linux-kernel - Re: [PATCH 01/16] mm: use untagged_addr() for get_user_pages

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Message-ID: <9145f3f9-4e14-df6a-87f5-663ad197e96e@oracle.com>
Date:   Tue, 11 Jun 2019 13:22:33 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Christoph Hellwig <hch@....de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-mips@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/16] mm: use untagged_addr() for get_user_pages_fast
 addresses

On 6/11/19 8:40 AM, Christoph Hellwig wrote:
> This will allow sparc64 to override its ADI tags for
> get_user_pages and get_user_pages_fast.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---

Commit message is sparc64 specific but the goal here is to allow any
architecture with memory tagging to use this. So I would suggest
rewording the commit log. Other than that:

Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>

>  mm/gup.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index ddde097cf9e4..6bb521db67ec 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2146,7 +2146,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>  	unsigned long flags;
>  	int nr = 0;
>  
> -	start &= PAGE_MASK;
> +	start = untagged_addr(start) & PAGE_MASK;
>  	len = (unsigned long) nr_pages << PAGE_SHIFT;
>  	end = start + len;
>  
> @@ -2219,7 +2219,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages,
>  	unsigned long addr, len, end;
>  	int nr = 0, ret = 0;
>  
> -	start &= PAGE_MASK;
> +	start = untagged_addr(start) & PAGE_MASK;
>  	addr = start;
>  	len = (unsigned long) nr_pages << PAGE_SHIFT;
>  	end = start + len;
>