Re: [PATCH v3 0/4] mm: clarify nofail memory allocation

[Michal Hocko <mhocko@suse.com>]

On Thu 22-08-24 14:56:08, Linus Torvalds wrote:
> On Thu, 22 Aug 2024 at 14:40, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > I did find three cases of kvcalloc(NOFAIL) in the nouveau driver and
> > one in erofs. It's not clear that any of them make much sense (or that
> > the erofs one is actually a large allocation).
> 
> Oh, and I missed one in btrfs because it needed five lines of context
> due to being the allocation from hell.
> 
> That said, yes, the vmalloc case at least has no fragmentation issues,
> but I do think even that needs to be size limited for sanity.
> 
> The size limit might be larger than a couple of pages, but not
> _hugely_ larger. You can't just say "I want a megabyte, and you can't
> fail me". That kind of code is garbage, and needs to be called out for
> being garbage.

yes, no objection here. Our current limits are too large for any
practical purpose. We still need a strategy how to communicate that
the size is not supported though. Just returning NULL is IMHO bad thing
because it adds potentially silent failure. In other subthread I was
contemplating about OOPS_ON which would simply terminate the user
context and kill it right away. What do you think about something like
that?
-- 
Michal Hocko
SUSE Labs