dm thin metadata: add dm_thin_changed_this_transaction

Introduce dm_thin_changed_this_transaction to dm-thin-metadata to publish a
useful bit of information we're already tracking.  This will help dm thin
decide when to commit.

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

2 files changed, 15 insertions, 3 deletions

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 5ae31185e47..4f5b11c195f 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1375,10 +1375,9 @@ static int __insert(struct dm_thin_device *td, dm_block_t block,
         if (r)
                 return r;
 
-        if (inserted) {
+        td->changed = 1;
+        if (inserted)
                 td->mapped_blocks++;
-                td->changed = 1;
-        }
 
         return 0;
 }
@@ -1422,6 +1421,17 @@ int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block)
         return r;
 }
 
+bool dm_thin_changed_this_transaction(struct dm_thin_device *td)
+{
+        int r;
+
+        down_read(&td->pmd->root_lock);
+        r = td->changed;
+        up_read(&td->pmd->root_lock);
+
+        return r;
+}
+
 int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result)
 {
         int r;
diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 7e6656c49bd..1632fec1660 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -148,6 +148,8 @@ int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block);
 /*
  * Queries.
  */
+bool dm_thin_changed_this_transaction(struct dm_thin_device *td);
+
 int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,
                                      dm_block_t *highest_mapped);