On 2019/8/20 上午12:57, David Sterba wrote:
> On Fri, Aug 16, 2019 at 11:03:33AM +0100, Filipe Manana wrote:
>>> Originally planned to use this feature to catch the exact update, but
>>> the problem is, with this pressure, we need an extra ioctl to wait the
>>> full subvolume drop to finish.
>>
>> That, the ioctl to wait (or better, poll) for subvolume removal to
>> complete (either all subvolumes or just a specific one), would be
>> useful.
> 
> The polling for subvolume drop is implemented using the SEARCH_TREE
> ioctl and provided as 'btrfs subvolume sync' command. Is there
> something that this approach does not provide and would need a new
> ioctl?
> 
That interface is good enough for my use case already.

Thanks,
Qu