Re: linux-next: manual merge of the mm tree with Linus' tree

Suren Baghdasaryan
2023-07-28T00:08:20Z

On Thu, Jul 27, 2023 at 4:50 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, Jul 27, 2023 at 04:40:20PM -0700, Suren Baghdasaryan wrote:
> > On Thu, Jul 27, 2023 at 4:29 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > >
> > > Hi all,
> > >
> > > On Fri, 28 Jul 2023 09:18:49 +1000 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > > >
> > > > Today's linux-next merge of the mm tree got a conflict in:
> > > >
> > > > mm/memory.c
> > > >
> > > > between commit:
> > > >
> > > > 657b5146955e ("mm: lock_vma_under_rcu() must check vma->anon_vma under vma lock")
> > > >
> > > > from Linus' tree and commits:
> > > >
> > > > 69f6bbd1317f ("mm: handle userfaults under VMA lock")
> > > > a3bdf38e85aa ("mm: allow per-VMA locks on file-backed VMAs")
> > > >
> > > > from the mm tree.
> > > >
> > > > I fixed it up (I think, please check - see below) and can carry the fix
> > > > as necessary. This is now fixed as far as linux-next is concerned, but
> > > > any non trivial conflicts should be mentioned to your upstream
> > > > maintainer when your tree is submitted for merging. You may also want
> > > > to consider cooperating with the maintainer of the conflicting tree to
> > > > minimise any particularly complex conflicts.
> > > >
> > > > --
> > > > Cheers,
> > > > Stephen Rothwell
> > > >
> > > > diff --cc mm/memory.c
> > > > index ca632b58f792,271982fab2b8..000000000000
> > > > --- a/mm/memory.c
> > > > +++ b/mm/memory.c
> > > > @@@ -5392,32 -5597,18 +5597,21 @@@ retry
> > > > if (!vma)
> > > > goto inval;
> > > >
> > > > - /* Only anonymous and tcp vmas are supported for now */
> > > > - if (!vma_is_anonymous(vma) && !vma_is_tcp(vma))
> > > > - /* find_mergeable_anon_vma uses adjacent vmas which are not locked */
> > > > - if (vma_is_anonymous(vma) && !vma->anon_vma)
> > > > -- goto inval;
> > > > --
> > > > if (!vma_start_read(vma))
> > > > goto inval;
> > > >
> > > > + /*
> > > > + * find_mergeable_anon_vma uses adjacent vmas which are not locked.
> > > > + * This check must happen after vma_start_read(); otherwise, a
> > > > + * concurrent mremap() with MREMAP_DONTUNMAP could dissociate the VMA
> > > > + * from its anon_vma.
> > > > + */
> > > > - if (unlikely(!vma->anon_vma && !vma_is_tcp(vma)))
> > > > - goto inval_end_read;
> > > > -
> > > > - /*
> > > > - * Due to the possibility of userfault handler dropping mmap_lock, avoid
> > > > - * it for now and fall back to page fault handling under mmap_lock.
> > > > - */
> > > > - if (userfaultfd_armed(vma))
> > > > ++ if (unlikely(vma_is_anonymous(vma) && !vma_is_tcp(vma)))
> >
> > Is the above extra '+' what compiler complains about?
> > Patches from Linus' tree remove some code from that function, so
> > applying them first should simplify the merge.
>
> I see you're unfamiliar with the output of git diff --cc ...

guilty as charged.

>