Date:   Wed, 8 Feb 2023 11:44:42 +0200
From:   Mike Rapoport <rppt@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        HORIGUCHI =?utf-8?B?TkFPWUEo5aCA5Y+jIOebtOS5nyk=?= 
        <naoya.horiguchi@nec.com>, Joe Perches <joe@perches.com>,
        Petr Mladek <pmladek@suse.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>
Subject: Re: [RFC v3 2/4] mm: move PG_slab flag to page_type
Message-ID: <Y+NvCts0JPBmAifu@kernel.org>
References: <20221218101901.373450-1-42.hyeyoo@gmail.com>
 <20221218101901.373450-3-42.hyeyoo@gmail.com>
 <15fda061-72d9-2ee9-0e9f-6f0f732a7382@suse.cz>
 <Y9dI88l2YJZfZ8ny@hyeyoo>
 <Y9dRlNhh6O99tg4E@casper.infradead.org>
 <59630801-42b4-22e8-0ef6-5a5b8636dfbd@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <59630801-42b4-22e8-0ef6-5a5b8636dfbd@redhat.com>
Precedence: bulk

On Fri, Feb 03, 2023 at 05:04:01PM +0100, David Hildenbrand wrote:
> On 30.01.23 06:11, Matthew Wilcox wrote:
> > On Mon, Jan 30, 2023 at 01:34:59PM +0900, Hyeonggon Yoo wrote:
> > > > Seems like quite some changes to page_type to accomodate SLAB, which is
> > > > hopefully going away soon(TM). Could we perhaps avoid that?
> > > 
> > > If it could be done with less changes, I'll try to avoid that.
> > 
> > Let me outline the idea I had for removing PG_slab:
> > 
> > Observe that PG_reserved and PG_slab are mutually exclusive.  Also,
> 
> I recall that there are SetPageReserved() calls on pages allocated via slab.

I did a quick scan, and it seems that all allocated reserved pages come
from alloc_pages() or vmalloc().
 
BTW, looking at the current usage of SetPageReserved, it seems that some
are bogus/historical and some would justify a different page type if we are
to have 15 bits for PG_kernel.

> -- 
> Thanks,
> 
> David / dhildenb

-- 
Sincerely yours,
Mike.