btrfs: add and use helper to commit the current transaction

We have several places that attach to the current transaction with
btrfs_attach_transaction_barrier() and then commit the transaction if
there is one. Add a helper and use it to deduplicate this pattern.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -4144,9 +4144,6 @@ void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 
 int btrfs_commit_super(struct btrfs_fs_info *fs_info)
 {
-	struct btrfs_root *root = fs_info->tree_root;
-	struct btrfs_trans_handle *trans;
-
 	mutex_lock(&fs_info->cleaner_mutex);
 	btrfs_run_delayed_iputs(fs_info);
 	mutex_unlock(&fs_info->cleaner_mutex);
@@ -4156,14 +4153,7 @@ int btrfs_commit_super(struct btrfs_fs_info *fs_info)
 	down_write(&fs_info->cleanup_work_sem);
 	up_write(&fs_info->cleanup_work_sem);
 
-	trans = btrfs_attach_transaction_barrier(root);
-	if (IS_ERR(trans)) {
-		int ret = PTR_ERR(trans);
-
-		return (ret == -ENOENT) ? 0 : ret;
-	}
-
-	return btrfs_commit_transaction(trans);
+	return btrfs_commit_current_transaction(fs_info->tree_root);
 }
 
 static void warn_about_uncommitted_trans(struct btrfs_fs_info *fs_info)

fs/btrfs/qgroup.c

@@ -1334,7 +1334,6 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info,
  */
 static int flush_reservations(struct btrfs_fs_info *fs_info)
 {
-	struct btrfs_trans_handle *trans;
 	int ret;
 
 	ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
@@ -1342,13 +1341,7 @@ static int flush_reservations(struct btrfs_fs_info *fs_info)
 		return ret;
 	btrfs_wait_ordered_roots(fs_info, U64_MAX, NULL);
 
-	trans = btrfs_attach_transaction_barrier(fs_info->tree_root);
-	if (IS_ERR(trans)) {
-		ret = PTR_ERR(trans);
-		return (ret == -ENOENT) ? 0 : ret;
-	}
-
-	return btrfs_commit_transaction(trans);
+	return btrfs_commit_current_transaction(fs_info->tree_root);
 }
 
 int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
@@ -4027,7 +4020,6 @@ int
 btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
 {
 	int ret = 0;
-	struct btrfs_trans_handle *trans;
 
 	ret = qgroup_rescan_init(fs_info, 0, 1);
 	if (ret)
@@ -4044,16 +4036,10 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
 	 * going to clear all tracking information for a clean start.
 	 */
 
-	trans = btrfs_attach_transaction_barrier(fs_info->fs_root);
-	if (IS_ERR(trans) && trans != ERR_PTR(-ENOENT)) {
+	ret = btrfs_commit_current_transaction(fs_info->fs_root);
+	if (ret) {
 		fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
-		return PTR_ERR(trans);
-	} else if (trans != ERR_PTR(-ENOENT)) {
-		ret = btrfs_commit_transaction(trans);
-		if (ret) {
-			fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
-			return ret;
-		}
+		return ret;
 	}
 
 	qgroup_rescan_zero_tracking(fs_info);
@@ -4189,7 +4175,6 @@ static int qgroup_unreserve_range(struct btrfs_inode *inode,
  */
 static int try_flush_qgroup(struct btrfs_root *root)
 {
-	struct btrfs_trans_handle *trans;
 	int ret;
 
 	/* Can't hold an open transaction or we run the risk of deadlocking. */
@@ -4212,15 +4197,7 @@ static int try_flush_qgroup(struct btrfs_root *root)
 		goto out;
 	btrfs_wait_ordered_extents(root, U64_MAX, NULL);
 
-	trans = btrfs_attach_transaction_barrier(root);
-	if (IS_ERR(trans)) {
-		ret = PTR_ERR(trans);
-		if (ret == -ENOENT)
-			ret = 0;
-		goto out;
-	}
-
-	ret = btrfs_commit_transaction(trans);
+	ret = btrfs_commit_current_transaction(root);
 out:
 	clear_bit(BTRFS_ROOT_QGROUP_FLUSHING, &root->state);
 	wake_up(&root->qgroup_flush_wait);

fs/btrfs/scrub.c

@@ -2441,7 +2441,6 @@ static int finish_extent_writes_for_zoned(struct btrfs_root *root,
 					  struct btrfs_block_group *cache)
 {
 	struct btrfs_fs_info *fs_info = cache->fs_info;
-	struct btrfs_trans_handle *trans;
 
 	if (!btrfs_is_zoned(fs_info))
 		return 0;
@@ -2450,14 +2449,7 @@ static int finish_extent_writes_for_zoned(struct btrfs_root *root,
 	btrfs_wait_nocow_writers(cache);
 	btrfs_wait_ordered_roots(fs_info, U64_MAX, cache);
 
-	trans = btrfs_attach_transaction_barrier(root);
-	if (IS_ERR(trans)) {
-		int ret = PTR_ERR(trans);
-
-		return (ret == -ENOENT) ? 0 : ret;
-	}
-
-	return btrfs_commit_transaction(trans);
+	return btrfs_commit_current_transaction(root);
 }
 
 static noinline_for_stack

fs/btrfs/send.c

@@ -7998,7 +7998,6 @@ static int send_subvol(struct send_ctx *sctx)
  */
 static int ensure_commit_roots_uptodate(struct send_ctx *sctx)
 {
-	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = sctx->parent_root;
 
 	if (root && root->node != root->commit_root)
@@ -8018,14 +8017,7 @@ static int ensure_commit_roots_uptodate(struct send_ctx *sctx)
 	 * an unnecessary update of the root's item in the root tree when
 	 * committing the transaction if that root wasn't changed before.
 	 */
-	trans = btrfs_attach_transaction_barrier(root);
-	if (IS_ERR(trans)) {
-		int ret = PTR_ERR(trans);
-
-		return (ret == -ENOENT) ? 0 : ret;
-	}
-
-	return btrfs_commit_transaction(trans);
+	return btrfs_commit_current_transaction(root);
 }
 
 /*

fs/btrfs/space-info.c

@@ -823,14 +823,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
 		 * because that does not wait for a transaction to fully commit
 		 * (only for it to be unblocked, state TRANS_STATE_UNBLOCKED).
 		 */
-		trans = btrfs_attach_transaction_barrier(root);
-		if (IS_ERR(trans)) {
-			ret = PTR_ERR(trans);
-			if (ret == -ENOENT)
-				ret = 0;
-			break;
-		}
-		ret = btrfs_commit_transaction(trans);
+		ret = btrfs_commit_current_transaction(root);
 		break;
 	default:
 		ret = -ENOSPC;

fs/btrfs/super.c

@@ -2257,9 +2257,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 
 static int btrfs_freeze(struct super_block *sb)
 {
-	struct btrfs_trans_handle *trans;
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
-	struct btrfs_root *root = fs_info->tree_root;
 
 	set_bit(BTRFS_FS_FROZEN, &fs_info->flags);
 	/*
@@ -2268,14 +2266,7 @@ static int btrfs_freeze(struct super_block *sb)
 	 * we want to avoid on a frozen filesystem), or do the commit
 	 * ourselves.
 	 */
-	trans = btrfs_attach_transaction_barrier(root);
-	if (IS_ERR(trans)) {
-		/* no transaction, don't bother */
-		if (PTR_ERR(trans) == -ENOENT)
-			return 0;
-		return PTR_ERR(trans);
-	}
-	return btrfs_commit_transaction(trans);
+	return btrfs_commit_current_transaction(fs_info->tree_root);
 }
 
 static int check_dev_super(struct btrfs_device *dev)

fs/btrfs/transaction.c

@@ -1989,6 +1989,25 @@ void btrfs_commit_transaction_async(struct btrfs_trans_handle *trans)
 	btrfs_put_transaction(cur_trans);
 }
 
+/*
+ * If there is a running transaction commit it or if it's already committing,
+ * wait for its commit to complete. Does not start and commit a new transaction
+ * if there isn't any running.
+ */
+int btrfs_commit_current_transaction(struct btrfs_root *root)
+{
+	struct btrfs_trans_handle *trans;
+
+	trans = btrfs_attach_transaction_barrier(root);
+	if (IS_ERR(trans)) {
+		int ret = PTR_ERR(trans);
+
+		return (ret == -ENOENT) ? 0 : ret;
+	}
+
+	return btrfs_commit_transaction(trans);
+}
+
 static void cleanup_transaction(struct btrfs_trans_handle *trans, int err)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;

fs/btrfs/transaction.h

@@ -268,6 +268,7 @@ void btrfs_maybe_wake_unfinished_drop(struct btrfs_fs_info *fs_info);
 int btrfs_clean_one_deleted_snapshot(struct btrfs_fs_info *fs_info);
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans);
 void btrfs_commit_transaction_async(struct btrfs_trans_handle *trans);
+int btrfs_commit_current_transaction(struct btrfs_root *root);
 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans);
 bool btrfs_should_end_transaction(struct btrfs_trans_handle *trans);
 void btrfs_throttle(struct btrfs_fs_info *fs_info);