Commit 5343cd93 authored by Boris Burkov's avatar Boris Burkov Committed by David Sterba
Browse files

btrfs: qgroup: simple quota auto hierarchy for nested subvolumes 



Consider the following sequence:

- enable quotas
- create subvol S id 256 at dir outer/
- create a qgroup 1/100
- add 0/256 (S's auto qgroup) to 1/100
- create subvol T id 257 at dir outer/inner/

With full qgroups, there is no relationship between 0/257 and either of
0/256 or 1/100. There is an inherit feature that the creator of inner/
can use to specify it ought to be in 1/100.

Simple quotas are targeted at container isolation, where such automatic
inheritance for not necessarily trusted/controlled nested subvol
creation would be quite helpful. Therefore, add a new default behavior
for simple quotas: when you create a nested subvol, automatically
inherit as parents any parents of the qgroup of the subvol the new inode
is going in.

In our example, 257/0 would also be under 1/100, allowing easy control
of a total quota over an arbitrary hierarchy of subvolumes.

I think this _might_ be a generally useful behavior, so it could be
interesting to put it behind a new inheritance flag that simple quotas
always use while traditional quotas let the user specify, but this is a
minimally intrusive change to start.

Signed-off-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent cecbb533

fs/btrfs/ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -652,7 +652,7 @@ static noinline int create_subvol(struct mnt_idmap *idmap, 
	/* Tree log can't currently deal with an inode which is a new root. */

	btrfs_set_log_full_commit(trans);



	ret = btrfs_qgroup_inherit(trans, 0, objectid, inherit);

	ret = btrfs_qgroup_inherit(trans, 0, objectid, root->root_key.objectid, inherit);

	if (ret)

		goto out;

fs/btrfs/qgroup.c

+54 −3
Original line number Diff line number Diff line
@@ -1549,8 +1549,7 @@ static int quick_update_accounting(struct btrfs_fs_info *fs_info, 
	return ret;

}



int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,

			      u64 dst)

int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src, u64 dst)

{

	struct btrfs_fs_info *fs_info = trans->fs_info;

	struct btrfs_qgroup *parent;
@@ -3018,6 +3017,47 @@ int btrfs_run_qgroups(struct btrfs_trans_handle *trans) 
	return ret;

}



static int qgroup_auto_inherit(struct btrfs_fs_info *fs_info,

			       u64 inode_rootid,

			       struct btrfs_qgroup_inherit **inherit)

{

	int i = 0;

	u64 num_qgroups = 0;

	struct btrfs_qgroup *inode_qg;

	struct btrfs_qgroup_list *qg_list;

	struct btrfs_qgroup_inherit *res;

	size_t struct_sz;

	u64 *qgids;



	if (*inherit)

		return -EEXIST;



	inode_qg = find_qgroup_rb(fs_info, inode_rootid);

	if (!inode_qg)

		return -ENOENT;



	num_qgroups = list_count_nodes(&inode_qg->groups);



	if (!num_qgroups)

		return 0;



	struct_sz = struct_size(res, qgroups, num_qgroups);

	if (struct_sz == SIZE_MAX)

		return -ERANGE;



	res = kzalloc(struct_sz, GFP_NOFS);

	if (!res)

		return -ENOMEM;

	res->num_qgroups = num_qgroups;

	qgids = res->qgroups;



	list_for_each_entry(qg_list, &inode_qg->groups, next_group)

		qgids[i] = qg_list->group->qgroupid;



	*inherit = res;

	return 0;

}



/*

 * Copy the accounting information between qgroups. This is necessary

 * when a snapshot or a subvolume is created. Throwing an error will
@@ -3025,7 +3065,8 @@ int btrfs_run_qgroups(struct btrfs_trans_handle *trans) 
 * when a readonly fs is a reasonable outcome.

 */

int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,

			 u64 objectid, struct btrfs_qgroup_inherit *inherit)

			 u64 objectid, u64 inode_rootid,

			 struct btrfs_qgroup_inherit *inherit)

{

	int ret = 0;

	int i;
@@ -3037,6 +3078,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, 
	struct btrfs_qgroup *dstgroup;

	struct btrfs_qgroup *prealloc;

	struct btrfs_qgroup_list **qlist_prealloc = NULL;

	bool free_inherit = false;

	bool need_rescan = false;

	u32 level_size = 0;

	u64 nums;
@@ -3073,6 +3115,13 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, 
		goto out;

	}



	if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE && !inherit) {

		ret = qgroup_auto_inherit(fs_info, inode_rootid, &inherit);

		if (ret)

			goto out;

		free_inherit = true;

	}



	if (inherit) {

		i_qgroups = (u64 *)(inherit + 1);

		nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
@@ -3256,6 +3305,8 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid, 
			kfree(qlist_prealloc[i]);

		kfree(qlist_prealloc);

	}

	if (free_inherit)

		kfree(inherit);

	kfree(prealloc);

	return ret;

}

fs/btrfs/qgroup.h

+3 −3
Original line number Diff line number Diff line
@@ -312,8 +312,7 @@ int btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info); 
void btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info);

int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,

				     bool interruptible);

int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,

			      u64 dst);

int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src, u64 dst);

int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,

			      u64 dst);

int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid);
@@ -343,7 +342,8 @@ int btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans, u64 bytenr, 
int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans);

int btrfs_run_qgroups(struct btrfs_trans_handle *trans);

int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,

			 u64 objectid, struct btrfs_qgroup_inherit *inherit);

			 u64 objectid, u64 inode_rootid,

			 struct btrfs_qgroup_inherit *inherit);

void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,

			       u64 ref_root, u64 num_bytes,

			       enum btrfs_qgroup_rsv_type type);

fs/btrfs/transaction.c

+9 −5
Original line number Diff line number Diff line
@@ -1620,8 +1620,8 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans, 
	int ret;



	/*

	 * Save some performance in the case that full qgroups are not enabled.

	 * If this check races with the ioctl, rescan will kick in anyway.

	 * Save some performance in the case that qgroups are not enabled. If

	 * this check races with the ioctl, rescan will kick in anyway.

	 */

	if (!btrfs_qgroup_full_accounting(fs_info))

		return 0;
@@ -1662,7 +1662,7 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans, 


	/* Now qgroup are all updated, we can inherit it to new qgroups */

	ret = btrfs_qgroup_inherit(trans, src->root_key.objectid, dst_objectid,

				   inherit);

				   parent->root_key.objectid, inherit);

	if (ret < 0)

		goto out;
@@ -1929,8 +1929,12 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, 
	 * To co-operate with that hack, we do hack again.

	 * Or snapshot will be greatly slowed down by a subtree qgroup rescan

	 */

	if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_FULL)

		ret = qgroup_account_snapshot(trans, root, parent_root,

					      pending->inherit, objectid);

	else if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)

		ret = btrfs_qgroup_inherit(trans, root->root_key.objectid, objectid,

					   parent_root->root_key.objectid, pending->inherit);

	if (ret < 0)

		goto fail;