linux-kernel - Re: About get_page for compound page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 20 Jul 2007 07:59:53 +0800
From:	"Fengwei Yin" <yfw.kernel@...il.com>
To:	"Peter Zijlstra" <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: About get_page for compound page

On 7/20/07, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2007-07-19 at 23:54 +0800, Fengwei Yin wrote:
> > Hi,
> > In get_page(), the parameter page is changed by
> >          page = compound_head(page);
> > if the page is not the first page of compound pages.
> >
> > My question: is this behavior correct?
>
> Yes it is, in general the page state of a compound page is kept in the
> first page of the set.
>
Yes. I know this. But
static inline void get_page(struct page *page)
                                                     ~~~~~~ changed by
this function.
{
         page = compound_head(page);
                    ~~~~~~~~~~~~~~~~~~~~~~~
         VM_BUG_ON(atomic_read(&page->_count) == 0);
         atomic_inc(&page->_count);
}

As I understand, just need update the first page reference count.
Or the caller aware of this bahavior?

Or change it to
static inline void get_page(struct page *page)
{
         struct page *head_page = compound_head(page);
         VM_BUG_ON(atomic_read(&head_page->_count) == 0);
         atomic_inc(&head_page->_count);
}

Regards
Yin, Fengwei
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/