linux-kernel - Re: vdso && f_op->mremap (Was: special_mapping

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Message-ID: <CALCETrWgq3jUWwfa9z9Hq-pnWCp+SCV-iQC4BuV=VXDU10rk+g@mail.gmail.com>
Date:	Mon, 22 Jun 2015 18:26:46 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Hugh Dickins <hughd@...gle.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: vdso && f_op->mremap (Was: special_mapping_fault() is broken)

On Mon, Jun 22, 2015 at 5:47 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 06/21, Oleg Nesterov wrote:
>>
>> Forgot to add Andy...
>
> Add Pavel ;)
>
> 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.

Oleg, can you let me know what patch, if any, I should be reviewing?

--Andy
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