dm zoned: add 'message' callback

Add callback for 'dmsetup message' to allow the reclaim process
to be triggered manually.
Eg.

	dmsetup message /dev/dm-X 0 message

will start the reclaim process even if the default threshold
of 50 percent of free random zones is not reached.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Bob Liu <bob.liu@oracle.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/admin-guide/device-mapper/dm-zoned.rst b/Documentation/admin-guide/device-mapper/dm-zoned.rst
index 4165fbf1aeb6..7547ce635161 100644
--- a/Documentation/admin-guide/device-mapper/dm-zoned.rst
+++ b/Documentation/admin-guide/device-mapper/dm-zoned.rst
@@ -160,3 +160,15 @@ where <nr_zones> is the total number of zones, <nr_unmap_rnd> is the number
 of unmapped (ie free) random zones, <nr_rnd> the total number of zones,
 <nr_unmap_seq> the number of unmapped sequential zones, and <nr_seq> the
 total number of sequential zones.
+
+Normally the reclaim process will be started once there are less than 50
+percent free random zones. In order to start the reclaim process manually
+even before reaching this threshold the 'dmsetup message' function can be
+used:
+
+Ex::
+
+	dmsetup message /dev/dm-X 0 reclaim
+
+will start the reclaim process and random zones will be moved to sequential
+zones.