Commit 907cbceb authored by Josef Bacik's avatar Josef Bacik
Browse files

Btrfs: optimize how we account for space in truncate 



Currently we're starting and stopping a transaction for no real reason, so kill
that and just reserve enough space as if we can truncate all in one transaction.
Also use btrfs_block_rsv_check() for our reserve to minimize the amount of space
we may have to allocate for our slack space.  Thanks,

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
parent 13553e52

fs/btrfs/inode.c

+29 −29
Original line number Diff line number Diff line
@@ -6482,6 +6482,7 @@ static int btrfs_truncate(struct inode *inode) 
	struct btrfs_trans_handle *trans;

	unsigned long nr;

	u64 mask = root->sectorsize - 1;

	u64 min_size = btrfs_calc_trans_metadata_size(root, 2);



	ret = btrfs_truncate_page(inode->i_mapping, inode->i_size);

	if (ret)
@@ -6530,17 +6531,21 @@ static int btrfs_truncate(struct inode *inode) 
	if (!rsv)

		return -ENOMEM;



	trans = btrfs_start_transaction(root, 4);

	/*

	 * 2 for the truncate slack space

	 * 1 for the orphan item we're going to add

	 * 1 for the orphan item deletion

	 * 1 for updating the inode.

	 */

	trans = btrfs_start_transaction(root, 5);

	if (IS_ERR(trans)) {

		err = PTR_ERR(trans);

		goto out;

	}



	/*

	 * Reserve space for the truncate process.  Truncate should be adding

	 * space, but if there are snapshots it may end up using space.

	 */

	ret = btrfs_truncate_reserve_metadata(trans, root, rsv);

	/* Migrate the slack space for the truncate to our reserve */

	ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv, rsv,

				      min_size);

	BUG_ON(ret);



	ret = btrfs_orphan_add(trans, inode);
@@ -6549,21 +6554,6 @@ static int btrfs_truncate(struct inode *inode) 
		goto out;

	}



	nr = trans->blocks_used;

	btrfs_end_transaction(trans, root);

	btrfs_btree_balance_dirty(root, nr);



	/*

	 * Ok so we've already migrated our bytes over for the truncate, so here

	 * just reserve the one slot we need for updating the inode.

	 */

	trans = btrfs_start_transaction(root, 1);

	if (IS_ERR(trans)) {

		err = PTR_ERR(trans);

		goto out;

	}

	trans->block_rsv = rsv;



	/*

	 * setattr is responsible for setting the ordered_data_close flag,

	 * but that is only tested during the last file release.  That
@@ -6585,19 +6575,29 @@ static int btrfs_truncate(struct inode *inode) 
		btrfs_add_ordered_operation(trans, root, inode);



	while (1) {

		ret = btrfs_block_rsv_check(trans, root, rsv, min_size, 0);

		if (ret) {

			/*

			 * This can only happen with the original transaction we

			 * started above, every other time we shouldn't have a

			 * transaction started yet.

			 */

			if (ret == -EAGAIN)

				goto end_trans;

			err = ret;

			break;

		}



		if (!trans) {

			trans = btrfs_start_transaction(root, 3);

			/* Just need the 1 for updating the inode */

			trans = btrfs_start_transaction(root, 1);

			if (IS_ERR(trans)) {

				err = PTR_ERR(trans);

				goto out;

			}



			ret = btrfs_truncate_reserve_metadata(trans, root,

							      rsv);

			BUG_ON(ret);

		}



		trans->block_rsv = rsv;

		}



		ret = btrfs_truncate_inode_items(trans, root, inode,

						 inode->i_size,
@@ -6613,7 +6613,7 @@ static int btrfs_truncate(struct inode *inode) 
			err = ret;

			break;

		}



end_trans:

		nr = trans->blocks_used;

		btrfs_end_transaction(trans, root);

		trans = NULL;

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