linux-kernel - Re: [PATCH] block: initialize the bounce pool if high memory may be added later

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Message-ID: <4EA03DDC.9070808@citrix.com>
Date:	Thu, 20 Oct 2011 16:27:24 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] block: initialize the bounce pool if high memory may
 be added later

On 11/10/11 12:53, David Vrabel wrote:
> init_emergency_pool() does not create the page pool for bouncing block
> requests if the current count of high pages is zero.  If high memory
> may be added later (either via memory hotplug or a balloon driver in a
> virtualized system) then a oops occurs if a request with a high page
> need bouncing because the pool does not exist.
> 
> So, always create the pool if memory hotplug is enabled and change the
> test so it's valid even if all high pages are currently in the balloon
> (the balloon drivers adjust totalhigh_pages but not max_pfn).

Jens, you don't seem to have picked up this patch yet.  Should it have
gone via Andrew Morton instead?

David

> Signed-off-by: David Vrabel <david.vrabel@...rix.com>
> ---
>  mm/bounce.c |    9 ++++-----
>  1 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/bounce.c b/mm/bounce.c
> index 1481de6..434fb4f 100644
> --- a/mm/bounce.c
> +++ b/mm/bounce.c
> @@ -14,6 +14,7 @@
>  #include <linux/init.h>
>  #include <linux/hash.h>
>  #include <linux/highmem.h>
> +#include <linux/bootmem.h>
>  #include <asm/tlbflush.h>
>  
>  #include <trace/events/block.h>
> @@ -26,12 +27,10 @@ static mempool_t *page_pool, *isa_page_pool;
>  #ifdef CONFIG_HIGHMEM
>  static __init int init_emergency_pool(void)
>  {
> -	struct sysinfo i;
> -	si_meminfo(&i);
> -	si_swapinfo(&i);
> -
> -	if (!i.totalhigh)
> +#ifndef CONFIG_MEMORY_HOTPLUG
> +	if (max_pfn <= max_low_pfn)
>  		return 0;
> +#endif
>  
>  	page_pool = mempool_create_page_pool(POOL_SIZE, 0);
>  	BUG_ON(!page_pool);

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