dm thin: commit before gathering status

Commit outstanding metadata before returning the status for a dm thin
pool so that the numbers reported are as up-to-date as possible.

The commit is not performed if the device is suspended or if
the DM_NOFLUSH_FLAG is supplied by userspace and passed to the target
through a new 'status_flags' parameter in the target's dm_status_fn.

The userspace dmsetup tool will support the --noflush flag with the
'dmsetup status' and 'dmsetup wait' commands from version 1.02.76
onwards.

Tested-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index a1a3e6df17b8..afd95986d099 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1054,6 +1054,7 @@ static void retrieve_status(struct dm_table *table,
         char *outbuf, *outptr;
         status_type_t type;
         size_t remaining, len, used = 0;
+        unsigned status_flags = 0;
 
         outptr = outbuf = get_result_buffer(param, param_size, &len);
 
@@ -1090,7 +1091,9 @@ static void retrieve_status(struct dm_table *table,
 
                 /* Get the status/table string from the target driver */
                 if (ti->type->status) {
-                        if (ti->type->status(ti, type, outptr, remaining)) {
+                        if (param->flags & DM_NOFLUSH_FLAG)
+                                status_flags |= DM_STATUS_NOFLUSH_FLAG;
+                        if (ti->type->status(ti, type, status_flags, outptr, remaining)) {
                                 param->flags |= DM_BUFFER_FULL_FLAG;
                                 break;
                         }