1 files changed, 75 insertions, 34 deletions

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index dcaa1d9dfbe4..99579c81ae0a 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -35,12 +35,17 @@
 /*
  * Check buffer ages in this interval (seconds)
  */
-#define DM_BUFIO_WORK_TIMER_SECS	10
+#define DM_BUFIO_WORK_TIMER_SECS	30
 
 /*
  * Free buffers when they are older than this (seconds)
  */
-#define DM_BUFIO_DEFAULT_AGE_SECS	60
+#define DM_BUFIO_DEFAULT_AGE_SECS	300
+
+/*
+ * The nr of bytes of cached data to keep around.
+ */
+#define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
 
 /*
  * The number of bvec entries that are embedded directly in the buffer.
@@ -216,6 +221,7 @@ static DEFINE_SPINLOCK(param_spinlock);
  * Buffers are freed after this timeout
  */
 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
+static unsigned dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 
 static unsigned long dm_bufio_peak_allocated;
 static unsigned long dm_bufio_allocated_kmem_cache;
@@ -1457,45 +1463,52 @@ static void drop_buffers(struct dm_bufio_client *c)
 }
 
 /*
- * Test if the buffer is unused and too old, and commit it.
+ * We may not be able to evict this buffer if IO pending or the client
+ * is still using it.  Caller is expected to know buffer is too old.
+ *
  * And if GFP_NOFS is used, we must not do any I/O because we hold
  * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
  * rerouted to different bufio client.
  */
-static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,
-				unsigned long max_jiffies)
+static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
 {
-	if (jiffies - b->last_accessed < max_jiffies)
-		return 0;
-
 	if (!(gfp & __GFP_FS)) {
 		if (test_bit(B_READING, &b->state) ||
 		    test_bit(B_WRITING, &b->state) ||
 		    test_bit(B_DIRTY, &b->state))
-			return 0;
+			return false;
 	}
 
 	if (b->hold_count)
-		return 0;
+		return false;
 
 	__make_buffer_clean(b);
 	__unlink_buffer(b);
 	__free_buffer_wake(b);
 
-	return 1;
+	return true;
 }
 
-static long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
-		   gfp_t gfp_mask)
+static unsigned get_retain_buffers(struct dm_bufio_client *c)
+{
+        unsigned retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
+        return retain_bytes / c->block_size;
+}
+
+static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
+			    gfp_t gfp_mask)
 {
 	int l;
 	struct dm_buffer *b, *tmp;
-	long freed = 0;
+	unsigned long freed = 0;
+	unsigned long count = nr_to_scan;
+	unsigned retain_target = get_retain_buffers(c);
 
 	for (l = 0; l < LIST_SIZE; l++) {
 		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
-			freed += __cleanup_old_buffer(b, gfp_mask, 0);
-			if (!--nr_to_scan)
+			if (__try_evict_buffer(b, gfp_mask))
+				freed++;
+			if (!--nr_to_scan || ((count - freed) <= retain_target))
 				return freed;
 			dm_bufio_cond_resched();
 		}
@@ -1697,31 +1710,56 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
 }
 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
 
-static void cleanup_old_buffers(void)
+static unsigned get_max_age_hz(void)
 {
-	unsigned long max_age = ACCESS_ONCE(dm_bufio_max_age);
-	struct dm_bufio_client *c;
+	unsigned max_age = ACCESS_ONCE(dm_bufio_max_age);
 
-	if (max_age > ULONG_MAX / HZ)
-		max_age = ULONG_MAX / HZ;
+	if (max_age > UINT_MAX / HZ)
+		max_age = UINT_MAX / HZ;
 
-	mutex_lock(&dm_bufio_clients_lock);
-	list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
-		if (!dm_bufio_trylock(c))
-			continue;
+	return max_age * HZ;
+}
 
-		while (!list_empty(&c->lru[LIST_CLEAN])) {
-			struct dm_buffer *b;
-			b = list_entry(c->lru[LIST_CLEAN].prev,
-				       struct dm_buffer, lru_list);
-			if (!__cleanup_old_buffer(b, 0, max_age * HZ))
-				break;
-			dm_bufio_cond_resched();
-		}
+static bool older_than(struct dm_buffer *b, unsigned long age_hz)
+{
+	return (jiffies - b->last_accessed) >= age_hz;
+}
+
+static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
+{
+	struct dm_buffer *b, *tmp;
+	unsigned retain_target = get_retain_buffers(c);
+	unsigned count;
+
+	dm_bufio_lock(c);
+
+	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
+	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
+		if (count <= retain_target)
+			break;
+
+		if (!older_than(b, age_hz))
+			break;
+
+		if (__try_evict_buffer(b, 0))
+			count--;
 
-		dm_bufio_unlock(c);
 		dm_bufio_cond_resched();
 	}
+
+	dm_bufio_unlock(c);
+}
+
+static void cleanup_old_buffers(void)
+{
+	unsigned long max_age_hz = get_max_age_hz();
+	struct dm_bufio_client *c;
+
+	mutex_lock(&dm_bufio_clients_lock);
+
+	list_for_each_entry(c, &dm_bufio_all_clients, client_list)
+		__evict_old_buffers(c, max_age_hz);
+
 	mutex_unlock(&dm_bufio_clients_lock);
 }
 
@@ -1846,6 +1884,9 @@ MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
 
+module_param_named(retain_bytes, dm_bufio_retain_bytes, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
+
 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");