rbd: add methods to set and get snapshot limits

Add a subcommand, rbd snap limit set <image> --limit <integer>, to
limit the number of snapshots that may be made of a given image.
To clear, use rbd snap limit clear <image>. Add an omap
key, 'snap_limit' to the RBD header for implementation. Add object
classes to set and query the limit. Older OSDs will ignore the limit.

Fixes: http://tracker.ceph.com/issues/15706
Signed-off-by: Douglas Fuller <dfuller@redhat.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/src/test/pybind/test_rbd.py b/src/test/pybind/test_rbd.py
index 04a3a3820da..bc34b08406c 100644
--- a/src/test/pybind/test_rbd.py
+++ b/src/test/pybind/test_rbd.py
@@ -12,7 +12,7 @@ from rados import (Rados,
                    LIBRADOS_OP_FLAG_FADVISE_RANDOM)
 from rbd import (RBD, Image, ImageNotFound, InvalidArgument, ImageExists,
                  ImageBusy, ImageHasSnapshots, ReadOnlyImage,
-                 FunctionNotSupported, ArgumentOutOfRange,
+                 FunctionNotSupported, ArgumentOutOfRange, DiskQuotaExceeded,
                  RBD_FEATURE_LAYERING, RBD_FEATURE_STRIPINGV2,
                  RBD_FEATURE_EXCLUSIVE_LOCK)
 
@@ -502,6 +502,19 @@ class TestImage(object):
         assert_raises(ImageNotFound, self.image.unprotect_snap, 'snap1')
         assert_raises(ImageNotFound, self.image.is_protected_snap, 'snap1')
 
+    def test_limit_snaps(self):
+        self.image.set_snap_limit(2)
+        eq(2, self.image.get_snap_limit())
+        self.image.create_snap('snap1')
+        self.image.create_snap('snap2')
+        assert_raises(DiskQuotaExceeded, self.image.create_snap, 'snap3')
+        self.image.remove_snap_limit()
+        self.image.create_snap('snap3')
+
+        self.image.remove_snap('snap1')
+        self.image.remove_snap('snap2')
+        self.image.remove_snap('snap3')
+
     @require_features([RBD_FEATURE_EXCLUSIVE_LOCK])
     def test_remove_with_exclusive_lock(self):
         assert_raises(ImageBusy, remove_image)