linux-kernel - Re: [PATCH] PM: HIBERNATION: skip the swap size check if the snapshot image size is anticipative

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Date:	Fri, 4 Nov 2011 23:29:45 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Barry Song <Barry.Song@....com>
Cc:	linux-pm@...ts.linux-foundation.org, pavel@....cz,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Barry Song <Baohua.Song@....com>,
	Xiangzhen Ye <Xiangzhen.Ye@....com>
Subject: Re: [PATCH] PM: HIBERNATION: skip the swap size check if the snapshot image size is anticipative

On Friday, November 04, 2011, Barry Song wrote:
> From: Barry Song <Baohua.Song@....com>
> 
> Current swsusp requires swap partitions even larger than real saved pages
> due to the worst compress ratio:
> but for an embedded system, which has limited storage space, then it might
> can't give the big size partition to save snapshot.
> In the another way, some embedded systems can definitely know the most size
> needed for snapshot since they run some specific application lists.
> So this patch provides the possibility for bootloader to tell kernel even
> the system has a little snapshot partition, but it is still enough.
> For example, if the system need to save 120MB memory, origin swsusp will require
> a 130MB partition to save snapshot. but if users know 30MB is enough for them(
> compressed image will be less than 30MB), they just make a 30MB partition.
> 
> Signed-off-by: Barry Song <Baohua.Song@....com>
> Cc: Xiangzhen Ye <Xiangzhen.Ye@....com>

I'm considering this as 3.3 material, so I'll take care of it after the current
merge window closes.

Thanks,
Rafael


> ---
>  this is another patch after I provide resumewait/resumedelay kernel params
>  to make swsusp support embedded systems better.
>  This patch is tested on CSR SiRFprimaII platform.
> 
>  Documentation/kernel-parameters.txt |    7 +++++++
>  kernel/power/swap.c                 |   13 +++++++++++++
>  2 files changed, 20 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index a0c5c5f..2ad2e9c 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2277,6 +2277,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  			in <PAGE_SIZE> units (needed only for swap files).
>  			See  Documentation/power/swsusp-and-swap-files.txt
>  
> +	swapenough	[SWSUSP]
> +			Tell kernel the swap partition size is enough and let kernel
> +			skip checking whether the swap partition has enough size to
> +			save snapshot.
> +			It is used for embedded systems, typically using NAND and SD
> +			card, which have not large space.
> +
>  	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
>  			read the resume files
>  
> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> index 11a594c..97c30b5 100644
> --- a/kernel/power/swap.c
> +++ b/kernel/power/swap.c
> @@ -36,6 +36,8 @@
>  
>  #define HIBERNATE_SIG	"S1SUSPEND"
>  
> +static int swapenough;
> +
>  /*
>   *	The swap map is a data structure used for keeping track of each page
>   *	written to a swap partition.  It consists of many swap_map_page
> @@ -772,6 +774,9 @@ static int enough_swap(unsigned int nr_pages, unsigned int flags)
>  	unsigned int free_swap = count_swap_pages(root_swap, 1);
>  	unsigned int required;
>  
> +	if (swapenough)
> +		return 1;
> +
>  	pr_debug("PM: Free swap pages: %u\n", free_swap);
>  
>  	required = PAGES_FOR_IO + ((flags & SF_NOCOMPRESS_MODE) ?
> @@ -1449,3 +1454,11 @@ static int swsusp_header_init(void)
>  }
>  
>  core_initcall(swsusp_header_init);
> +
> +static int __init swapenough_setup(char *str)
> +{
> +	swapenough = 1;
> +	return 1;
> +}
> +
> +__setup("swapenough", swapenough_setup);
> 

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