Date: Tue, 21 Mar 2017 20:10:05 +0900
From: Minchan Kim <minchan@kernel.org>
To: <js1304@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        <linux-kernel@vger.kernel.org>, <kernel-team@lge.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 1/4] mm/zsmalloc: always set movable/highmem flag to the
 zspage
Message-ID: <20170321111005.GA28016@bbox>
References: <1489632398-31501-1-git-send-email-iamjoonsoo.kim@lge.com>
 <1489632398-31501-2-git-send-email-iamjoonsoo.kim@lge.com>
MIME-Version: 1.0
In-Reply-To: <1489632398-31501-2-git-send-email-iamjoonsoo.kim@lge.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 990
Lines: 19

Hi Joonsoo,

On Thu, Mar 16, 2017 at 11:46:35AM +0900, js1304@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> Zspage is always movable and is used through zs_map_object() function
> which returns directly accessible pointer that contains content of
> zspage. It is independent on the user's allocation flag.
> Therefore, it's better to always set movable/highmem flag to the zspage.
> After that, we don't need __GFP_MOVABLE/__GFP_HIGHMEM clearing in
> cache_alloc_handle()/cache_alloc_zspage() since there is no zs_malloc
> caller who specifies __GFP_MOVABLE/__GFP_HIGHMEM.

Hmm, I wanted this when you pointed out to me firstly but when I think
again, I don't see it's improvement. Sorry for that.
The zs_malloc is exported symbol and it has gfp_t argument so user can
do whatever he want with any zone modifiers flags. IOW, if someuser want
to allocate pages from {normal|dma} zone by whatever reason, he can
omit __GFP_HIGHMEM from the gfp flag to fullfill the goal.