Do not wait for event on device without table.
 

If there is DM device with no table present, do not
try to wait for change event. Otherwise it can
wait forever and block already removed device.

Simple reproducible:
dmsetup create x --notable
dmsetup wait x 0 &
dmsetup remove x

Now it waits for device, which is no longer accesible through dm-ioctl.

Signed-off-by: Milan Broz <mbroz@redhat.com>
---
drivers/md/dm-ioctl.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 1d66932..a0ac379 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1023,6 +1023,15 @@ static int dev_wait(struct dm_ioctl *param, size_t param_size)
return -ENXIO;

/*
+ * Do not wait if no table present
+ */
+ if (!(table = dm_get_live_or_inactive_table(md, param))) {
+ r = -ENXIO;
+ goto out;
+ }
+ dm_table_put(table);
+
+ /*
* Wait for a notification event
*/
if (dm_wait_event(md, param->event_nr)) {
--
1.6.6

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