[PATCH v2] PM: hibernate: Support to select compression algorithm

[Nikhil V <quic_nprakash@quicinc.com>]

Currently the default compression algorithm is selected based on
compile time options. Introduce a module parameter "hibernate.compressor"
to override this behaviour.

Different compression algorithms have different characteristics and
hibernation may benefit when it uses any of these algorithms, especially
when a secondary algorithm(LZ4) offers better decompression speeds over a
default algorithm(LZO), which in turn reduces hibernation image restore
time.

Users can override the default algorithm in two ways:
 1) Passing "hibernate.compressor" as kernel command line parameter.
    Usage:
    	LZO: hibernate.compressor=lzo
    	LZ4: hibernate.compressor=lz4

 2) Specifying the algorithm at runtime.
    Usage:
	LZO: echo lzo > /sys/module/hibernate/parameters/compressor
	LZ4: echo lz4 > /sys/module/hibernate/parameters/compressor

Currently LZO and LZ4 are the supported algorithms. LZO is the default
compression algorithm used with hibernation.

Signed-off-by: Nikhil V <quic_nprakash@quicinc.com>
---
This patch is dependent on the patch series, [1] (patches 1/4 to 3/4).
This is picked in linux-next, [2].
 [1] https://lore.kernel.org/all/cover.1705927916.git.quic_nprakash@quicinc.com/
 [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/kernel/power?h=next-20240212

Changes in v2:
 Changes to incorporate suggestions from Randy Dunlap:
  - Update documentation to specify the default compression algorithm.
 Link to v1:
  https://lore.kernel.org/all/3776355f920c1af44490e076072f93bafdf128cc.1707740870.git.quic_nprakash@quicinc.com/

 .../admin-guide/kernel-parameters.txt         | 11 ++++
 kernel/power/hibernate.c                      | 57 ++++++++++++++++++-
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 31b3a25680d0..8f7fb911b2cc 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1748,6 +1748,17 @@
 				(that will set all pages holding image data
 				during restoration read-only).
 
+	hibernate.compressor= 	[HIBERNATION] Compression algorithm to be
+				used with hibernation.
+				Format: { lzo | lz4 }
+				Default: lzo
+
+				lzo: Select LZO compression algorithm to
+				compress/decompress hibernation image.
+
+				lz4: Select LZ4 compression algorithm to
+				compress/decompress hibernation image.
+
 	highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
 			size of <nn>. This works even on boxes that have no
 			highmem otherwise. This also works to reduce highmem
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 219191d6d0e8..43b1a82e800c 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -47,7 +47,7 @@ dev_t swsusp_resume_device;
 sector_t swsusp_resume_block;
 __visible int in_suspend __nosavedata;
 
-static const char *default_compressor = CONFIG_HIBERNATION_DEF_COMP;
+static char hibernate_compressor[CRYPTO_MAX_ALG_NAME] = CONFIG_HIBERNATION_DEF_COMP;
 
 /*
  * Compression/decompression algorithm to be used while saving/loading
@@ -748,7 +748,7 @@ int hibernate(void)
 	 * Query for the compression algorithm support if compression is enabled.
 	 */
 	if (!nocompress) {
-		strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
+		strscpy(hib_comp_algo, hibernate_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);
 			return -EOPNOTSUPP;
@@ -999,7 +999,7 @@ static int software_resume(void)
 		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));
+			strscpy(hib_comp_algo, COMPRESSION_ALGO_LZO, 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;
@@ -1422,6 +1422,57 @@ static int __init nohibernate_setup(char *str)
 	return 1;
 }
 
+static const char * const comp_alg_enabled[] = {
+#if IS_ENABLED(CONFIG_CRYPTO_LZO)
+	COMPRESSION_ALGO_LZO,
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_LZ4)
+	COMPRESSION_ALGO_LZ4,
+#endif
+};
+
+static int hibernate_compressor_param_set(const char *compressor,
+		const struct kernel_param *kp)
+{
+	unsigned int sleep_flags;
+	int index, ret;
+
+	sleep_flags = lock_system_sleep();
+
+	index = sysfs_match_string(comp_alg_enabled, compressor);
+	if (index >= 0) {
+		ret = param_set_copystring(comp_alg_enabled[index], kp);
+		if (!ret)
+			strscpy(hib_comp_algo, comp_alg_enabled[index],
+				sizeof(hib_comp_algo));
+	} else {
+		ret = index;
+	}
+
+	unlock_system_sleep(sleep_flags);
+
+	if (ret)
+		pr_debug("Cannot set specified compressor %s\n",
+			 compressor);
+
+	return ret;
+}
+
+static const struct kernel_param_ops hibernate_compressor_param_ops = {
+	.set    = hibernate_compressor_param_set,
+	.get    = param_get_string,
+};
+
+static struct kparam_string hibernate_compressor_param_string = {
+	.maxlen = sizeof(hibernate_compressor),
+	.string = hibernate_compressor,
+};
+
+module_param_cb(compressor, &hibernate_compressor_param_ops,
+		&hibernate_compressor_param_string, 0644);
+MODULE_PARM_DESC(compressor,
+		 "Compression algorithm to be used with hibernation");
+
 __setup("noresume", noresume_setup);
 __setup("resume_offset=", resume_offset_setup);
 __setup("resume=", resume_setup);
-- 
2.17.1