = false;
   int op = m->get_op();
 
   // flushsnap?
@@ -2723,6 +2724,13 @@ void Locker::handle_client_caps(MClientCaps *m)
     snapid_t snap = realm->get_snap_following(follows);
     dout(10) << "  flushsnap follows " << follows << " -> snap " << snap << dendl;
 
+    auto p = head_in->client_need_snapflush.begin();
+    if (p != head_in->client_need_snapflush.end() && p->first < snap) {
+      head_in->auth_pin(this); // prevent subtree frozen
+      need_unpin = true;
+      _do_null_snapflush(head_in, client, snap);
+    }
+
     CInode *in = head_in;
     if (snap != CEPH_NOSNAP) {
       in = mdcache->pick_inode_snap(head_in, snap - 1);
@@ -2750,8 +2758,6 @@ void Locker::handle_client_caps(MClientCaps *m)
       // this cap now follows a later snap (i.e. the one initiating this flush, or later)
       if (in == head_in)
        cap->client_follows = snap < CEPH_NOSNAP ? snap : realm->get_newest_seq();
-      else if (head_in->client_need_snapflush.begin()->first < snap)
-       _do_null_snapflush(head_in, client, snap);
    
       _do_snap_update(in, snap, m->get_dirty(), follows, client, m, ack);
 
@@ -2807,6 +2813,8 @@ void Locker::handle_client_caps(MClientCaps *m)
     //  update/release).
     if (!head_in->client_need_snapflush.empty()) {
       if ((cap->issued() & CEPH_CAP_ANY_FILE_WR) == 0) {
+       head_in->auth_pin(this); // prevent subtree frozen
+       need_unpin = true;
        _do_null_snapflush(head_in, client);
       } else {
        dout(10) << " revocation in progress, not making any conclusions about null snapflushes" << dendl;
@@ -2862,6 +2870,8 @@ void Locker::handle_client_caps(MClientCaps *m)
   }
 
  out:
+  if (need_unpin)
+    head_in->auth_unpin(this);
   m->put();
 }