linux-kernel - Re: [PATCH] z3fold: the 3-fold allocator for compressed pages

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] [day] [month] [year] [list]

Date:	Thu, 14 Apr 2016 20:21:36 +0200
From:	Vitaly Wool <vitalywool@...il.com>
To:	Seth Jennings <sjenning@...hat.com>
Cc:	Vlastimil Babka <vbabka@...e.cz>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Streetman <ddstreet@...e.org>
Subject: Re: [PATCH] z3fold: the 3-fold allocator for compressed pages

>> On Thu, Apr 14, 2016 at 5:53 PM, Seth Jennings <sjenning@...hat.com> wrote:

<snip>
>>> This also means that the unbuddied list is broken in this
>>> implementation.  num_free_chunks() is calculating the _total_ free
>>> space in the page.  But that is not that the _usable_ free space by a
>>> single object, if the middle object has partitioned that free space.
>>
>> Once again, there is the code in z3fold_free() that makes sure the
>> free space within the page is contiguous so I don't think the
>> unbuddied list is, or will be, broken.
>
> Didn't see the relocation before.  However, that brings up another
> question.  How is the code moving objects when the location of that
> object is encoded in the handle that has already been given to the
> user?

Relocation is only necessary when there is one remaining object and it
is in the middle. In that case the 'first_num' variable is incremented
so its handle already given to user will be resolved as the first
object and not the middle.

~vitaly