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Date:   Mon, 12 Jun 2023 09:59:19 -0400
From:   Peter Xu <peterx@redhat.com>
To:     Suren Baghdasaryan <surenb@google.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,
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        viro@zeniv.linux.org.uk, brauner@kernel.org,
        pasha.tatashin@soleen.com, linux-mm@kvack.org,
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Subject: Re: [PATCH v2 2/6] mm: handle swap page faults under VMA lock if
 page is uncontended
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On Fri, Jun 09, 2023 at 03:34:34PM -0700, Suren Baghdasaryan wrote:
> On Fri, Jun 9, 2023 at 1:45 PM 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 release
> > > > 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.

Yes that'll be appreciated.  IMHO keeping changing semantics of
FAULT_FLAG_VMA_LOCK for the folio lock function in the same small series is
confusing.

-- 
Peter Xu