mm/zswap: allow setting default status, compressor and allocator in Kconfig

The compressed cache for swap pages (zswap) currently needs from 1 to 3
extra kernel command line parameters in order to make it work: it has to
be enabled by adding a "zswap.enabled=1" command line parameter and if one
wants a different compressor or pool allocator than the default lzo / zbud
combination then these choices also need to be specified on the kernel
command line in additional parameters.

Using a different compressor and allocator for zswap is actually pretty
common as guides often recommend using the lz4 / z3fold pair instead of
the default one.  In such case it is also necessary to remember to enable
the appropriate compression algorithm and pool allocator in the kernel
config manually.

Let's avoid the need for adding these kernel command line parameters and
automatically pull in the dependencies for the selected compressor
algorithm and pool allocator by adding an appropriate default switches to
Kconfig.

The default values for these options match what the code was using
previously as its defaults.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Link: http://lkml.kernel.org/r/20200202000112.456103-1-mail@maciej.szmigiero.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 12 deletions

diff --git a/mm/zswap.c b/mm/zswap.c
index 55094e63b72d..fbb782924ccc 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -77,8 +77,8 @@ static bool zswap_pool_reached_full;
 
 #define ZSWAP_PARAM_UNSET ""
 
-/* Enable/disable zswap (disabled by default) */
-static bool zswap_enabled;
+/* Enable/disable zswap */
+static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
 static int zswap_enabled_param_set(const char *,
 				   const struct kernel_param *);
 static struct kernel_param_ops zswap_enabled_param_ops = {
@@ -88,8 +88,7 @@ static struct kernel_param_ops zswap_enabled_param_ops = {
 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
 
 /* Crypto compressor to use */
-#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
-static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
+static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 static int zswap_compressor_param_set(const char *,
 				      const struct kernel_param *);
 static struct kernel_param_ops zswap_compressor_param_ops = {
@@ -101,8 +100,7 @@ module_param_cb(compressor, &zswap_compressor_param_ops,
 		&zswap_compressor, 0644);
 
 /* Compressed storage zpool to use */
-#define ZSWAP_ZPOOL_DEFAULT "zbud"
-static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
+static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 static struct kernel_param_ops zswap_zpool_param_ops = {
 	.set =		zswap_zpool_param_set,
@@ -599,11 +597,12 @@ static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 	bool has_comp, has_zpool;
 
 	has_comp = crypto_has_comp(zswap_compressor, 0, 0);
-	if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
+	if (!has_comp && strcmp(zswap_compressor,
+				CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
 		pr_err("compressor %s not available, using default %s\n",
-		       zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
+		       zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
 		param_free_charp(&zswap_compressor);
-		zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
+		zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 		has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 	}
 	if (!has_comp) {
@@ -614,11 +613,12 @@ static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 	}
 
 	has_zpool = zpool_has_pool(zswap_zpool_type);
-	if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
+	if (!has_zpool && strcmp(zswap_zpool_type,
+				 CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
 		pr_err("zpool %s not available, using default %s\n",
-		       zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
+		       zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
 		param_free_charp(&zswap_zpool_type);
-		zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
+		zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 		has_zpool = zpool_has_pool(zswap_zpool_type);
 	}
 	if (!has_zpool) {