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Date: Thu, 10 May 2012 10:11:27 -0500
From: Seth Jennings <sjenning@linux.vnet.ibm.com>
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To: Nitin Gupta <ngupta@vflare.org>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Minchan Kim <minchan@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Magenheimer <dan.magenheimer@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/4] zsmalloc use zs_handle instead of void *
References: <1336027242-372-1-git-send-email-minchan@kernel.org> <1336027242-372-3-git-send-email-minchan@kernel.org> <4FA28907.9020300@vflare.org> <4FA2A2F0.3030509@linux.vnet.ibm.com> <4FA33DF6.8060107@kernel.org> <20120509201918.GA7288@kroah.com> <4FAB21E7.7020703@kernel.org> <20120510140215.GC26152@phenom.dumpdata.com> <4FABD503.4030808@vflare.org>
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On 05/10/2012 09:47 AM, Nitin Gupta wrote:

> On 5/10/12 10:02 AM, Konrad Rzeszutek Wilk wrote:
>> struct zs {
>>     void *ptr;
>> };
>>
>> And pass that structure around?
>>
> 
> A minor problem is that we store this handle value in a radix tree node.
> If we wrap it as a struct, then we will not be able to store it directly
> in the node -- the node will have to point to a 'struct zs'. This will
> unnecessarily waste sizeof(void *) for every object stored.


I don't think so. You can use the fact that for a struct zs var, &var
and &var->ptr are the same.

For the structure above:

void * zs_to_void(struct zs *p) { return p->ptr; }
struct zs * void_to_zs(void *p) { return (struct zs *)p; }

Right?

--
Seth