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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Fri, 9 Jun 2023 15:34:34 -0700
Message-ID: <CAJuCfpFAh2KOhpCQ-4b+pzY+1GxOGk=eqj6pBj04gc_8eqB6QQ@mail.gmail.com>
Subject: Re: [PATCH v2 2/6] mm: handle swap page faults under VMA lock if page
 is uncontended
To:     Peter Xu <peterx@redhat.com>
Cc:     Matthew Wilcox <willy@infradead.org>, akpm@linux-foundation.org,
        hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com,
        jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com,
        michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com,
        vbabka@suse.cz, minchan@google.com, dave@stgolabs.net,
        punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com,
        apopple@nvidia.com, ying.huang@intel.com, david@redhat.com,
        yuzhao@google.com, dhowells@redhat.com, hughd@google.com,
        viro@zeniv.linux.org.uk, brauner@kernel.org,
        pasha.tatashin@soleen.com, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com
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On Fri, Jun 9, 2023 at 1:45=E2=80=AFPM Peter Xu <peterx@redhat.com> wrote:
>
> On Fri, Jun 09, 2023 at 09:35:49PM +0100, Matthew Wilcox wrote:
> > On Fri, Jun 09, 2023 at 04:25:42PM -0400, Peter Xu wrote:
> > > >  bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *=
mm,
> > > >                    unsigned int flags)
> > > >  {
> > > > + /* Can't do this if not holding mmap_lock */
> > > > + if (flags & FAULT_FLAG_VMA_LOCK)
> > > > +         return false;
> > >
> > > If here what we need is the page lock, can we just conditionally rele=
ase
> > > either mmap lock or vma lock depending on FAULT_FLAG_VMA_LOCK?
> >
> > See patch 5 ...
>
> Just reaching.. :)
>
> Why not in one shot, then?

I like small incremental changes, but I can squash them if that helps
in having a complete picture.

>
> --
> Peter Xu
>