On 2018年07月27日 09:43, Misono Tomohiro wrote:
> 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.tomoh...@jp.fujitsu.com>
>>>> Signed-off-by: Qu Wenruo <w...@suse.com>
>>>> ---
>>>> 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")Since qgroup_rescan_init() has nothing do to with transaction, it looks OK even with Nikolay's patch. > > 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... IIRC I also failed to reproduce it, thus can't provide much help for that thread. Thanks, Qu > > Thanks, > Tomohiro Misono > >> >> So I think it's OK. >> >> Thanks, >> Qu >> >> >
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