librbd/mirror: detect trashed snapshots in UnlinkPeerRequest

If two instances of UnlinkPeerRequest race with each other (e.g. due
to rbd-mirror daemon unlinking from a previous mirror snapshot and the
user taking another mirror snapshot at same time), the snapshot that
UnlinkPeerRequest was created for may be in the process of being removed
(which may mean trashed by SnapshotRemoveRequest::trash_snap()) or fully
removed by the time unlink_peer() grabs the image lock.  Because trashed
snapshots weren't handled explicitly, UnlinkPeerRequest could spuriously
fail with EINVAL ("not mirror snapshot" case) instead of the expected
ENOENT ("missing snapshot" case).  This in turn could lead to spurious
ImageReplayer failures with it stopping prematurely.

Fixes: https://tracker.ceph.com/issues/68279
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/src/librbd/mirror/snapshot/UnlinkPeerRequest.cc b/src/librbd/mirror/snapshot/UnlinkPeerRequest.cc
index e89a438754172447a4e25b024567ec8cf128a860..2063cd0ba319ae2cde8b337b914ecdeec673da0d 100644 (file)
--- a/src/librbd/mirror/snapshot/UnlinkPeerRequest.cc
+++ b/src/librbd/mirror/snapshot/UnlinkPeerRequest.cc
@@ -79,10 +79,13 @@ void UnlinkPeerRequest<I>::unlink_peer() {
     }
   }
 
-  if (r == -ENOENT) {
-    ldout(cct, 15) << "missing snapshot: snap_id=" << m_snap_id << dendl;
+  if (r == -ENOENT ||
+      std::holds_alternative<cls::rbd::TrashSnapshotNamespace>(
+        snap_namespace)) {
+    ldout(cct, 15) << "missing or trashed snapshot: snap_id=" << m_snap_id
+                   << dendl;
     m_image_ctx->image_lock.unlock_shared();
-    finish(r);
+    finish(-ENOENT);
     return;
   }
 

diff --git a/src/test/librbd/mirror/snapshot/test_mock_UnlinkPeerRequest.cc b/src/test/librbd/mirror/snapshot/test_mock_UnlinkPeerRequest.cc
index 96e1cb9ee8dbf6365c427fe040475253a7b8c54e..4626580c4635fed88dd255dfbd8bed44c28050ba 100644 (file)
--- a/src/test/librbd/mirror/snapshot/test_mock_UnlinkPeerRequest.cc
+++ b/src/test/librbd/mirror/snapshot/test_mock_UnlinkPeerRequest.cc
@@ -291,6 +291,31 @@ TEST_F(TestMockMirrorSnapshotUnlinkPeerRequest, SnapshotDNE) {
   ASSERT_EQ(-ENOENT, ctx.wait());
 }
 
+TEST_F(TestMockMirrorSnapshotUnlinkPeerRequest, TrashedSnapshot) {
+  REQUIRE_FORMAT_V2();
+
+  librbd::ImageCtx *ictx;
+  ASSERT_EQ(0, open_image(m_image_name, &ictx));
+
+  MockTestImageCtx mock_image_ctx(*ictx);
+  cls::rbd::TrashSnapshotNamespace ns{
+    cls::rbd::SNAPSHOT_NAMESPACE_TYPE_MIRROR, "mirror_snap"};
+  auto snap_id = snap_create(mock_image_ctx, ns, "trash_snap");
+
+  expect_get_snap_info(mock_image_ctx, snap_id);
+
+  InSequence seq;
+
+  expect_is_refresh_required(mock_image_ctx, true);
+  expect_refresh_image(mock_image_ctx, 0);
+
+  C_SaferCond ctx;
+  auto req = new MockUnlinkPeerRequest(&mock_image_ctx, snap_id, "peer_uuid",
+                                       true, &ctx);
+  req->send();
+  ASSERT_EQ(-ENOENT, ctx.wait());
+}
+
 TEST_F(TestMockMirrorSnapshotUnlinkPeerRequest, PeerDNE) {
   REQUIRE_FORMAT_V2();