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Subject[PATCH 3.8 51/81] dm thin: avoid metadata commit if a pool's thin devices haven't changed
Date
3.8.13.20 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mike Snitzer <snitzer@redhat.com>

commit 4d1662a30dde6e545086fe0e8fd7e474c4e0b639 upstream.

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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/md/dm-thin-metadata.c | 17 +++++++++++++++++
drivers/md/dm-thin-metadata.h | 2 ++
drivers/md/dm-thin.c | 3 ++-
3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 6727958..4f67945 100644
--- 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 149d326..457dea1 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -160,6 +160,8 @@ 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 3bc2d39..e66e366 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1267,7 +1267,8 @@ 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)) {
--
1.8.3.2


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