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

[Barry Song]

From: Barry Song <Baohua.Song at csr.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 at csr.com>
Cc: Xiangzhen Ye <Xiangzhen.Ye at csr.com>
---
 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);
-- 
1.7.1



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