Re: [PATCH v2] btrfs: reject refs=0 subvolume without DEAD in SUBVOL_SYNC_WAIT

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2026/11/14 03:00, David Sterba 写道:
> On Tue, Nov 10, 2026 at 07:00:34AM +1030, Qu Wenruo wrote:
>>
>>
>> 在 2026/11/10 05:17, David Sterba 写道:
>>> On Sun, Nov 01, 2026 at 05:48:21PM +1030, Qu Wenruo wrote:
>>>> With that said, there are more problems with the ioctl.
>>>>
>>>> - No real user
>>>>      No one is utilizing BTRFS_SUBVOL_SYNC* flags. Btrfs-progs itself
>>>>      doesn't even bother it.
>>>>
>>>>      So all these fixes are very low priority, unless there are some wild
>>>>      programs utilizing this.
>>>>
>>>>      But even btrfs-progs doesn't utilize them, the possibility are very
>>>>      low.
>>>
>>> Obviously the ioctl was added so progs 'subvol sync' can use it for
>>> non-root users. I started working on it but there's a problem with the
>>> behaviour change between the user types. Root has full access and
>>> reports the progress while with this ioctl there were some problems I
>>> don't remember. The ioctl was designed to emulate all modes that root
>>> can do so it should be possible to get 1:1 output.
>>
>> Are you still planning to implement the full root-less subvolume wait in
>> progs?
> 
> Yes, but I don't have an ETA.
> 
>> Or is this feature deprecated and we can eventually remove it to reduce
>> LLM bug reports?
> 
> I don't understand what would need to be deprecated, it's a new ioctl
> missing the userspace counterpart to implement an unprivileged
> functionality where it makes sense.

Then at least hide it under experimental features until the user space 
counter part is in a good shape, so that no random LLM report or syzbot 
steps into this ioctl?