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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Tue, 2 Feb 2021 17:55:50 -0800
Message-ID: <CAJuCfpEirOiisM-xouZB7JRBDpERdvWb2gfaq003+rs0b4M83Q@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm: replace BUG_ON in vm_insert_page with a return of
 an error
To:     Minchan Kim <minchan@kernel.org>
Cc:     Sumit Semwal <sumit.semwal@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@infradead.org>,
        Liam Mark <lmark@codeaurora.org>, labbott@redhat.com,
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        Chris Goldsworthy <cgoldswo@codeaurora.org>,
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On Tue, Feb 2, 2021 at 5:31 PM Minchan Kim <minchan@kernel.org> wrote:
>
> On Tue, Feb 02, 2021 at 04:31:33PM -0800, Suren Baghdasaryan wrote:
> > Replace BUG_ON(vma->vm_flags & VM_PFNMAP) in vm_insert_page with
> > WARN_ON_ONCE and returning an error. This is to ensure users of the
> > vm_insert_page that set VM_PFNMAP are notified of the wrong flag usage
> > and get an indication of an error without panicing the kernel.
> > This will help identifying drivers that need to clear VM_PFNMAP before
> > using dmabuf system heap which is moving to use vm_insert_page.
> >
> > Suggested-by: Christoph Hellwig <hch@infradead.org>
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >  mm/memory.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index feff48e1465a..e503c9801cd9 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1827,7 +1827,8 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
> >               return -EINVAL;
> >       if (!(vma->vm_flags & VM_MIXEDMAP)) {
> >               BUG_ON(mmap_read_trylock(vma->vm_mm));
>
> Better to replace above BUG_ON with WARN_ON_ONCE, too?

If nobody objects I'll do that in the next respin. Thanks!

>
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