lkml.org 
[lkml]   [2018]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 3/5] x86: pgtable: Drop pXd_none() checks from pXd_free_pYd_table()
Date
On Mon, 2018-09-17 at 12:33 +0100, Will Deacon wrote:
> On Fri, Sep 14, 2018 at 08:37:48PM +0000, Kani, Toshi wrote:
> > On Wed, 2018-09-12 at 11:26 +0100, Will Deacon wrote:
> > > Now that the core code checks this for us, we don't need to do it in the
> > > backend.
> > >
> > > Cc: Chintan Pandya <cpandya@codeaurora.org>
> > > Cc: Toshi Kani <toshi.kani@hpe.com>
> > > Cc: Thomas Gleixner <tglx@linutronix.de>
> > > Cc: Michal Hocko <mhocko@suse.com>
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > Signed-off-by: Will Deacon <will.deacon@arm.com>
> > > ---
> > > arch/x86/mm/pgtable.c | 6 ------
> > > 1 file changed, 6 deletions(-)
> > >
> > > diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> > > index ae394552fb94..b4919c44a194 100644
> > > --- a/arch/x86/mm/pgtable.c
> > > +++ b/arch/x86/mm/pgtable.c
> > > @@ -796,9 +796,6 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
> > > pte_t *pte;
> > > int i;
> > >
> > > - if (pud_none(*pud))
> > > - return 1;
> > > -
> >
> > Do we need to remove this safe guard? I feel list this is same as
> > kfree() accepting NULL.
>
> I think two big differences with kfree() are (1) that this function has
> exactly one caller in the tree and (2) it's implemented per-arch. Therefore
> we're in a good position to give it some simple semantics and implement
> those. Of course, if the x86 people would like to keep the redundant check,
> that's up to them, but I think it makes the function more confusing and
> tempts people into calling it for present entries.

With patch 1/5 change to have pXd_present() check, I agree that we can
remove this pXd_none() check to avoid any confusion.

Reviewed-by: Toshi Kani <toshi.kani@hpe.com>

Thanks,
-Toshi

\
 
 \ /
  Last update: 2018-09-17 20:43    [W:0.090 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site