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rbd: do not treat standalone as flatten

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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>
This commit is contained in:
Ilya Dryomov 2015-01-19 22:57:39 +03:00 committed by Ilya Dryomov
parent bf91c31508
commit cf32bd9c86
1 changed files with 10 additions and 20 deletions
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30
drivers/block/rbd.c
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@ -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: