Re: [PATCH] mm: use PageAnon() and PageKsm() helpers in page_anon_vma()

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Wed, Apr 01, 2015 at 12:57:45PM -0700, Andrew Morton wrote:
> On Wed, 1 Apr 2015 14:50:54 +0300 "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
> 
> > >From adc384977898173d65c2567fc5eb421da9b272e0 Mon Sep 17 00:00:00 2001
> > From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> > Date: Wed, 1 Apr 2015 14:33:56 +0300
> > Subject: [PATCH] mm: uninline and cleanup page-mapping related helpers
> > 
> > Most-used page->mapping helper -- page_mapping() -- has already
> > uninlined. Let's uninline also page_rmapping() and page_anon_vma().
> > It saves us depending on configuration around 400 bytes in text:
> > 
> >    text	   data	    bss	    dec	    hex	filename
> >  660318	  99254	 410000	1169572	 11d8a4	mm/built-in.o-before
> >  659854	  99254	 410000	1169108	 11d6d4	mm/built-in.o
> 
> Well, code size isn't the only thing to care about.  Some functions
> really should be inlined for performance reasons even if that makes the
> overall code larger.  But the changes you're proposing here look OK to
> me.
> 
> > As side effect page_anon_vma() now works properly on tail pages.
> 
> Let's fix the bug in a separate patch, please.  One which can be
> backported to earlier kernels if that should be needed.  ie: it should
> precede any uninlining.

The bug is not triggerable in current upsteam. AFAIK, we don't call
page_anon_vma() on tail pages of THP, since we don't map THP with PTEs
yet. For rest of cases we will get NULL, which is valid answer.

Do you still want "page = compound_head(page);" line in separate patch?

-- 
 Kirill A. Shutemov

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