linux-kernel - RE: [PATCH v3 3/3] xen/privcmd: Convert get_user_pages*() to pin_user

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Message-ID: <003a01d658ed$1858e220$490aa660$@xen.org>
Date:   Mon, 13 Jul 2020 09:10:38 +0100
From:   Paul Durrant <xadimgnik@...il.com>
To:     "'Souptick Joarder'" <jrdr.linux@...il.com>,
        <boris.ostrovsky@...cle.com>, <jgross@...e.com>,
        <sstabellini@...nel.org>
Cc:     <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
        "'John Hubbard'" <jhubbard@...dia.com>,
        "'Paul Durrant'" <xadimgnik@...il.com>
Subject: RE: [PATCH v3 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*()

> -----Original Message-----
> From: Souptick Joarder <jrdr.linux@...il.com>
> Sent: 12 July 2020 04:40
> To: boris.ostrovsky@...cle.com; jgross@...e.com; sstabellini@...nel.org
> Cc: xen-devel@...ts.xenproject.org; linux-kernel@...r.kernel.org; Souptick Joarder
> <jrdr.linux@...il.com>; John Hubbard <jhubbard@...dia.com>; Paul Durrant <xadimgnik@...il.com>
> Subject: [PATCH v3 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*()
> 
> In 2019, we introduced pin_user_pages*() and now we are converting
> get_user_pages*() to the new API as appropriate. [1] & [2] could
> be referred for more information. This is case 5 as per document [1].
> 
> [1] Documentation/core-api/pin_user_pages.rst
> 
> [2] "Explicit pinning of user-space pages":
>         https://lwn.net/Articles/807108/
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> Reviewed-by: Juergen Gross <jgross@...e.com>
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Paul Durrant <xadimgnik@...il.com>

Reviewed-by: Paul Durrant <paul@....org>

> ---
>  drivers/xen/privcmd.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 079d35b..63abe6c 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -593,7 +593,7 @@ static int lock_pages(
>  		if (requested > nr_pages)
>  			return -ENOSPC;
> 
> -		page_count = get_user_pages_fast(
> +		page_count = pin_user_pages_fast(
>  			(unsigned long) kbufs[i].uptr,
>  			requested, FOLL_WRITE, pages);
>  		if (page_count < 0)
> @@ -609,13 +609,7 @@ static int lock_pages(
> 
>  static void unlock_pages(struct page *pages[], unsigned int nr_pages)
>  {
> -	unsigned int i;
> -
> -	for (i = 0; i < nr_pages; i++) {
> -		if (!PageDirty(pages[i]))
> -			set_page_dirty_lock(pages[i]);
> -		put_page(pages[i]);
> -	}
> +	unpin_user_pages_dirty_lock(pages, nr_pages, true);
>  }
> 
>  static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> --
> 1.9.1