linux-kernel - Re: [PATCH 2/2] fs/aio.c: use get_user_pages_non_movable() to pin ring pages when support memory hotremove

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Date:	Mon, 04 Feb 2013 10:18:03 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Lin Feng <linfeng@...fujitsu.com>
Cc:	akpm@...ux-foundation.org, mgorman@...e.de, bcrl@...ck.org,
	viro@...iv.linux.org.uk, khlebnikov@...nvz.org, walken@...gle.com,
	kamezawa.hiroyu@...fujitsu.com, minchan@...nel.org,
	riel@...hat.com, rientjes@...gle.com,
	isimatu.yasuaki@...fujitsu.com, wency@...fujitsu.com,
	laijs@...fujitsu.com, jiang.liu@...wei.com, linux-mm@...ck.org,
	linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] fs/aio.c: use get_user_pages_non_movable() to pin ring pages when support memory hotremove

Lin Feng <linfeng@...fujitsu.com> writes:

> This patch gets around the aio ring pages can't be migrated bug caused by
> get_user_pages() via using the new function. It only works as configed with
> CONFIG_MEMORY_HOTREMOVE, otherwise it uses the old version of get_user_pages().
>
> Cc: Benjamin LaHaise <bcrl@...ck.org>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Reviewed-by: Tang Chen <tangchen@...fujitsu.com>
> Reviewed-by: Gu Zheng <guz.fnst@...fujitsu.com>
> Signed-off-by: Lin Feng <linfeng@...fujitsu.com>
> ---
>  fs/aio.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 71f613c..0e9b30a 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -138,9 +138,15 @@ static int aio_setup_ring(struct kioctx *ctx)
>  	}
>  
>  	dprintk("mmap address: 0x%08lx\n", info->mmap_base);
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +	info->nr_pages = get_user_pages_non_movable(current, ctx->mm,
> +					info->mmap_base, nr_pages,
> +					1, 0, info->ring_pages, NULL);
> +#else
>  	info->nr_pages = get_user_pages(current, ctx->mm,
>  					info->mmap_base, nr_pages, 
>  					1, 0, info->ring_pages, NULL);
> +#endif

Can't you hide this in your 1/1 patch, by providing this function as
just a static inline wrapper around get_user_pages when
CONFIG_MEMORY_HOTREMOVE is not enabled?

Cheers,
Jeff
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