Re: [PATCH 0/2] memcg: mm_update_next_owner() should skip kthreads

[Hugh Dickins <hughd@google.com>]

On Sat, 19 Apr 2014, Oleg Nesterov wrote:
> On 04/19, Pavel Machek wrote:
> >
> > > > Hmm. I seem to see a bug in this function, it can be fulled by use_mm,
> > > > but I am not sure this can explain the problem. I'll send a patch.
> > >
> > > Untested, please review. But it really looks "obviously wrong", and note
> > > that unuse_mm() doesn't do mm_update_next_owner(). (just in case, do not
> > > confuse it with unuse_mm() in mm/swapfile.c).
> >
> > Having two functions, one exported, one static with same name -- that
> > sounds quite evil, right?
> 
> Yes, agreed.

Doubly agreed; though it seems to have escaped causing confusion
for several years, so no great hurry to resolve it.

> 
> > mmu_context.c: * unuse_mm
> > mmu_context.c:void unuse_mm(struct mm_struct *mm)
> > mmu_context.c:EXPORT_SYMBOL_GPL(unuse_mm);
> > swapfile.c:static int unuse_mm(struct mm_struct *mm,
> 
> Yes, I was thinking about s/unuse_mm/unswap_mm/ change in swapfile.c,
> but then we should probaly rename other "unuse" functions there, and
> shmem_unuse/try_to_unuse are not static.

My preference is "swapoff" instead of "unuse" throughout there:
it saves having to explain that "unuse" implies "swapoff" each
time we send in a patch making a change to that code.

But I'd prefer you hold off for the moment: Kelley Nielsen is currently
preparing a patchset reworking try_to_unuse, and I suggested a few days
ago to include such renaming in that patchset.

Partly driven by s390's recent 45961722f8e3 "mm: add support for
discard of unused ptes" which adds further confusion with pte_unused().

Hugh