dm thin: commit outstanding data every second

Commit unwritten data every second to prevent too much building up. Released blocks don't become available until after the next commit (for crash resilience). Prior to this patch commits were only triggered by a message to the target or a REQ_{FLUSH,FUA} bio. This allowed far too big a position to build up. The interval is hard-coded to 1 second. This is a sensible setting. I'm not making this user configurable, since there isn't much to be gained by tweaking this - and a lot lost by setting it far too high. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>

dm thin: commit outstanding data every second
Commit unwritten data every second to prevent too much building up. Released blocks don't become available until after the next commit (for crash resilience). Prior to this patch commits were only triggered by a message to the target or a REQ_{FLUSH,FUA} bio. This allowed far too big a position to build up. The interval is hard-coded to 1 second. This is a sensible setting. I'm not making this user configurable, since there isn't much to be gained by tweaking this - and a lot lost by setting it far too high. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Joe Thornber · Alasdair G Kergon · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent 31998ef193
Showing 1 changed file with 26 additions and 2 deletions Side-by-side Diff
drivers/md/dm-thin.c
@@ -23,6 +23,7 @@
 #define DEFERRED_SET_SIZE 64
 #define MAPPING_POOL_SIZE 1024
 #define PRISON_CELLS 1024
+#define COMMIT_PERIOD HZ
  
 /*
  * The block size of the device holding pool data must be
  
@@ -520,8 +521,10 @@
  
 	struct workqueue_struct *wq;
 	struct work_struct worker;
+	struct delayed_work waker;
  
 	unsigned ref_count;
+	unsigned long last_commit_jiffies;
  
 	spinlock_t lock;
 	struct bio_list deferred_bios;
@@ -1271,6 +1274,12 @@
 	}
 }
  
+static int need_commit_due_to_time(struct pool *pool)
+{
+	return jiffies < pool->last_commit_jiffies ||
+	       jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
+}
+
 static void process_deferred_bios(struct pool *pool)
 {
 	unsigned long flags;
@@ -1312,7 +1321,7 @@
 	bio_list_init(&pool->deferred_flush_bios);
 	spin_unlock_irqrestore(&pool->lock, flags);
  
-	if (bio_list_empty(&bios))
+	if (bio_list_empty(&bios) && !need_commit_due_to_time(pool))
 		return;
  
 	r = dm_pool_commit_metadata(pool->pmd);
@@ -1323,6 +1332,7 @@
 			bio_io_error(bio);
 		return;
 	}
+	pool->last_commit_jiffies = jiffies;
  
 	while ((bio = bio_list_pop(&bios)))
 		generic_make_request(bio);
@@ -1336,6 +1346,17 @@
 	process_deferred_bios(pool);
 }
  
+/*
+ * We want to commit periodically so that not too much
+ * unwritten data builds up.
+ */
+static void do_waker(struct work_struct *ws)
+{
+	struct pool *pool = container_of(to_delayed_work(ws), struct pool, waker);
+	wake_worker(pool);
+	queue_delayed_work(pool->wq, &pool->waker, COMMIT_PERIOD);
+}
+
 /*----------------------------------------------------------------*/
  
 /*
@@ -1545,6 +1566,7 @@
 	}
  
 	INIT_WORK(&pool->worker, do_worker);
+	INIT_DELAYED_WORK(&pool->waker, do_waker);
 	spin_lock_init(&pool->lock);
 	bio_list_init(&pool->deferred_bios);
 	bio_list_init(&pool->deferred_flush_bios);
@@ -1571,6 +1593,7 @@
 		goto bad_endio_hook_pool;
 	}
 	pool->ref_count = 1;
+	pool->last_commit_jiffies = jiffies;
 	pool->pool_md = pool_md;
 	pool->md_dev = metadata_dev;
 	__pool_table_insert(pool);
@@ -1900,7 +1923,7 @@
 	__requeue_bios(pool);
 	spin_unlock_irqrestore(&pool->lock, flags);
  
-	wake_worker(pool);
+	do_waker(&pool->waker.work);
 }
  
 static void pool_postsuspend(struct dm_target *ti)
@@ -1909,6 +1932,7 @@
 	struct pool_c *pt = ti->private;
 	struct pool *pool = pt->pool;
  
+	cancel_delayed_work(&pool->waker);
 	flush_workqueue(pool->wq);
  
 	r = dm_pool_commit_metadata(pool->pmd);
...	...	@@ -23,6 +23,7 @@
23	23	#define DEFERRED_SET_SIZE 64
24	24	#define MAPPING_POOL_SIZE 1024
25	25	#define PRISON_CELLS 1024
	26	+#define COMMIT_PERIOD HZ
26	27
27	28	/*
28	29	* The block size of the device holding pool data must be
29	30
...	...	@@ -520,8 +521,10 @@
520	521
521	522	struct workqueue_struct *wq;
522	523	struct work_struct worker;
	524	+ struct delayed_work waker;
523	525
524	526	unsigned ref_count;
	527	+ unsigned long last_commit_jiffies;
525	528
526	529	spinlock_t lock;
527	530	struct bio_list deferred_bios;
...	...	@@ -1271,6 +1274,12 @@
1271	1274	}
1272	1275	}
1273	1276
	1277	+static int need_commit_due_to_time(struct pool *pool)
	1278	+{
	1279	+ return jiffies < pool->last_commit_jiffies \|\|
	1280	+ jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
	1281	+}
	1282	+
1274	1283	static void process_deferred_bios(struct pool *pool)
1275	1284	{
1276	1285	unsigned long flags;
...	...	@@ -1312,7 +1321,7 @@
1312	1321	bio_list_init(&pool->deferred_flush_bios);
1313	1322	spin_unlock_irqrestore(&pool->lock, flags);
1314	1323
1315		- if (bio_list_empty(&bios))
	1324	+ if (bio_list_empty(&bios) && !need_commit_due_to_time(pool))
1316	1325	return;
1317	1326
1318	1327	r = dm_pool_commit_metadata(pool->pmd);
...	...	@@ -1323,6 +1332,7 @@
1323	1332	bio_io_error(bio);
1324	1333	return;
1325	1334	}
	1335	+ pool->last_commit_jiffies = jiffies;
1326	1336
1327	1337	while ((bio = bio_list_pop(&bios)))
1328	1338	generic_make_request(bio);
...	...	@@ -1336,6 +1346,17 @@
1336	1346	process_deferred_bios(pool);
1337	1347	}
1338	1348
	1349	+/*
	1350	+ * We want to commit periodically so that not too much
	1351	+ * unwritten data builds up.
	1352	+ */
	1353	+static void do_waker(struct work_struct *ws)
	1354	+{
	1355	+ struct pool *pool = container_of(to_delayed_work(ws), struct pool, waker);
	1356	+ wake_worker(pool);
	1357	+ queue_delayed_work(pool->wq, &pool->waker, COMMIT_PERIOD);
	1358	+}
	1359	+
1339	1360	/----------------------------------------------------------------/
1340	1361
1341	1362	/*
...	...	@@ -1545,6 +1566,7 @@
1545	1566	}
1546	1567
1547	1568	INIT_WORK(&pool->worker, do_worker);
	1569	+ INIT_DELAYED_WORK(&pool->waker, do_waker);
1548	1570	spin_lock_init(&pool->lock);
1549	1571	bio_list_init(&pool->deferred_bios);
1550	1572	bio_list_init(&pool->deferred_flush_bios);
...	...	@@ -1571,6 +1593,7 @@
1571	1593	goto bad_endio_hook_pool;
1572	1594	}
1573	1595	pool->ref_count = 1;
	1596	+ pool->last_commit_jiffies = jiffies;
1574	1597	pool->pool_md = pool_md;
1575	1598	pool->md_dev = metadata_dev;
1576	1599	__pool_table_insert(pool);
...	...	@@ -1900,7 +1923,7 @@
1900	1923	__requeue_bios(pool);
1901	1924	spin_unlock_irqrestore(&pool->lock, flags);
1902	1925
1903		- wake_worker(pool);
	1926	+ do_waker(&pool->waker.work);
1904	1927	}
1905	1928
1906	1929	static void pool_postsuspend(struct dm_target *ti)
...	...	@@ -1909,6 +1932,7 @@
1909	1932	struct pool_c *pt = ti->private;
1910	1933	struct pool *pool = pt->pool;
1911	1934
	1935	+ cancel_delayed_work(&pool->waker);
1912	1936	flush_workqueue(pool->wq);
1913	1937
1914	1938	r = dm_pool_commit_metadata(pool->pmd);