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Re: [PATCH] mm: add gfp_mask parameter to vm_map_ram()

To: Tejun Heo <tj@xxxxxxxxxx>
Subject: Re: [PATCH] mm: add gfp_mask parameter to vm_map_ram()
From: Minchan Kim <minchan@xxxxxxxxxx>
Date: Thu, 14 Jun 2012 11:39:36 +0900
Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>, Dave Chinner <dchinner@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Linux Memory Management List <linux-mm@xxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20120614022132.GA3766@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Newsgroups: gmane.linux.kernel.mm, gmane.linux.file-systems, gmane.linux.kernel
References: <20120612012134.GA7706@localhost> <20120613123932.GA1445@localhost> <20120614012026.GL3019@xxxxxxxxxxxxxxxx> <20120614014902.GB7289@localhost> <4FD94779.3030108@xxxxxxxxxx> <20120614022132.GA3766@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
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On 06/14/2012 11:21 AM, Tejun Heo wrote:

> Hello, guys.
> 
> On Thu, Jun 14, 2012 at 11:07:53AM +0900, Minchan Kim wrote:
>> It shouldn't work because vmap_page_range still can allocate
>> GFP_KERNEL by pud_alloc in vmap_pud_range.  For it, I tried [1] but
>> other mm guys want to add WARNING [2] so let's avoiding gfp context
>> passing.
>>
>> [1] https://lkml.org/lkml/2012/4/23/77
>> [2] https://lkml.org/lkml/2012/5/2/340
> 
> Yeah, vmalloc area doesn't support !GFP_KERNEL allocations and as
> Minchan said, changing this would require updating page table
> allocation functions on all archs.  This is the same reason why percpu
> allocator doesn't support !GFP_KERNEL allocations which in turn made
> blk-throttle implement its own private percpu pool.
> 
> If xfs can't live without GFP_NOFS vmalloc allocations, either it has
> to implement its own pool or maybe it's time to implement !GFP_KERNEL
> allocs for vmalloc area.  I don't know.


There is another example in ARM. 
http://www.spinics.net/lists/arm-kernel/msg179202.html
They try to make pool for atomic vmalloc support. :(
Only GFP_KERNEL support vmalloc spreads out many pools in system, Sigh. 

-- 
Kind regards,
Minchan Kim

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