netdev - Re: [net-next][PATCH 1/2] rds: handle unsupported rdma request to fs dax memory

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Date:   Fri, 26 Apr 2019 10:37:02 +0800
From:   Yanjun Zhu <yanjun.zhu@...cle.com>
To:     Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [net-next][PATCH 1/2] rds: handle unsupported rdma request to fs
 dax memory


On 2019/4/26 8:44, Santosh Shilimkar wrote:
> From: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
>
> RDS doesn't support RDMA on memory apertures that require On Demand
> Paging (ODP), such as FS DAX memory. User applications can try to use
> RDS to perform RDMA over such memories and since it doesn't report any
> failure, it can lead to unexpected issues like memory corruption when
> a couple of out of sync file system operations like ftruncate etc. are
> performed.
>
> The patch adds a check so that such an attempt to RDMA to/from memory
> apertures requiring ODP will fail.
>
> Reviewed-by: Håkon Bugge <haakon.bugge@...cle.com>
> Reviewed-tested-by: Zhu Yanjun <yanjun.zhu@...cle.com>

Thanks a lot. Santosh.

Zhu Yanjun

> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com>
> ---
>   net/rds/rdma.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/rds/rdma.c b/net/rds/rdma.c
> index 182ab84..5010100 100644
> --- a/net/rds/rdma.c
> +++ b/net/rds/rdma.c
> @@ -158,8 +158,9 @@ static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,
>   {
>   	int ret;
>   
> -	ret = get_user_pages_fast(user_addr, nr_pages, write, pages);
> -
> +      /* get_user_pages return -EOPNOTSUPP for fs_dax memory */
> +	ret = get_user_pages_longterm(user_addr, nr_pages,
> +				      write, pages, NULL);
>   	if (ret >= 0 && ret < nr_pages) {
>   		while (ret--)
>   			put_page(pages[ret]);