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Subject[39/91] dm snapshot: iterate origin and cow devices
2.6.34-stable review patch.  If anyone has any objections, please let us know.


From: Mikulas Patocka <>

commit 1e5554c8428bc7209a83e2d07ca724be4d981ce3 upstream.

Iterate both origin and snapshot devices

iterate_devices method should call the callback for all the devices where
the bio may be remapped. Thus, snapshot_iterate_devices should call the callback
for both snapshot and origin underlying devices because it remaps some bios
to the snapshot and some to the origin.

snapshot_iterate_devices called the callback only for the origin device.
This led to badly calculated device limits if snapshot and origin were placed
on different types of disks.

Signed-off-by: Mikulas Patocka <>
Reviewed-by: Mike Snitzer <>
Signed-off-by: Alasdair G Kergon <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/md/dm-snap.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1899,8 +1899,14 @@ static int snapshot_iterate_devices(stru
iterate_devices_callout_fn fn, void *data)
struct dm_snapshot *snap = ti->private;
+ int r;

- return fn(ti, snap->origin, 0, ti->len, data);
+ r = fn(ti, snap->origin, 0, ti->len, data);
+ if (!r)
+ r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
+ return r;

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