linux-kernel - Re: [PATCH v4 RESEND 0/2] Align mmap address for DAX pmd mappings

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Date:   Fri, 9 Sep 2016 17:21:40 +0000
From:   "Kani, Toshimitsu" <toshi.kani@....com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
CC:     "hughd@...gle.com" <hughd@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "mawilcox@...rosoft.com" <mawilcox@...rosoft.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "kirill@...temov.name" <kirill@...temov.name>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>,
        "tytso@....edu" <tytso@....edu>,
        "david@...morbit.com" <david@...morbit.com>,
        "jack@...e.cz" <jack@...e.cz>
Subject: Re: [PATCH v4 RESEND 0/2] Align mmap address for DAX pmd mappings

On Fri, 2016-09-09 at 15:36 +0300, Kirill A. Shutemov wrote:
> On Thu, Sep 08, 2016 at 11:21:46PM +0000, Kani, Toshimitsu wrote:
> > 
> > On Thu, 2016-09-08 at 07:48 -0600, Kani, Toshimitsu wrote:
> > > 
> > > On Thu, 2016-09-08 at 13:57 +0300, Kirill A. Shutemov wrote:
> > > > 
> > > > On Mon, Aug 29, 2016 at 10:00:43PM +0000, Kani, Toshimitsu
> > > > wrote:
> >  :
> > > > > Looking further, these shmem_huge handlings only check pre-
> > > > > conditions.  So, we should be able to make shmem_get_unmapped
> > > > > _are a() as a wrapper, which checks such shmem-specific
> > > > > conitions, and then call __thp_get_unmapped_area() for the
> > > > > actual work.  All DAX-specific checks are performed in
> > > > > thp_get_unmapped_area() as well.  We can make
> > > > >  __thp_get_unmapped_area() as a common
> > > > > function.
> > > > > 
> > > > > I'd prefer to make such change as a separate item,
> > > > 
> > > > Do you have plan to submit such change?
> > > 
> > > Yes, I will submit the change once I finish testing.
> > 
> > I found a bug in the current code, and need some clarification.
> >  The if-statement below is reverted.
> 
> <two-hands-facepalm>
> 
> Yeah. It was repored by Hillf[1]. The fixup got lost. :(
> 
> Could you post a proper patch with the fix?
>
> I would be nice to credit Hillf there too.
> 
> [1] http://lkml.kernel.org/r/054f01d1c86f$2994d5c0$7cbe8140$@alibaba-
> inc.com

Yes, I will submit the fix as well.

I will not change the default value of sbinfo->huge in this fix.  So,
user will have to specify "huge=" option to enable huge page mappings.
 If this is not desireable, we will need a separate patch.

Thanks,
-Toshi