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, 7 insertions, 2 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 087e9b34d290..af1fc3b2c2ad 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -5,6 +5,7 @@
  */
 
 #include "dm-thin-metadata.h"
+#include "dm.h"
 
 #include <linux/device-mapper.h>
 #include <linux/dm-io.h>
@@ -2619,7 +2620,7 @@ static void emit_flags(struct pool_features *pf, char *result,
  *    <used data sectors>/<total data sectors> <held metadata root>
  */
 static int pool_status(struct dm_target *ti, status_type_t type,
-                       char *result, unsigned maxlen)
+                       unsigned status_flags, char *result, unsigned maxlen)
 {
         int r;
         unsigned sz = 0;
@@ -2641,6 +2642,10 @@ static int pool_status(struct dm_target *ti, status_type_t type,
                         break;
                 }
 
+                /* Commit to ensure statistics aren't out-of-date */
+                if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
+                        (void) commit_or_fallback(pool);
+
                 r = dm_pool_get_metadata_transaction_id(pool->pmd,
                                                         &transaction_id);
                 if (r)
@@ -2968,7 +2973,7 @@ static void thin_postsuspend(struct dm_target *ti)
  * <nr mapped sectors> <highest mapped sector>
  */
 static int thin_status(struct dm_target *ti, status_type_t type,
-                       char *result, unsigned maxlen)
+                       unsigned status_flags, char *result, unsigned maxlen)
 {
         int r;
         ssize_t sz = 0;