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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Aug 22, 2024 at 7:47 PM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Thu 22-08-24 14:56:08, Linus Torvalds wrote:
> > On Thu, 22 Aug 2024 at 14:40, Linus Torvalds
> > <torvalds@xxxxxxxxxxxxxxxxxxxx> 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?

Personally, I fully support this approach that falls between BUG_ON
and returning NULL. Regarding the concern about 'leaving locks
behind' you have in that subthread,  I believe there's no difference
when returning NULL, as it could still leave locks behind but offers
a chance for the calling process to avoid an immediate crash.

> --
> Michal Hocko
> SUSE Labs

Thanks
Barry





[Index of Archives]     [KVM Development]     [Libvirt Development]     [Libvirt Users]     [CentOS Virtualization]     [Netdev]     [Ethernet Bridging]     [Linux Wireless]     [Kernel Newbies]     [Security]     [Linux for Hams]     [Netfilter]     [Bugtraq]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux Admin]     [Samba]

  Powered by Linux