7 files changed, 46 insertions, 33 deletions

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 5627f53ca115..3ceaacdd4ba5 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1073,18 +1073,21 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 	spin_lock(&block_group->lock);
 	block_group->removed = 1;
 	/*
-	 * At this point trimming can't start on this block group, because we
-	 * removed the block group from the tree fs_info->block_group_cache_tree
-	 * so no one can't find it anymore and even if someone already got this
-	 * block group before we removed it from the rbtree, they have already
-	 * incremented block_group->trimming - if they didn't, they won't find
-	 * any free space entries because we already removed them all when we
-	 * called btrfs_remove_free_space_cache().
+	 * At this point trimming or scrub can't start on this block group,
+	 * because we removed the block group from the rbtree
+	 * fs_info->block_group_cache_tree so no one can't find it anymore and
+	 * even if someone already got this block group before we removed it
+	 * from the rbtree, they have already incremented block_group->frozen -
+	 * if they didn't, for the trimming case they won't find any free space
+	 * entries because we already removed them all when we called
+	 * btrfs_remove_free_space_cache().
 	 *
 	 * And we must not remove the extent map from the fs_info->mapping_tree
 	 * to prevent the same logical address range and physical device space
-	 * ranges from being reused for a new block group. This is because our
-	 * fs trim operation (btrfs_trim_fs() / btrfs_ioctl_fitrim()) is
+	 * ranges from being reused for a new block group. This is needed to
+	 * avoid races with trimming and scrub.
+	 *
+	 * An fs trim operation (btrfs_trim_fs() / btrfs_ioctl_fitrim()) is
 	 * completely transactionless, so while it is trimming a range the
 	 * currently running transaction might finish and a new one start,
 	 * allowing for new block groups to be created that can reuse the same
@@ -1095,7 +1098,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 	 * in place until the extents have been discarded completely when
 	 * the transaction commit has completed.
 	 */
-	remove_em = (atomic_read(&block_group->trimming) == 0);
+	remove_em = (atomic_read(&block_group->frozen) == 0);
 	spin_unlock(&block_group->lock);
 
 	mutex_unlock(&fs_info->chunk_mutex);
@@ -1444,7 +1447,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 
 		/* Implicit trim during transaction commit. */
 		if (trimming)
-			btrfs_get_block_group_trimming(block_group);
+			btrfs_freeze_block_group(block_group);
 
 		/*
 		 * Btrfs_remove_chunk will abort the transaction if things go
@@ -1454,7 +1457,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 
 		if (ret) {
 			if (trimming)
-				btrfs_put_block_group_trimming(block_group);
+				btrfs_unfreeze_block_group(block_group);
 			goto end_trans;
 		}
 
@@ -1803,7 +1806,7 @@ static struct btrfs_block_group *btrfs_create_block_group_cache(
 	INIT_LIST_HEAD(&cache->dirty_list);
 	INIT_LIST_HEAD(&cache->io_list);
 	btrfs_init_free_space_ctl(cache);
-	atomic_set(&cache->trimming, 0);
+	atomic_set(&cache->frozen, 0);
 	mutex_init(&cache->free_space_lock);
 	btrfs_init_full_stripe_locks_tree(&cache->full_stripe_locks_root);
 
diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 107bb557ca8d..04967ea7ba2c 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -129,8 +129,17 @@ struct btrfs_block_group {
 	/* For read-only block groups */
 	struct list_head ro_list;
 
+	/*
+	 * When non-zero it means the block group's logical address and its
+	 * device extents can not be reused for future block group allocations
+	 * until the counter goes down to 0. This is to prevent them from being
+	 * reused while some task is still using the block group after it was
+	 * deleted - we want to make sure they can only be reused for new block
+	 * groups after that task is done with the deleted block group.
+	 */
+	atomic_t frozen;
+
 	/* For discard operations */
-	atomic_t trimming;
 	struct list_head discard_list;
 	int discard_index;
 	u64 discard_eligible_time;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 86ec25250ac5..242f974a4451 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2481,8 +2481,8 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 			 struct btrfs_ref *generic_ref);
 
 int btrfs_extent_readonly(struct btrfs_fs_info *fs_info, u64 bytenr);
-void btrfs_get_block_group_trimming(struct btrfs_block_group *cache);
-void btrfs_put_block_group_trimming(struct btrfs_block_group *cache);
+void btrfs_freeze_block_group(struct btrfs_block_group *cache);
+void btrfs_unfreeze_block_group(struct btrfs_block_group *cache);
 void btrfs_clear_space_info_full(struct btrfs_fs_info *info);
 
 enum btrfs_reserve_flush_enum {
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3593f8cce9e5..140011edcad7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2916,7 +2916,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 						   &trimmed);
 
 		list_del_init(&block_group->bg_list);
-		btrfs_put_block_group_trimming(block_group);
+		btrfs_unfreeze_block_group(block_group);
 		btrfs_put_block_group(block_group);
 
 		if (ret) {
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 3613da065a73..e9cfe9da6bbe 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3762,12 +3762,12 @@ out:
 	return ret;
 }
 
-void btrfs_get_block_group_trimming(struct btrfs_block_group *cache)
+void btrfs_freeze_block_group(struct btrfs_block_group *cache)
 {
-	atomic_inc(&cache->trimming);
+	atomic_inc(&cache->frozen);
 }
 
-void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
+void btrfs_unfreeze_block_group(struct btrfs_block_group *block_group)
 {
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
 	struct extent_map_tree *em_tree;
@@ -3775,7 +3775,7 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 	bool cleanup;
 
 	spin_lock(&block_group->lock);
-	cleanup = (atomic_dec_and_test(&block_group->trimming) &&
+	cleanup = (atomic_dec_and_test(&block_group->frozen) &&
 		   block_group->removed);
 	spin_unlock(&block_group->lock);
 
@@ -3795,8 +3795,9 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 		free_extent_map(em);
 
 		/*
-		 * We've left one free space entry and other tasks trimming
-		 * this block group have left 1 entry each one. Free them.
+		 * We may have left one free space entry and other possible
+		 * tasks trimming this block group have left 1 entry each one.
+		 * Free them if any.
 		 */
 		__btrfs_remove_free_space_cache(block_group->free_space_ctl);
 	}
@@ -3816,7 +3817,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, false);
@@ -3829,7 +3830,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	if (rem)
 		reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
 out:
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 	return ret;
 }
 
@@ -3846,11 +3847,11 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, async);
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 
 	return ret;
 }
@@ -3868,13 +3869,13 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-	btrfs_get_block_group_trimming(block_group);
+	btrfs_freeze_block_group(block_group);
 	spin_unlock(&block_group->lock);
 
 	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
 			   async);
 
-	btrfs_put_block_group_trimming(block_group);
+	btrfs_unfreeze_block_group(block_group);
 
 	return ret;
 }
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 7c50ac5b6876..2486f58d8205 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3583,7 +3583,7 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 			btrfs_put_block_group(cache);
 			goto skip;
 		}
-		btrfs_get_block_group_trimming(cache);
+		btrfs_freeze_block_group(cache);
 		spin_unlock(&cache->lock);
 
 		/*
@@ -3641,7 +3641,7 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 		} else {
 			btrfs_warn(fs_info,
 				   "failed setting block group ro: %d", ret);
-			btrfs_put_block_group_trimming(cache);
+			btrfs_unfreeze_block_group(cache);
 			btrfs_put_block_group(cache);
 			scrub_pause_off(fs_info);
 			break;
@@ -3728,7 +3728,7 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 			spin_unlock(&cache->lock);
 		}
 
-		btrfs_put_block_group_trimming(cache);
+		btrfs_unfreeze_block_group(cache);
 		btrfs_put_block_group(cache);
 		if (ret)
 			break;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 96eb313a5080..f58d0fdc5078 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -142,7 +142,7 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
 						 struct btrfs_block_group,
 						 bg_list);
 			list_del_init(&cache->bg_list);
-			btrfs_put_block_group_trimming(cache);
+			btrfs_unfreeze_block_group(cache);
 			btrfs_put_block_group(cache);
 		}
 		WARN_ON(!list_empty(&transaction->dev_update_list));