RE: [PATCH 1/5] mm: Refactor do_wp_page, extract the reuse case

[Shachar Raindel <raindel@mellanox.com>]

> -----Original Message-----
> From: Kirill A. Shutemov [mailto:kirill@shutemov.name]
> Sent: Monday, December 01, 2014 2:31 PM
> To: Shachar Raindel
> Cc: linux-mm@kvack.org; kirill.shutemov@linux.intel.com;
> mgorman@suse.de; riel@redhat.com; ak@linux.intel.com;
> matthew.r.wilcox@intel.com; dave.hansen@linux.intel.com; n-
> horiguchi@ah.jp.nec.com; akpm@linux-foundation.org; torvalds@linux-
> foundation.org; Haggai Eran; aarcange@redhat.com; pfeiner@google.com;
> hannes@cmpxchg.org; Sagi Grimberg; walken@google.com
> Subject: Re: [PATCH 1/5] mm: Refactor do_wp_page, extract the reuse case
> 
> On Mon, Dec 01, 2014 at 02:04:41PM +0200, Shachar Raindel wrote:
> > When do_wp_page is ending, in several cases it needs to reuse the
> > existing page. This is achieved by making the page table writable,
> > and possibly updating the page-cache state.
> >
> > Currently, this logic was "called" by using a goto jump. This makes
> > following the control flow of the function harder. It is also
> > against the coding style guidelines for using goto.
> >
> > As the code can easily be refactored into a specialized function,
> > refactor it out and simplify the code flow in do_wp_page.
> >
> > Signed-off-by: Shachar Raindel <raindel@mellanox.com>
> > ---
> >  mm/memory.c | 136 ++++++++++++++++++++++++++++++++++-----------------
> ---------
> >  1 file changed, 78 insertions(+), 58 deletions(-)
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 3e50383..61334e9 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2020,6 +2020,75 @@ static int do_page_mkwrite(struct
> vm_area_struct *vma, struct page *page,
> >  }
> >
> >  /*
> > + * Handle write page faults for pages that can be reused in the
> current vma
> > + *
> > + * This can happen either due to the mapping being with the VM_SHARED
> flag,
> > + * or due to us being the last reference standing to the page. In
> either
> > + * case, all we need to do here is to mark the page as writable and
> update
> > + * any related book-keeping.
> > + */
> > +static int wp_page_reuse(struct mm_struct *mm, struct vm_area_struct
> *vma,
> > +			 unsigned long address, pte_t *page_table,
> > +			 spinlock_t *ptl, pte_t orig_pte,
> > +			 struct page *recycled_page, int dirty_page,
> 
> recycled_page? what's wrong with old_page?
> 

You are reusing the page in this function, so I was feeling that naming it
"old" is less indicative than "recycled". However, if you prefer "old", I
am happy with it.

> Otherwise:
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> 

Thanks :)

--Shachar

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