linux-kernel - RE: [PATCH RESEND] rapidio: use get_user_pages

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Date:   Wed, 25 Jan 2017 14:35:29 +0000
From:   "Bounine, Alexandre" <Alexandre.Bounine@....com>
To:     Lorenzo Stoakes <lstoakes@...il.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matt Porter <mporter@...nel.crashing.org>
Subject: RE: [PATCH RESEND] rapidio: use get_user_pages_unlocked()

Acked-by: Alexandre Bounine <alexandre.bounine@....com>

> -----Original Message-----
> From: Lorenzo Stoakes [mailto:lstoakes@...il.com]
> Sent: Tuesday, January 03, 2017 3:50 PM
> To: Matt Porter; Bounine, Alexandre
> Cc: linux-mm@...ck.org; linux-kernel@...r.kernel.org; Andrew Morton;
> Lorenzo Stoakes
> Subject: [PATCH RESEND] rapidio: use get_user_pages_unlocked()
> 
> Moving from get_user_pages() to get_user_pages_unlocked() simplifies
> the code
> and takes advantage of VM_FAULT_RETRY functionality when faulting in
> pages.
> 
> Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
> ---
>  drivers/rapidio/devices/rio_mport_cdev.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/rapidio/devices/rio_mport_cdev.c
> b/drivers/rapidio/devices/rio_mport_cdev.c
> index 9013a585507e..50b617af81bd 100644
> --- a/drivers/rapidio/devices/rio_mport_cdev.c
> +++ b/drivers/rapidio/devices/rio_mport_cdev.c
> @@ -889,17 +889,16 @@ rio_dma_transfer(struct file *filp, u32
> transfer_mode,
>  			goto err_req;
>  		}
> 
> -		down_read(&current->mm->mmap_sem);
> -		pinned = get_user_pages(
> +		pinned = get_user_pages_unlocked(
>  				(unsigned long)xfer->loc_addr & PAGE_MASK,
>  				nr_pages,
> -				dir == DMA_FROM_DEVICE ? FOLL_WRITE : 0,
> -				page_list, NULL);
> -		up_read(&current->mm->mmap_sem);
> +				page_list,
> +				dir == DMA_FROM_DEVICE ? FOLL_WRITE : 0);
> 
>  		if (pinned != nr_pages) {
>  			if (pinned < 0) {
> -				rmcd_error("get_user_pages err=%ld", pinned);
> +				rmcd_error("get_user_pages_unlocked err=%ld",
> +					   pinned);
>  				nr_pages = 0;
>  			} else
>  				rmcd_error("pinned %ld out of %ld pages",
> --
> 2.11.0