linux-kernel - Re: [PATCH] mm: add gfp_mask parameter to vm_map

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Date:	Thu, 14 Jun 2012 11:21:32 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Dave Chinner <dchinner@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	xfs@....sgi.com
Subject: Re: [PATCH] mm: add gfp_mask parameter to vm_map_ram()

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.

Thanks.

-- 
tejun
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