rbd: do not treat standalone as flatten
authorIlya Dryomov <idryomov@redhat.com>
Mon, 19 Jan 2015 19:57:39 +0000 (22:57 +0300)
committerIlya Dryomov <idryomov@gmail.com>
Thu, 19 Feb 2015 10:31:39 +0000 (13:31 +0300)
If the clone is resized down to 0, it becomes standalone.  If such
resize is carried over while an image is mapped we would detect this
and call rbd_dev_parent_put() which means "let go of all parent state,
including the spec(s) of parent images(s)".  This leads to a mismatch
between "rbd info" and sysfs parent fields, so a fix is in order.

    # rbd create --image-format 2 --size 1 foo
    # rbd snap create foo@snap
    # rbd snap protect foo@snap
    # rbd clone foo@snap bar
    # DEV=$(rbd map bar)
    # rbd resize --allow-shrink --size 0 bar
    # rbd resize --size 1 bar
    # rbd info bar | grep parent
            parent: rbd/foo@snap

Before:

    # cat /sys/bus/rbd/devices/0/parent
    (no parent image)

After:

    # cat /sys/bus/rbd/devices/0/parent
    pool_id 0
    pool_name rbd
    image_id 10056b8b4567
    image_name foo
    snap_id 2
    snap_name snap
    overlap 0

Signed-off-by: Ilya Dryomov <idryomov@redhat.com>
Reviewed-by: Josh Durgin <jdurgin@redhat.com>
Reviewed-by: Alex Elder <elder@linaro.org>
drivers/block/rbd.c

index b85d52005a21b0e1928a053c73ce42fc7641ab66..e818c2a6ffb1c4990300a29217c7c1f28095e480 100644 (file)
@@ -4273,32 +4273,22 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
        }
 
        /*
-        * We always update the parent overlap.  If it's zero we
-        * treat it specially.
+        * We always update the parent overlap.  If it's zero we issue
+        * a warning, as we will proceed as if there was no parent.
         */
-       rbd_dev->parent_overlap = overlap;
        if (!overlap) {
-
-               /* A null parent_spec indicates it's the initial probe */
-
                if (parent_spec) {
-                       /*
-                        * The overlap has become zero, so the clone
-                        * must have been resized down to 0 at some
-                        * point.  Treat this the same as a flatten.
-                        */
-                       rbd_dev_parent_put(rbd_dev);
-                       pr_info("%s: clone image now standalone\n",
-                               rbd_dev->disk->disk_name);
+                       /* refresh, careful to warn just once */
+                       if (rbd_dev->parent_overlap)
+                               rbd_warn(rbd_dev,
+                                   "clone now standalone (overlap became 0)");
                } else {
-                       /*
-                        * For the initial probe, if we find the
-                        * overlap is zero we just pretend there was
-                        * no parent image.
-                        */
-                       rbd_warn(rbd_dev, "ignoring parent with overlap 0");
+                       /* initial probe */
+                       rbd_warn(rbd_dev, "clone is standalone (overlap 0)");
                }
        }
+       rbd_dev->parent_overlap = overlap;
+
 out:
        ret = 0;
 out_err: