[PATCH RESEND v2 3/4] PM: hibernate: Add support for LZ4 compression for hibernation

[Nikhil V]

Extend the support for LZ4 compression to be used with hibernation.
The main idea is that different compression algorithms
have different characteristics and hibernation may benefit when it uses
any of these algorithms: a default algorithm, having higher
compression rate but is slower(compression/decompression) and a
secondary algorithm, that is faster(compression/decompression) but has
lower compression rate.

LZ4 algorithm has better decompression speeds over LZO. This reduces
the hibernation image restore time.
As per test results:
                                    LZO             LZ4
Size before Compression(bytes)   682696704       682393600
Size after Compression(bytes)    146502402       155993547
Decompression Rate               335.02 MB/s     501.05 MB/s
Restore time                       4.4s             3.8s

LZO is the default compression algorithm used for hibernation. Enable
CONFIG_HIBERNATION_COMP_LZ4 to set the default compressor as LZ4.

Signed-off-by: Nikhil V <quic_nprakash@xxxxxxxxxxx>
---
 kernel/power/Kconfig     |  5 +++++
 kernel/power/hibernate.c | 25 ++++++++++++++++++++++---
 kernel/power/power.h     | 14 ++++++++++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index d4167159bae8..afce8130d8b9 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -101,11 +101,16 @@ config HIBERNATION_COMP_LZO
 	bool "lzo"
 	depends on CRYPTO_LZO
 
+config HIBERNATION_COMP_LZ4
+	bool "lz4"
+	depends on CRYPTO_LZ4
+
 endchoice
 
 config HIBERNATION_DEF_COMP
 	string
 	default "lzo" if HIBERNATION_COMP_LZO
+	default "lz4" if HIBERNATION_COMP_LZ4
 	help
 	  Default compressor to be used for hibernation.
 
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index fe0a3c5b8cfe..274327232dab 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -721,6 +721,9 @@ static int load_image_and_restore(void)
 	return error;
 }
 
+#define COMPRESSION_ALGO_LZO "lzo"
+#define COMPRESSION_ALGO_LZ4 "lz4"
+
 /**
  * hibernate - Carry out system hibernation, including saving the image.
  */
@@ -780,11 +783,24 @@ int hibernate(void)
 
 		if (hibernation_mode == HIBERNATION_PLATFORM)
 			flags |= SF_PLATFORM_MODE;
-		if (nocompress)
+		if (nocompress) {
 			flags |= SF_NOCOMPRESS_MODE;
-		else
+		} else {
 		        flags |= SF_CRC32_MODE;
 
+			/*
+			 * By default, LZO compression is enabled. Use SF_COMPRESSION_ALG_LZ4
+			 * to override this behaviour and use LZ4.
+			 *
+			 * Refer kernel/power/power.h for more details
+			 */
+
+			if (!strcmp(hib_comp_algo, COMPRESSION_ALGO_LZ4))
+				flags |= SF_COMPRESSION_ALG_LZ4;
+			else
+				flags |= SF_COMPRESSION_ALG_LZO;
+		}
+
 		pm_pr_dbg("Writing hibernation image.\n");
 		error = swsusp_write(flags);
 		swsusp_free();
@@ -974,7 +990,10 @@ static int software_resume(void)
 	 * the algorithm support.
 	 */
 	if (!(swsusp_header_flags & SF_NOCOMPRESS_MODE)) {
-		strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
+		if (swsusp_header_flags & SF_COMPRESSION_ALG_LZ4)
+			strscpy(hib_comp_algo, COMPRESSION_ALGO_LZ4, sizeof(hib_comp_algo));
+		else
+			strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
 		if (crypto_has_comp(hib_comp_algo, 0, 0) != 1) {
 			pr_err("%s compression is not available\n", hib_comp_algo);
 			error = -EOPNOTSUPP;
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 88836e627512..7baeba100da5 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -167,11 +167,25 @@ extern int swsusp_swap_in_use(void);
  * Flags that can be passed from the hibernatig hernel to the "boot" kernel in
  * the image header.
  */
+#define SF_COMPRESSION_ALG_LZO	0 /* dummy, details given  below */
 #define SF_PLATFORM_MODE	1
 #define SF_NOCOMPRESS_MODE	2
 #define SF_CRC32_MODE	        4
 #define SF_HW_SIG		8
 
+/*
+ * Bit to indicate the compression algorithm to be used(for LZ4). The same
+ * could be checked while saving/loading image to/from disk to use the
+ * corresponding algorithms.
+ *
+ * By default, LZO compression is enabled if SF_CRC32_MODE is set. Use
+ * SF_COMPRESSION_ALG_LZ4 to override this behaviour and use LZ4.
+ *
+ * SF_CRC32_MODE, SF_COMPRESSION_ALG_LZO(dummy) -> Compression, LZO
+ * SF_CRC32_MODE, SF_COMPRESSION_ALG_LZ4 -> Compression, LZ4
+ */
+#define SF_COMPRESSION_ALG_LZ4	16
+
 /* kernel/power/hibernate.c */
 int swsusp_check(bool exclusive);
 extern void swsusp_free(void);
-- 
2.17.1