From: Mikulas Patocka <mpatocka@redhat.com>
Date: Thu, 12 Sep 2019 10:44:47 +0200
Subject: [PATCH] dm bufio: remove old-style buffer cleanup
Git-commit: b132ff333201784e67654663360a1a4fb103ebe2
Patch-mainline: v5.4-rc1
References: bsc#1175995,jsc#SLE-15608

Remove code that cleans up buffers if the cache size grows over the limit.

The next commit will introduce a new global cleanup.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/md/dm-bufio.c | 61 +++------------------------------------------------
 1 file changed, 3 insertions(+), 58 deletions(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 2451a4d68aed..c0647cce2128 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -33,7 +33,7 @@
 
 #define DM_BUFIO_MEMORY_PERCENT		2
 #define DM_BUFIO_VMALLOC_PERCENT	25
-#define DM_BUFIO_WRITEBACK_PERCENT	75
+#define DM_BUFIO_WRITEBACK_RATIO	3
 
 /*
  * Check buffer ages in this interval (seconds)
@@ -211,11 +211,6 @@ static unsigned long dm_bufio_current_allocated;
 
 /*----------------------------------------------------------------*/
 
-/*
- * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
- */
-static unsigned long dm_bufio_cache_size_per_client;
-
 /*
  * The current number of clients.
  */
@@ -227,8 +222,7 @@ static int dm_bufio_client_count;
 static LIST_HEAD(dm_bufio_all_clients);
 
 /*
- * This mutex protects dm_bufio_cache_size_latch,
- * dm_bufio_cache_size_per_client and dm_bufio_client_count
+ * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
  */
 static DEFINE_MUTEX(dm_bufio_clients_lock);
 
@@ -340,9 +334,6 @@ static void __cache_size_refresh(void)
 			      dm_bufio_default_cache_size);
 		dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 	}
-
-	dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
-					 (dm_bufio_client_count ? : 1);
 }
 
 /*
@@ -923,36 +914,6 @@ static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
 	}
 }
 
-/*
- * Get writeback threshold and buffer limit for a given client.
- */
-static void __get_memory_limit(struct dm_bufio_client *c,
-			       unsigned long *threshold_buffers,
-			       unsigned long *limit_buffers)
-{
-	unsigned long buffers;
-
-	if (unlikely(READ_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
-		if (mutex_trylock(&dm_bufio_clients_lock)) {
-			__cache_size_refresh();
-			mutex_unlock(&dm_bufio_clients_lock);
-		}
-	}
-
-	buffers = dm_bufio_cache_size_per_client;
-	if (likely(c->sectors_per_block_bits >= 0))
-		buffers >>= c->sectors_per_block_bits + SECTOR_SHIFT;
-	else
-		buffers /= c->block_size;
-
-	if (buffers < c->minimum_buffers)
-		buffers = c->minimum_buffers;
-
-	*limit_buffers = buffers;
-	*threshold_buffers = mult_frac(buffers,
-				       DM_BUFIO_WRITEBACK_PERCENT, 100);
-}
-
 /*
  * Check if we're over watermark.
  * If we are over threshold_buffers, start freeing buffers.
@@ -961,23 +922,7 @@ static void __get_memory_limit(struct dm_bufio_client *c,
 static void __check_watermark(struct dm_bufio_client *c,
 			      struct list_head *write_list)
 {
-	unsigned long threshold_buffers, limit_buffers;
-
-	__get_memory_limit(c, &threshold_buffers, &limit_buffers);
-
-	while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
-	       limit_buffers) {
-
-		struct dm_buffer *b = __get_unclaimed_buffer(c);
-
-		if (!b)
-			return;
-
-		__free_buffer_wake(b);
-		cond_resched();
-	}
-
-	if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
+	if (c->n_buffers[LIST_DIRTY] > c->n_buffers[LIST_CLEAN] * DM_BUFIO_WRITEBACK_RATIO)
 		__write_dirty_buffers_async(c, 1, write_list);
 }
 
-- 
2.16.4