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Date: Mon, 18 Jul 2016 14:51:50 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: David Rientjes <rientjes@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mem-hotplug: use GFP_HIGHUSER_MOVABLE in,
 alloc_migrate_target()
Message-ID: <20160718055150.GF9460@js1304-P5Q-DELUXE>
References: <57884EAA.9030603@huawei.com>
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On Fri, Jul 15, 2016 at 10:47:06AM +0800, Xishi Qiu wrote:
> alloc_migrate_target() is called from migrate_pages(), and the page
> is always from user space, so we can add __GFP_HIGHMEM directly.

No, all migratable pages are not from user space. For example,
blockdev file cache has __GFP_MOVABLE and migratable but it has no
__GFP_HIGHMEM and __GFP_USER.

And, zram's memory isn't GFP_HIGHUSER_MOVABLE but has __GFP_MOVABLE.

Thanks.

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Date: Mon, 18 Jul 2016 14:51:50 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 1/2] mem-hotplug: use GFP_HIGHUSER_MOVABLE in,
 alloc_migrate_target()
Message-ID: <20160718055150.GF9460@js1304-P5Q-DELUXE>
References: <57884EAA.9030603@huawei.com>
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To: Xishi Qiu <qiuxishi@huawei.com>
Cc: David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>

On Fri, Jul 15, 2016 at 10:47:06AM +0800, Xishi Qiu wrote:
> alloc_migrate_target() is called from migrate_pages(), and the page
> is always from user space, so we can add __GFP_HIGHMEM directly.

No, all migratable pages are not from user space. For example,
blockdev file cache has __GFP_MOVABLE and migratable but it has no
__GFP_HIGHMEM and __GFP_USER.

And, zram's memory isn't GFP_HIGHUSER_MOVABLE but has __GFP_MOVABLE.

Thanks.

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