On 2018/07/27 10:19, Qu Wenruo wrote:
>
>
> On 2018年07月27日 09:10, Misono Tomohiro wrote:
>> On 2018/07/26 18:15, Qu Wenruo wrote:
>>> Between btrfs_quota_enable() finished and rescan kicked in, there is a
>>> small window that quota status has (ON | INCONSISTENT) bits set but
>>> without RESCAN bits set.
>>>
>>> And transaction is committed inside the window and then power loss
>>> happens, we will have a quota tree with all qgroup numbers set to 0, and
>>> not RESCAN bit set.
>>>
>>> At next mount time, qgroup rescan will not kick in due to the missing of
>>> RESCAN bit, user needs to kick in rescan manually.
>>>
>>> This patch will fix it by setting RESCAN bit at btrfs_quota_enable(),
>>> so even after power loss we will still kick in rescan automatically.
>>>
>>> Suggested-by: Misono Tomohiro <misono.tomohiro@xxxxxxxxxxxxxx>
>>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>>> ---
>>> fs/btrfs/qgroup.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
>>> index c25dc47210a3..13c1c7dd278d 100644
>>> --- a/fs/btrfs/qgroup.c
>>> +++ b/fs/btrfs/qgroup.c
>>> @@ -930,7 +930,8 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
>>> btrfs_set_qgroup_status_generation(leaf, ptr, trans->transid);
>>> btrfs_set_qgroup_status_version(leaf, ptr, BTRFS_QGROUP_STATUS_VERSION);
>>> fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON |
>>> - BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
>>> + BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT |
>>> + BTRFS_QGROUP_STATUS_FLAG_RESCAN;
>>> btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags);
>>> btrfs_set_qgroup_status_rescan(leaf, ptr, 0);
>>>
>>> @@ -987,7 +988,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
>>> fs_info->quota_root = quota_root;
>>> set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
>>> spin_unlock(&fs_info->qgroup_lock);
>>> - ret = qgroup_rescan_init(fs_info, 0, 1);
>>> + ret = qgroup_rescan_init(fs_info, 0, 0);
>>> if (!ret) {
>>> qgroup_rescan_zero_tracking(fs_info);
>>> btrfs_queue_work(fs_info->qgroup_rescan_workers,
>>>
>>
>> This is what I think at first, but is it ok not holding fs_info->qgroup_ioctl_lock
>> in brfs_qgroup_rescan() as you concerned in previous thread?
>
> I think it's OK, since we have larger mutex (subvol_sem) for
> quota_enable/disable() so there will be no concurrency modifying flags.
> And we're holding trans handler from btrfs_ioctl_quota_ctl(),
> transaction won't be committed in btrfs_quota_enable().
Ok, but nikolay's patch in misc-next moves transaction commit in btrfs_quota_enable():
https://patchwork.kernel.org/patch/10508819/
("btrfs: qgroups: Move transaction management inside btrfs_quota_enable/disable")
This is related to https://marc.info/?l=linux-btrfs&m=152999289017582.
However, it seems that other people does not see the problem,
so I'm not sure how the above patch ends up...
Thanks,
Tomohiro Misono
>
> So I think it's OK.
>
> Thanks,
> Qu
>
>
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