Subject: Re: [PATCH v3 1/6] mm: add definition of PMD_PAGE_ORDER

From: Mike Rapoport <[email-masked]>
Date: Thu, 6 Aug 2020 14:10:36 +0300

On Thu, Aug 06, 2020 at 01:11:12PM +0300, Kirill A. Shutemov wrote:
> On Tue, Aug 04, 2020 at 12:50:30PM +0300, Mike Rapoport wrote:
> > From: Mike Rapoport <[email-masked]>
> > 
> > The definition of PMD_PAGE_ORDER denoting the number of base pages in the
> > second-level leaf page is already used by DAX and maybe handy in other
> > cases as well.
> > 
> > Several architectures already have definition of PMD_ORDER as the size of
> > second level page table, so to avoid conflict with these definitions use
> > PMD_PAGE_ORDER name and update DAX respectively.
> > 
> > Signed-off-by: Mike Rapoport <[email-masked]>
> > ---
> >  fs/dax.c                | 10 +++++-----
> >  include/linux/pgtable.h |  3 +++
> >  2 files changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 11b16729b86f..b91d8c8dda45 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -50,7 +50,7 @@ static inline unsigned int pe_order(enum page_entry_size pe_size)
> >  #define PG_PMD_NR	(PMD_SIZE >> PAGE_SHIFT)
> >  
> >  /* The order of a PMD entry */
> > -#define PMD_ORDER	(PMD_SHIFT - PAGE_SHIFT)
> > +#define PMD_PAGE_ORDER	(PMD_SHIFT - PAGE_SHIFT)
> 
> Hm. Wouldn't it conflict with definition in pgtable.h? Or should we
> include it instead?

Actually I meant to remove it here and keep only the definition in
pgtable.h.
Will fix.

> > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > index 56c1e8eb7bb0..79f8443609e7 100644
> > --- a/include/linux/pgtable.h
> > +++ b/include/linux/pgtable.h
> > @@ -28,6 +28,9 @@
> >  #define USER_PGTABLES_CEILING	0UL
> >  #endif
> >  
> > +/* Number of base pages in a second level leaf page */
> > +#define PMD_PAGE_ORDER	(PMD_SHIFT - PAGE_SHIFT)
> > +
> >  /*
> >   * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
> >   *
> 
> -- 
>  Kirill A. Shutemov

-- 
Sincerely yours,
Mike.

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