On 2019/8/3 下午1:31, Andrei Borzenkov wrote: > 03.08.2019 2:09, Qu Wenruo пишет: >> >> >> On 2019/8/3 上午2:08, Andrei Borzenkov wrote: >>> bor@tw:~> sudo btrfs qgroup show . >>> ERROR: cannot find the qgroup 0/789 >>> bor@tw:~> >>> >>> Fine. This openSUSE with snapper which creates and automatically >>> destroys snapshots and apparently either kernel or snapper now also >>> remove corresponding qgroup. I played with snapshots and created several >>> top level qgroups that included snapshot qgroups existing at this time. >>> Now these snapshots are gone, their qgroups are gone ... >> >> Kernel version please. >> >> IIRC latest upstream kernel doesn't remove the level 0 qgroup. > > Yes? > >> It may be the userspace doing it improperly. >> > > Not sure what "improperly" means here. snapper removes qgroup after > deleting snapshot. What is "improper" here? Doing without using the qgroup ioctl, but some extra flag in snapshot creation/deletion, which can also add relation at subv/snapshot creation time. > > Snapper obviously does not track every parent-child relationship beyond > what it itself cares about (single summary qrgoup that includes all > snapshots). > >>> and what can I >>> do? I have no way to even know what is wrong because the very command >>> that shows it fails immediately. >>> >>> bor@tw:~/python-btrfs/examples> sudo ./show_tree_keys.py 8 . | grep 0/789 >>> (0/789 QGROUP_RELATION 2/792) >>> (0/789 QGROUP_RELATION 2/793) >>> (0/789 QGROUP_RELATION 2/795) >>> (0/789 QGROUP_RELATION 2/799) >>> (0/789 QGROUP_RELATION 2/800) >>> (0/789 QGROUP_RELATION 2/803) >>> (0/789 QGROUP_RELATION 2/804) >>> (0/789 QGROUP_RELATION 2/805) >>> (0/789 QGROUP_RELATION 2/806) >>> (0/789 QGROUP_RELATION 2/807) >>> (0/789 QGROUP_RELATION 2/808) >>> (0/789 QGROUP_RELATION 2/809) >>> (0/789 QGROUP_RELATION 2/814) >>> (0/789 QGROUP_RELATION 2/818) >>> (0/789 QGROUP_RELATION 2/819) >>> (2/792 QGROUP_RELATION 0/789) >>> (2/793 QGROUP_RELATION 0/789) >>> (2/795 QGROUP_RELATION 0/789) >>> (2/799 QGROUP_RELATION 0/789) >>> (2/800 QGROUP_RELATION 0/789) >>> (2/803 QGROUP_RELATION 0/789) >>> (2/804 QGROUP_RELATION 0/789) >>> (2/805 QGROUP_RELATION 0/789) >>> (2/806 QGROUP_RELATION 0/789) >>> (2/807 QGROUP_RELATION 0/789) >>> (2/808 QGROUP_RELATION 0/789) >>> (2/809 QGROUP_RELATION 0/789) >>> (2/814 QGROUP_RELATION 0/789) >>> (2/818 QGROUP_RELATION 0/789) >>> (2/819 QGROUP_RELATION 0/789) >>> bor@tw:~/python-btrfs/examples> >>> >>> And even if I find it out, I cannot fix it anyway >> >> Furthermore, latest kernel should automatically remove the relation when >> deleting the qgroup. >> > > Yes, seems to be the case now with 5.2.3. > >> Would you please provide the (minimal) script/reproducer causing the >> situation and kernel version? >> > > I cannot reproduce it on purpose with kernel 5.2.3 and btrfsprogs 5.1. I > do not remember when I created the configuration in question, it > probably was late 4.x or early 5.x. System was periodically updated > since then and I noticed it only now. > > Actually kernel should be dropping parent-child relation when removing > child since kernel 4.1 (commit > f5a6b1c53bdd44f79e3904c0f5e59f956b49b2c8). May be there is (was) some > other code path that skipped it. > > OTOH this is not atomic. First qgroup item itself is removed, then > relation. If removing relation fails for whatever reason item itself is > already gone and we have situation above. You're right about the removal, although the term is not "atomic". For qgroup item deletion, we can return -ENOENT or other serious tree corruption error from btrfs_search_slot()/btrfs_del_item(). But even for -ENOENT case, we still tries to delete the relation item. So that part is OK. The problem is the del_qgroup_relation part, where if we hit even -ENOENT we abort deleting even if we may have extra items needs to delete. We need a little more polish on the error handler. So is the btrfs_del_qgroup_relation() where it doesn't delete all relations, but only one. I'll soon send out patches to address your bugs. Thanks, Qu > >> Thanks, >> Qu >> >>> >>> bor@tw:~/python-btrfs/examples> sudo btrfs qgroup remove 0/789 2/792 . >>> ERROR: unable to assign quota group: Invalid argument >>> bor@tw:~/python-btrfs/examples> >>> >>> I can remove parent qgroup, but it does not clean up parent-child >>> relationship >>> >>> bor@tw:~/python-btrfs/examples> sudo btrfs qgroup destroy 2/792 . >>> bor@tw:~/python-btrfs/examples> sudo ./show_tree_keys.py 8 . | grep 2/792 >>> (0/789 QGROUP_RELATION 2/792) >>> (2/792 QGROUP_RELATION 0/789) >>> bor@tw:~/python-btrfs/examples> >>> >> > >
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