linux-kernel - Re: [PATCH 09/24] mm/memblock: Add memblock memory allocation apis

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Message-Id: <20131202163136.f31f39c5940c0ba6d20f4a00@linux-foundation.org>
Date:	Mon, 2 Dec 2013 16:31:36 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	<tj@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>, <linux-arm-kernel@...ts.infradead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Grygorii Strashko <grygorii.strashko@...com>
Subject: Re: [PATCH 09/24] mm/memblock: Add memblock memory allocation apis

On Fri, 8 Nov 2013 18:41:45 -0500 Santosh Shilimkar <santosh.shilimkar@...com> wrote:

> Introduce memblock memory allocation APIs which allow to support
> PAE or LPAE extension on 32 bits archs where the physical memory start
> address can be beyond 4GB. In such cases, existing bootmem APIs which
> operate on 32 bit addresses won't work and needs memblock layer which
> operates on 64 bit addresses.
> 
> So we add equivalent APIs so that we can replace usage of bootmem
> with memblock interfaces. Architectures already converted to NO_BOOTMEM
> use these new interfaces and other which still uses bootmem, these new
> APIs just fallback to exiting bootmem APIs. So no functional change as
> such.
> 
> In long run, once all the achitectures moves to NO_BOOTMEM, we can get rid of
> bootmem layer completely. This is one step to remove the core code dependency
> with bootmem and also gives path for architectures to move away from bootmem.
> 
> The proposed interface will became active if both CONFIG_HAVE_MEMBLOCK
> and CONFIG_NO_BOOTMEM are specified by arch. In case !CONFIG_NO_BOOTMEM,
> the memblock() wrappers will fallback to the existing bootmem apis so
> that arch's not converted to NO_BOOTMEM continue to work as is.
> 
> The meaning of MEMBLOCK_ALLOC_ACCESSIBLE and MEMBLOCK_ALLOC_ANYWHERE is
> kept same.
> 
> ...
>
> +static void * __init _memblock_virt_alloc_try_nid_nopanic(
> +				phys_addr_t size, phys_addr_t align,
> +				phys_addr_t from, phys_addr_t max_addr,
> +				int nid)
> +{
> +	phys_addr_t alloc;
> +	void *ptr;
> +
> +	if (WARN_ON_ONCE(slab_is_available())) {
> +		if (nid == MAX_NUMNODES)
> +			return kzalloc(size, GFP_NOWAIT);
> +		else
> +			return kzalloc_node(size, GFP_NOWAIT, nid);
> +	}

The use of MAX_NUMNODES is a bit unconventional here.  I *think* we
generally use NUMA_NO_NODE to indicate "don't care".  I Also *think*
that if this code did s/MAX_NUMNODES/NUMA_NO_NODE/g then the above
simply becomes

	return kzalloc_node(size, GFP_NOWAIT, nid);

and kzalloc_node() handles NUMA_NO_NODE appropriately.

I *think* ;)  Please check all this.


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