linux-kernel - Re: [PATCH 3/6] mm/gup: make __gup_longterm

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Date:   Wed, 2 Dec 2020 08:33:12 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, vbabka@...e.cz, mhocko@...e.com,
        david@...hat.com, osalvador@...e.de, dan.j.williams@...el.com,
        sashal@...nel.org, tyhicks@...ux.microsoft.com,
        iamjoonsoo.kim@....com, mike.kravetz@...cle.com,
        rostedt@...dmis.org, mingo@...hat.com, jgg@...pe.ca,
        peterz@...radead.org, mgorman@...e.de, willy@...radead.org,
        rientjes@...gle.com, jhubbard@...dia.com
Subject: Re: [PATCH 3/6] mm/gup: make __gup_longterm_locked common

On Wed, Dec 02, 2020 at 08:31:45AM -0800, 'Ira Weiny' wrote:
> On Wed, Dec 02, 2020 at 12:23:27AM -0500, Pavel Tatashin wrote:
> > __gup_longterm_locked() has CMA || FS_DAX version and a common stub
> > version. In the preparation of prohibiting longterm pinning of pages from
> > movable zone make the CMA || FS_DAX version common, and delete the stub
> > version.
> > 
> > Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> > ---
> >  mm/gup.c | 13 -------------
> >  1 file changed, 13 deletions(-)
> > 
> > diff --git a/mm/gup.c b/mm/gup.c
> > index 3a76c005a3e2..0e2de888a8b0 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1567,7 +1567,6 @@ struct page *get_dump_page(unsigned long addr)
> >  }
> >  #endif /* CONFIG_ELF_CORE */
> >  
> > -#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
> >  #ifdef CONFIG_FS_DAX
> >  static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
> >  {
> > @@ -1757,18 +1756,6 @@ static long __gup_longterm_locked(struct mm_struct *mm,
> >  		kfree(vmas_tmp);
> >  	return rc;
> >  }
> 
> Isn't this going to potentially allocate vmas_tmp only to not need it when
> !FS_DAX and !CMA?

To clarify, when FOLL_LONGTERM is set...

IRa

> 
> Ira
> 
> > -#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
> > -static __always_inline long __gup_longterm_locked(struct mm_struct *mm,
> > -						  unsigned long start,
> > -						  unsigned long nr_pages,
> > -						  struct page **pages,
> > -						  struct vm_area_struct **vmas,
> > -						  unsigned int flags)
> > -{
> > -	return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
> > -				       NULL, flags);
> > -}
> > -#endif /* CONFIG_FS_DAX || CONFIG_CMA */
> >  
> >  static bool is_valid_gup_flags(unsigned int gup_flags)
> >  {
> > -- 
> > 2.25.1
> > 
> > 
>