From: Dave Hansen <dave.hansen@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>,
Andrey Ryabinin <a.ryabinin@samsung.com>,
Sasha Levin <sasha.levin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andi Kleen <ak@linux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>, Ning Qu <quning@gmail.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Dave Jones <davej@redhat.com>,
stable@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Konstantin Khlebnikov <koct9i@gmail.com>,
Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH] mm: don't allow fault_around_bytes to be 0
Date: Mon, 28 Jul 2014 08:26:41 -0700 [thread overview]
Message-ID: <53D66BB1.8080905@linux.intel.com> (raw)
In-Reply-To: <20140728093611.GA3975@node.dhcp.inet.fi>
On 07/28/2014 02:36 AM, Kirill A. Shutemov wrote:
> +++ b/mm/memory.c
> @@ -2786,7 +2786,8 @@ static int fault_around_bytes_set(void *data, u64 val)
> {
> if (val / PAGE_SIZE > PTRS_PER_PTE)
> return -EINVAL;
> - fault_around_bytes = val;
> + /* rounddown_pow_of_two(0) is not defined */
> + fault_around_bytes = max(val, PAGE_SIZE);
> return 0;
> }
It's also possible to race and have fault_around_bytes change between
when fault_around_mask() and fault_around_pages() are called so that
they don't match any more. The min()/max() in do_fault_around() should
keep this from doing anything _too_ nasty, but it's worth thinking about
at least.
The safest thing to do might be to use an ACCESS_ONCE() at the beginning
of do_fault_around() for fault_around_bytes and generate
fault_around_mask() from the ACCESS_ONCE() result.
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next prev parent reply other threads:[~2014-07-28 15:26 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 19:53 [PATCHv3 0/2] mm: map few pages around fault address if they are in page cache Kirill A. Shutemov
2014-02-27 19:53 ` [PATCHv3 1/2] mm: introduce vm_ops->map_pages() Kirill A. Shutemov
2014-02-27 21:59 ` Dave Hansen
2014-02-27 22:06 ` Linus Torvalds
2014-02-27 22:34 ` Dave Hansen
2014-02-28 0:18 ` Kirill A. Shutemov
2014-02-28 11:50 ` Benjamin Herrenschmidt
2014-02-27 22:08 ` Andrew Morton
2014-03-03 23:16 ` Andrew Morton
2014-03-04 1:26 ` Kirill A. Shutemov
2014-03-05 0:04 ` Rusty Russell
2014-03-05 20:02 ` Andrew Morton
2014-07-24 3:33 ` Sasha Levin
2014-07-24 6:53 ` Andrey Ryabinin
2014-07-24 12:48 ` Sasha Levin
2014-07-24 13:05 ` Sasha Levin
2014-07-24 13:30 ` Konstantin Khlebnikov
2014-07-28 7:43 ` [PATCH] mm: don't allow fault_around_bytes to be 0 Andrey Ryabinin
2014-07-28 7:47 ` Andrey Ryabinin
2014-07-28 9:36 ` Kirill A. Shutemov
2014-07-28 10:27 ` Andrey Ryabinin
2014-07-28 10:52 ` Kirill A. Shutemov
2014-07-28 12:32 ` Sasha Levin
2014-07-28 22:43 ` David Rientjes
2014-07-28 15:26 ` Dave Hansen [this message]
2014-02-27 19:53 ` [PATCHv3 2/2] mm: implement ->map_pages for page cache Kirill A. Shutemov
2014-02-27 21:47 ` Andrew Morton
2014-02-28 0:31 ` Kirill A. Shutemov
2014-04-02 18:03 ` Konstantin Khlebnikov
2014-04-02 19:07 ` Kirill A. Shutemov
2014-02-27 21:28 ` [PATCHv3 0/2] mm: map few pages around fault address if they are in " Linus Torvalds
2014-02-28 0:10 ` Kirill A. Shutemov
2014-02-28 3:52 ` Wilcox, Matthew R
2014-02-28 23:08 ` Linus Torvalds
2014-03-12 14:22 ` Kirill A. Shutemov
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