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Message-ID: <abe0c086-8c5a-d6fb-63c4-bf75528d0ec5@huawei.com>
Date: Fri, 4 Aug 2017 11:02:46 +0300
From: Igor Stoppa <igor.stoppa@...wei.com>
To: Michal Hocko <mhocko@...nel.org>
CC: Jerome Glisse <jglisse@...hat.com>, Linux-MM <linux-mm@...ck.org>,
LKML
<linux-kernel@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Kees Cook <keescook@...gle.com>
Subject: Re: [RFC] Tagging of vmalloc pages for supporting the pmalloc
allocator
On 03/08/17 18:15, Michal Hocko wrote:
> I would check the one where we have mapping. It is rather unlikely
> vmalloc users would touch this one.
That was also the initial recommendation from Jerome Glisse, but it
seemed unusable, because of the related comment.
I should have asked for clarifications back then :-(
But it's never too late ...
struct page {
/* First double word block */
unsigned long flags; /* Atomic flags, some possibly
* updated asynchronously */
union {
struct address_space *mapping; /* If low bit clear, points to
* inode address_space, or NULL.
* If page mapped as anonymous
* memory, low bit is set, and
* it points to anon_vma object:
* see PAGE_MAPPING_ANON below.
*/
...
}
mapping seems to be used exclusively in 2 ways, based on the value of
its lower bit.
Therefore I discarded it as valid option ("private", otoh was far more
alluring), but maybe I could wrap it inside a union, together with vm_area?
---
thanks, igor
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