linux-kernel - Re: [PATCH] mmap: allow MAP_HUGETLB for hugetlbfs files v2

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Date:	Thu, 20 Jun 2013 09:31:45 +0800
From:	Jianguo Wu <wujianguo@...wei.com>
To:	Jörn Engel <joern@...fs.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mmap: allow MAP_HUGETLB for hugetlbfs files v2

Hi Joern,

I cannot apply this patch to Linus tree, as the code has been modified since
commit af73e4d9506d ("hugetlbfs: fix mmap failure in unaligned size request").

Thanks,
Jianguo Wu

On 2013/6/20 0:25, Jörn Engel wrote:

> It is counterintuitive at best that mmap'ing a hugetlbfs file with
> MAP_HUGETLB fails, while mmap'ing it without will a) succeed and b)
> return huge pages.
> v2: use is_file_hugepages(), as suggested by Jianguo
> 
> Signed-off-by: Joern Engel <joern@...fs.org>
> Cc: Jianguo Wu <wujianguo@...wei.com>
> ---
>  mm/mmap.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 2a594246..cdc8e7a 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1322,11 +1322,12 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
>  
>  	if (!(flags & MAP_ANONYMOUS)) {
>  		audit_mmap_fd(fd, flags);
> -		if (unlikely(flags & MAP_HUGETLB))
> -			return -EINVAL;
>  		file = fget(fd);
>  		if (!file)
>  			goto out;
> +		retval = -EINVAL;
> +		if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
> +			goto out_fput;
>  	} else if (flags & MAP_HUGETLB) {
>  		struct user_struct *user = NULL;
>  		/*
> @@ -1346,6 +1347,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
>  	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
>  
>  	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
> +out_fput:
>  	if (file)
>  		fput(file);
>  out:



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