Re: [PATCH v2 0/4] btrfs: introduce btrfs specific bdev holder ops and implement mark_dead() call back

[Qu Wenruo <wqu@suse.com>]

在 2025/6/9 15:08, Christoph Hellwig 写道:
> On Mon, Jun 09, 2025 at 03:01:32PM +0930, Qu Wenruo wrote:
>>
>>
>> 在 2025/6/9 14:51, Christoph Hellwig 写道:
>>> No full reivew yet, but I think in the long run your maintainance
>>> burdern will be a lot lower if you implement my suggestion of using
>>> the generic code and adding a new devloss super_uperation.
>>
>> The main problem here is, we didn't go through setup_bdev_super() at all,
>> and the super_block structure itself only supports one bdev.
>>
>> Thus even if we implement a devloss call back in super ops, it will still
>> require quite some extra works to make btrfs to go through the
>> setup_bdev_super().
> 
> Why do you need setup_bdev_super?  Everything relevant is already
> open coded in btrfs, you'll just need to use fs_holder_ops and ensure
> the sb is stored as holder in every block device.
> 
> The other nice thing is that you can also stage the changes, i.e.
> first resurrect the old holder cleanups, then support ->shutdown,
> then add the new ->devloss callback to not shut down the entire file
> system if there is enough redundancy.
> 
>> Although I have to admit, if all btrfs bdevs go through fs_holder_ops, it
>> indeed solves a lot of extra races more easily (freeze ioctl vs bdev freeze
>> call back races).
>>
>>>
>>> This might require resurrecting my old holder cleanup that Johannes
>>> reposted about a year ago.
>>>
>> Maybe it's time to revive that series, mind to share the link to that
>> series?
> 
> My original posting:
> 
> https://lore.kernel.org/linux-btrfs/b083ae24-2273-479f-8c9e-96cb9ef083b8@wdc.com/
> 
> Rebase from Johannes:
> 
> https://lore.kernel.org/linux-btrfs/20240214-hch-device-open-v1-0-b153428b4f72@wdc.com/
> 

Thanks a lot, I'll give that series a review and rebase.

It will be great if we do not need to introduce any extra per-device 
specific freeze/thaw serialization inside btrfs.

Thanks,
Qu