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Date: Fri, 27 Feb 2009 09:16:50 +0100
From: Johannes Weiner <hannes@...xchg.org>
To: Tejun Heo <tj@...nel.org>
Cc: Ingo Molnar <mingo@...e.hu>, hpa@...or.com, mingo@...hat.com,
tglx@...utronix.de, linux-kernel@...r.kernel.org,
linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/percpu] bootmem: clean up arch-specific bootmem wrapping
On Wed, Feb 25, 2009 at 01:52:35PM +0900, Tejun Heo wrote:
> Commit c132937556f56ee4b831ef4b23f1846e05fde102 tried to clean up
> bootmem arch wrapper but it wasn't quite correct. Before the commit,
> the followings were broken.
>
> * Low level interface functions prefixed with __ ignored arch
> preference.
>
> * reserve_bootmem(...) can't be mapped into
> reserve_bootmem_node(NODE_DATA(0)->bdata, ...) because the node is
> not preference here. The region specified MUST fall into the
> specified region; otherwise, it will panic.
>
> After the commit,
>
> * If allocation fails for the arch preferred node, it should fallback
> to whatever is available. Instead, it simply failed allocation.
>
> There are too many internal details to allow generic wrapping and
> still keep things simple for archs. Plus, all that arch wants is a
> way to prefer certain node over another.
>
> This patch drops the generic wrapping around alloc_bootmem_core() and
> add alloc_bootmem_core() instead. If necessary, arch can define
> bootmem_arch_referred_node() macro or function which takes all
> allocation information and returns the preferred node. bootmem
> generic code will always try the preferred node first and then
> fallback to other nodes as usual.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Johannes Weiner <hannes@...xchg.org>
> ---
> It turns out reserve_bootmem() shouldn't be wrapped in the first
> place. I hope I got it right this time. Can you please review this
> one? And I didn't think your comment was rude at all, no worries.
You are right! Sorry, I missed that. Yes, reserve_bootmem() operates
on ranges disregarding nodes.
> arch/x86/include/asm/mmzone_32.h | 8 +-----
> mm/bootmem.c | 45 ++++++++++++++++++++++++++-------------
> 2 files changed, 32 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
> index eeacf67..ede6998 100644
> --- a/arch/x86/include/asm/mmzone_32.h
> +++ b/arch/x86/include/asm/mmzone_32.h
> @@ -92,12 +92,8 @@ static inline int pfn_valid(int pfn)
>
> #ifdef CONFIG_NEED_MULTIPLE_NODES
> /* always use node 0 for bootmem on this numa platform */
> -#define alloc_bootmem_core(__bdata, size, align, goal, limit) \
> -({ \
> - bootmem_data_t __maybe_unused * __abm_bdata_dummy = (__bdata); \
> - __alloc_bootmem_core(NODE_DATA(0)->bdata, \
> - (size), (align), (goal), (limit)); \
> -})
> +#define bootmem_arch_preferred_node(__bdata, size, align, goal, limit) \
> + (NODE_DATA(0)->bdata)
> #endif /* CONFIG_NEED_MULTIPLE_NODES */
>
> #endif /* _ASM_X86_MMZONE_32_H */
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index d7140c0..daf9271 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -37,16 +37,6 @@ static struct list_head bdata_list __initdata = LIST_HEAD_INIT(bdata_list);
>
> static int bootmem_debug;
>
> -/*
> - * If an arch needs to apply workarounds to bootmem allocation, it can
> - * set CONFIG_HAVE_ARCH_BOOTMEM and define a wrapper around
> - * __alloc_bootmem_core().
> - */
> -#ifndef CONFIG_HAVE_ARCH_BOOTMEM
> -#define alloc_bootmem_core(bdata, size, align, goal, limit) \
> - __alloc_bootmem_core((bdata), (size), (align), (goal), (limit))
> -#endif
> -
> static int __init bootmem_debug_setup(char *buf)
> {
> bootmem_debug = 1;
> @@ -436,9 +426,9 @@ static unsigned long align_off(struct bootmem_data *bdata, unsigned long off,
> return ALIGN(base + off, align) - base;
> }
>
> -static void * __init __alloc_bootmem_core(struct bootmem_data *bdata,
> - unsigned long size, unsigned long align,
> - unsigned long goal, unsigned long limit)
> +static void * __init alloc_bootmem_core(struct bootmem_data *bdata,
> + unsigned long size, unsigned long align,
> + unsigned long goal, unsigned long limit)
> {
> unsigned long fallback = 0;
> unsigned long min, max, start, sidx, midx, step;
> @@ -538,17 +528,34 @@ find_block:
> return NULL;
> }
>
> +static void * __init alloc_arch_preferred_bootmem(bootmem_data_t *bdata,
> + unsigned long size, unsigned long align,
> + unsigned long goal, unsigned long limit)
> +{
> +#ifdef CONFIG_HAVE_ARCH_BOOTMEM
> + bootmem_data_t *p_bdata;
> +
> + p_bdata = bootmem_arch_preferred_node(bdata, size, align, goal, limit);
> + if (p_bdata)
> + return alloc_bootmem_core(p_bdata, size, align, goal, limit);
> +#endif
> + return NULL;
> +}
> +
> static void * __init ___alloc_bootmem_nopanic(unsigned long size,
> unsigned long align,
> unsigned long goal,
> unsigned long limit)
> {
> bootmem_data_t *bdata;
> + void *region;
>
> restart:
> - list_for_each_entry(bdata, &bdata_list, list) {
> - void *region;
> + region = alloc_arch_preferred_bootmem(NULL, size, align, goal, limit);
> + if (region)
> + return region;
>
> + list_for_each_entry(bdata, &bdata_list, list) {
> if (goal && bdata->node_low_pfn <= PFN_DOWN(goal))
> continue;
> if (limit && bdata->node_min_pfn >= PFN_DOWN(limit))
> @@ -626,6 +633,10 @@ static void * __init ___alloc_bootmem_node(bootmem_data_t *bdata,
> {
> void *ptr;
>
> + ptr = alloc_arch_preferred_bootmem(bdata, size, align, goal, limit);
> + if (ptr)
> + return ptr;
> +
> ptr = alloc_bootmem_core(bdata, size, align, goal, limit);
> if (ptr)
> return ptr;
> @@ -682,6 +693,10 @@ void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size,
> {
> void *ptr;
>
> + ptr = alloc_arch_preferred_bootmem(pgdat->bdata, size, align, goal, 0);
> + if (ptr)
> + return ptr;
> +
> ptr = alloc_bootmem_core(pgdat->bdata, size, align, goal, 0);
> if (ptr)
> return ptr;
Well, okay.
It is a bugfix for preferring the arch node even with the __interface.
But it brings ifdeffery/special casing to bootmem that was before in a
header file and is only for a very rare hardware setup, so I don't
think it is a cleanup, rather a necessity.
For now, let's just go with it.
Acked-by: Johannes Weiner <hannes@...xchg.org>
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