Commit e09fe2d2 authored Feb 27, 2015 by Qu Wenruo Committed by Chris Mason Apr 13, 2015

btrfs: Don't allow subvolid >= (1 << BTRFS_QGROUP_LEVEL_SHIFT) to be created



Btrfs will create qgroup on subvolume creation if quota is enabled, but
qgroup uses the high bits(currently 16 bits) as level, to build the
inheritance.

However it is fully possible a subvolume can be created with a
subvolumeid larger than 1 << BTRFS_QGROUP_LEVEL_SHIFT, so it will be
considered as level 1 and can't be assigned to other qgroup in level 1.

This patch will prevent such things so qgroup inheritance will not be
screwed up.
The downside is very clear, btrfs subvolume number limit will decrease
from (u64 max - 256(fisrt free objectid) - 256(last free objectid)) to
(u48 max -256(first free objectid)).
But we still have near u48(that's 15 digits in dec), so that should not
be a huge problem.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 8465ecec

fs/btrfs/ctree.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -4219,7 +4219,8 @@ int btree_readahead_hook(struct btrfs_root root, struct extent_buffer eb,
		static inline int is_fstree(u64 rootid)
		{
		if (rootid == BTRFS_FS_TREE_OBJECTID \|\|
		(s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
		((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID &&
		!btrfs_qgroup_level(rootid)))
		return 1;
		return 0;
		}

fs/btrfs/ioctl.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -456,6 +456,13 @@ static noinline int create_subvol(struct inode *dir,
		if (ret)
		return ret;

		/*
		* Don't create subvolume whose level is not zero. Or qgroup will be
		* screwed up since it assume subvolme qgroup's level to be 0.
		*/
		if (btrfs_qgroup_level(objectid))
		return -ENOSPC;

		btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
		/*
		* The same as the snapshot creation, please see the comment

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