Re: [PATCH v2 1/1] fs/writeback: skip AS_NO_DATA_INTEGRITY mappings in wait_sb_inodes()

[Jan Kara <jack@suse.cz>]

On Tue 06-01-26 14:13:55, Miklos Szeredi wrote:
> On Tue, 6 Jan 2026 at 11:05, David Hildenbrand (Red Hat)
> <david@kernel.org> wrote:
> 
> > > So I understand your patch fixes the regression with suspend blocking but I
> > > don't have a high confidence we are not just starting a whack-a-mole game
> 
> Joanne did a thorough analysis, so I still have hope.  Missing a case
> in such a complex thing is not unexpected.
> 
> > Yes, I think so, and I think it is [1] not even only limited to
> > writeback [2].
> 
> You are referring to DoS against compaction?
> 
> It is a much more benign issue, since compaction will just skip locked
> pages, AFAIU (wasn't always so:
> https://lore.kernel.org/all/1288817005.4235.11393.camel@nimitz/).
> 
> Not saying it shouldn't be fixed, but it should be a separate discussion.
> 
> > To handle the bigger picture (I raised another problematic instance in
> > [4]): I don't know how to handle that without properly fixing fuse. Fuse
> > folks should really invest some time to solve this problem for good.
> 
> Fixing it generically in fuse would necessarily involve bringing back
> some sort of temp buffer.  The performance penalty could be minimized,
> but complexity is what really hurts.
> 
> Maybe doing whack-a-mole results in less mess overall :-/

OK, I was wondering about the bigger picture and now I see there's none :)
I can live with this workaround for now as its blast radius is relatively
small and we can see if some other practical issues appear in the future
(in which case I'll probably push for a more systemic solution).

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