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

[Christoph Hellwig <hch@infradead.org>]

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/