dm cache: avoid calls to prealloc_free_structs() if possible

If no work was performed then prealloc_data_structs() wasn't ever called
so there isn't any need to call prealloc_free_structs().

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

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 408dd276d6c98d7ea3ae2d644142dfbe225658fb..b680da5d7b93b5f68d65c0449df1b87b8e1b528b 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1946,6 +1946,7 @@ static int commit_if_needed(struct cache *cache)
 
 static void process_deferred_bios(struct cache *cache)
 {
+       bool prealloc_used = false;
        unsigned long flags;
        struct bio_list bios;
        struct bio *bio;
@@ -1980,13 +1981,16 @@ static void process_deferred_bios(struct cache *cache)
                        process_discard_bio(cache, &structs, bio);
                else
                        process_bio(cache, &structs, bio);
+               prealloc_used = true;
        }
 
-       prealloc_free_structs(cache, &structs);
+       if (prealloc_used)
+               prealloc_free_structs(cache, &structs);
 }
 
 static void process_deferred_cells(struct cache *cache)
 {
+       bool prealloc_used = false;
        unsigned long flags;
        struct dm_bio_prison_cell *cell, *tmp;
        struct list_head cells;
@@ -2014,9 +2018,11 @@ static void process_deferred_cells(struct cache *cache)
                }
 
                process_cell(cache, &structs, cell);
+               prealloc_used = true;
        }
 
-       prealloc_free_structs(cache, &structs);
+       if (prealloc_used)
+               prealloc_free_structs(cache, &structs);
 }
 
 static void process_deferred_flush_bios(struct cache *cache, bool submit_bios)
@@ -2061,6 +2067,7 @@ static void process_deferred_writethrough_bios(struct cache *cache)
 
 static void writeback_some_dirty_blocks(struct cache *cache)
 {
+       bool prealloc_used = false;
        dm_oblock_t oblock;
        dm_cblock_t cblock;
        struct prealloc structs;
@@ -2080,9 +2087,11 @@ static void writeback_some_dirty_blocks(struct cache *cache)
                }
 
                writeback(cache, &structs, oblock, cblock, old_ocell);
+               prealloc_used = true;
        }
 
-       prealloc_free_structs(cache, &structs);
+       if (prealloc_used)
+               prealloc_free_structs(cache, &structs);
 }
 
 /*----------------------------------------------------------------