dm thin: switch to an atomic_t for tracking pending new block preparations

Previously we used separate boolean values to track quiescing and copying actions. By switching to an atomic_t we can support blocks that need a partial copy and partial zero. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>

dm thin: switch to an atomic_t for tracking pending new block preparations
Previously we used separate boolean values to track quiescing and copying actions. By switching to an atomic_t we can support blocks that need a partial copy and partial zero. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Joe Thornber · Mike Snitzer
1 parent 6afbc01d75
Showing 1 changed file with 16 additions and 13 deletions Side-by-side Diff
drivers/md/dm-thin.c
@@ -554,11 +554,16 @@
 struct dm_thin_new_mapping {
 	struct list_head list;
  
-	bool quiesced:1;
-	bool prepared:1;
 	bool pass_discard:1;
 	bool definitely_not_shared:1;
  
+	/*
+	 * Track quiescing, copying and zeroing preparation actions.  When this
+	 * counter hits zero the block is prepared and can be inserted into the
+	 * btree.
+	 */
+	atomic_t prepare_actions;
+
 	int err;
 	struct thin_c *tc;
 	dm_block_t virt_block;
  
@@ -575,11 +580,11 @@
 	bio_end_io_t *saved_bi_end_io;
 };
  
-static void __maybe_add_mapping(struct dm_thin_new_mapping *m)
+static void __complete_mapping_preparation(struct dm_thin_new_mapping *m)
 {
 	struct pool *pool = m->tc->pool;
  
-	if (m->quiesced && m->prepared) {
+	if (atomic_dec_and_test(&m->prepare_actions)) {
 		list_add_tail(&m->list, &pool->prepared_mappings);
 		wake_worker(pool);
 	}
@@ -594,8 +599,7 @@
 	m->err = read_err || write_err ? -EIO : 0;
  
 	spin_lock_irqsave(&pool->lock, flags);
-	m->prepared = true;
-	__maybe_add_mapping(m);
+	__complete_mapping_preparation(m);
 	spin_unlock_irqrestore(&pool->lock, flags);
 }
  
@@ -609,8 +613,7 @@
 	m->err = err;
  
 	spin_lock_irqsave(&pool->lock, flags);
-	m->prepared = true;
-	__maybe_add_mapping(m);
+	__complete_mapping_preparation(m);
 	spin_unlock_irqrestore(&pool->lock, flags);
 }
  
@@ -836,7 +839,9 @@
 	m->cell = cell;
  
 	if (!dm_deferred_set_add_work(pool->shared_read_ds, &m->list))
-		m->quiesced = true;
+		atomic_set(&m->prepare_actions, 1); /* copy only */
+	else
+		atomic_set(&m->prepare_actions, 2); /* quiesce + copy */
  
 	/*
 	 * IO to pool_dev remaps to the pool target's data_dev.
@@ -896,8 +901,7 @@
 	struct pool *pool = tc->pool;
 	struct dm_thin_new_mapping *m = get_next_mapping(pool);
  
-	m->quiesced = true;
-	m->prepared = false;
+	atomic_set(&m->prepare_actions, 1); /* no need to quiesce */
 	m->tc = tc;
 	m->virt_block = virt_block;
 	m->data_block = data_block;
@@ -3361,8 +3365,7 @@
 		spin_lock_irqsave(&pool->lock, flags);
 		list_for_each_entry_safe(m, tmp, &work, list) {
 			list_del(&m->list);
-			m->quiesced = true;
-			__maybe_add_mapping(m);
+			__complete_mapping_preparation(m);
 		}
 		spin_unlock_irqrestore(&pool->lock, flags);
 	}
...	...	@@ -554,11 +554,16 @@
554	554	struct dm_thin_new_mapping {
555	555	struct list_head list;
556	556
557		- bool quiesced:1;
558		- bool prepared:1;
559	557	bool pass_discard:1;
560	558	bool definitely_not_shared:1;
561	559
	560	+ /*
	561	+ * Track quiescing, copying and zeroing preparation actions. When this
	562	+ * counter hits zero the block is prepared and can be inserted into the
	563	+ * btree.
	564	+ */
	565	+ atomic_t prepare_actions;
	566	+
562	567	int err;
563	568	struct thin_c *tc;
564	569	dm_block_t virt_block;
565	570
...	...	@@ -575,11 +580,11 @@
575	580	bio_end_io_t *saved_bi_end_io;
576	581	};
577	582
578		-static void __maybe_add_mapping(struct dm_thin_new_mapping *m)
	583	+static void __complete_mapping_preparation(struct dm_thin_new_mapping *m)
579	584	{
580	585	struct pool *pool = m->tc->pool;
581	586
582		- if (m->quiesced && m->prepared) {
	587	+ if (atomic_dec_and_test(&m->prepare_actions)) {
583	588	list_add_tail(&m->list, &pool->prepared_mappings);
584	589	wake_worker(pool);
585	590	}
...	...	@@ -594,8 +599,7 @@
594	599	m->err = read_err \|\| write_err ? -EIO : 0;
595	600
596	601	spin_lock_irqsave(&pool->lock, flags);
597		- m->prepared = true;
598		- __maybe_add_mapping(m);
	602	+ __complete_mapping_preparation(m);
599	603	spin_unlock_irqrestore(&pool->lock, flags);
600	604	}
601	605
...	...	@@ -609,8 +613,7 @@
609	613	m->err = err;
610	614
611	615	spin_lock_irqsave(&pool->lock, flags);
612		- m->prepared = true;
613		- __maybe_add_mapping(m);
	616	+ __complete_mapping_preparation(m);
614	617	spin_unlock_irqrestore(&pool->lock, flags);
615	618	}
616	619
...	...	@@ -836,7 +839,9 @@
836	839	m->cell = cell;
837	840
838	841	if (!dm_deferred_set_add_work(pool->shared_read_ds, &m->list))
839		- m->quiesced = true;
	842	+ atomic_set(&m->prepare_actions, 1); /* copy only */
	843	+ else
	844	+ atomic_set(&m->prepare_actions, 2); /* quiesce + copy */
840	845
841	846	/*
842	847	* IO to pool_dev remaps to the pool target's data_dev.
...	...	@@ -896,8 +901,7 @@
896	901	struct pool *pool = tc->pool;
897	902	struct dm_thin_new_mapping *m = get_next_mapping(pool);
898	903
899		- m->quiesced = true;
900		- m->prepared = false;
	904	+ atomic_set(&m->prepare_actions, 1); /* no need to quiesce */
901	905	m->tc = tc;
902	906	m->virt_block = virt_block;
903	907	m->data_block = data_block;
...	...	@@ -3361,8 +3365,7 @@
3361	3365	spin_lock_irqsave(&pool->lock, flags);
3362	3366	list_for_each_entry_safe(m, tmp, &work, list) {
3363	3367	list_del(&m->list);
3364		- m->quiesced = true;
3365		- __maybe_add_mapping(m);
	3368	+ __complete_mapping_preparation(m);
3366	3369	}
3367	3370	spin_unlock_irqrestore(&pool->lock, flags);
3368	3371	}