From a7eca15f006bac3398b41f03e776c5652f3fcf11 Mon Sep 17 00:00:00 2001
From: Fei Long Wang <flwang@catalyst.net.nz>
Date: Wed, 16 Nov 2016 14:33:58 +1300
Subject: [PATCH] Avoid deleting location data if current image is not the
 owner

Change-Id: Ia949818a75b9162b8cace07a24f6276e3492a503
---
 glance/db/simple/api.py     | 17 +++++++++++++++++
 glance/db/sqlalchemy/api.py | 13 +++++++++++++
 glance/location.py          | 20 ++++++++++++++++----
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/glance/db/simple/api.py b/glance/db/simple/api.py
index fd3d5ee..a24123f 100644
--- a/glance/db/simple/api.py
+++ b/glance/db/simple/api.py
@@ -619,6 +619,23 @@ def image_location_delete(context, image_id, location_id, status,
         raise exception.NotFound(msg)
 
 
+def image_locations_with_url(context, location):
+    locations = []
+    try:
+        for loc in DATA['locations']:
+            if loc['url'] == location['url']:
+                locations.append(loc)
+        keyfn = lambda x: (x[sort_key] if x[sort_key] is not None else '',
+                           x['created_at'], x['id'])
+        locations.sort(key=keyfn)
+        return locations
+    except sa_orm.exc.NoResultFound:
+        msg = (_("No location found with url %(loc)s") %
+               dict(loc=location['url']))
+        LOG.warn(msg)
+    return locations
+
+
 def _image_locations_set(context, image_id, locations):
     # NOTE(zhiyan): 1. Remove records from DB for deleted locations
     used_loc_ids = [loc['id'] for loc in locations if loc.get('id')]
diff --git a/glance/db/sqlalchemy/api.py b/glance/db/sqlalchemy/api.py
index 77ab684..5424b08 100644
--- a/glance/db/sqlalchemy/api.py
+++ b/glance/db/sqlalchemy/api.py
@@ -938,6 +938,19 @@ def image_location_delete(context, image_id, location_id, status,
         raise exception.NotFound(msg)
 
 
+def image_locations_with_url(context, location, session=None):
+    try:
+        session = session or get_session()
+        locations = session.query(models.ImageLocation).filter_by(
+            value=location['url']).order_by(models.ImageLocation.created_at).all()
+        return locations
+    except sa_orm.exc.NoResultFound:
+        msg = (_("No location found with url %(loc)s") %
+               dict(loc=location['url']))
+        LOG.warn(msg)
+        return []
+
+
 def _image_locations_set(context, image_id, locations, session=None):
     # NOTE(zhiyan): 1. Remove records from DB for deleted locations
     session = session or get_session()
diff --git a/glance/location.py b/glance/location.py
index f7f2250..9ebc6c0 100644
--- a/glance/location.py
+++ b/glance/location.py
@@ -400,10 +400,22 @@ class ImageProxy(glance.domain.proxy.Image):
         self.image.delete()
         if self.image.locations:
             for location in self.image.locations:
-                self.store_utils.delete_image_location_from_backend(
-                    self.context,
-                    self.image.image_id,
-                    location)
+                locs = self.image.db_api.image_locations_with_url(self.context,
+                                                                  location)
+                # NOTE(flwang): 1. If current image is the "owner" of this
+                # location, the location can be deleted, no matter if there
+                # is another image using it. 2. If current image is not the
+                # "owner" of this location, the location's back end data can't
+                # be deleted.
+                # The locations list returned by function
+                # "image_locations_with_url" are sorted by the creation time
+                # of the location, because technically, the location owner is
+                # the image who created the location at the first time.
+                if len(locs) > 0 and locs[0].image_id == self.image.image_id:
+                    self.store_utils.delete_image_location_from_backend(
+                        self.context,
+                        self.image.image_id,
+                        location)
 
     def set_data(self, data, size=None):
         if size is None:
-- 
1.9.1