linux-kernel - Re: [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse

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Message-ID: <CAJuCfpGaxhpePj8KN3S=Q7jMUjaeWZfoBTAHqjodhoH5MV-9yQ@mail.gmail.com>
Date:   Tue, 5 Oct 2021 14:30:48 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Liam Howlett <liam.howlett@...cle.com>
Cc:     Rolf Eike Beer <eb@...ix.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Colin Cross <ccross@...gle.com>,
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Subject: Re: [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse

On Tue, Oct 5, 2021 at 2:00 PM Liam Howlett <liam.howlett@...cle.com> wrote:
>
> * Suren Baghdasaryan <surenb@...gle.com> [211004 12:18]:
> > On Mon, Oct 4, 2021 at 12:03 AM Rolf Eike Beer <eb@...ix.com> wrote:
> > >
> > > > --- a/mm/madvise.c
> > > > +++ b/mm/madvise.c
> > > > @@ -63,76 +63,20 @@ static int madvise_need_mmap_write(int behavior)
> > > >  }
> > > >
> > > >  /*
> > > > - * We can potentially split a vm area into separate
> > > > - * areas, each area with its own behavior.
> > > > + * Update the vm_flags on regiion of a vma, splitting it or merging it as
> > >                                 ^^
> >
> > Thanks! Will fix in the next version.
>
> Since you'll be respinning for this comment, can you please point out
> that the split will keep the VMA as [vma->vm_start, new_end)?  That is,
> __split_vma() is passed 0 for new_below.  It might prove useful since
> the code is being reused.

Hmm. There are two cases here:

        if (start != vma->vm_start) {
                ...
                error = __split_vma(mm, vma, start, 1);
        }

and

        if (end != vma->vm_end) {
                ...
                error = __split_vma(mm, vma, end, 0);
        }

so, I don't think such a comment would be completely correct, no?

>
> Thanks,
> Liam
>
> >
> > >
> > > Eike
> > > --
> > > Rolf Eike Beer, emlix GmbH, http://www.emlix.com
> > > Fon +49 551 30664-0, Fax +49 551 30664-11
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> > >
> > > emlix - smart embedded open source
> > >
> > > --
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> >