On Thu, Mar 18, 2021 at 02:22:20AM +0000, Sidong Yang wrote: > On Wed, Mar 17, 2021 at 07:36:47PM +0100, David Sterba wrote: > > On Tue, Mar 16, 2021 at 01:27:46PM +0000, Sidong Yang wrote: > > > When user assign qgroup with qgroup id that is too big to exceeds > > > range and invade level value, and it works without any error. but > > > this action would be make undefined error. this code make sure that > > > qgroup id doesn't exceed range(0 ~ 2^48-1). > > > > Should the level be also validate? The function parse_qgroupid does not > > do full validation, so eg 0//0 would be parsed as a path and not as a > > typo, level larger than 64K will be silently clamped. > > I agree. 0//0 would be parsed as path but it failed in > btrfs_util_is_subvolume() and goes to err. I understand that upper 16 > bits of qgroupid is for level. so, The valid llevel range is [0~2^16-1]. > But I can't get it that level larger than 64K will be clampled.
The way the level gets stored into the final qgroup id is level << 48. For example invalid values 70000/281474976710779 would be stored as subvol id 123 and level 4465, where the u64 is 0x117100000000007b > one more question about that, I see that the ioctl calls just store the > qgroupid without any opeartion with level. is the level meaningless in > kernel? The quota groups are hierarchical and the level denotes the level, where 0/subvolid is the lowest always attached to a subvolume and the higher levels are artificial and may contain any qgroups and do the whole accounting on the subtree. The original design doc .pdf can be found in https://git.kernel.org/pub/scm/linux/kernel/git/arne/qgroups-doc.git/tree/
