dm cache: avoid preallocation if no work in writeback_some_dirty_blocks()

Refactor writeback_some_dirty_blocks() to avoid prealloc_data_structs()
if the policy doesn't have any dirty blocks ready for writeback.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 4 insertions, 9 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index c8a160b37412..408dd276d6c9 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2061,7 +2061,6 @@ static void process_deferred_writethrough_bios(struct cache *cache)
 
 static void writeback_some_dirty_blocks(struct cache *cache)
 {
-        int r = 0;
         dm_oblock_t oblock;
         dm_cblock_t cblock;
         struct prealloc structs;
@@ -2071,15 +2070,11 @@ static void writeback_some_dirty_blocks(struct cache *cache)
         memset(&structs, 0, sizeof(structs));
 
         while (spare_migration_bandwidth(cache)) {
-                if (prealloc_data_structs(cache, &structs))
-                        break;
-
-                r = policy_writeback_work(cache->policy, &oblock, &cblock, busy);
-                if (r)
-                        break;
+                if (policy_writeback_work(cache->policy, &oblock, &cblock, busy))
+                        break; /* no work to do */
 
-                r = get_cell(cache, oblock, &structs, &old_ocell);
-                if (r) {
+                if (prealloc_data_structs(cache, &structs) ||
+                    get_cell(cache, oblock, &structs, &old_ocell)) {
                         policy_set_dirty(cache->policy, oblock);
                         break;
                 }