dm thin: avoid metadata commit if a pool's thin devices haven't changed

Commit 905e51b ("dm thin: commit outstanding data every second")
introduced a periodic commit.  This commit occurs regardless of whether
any thin devices have made changes.

Fix the periodic commit to check if any of a pool's thin devices have
changed using dm_pool_changed_this_transaction().

Reported-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 7da3476..3bb4506 100644 (file)
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1489,6 +1489,23 @@ bool dm_thin_changed_this_transaction(struct dm_thin_device *td)
        return r;
 }
 
+bool dm_pool_changed_this_transaction(struct dm_pool_metadata *pmd)
+{
+       bool r = false;
+       struct dm_thin_device *td, *tmp;
+
+       down_read(&pmd->root_lock);
+       list_for_each_entry_safe(td, tmp, &pmd->thin_devices, list) {
+               if (td->changed) {
+                       r = td->changed;
+                       break;
+               }
+       }
+       up_read(&pmd->root_lock);
+
+       return r;
+}
+
 bool dm_thin_aborted_changes(struct dm_thin_device *td)
 {
        bool r;

diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 9a36856..dd6088a 100644 (file)
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -161,6 +161,8 @@ int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block);
  */
 bool dm_thin_changed_this_transaction(struct dm_thin_device *td);
 
+bool dm_pool_changed_this_transaction(struct dm_pool_metadata *pmd);
+
 bool dm_thin_aborted_changes(struct dm_thin_device *td);
 
 int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index faaf944..d501e43 100644 (file)
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1357,7 +1357,8 @@ static void process_deferred_bios(struct pool *pool)
        bio_list_init(&pool->deferred_flush_bios);
        spin_unlock_irqrestore(&pool->lock, flags);
 
-       if (bio_list_empty(&bios) && !need_commit_due_to_time(pool))
+       if (bio_list_empty(&bios) &&
+           !(dm_pool_changed_this_transaction(pool->pmd) && need_commit_due_to_time(pool)))
                return;
 
        if (commit(pool)) {