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Date: Wed, 24 Jun 2015 15:53:34 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>, Benjamin LaHaise <bcrl@kvack.org>,
        Hugh Dickins <hughd@google.com>, Jeff Moyer <jmoyer@redhat.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Pavel Emelyanov <xemul@parallels.com>
Subject: Re: [PATCH 0/1] mm: move ->mremap() from file_operations to
	vm_operations_struct
Message-ID: <20150624135334.GA780@redhat.com>
References: <20150623180225.GA12882@redhat.com> <CALCETrVyKgZEdDZTYVMPPoUAyNFudFFPkDaTOnyhzW+jBJjRxA@mail.gmail.com>
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On 06/23, Andy Lutomirski wrote:
>
> On Tue, Jun 23, 2015 at 11:02 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> > On 06/22, Andy Lutomirski wrote:
> >>
> >> On Mon, Jun 22, 2015 at 5:47 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> >> >
> >> > I never understood why ->mremap() lives in file_operations, not in
> >> > vm_operations_struct. To me vma->vm_file->f_op in move_vma() just
> >> > looks strange, vma->vm_ops->mremap(new_vma) looks "obviously better".
> >> >
> >> > And afaics more useful. CRIU remaps vdso, but this does not update
> >> > mm->context.vdso. OK, probably this does not matter currently, CRIU
> >> > can't c/r the compat tasks, and 64-bit apps do not use context.vdso.
> >> > Afaics. Still, I think we might want to have special_mapping_remap()
> >> > and we can't do this because ->vm_file == NULL.
> >>
> >> I would like this.  Then I could clean up and resubmit my patch to
> >> keep context.vdso up to date.
> >
> > Cough... where can I find this patch ? ;)
> >
>
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=vdso/vma_tracking

Aha, thanks. So yes, looks like your "Add a mechanism to track the current
address of a special mapping" can rely on vm_ops->mremap().

Oleg.