Re: [Lsf-pc] [LSF/MM/BPF TOPIC] Where is fuse going? API cleanup, restructuring and more

[Jan Kara <jack@suse.cz>]

Hi Gao!

On Mon 23-03-26 18:05:17, Gao Xiang wrote:
> On 2026/3/23 17:43, Jan Kara wrote:
> > And yes, when you have immutable filesystem, things are much simpler
> > because the data structures and algorithms can be much simpler and as you
> > wrote a lot of these inconsistencies don't matter (at least for the
> > kernel). But once you add ability to modify the filesystem - here I don't
> > think it matters whether through CoW or other means - things get
> > complicated quickly and it gets much more complex to make your code
> > resilient to all kinds of inconsistencies...
> 
> I only consider the COW approach using OverlayFS for example,
> it just copies up (meta)data into another filesystem (the
> semantics is just like copy the file in the userspace) and
> the immutable filesystem image won't change in any case.
> 
> Overlayfs write goes through normal user write and the
> writable filesystem is consistent, so I don't think it does
> matter.  Or am I missing something? (e.g could you point
> out some case which OverlayFS cannot handle properly?)

No, you are correct. For the usecases where immutable fs + overlayfs +
empty initial writeable filesystem works, this is a safe design.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR