Re: [PATCH v4 0/3] mm/khugepaged: fix khugepaged+shmem races

[Andrew Morton]

On Fri, 3 Mar 2023 10:35:53 -0500 Peter Xu <peterx@xxxxxxxxxx> wrote:

> On Fri, Feb 17, 2023 at 05:54:36PM +0900, David Stevens wrote:
> > From: David Stevens <stevensd@xxxxxxxxxxxx>
> > 
> > Fix two races in khugepaged+shmem that cause issues with userfaultfd and
> > lseek, respectively.
> > 
> > v3 -> v4:
> >  - Base changes on mm-everything (fba720cb4dc0)
> >  - Add patch to refactor error handling control flow in collapse_file
> >  - Rebase userfaultfd patch with no significant logic changes
> >  - Different approach for fixing lseek race
> 
> I just noticed this one hasn't landed unstable, so I guess I just posted a
> trivial cleanup that can conflict with this so it won't apply cleanly..
> 
> https://lore.kernel.org/r/20230303151218.311015-1-peterx@xxxxxxxxxx
> 
> The resolution will be fairly straightforward though, and I'm happy to
> rebase that one to this since this targets a real bug so should have higher
> priority.

Even without the above patch ("mm/khugepaged: Cleanup memcg uncharge
for failure path") I'm seeing a big reject in khugepaged.c.  Might be
easily fixed, didn't look.

> I guess it's possible Andrew thought the series has unsettled comment so
> Andrew could just have ignored that whole set in the mark ups.  A repost
> could possibly clarify that.

Yes please.  Lets gather the acks thus far, rebase on
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm's mm-unstable
branch and resend?

> Again, it'll always great to get another eye on this slightly involved
> series. Matthew / Yang were already on the list, also copying Zach for his
> recent works on khugepaged just in case he spots anything wrong.