dm bio prison: switch to using a red black tree

Previously it was using a fixed sized hash table.  There are times
when very many concurrent cells are held (such as when processing a very
large discard).  When this happens the hash table performance becomes
very poor.

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

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 7130505c2425..69de8b43ca12 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -95,7 +95,6 @@ static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio)
 
 /*----------------------------------------------------------------*/
 
-#define PRISON_CELLS 1024
 #define MIGRATION_POOL_SIZE 128
 #define COMMIT_PERIOD HZ
 #define MIGRATION_COUNT_WINDOW 10
@@ -2327,7 +2326,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
         INIT_DELAYED_WORK(&cache->waker, do_waker);
         cache->last_commit_jiffies = jiffies;
 
-        cache->prison = dm_bio_prison_create(PRISON_CELLS);
+        cache->prison = dm_bio_prison_create();
         if (!cache->prison) {
                 *error = "could not create bio prison";
                 goto bad;