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.
prev parent reply other threads:[~2014-07-28 15:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <53D07E96.5000006@oracle.com>
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]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53D66BB1.8080905@linux.intel.com \
--to=dave.hansen@linux.intel.com \
--cc=a.ryabinin@samsung.com \
--cc=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=davej@redhat.com \
--cc=david@fromorbit.com \
--cc=hughd@google.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kirill@shutemov.name \
--cc=koct9i@gmail.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=matthew.r.wilcox@intel.com \
--cc=mgorman@suse.de \
--cc=quning@gmail.com \
--cc=riel@redhat.com \
--cc=sasha.levin@oracle.com \
--cc=stable@vger.kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox