[PATCH -next v9 3/3] mm/zswap: delay the initialization of zswap

Liu Shixin
2023-04-11T08:46:40Z

Since some users may not use zswap, the zswap_pool is wasted. Save memory
by delaying the initialization of zswap until enabled.

Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
mm/zswap.c | 71 +++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 54 insertions(+), 17 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 9169c2baee87..af97e8f9d678 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -81,6 +81,8 @@ static bool zswap_pool_reached_full;

#define ZSWAP_PARAM_UNSET ""

+static int zswap_setup(void);
+
/* Enable/disable zswap */
static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
static int zswap_enabled_param_set(const char *,
@@ -222,6 +224,9 @@ enum zswap_init_type {

static enum zswap_init_type zswap_init_state;

+/* used to ensure the integrity of initialization */
+static DEFINE_MUTEX(zswap_init_lock);
+
/* init completed, but couldn't create the initial pool */
static bool zswap_has_pool;

@@ -654,7 +659,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
return NULL;
}

-static __init struct zswap_pool *__zswap_pool_create_fallback(void)
+static struct zswap_pool *__zswap_pool_create_fallback(void)
{
bool has_comp, has_zpool;

@@ -755,29 +760,43 @@ static void zswap_pool_put(struct zswap_pool *pool)
* param callbacks
**********************************/

+static bool zswap_pool_changed(const char *s, const struct kernel_param *kp)
+{
+ /* no change required */
+ if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
+ return false;
+ return true;
+}
+
/* val must be a null-terminated string */
static int __zswap_param_set(const char *val, const struct kernel_param *kp,
char *type, char *compressor)
{
struct zswap_pool *pool, *put_pool = NULL;
char *s = strstrip((char *)val);
- int ret;
+ int ret = 0;
+ bool new_pool = false;

+ mutex_lock(&zswap_init_lock);
switch (zswap_init_state) {
case ZSWAP_UNINIT:
/* if this is load-time (pre-init) param setting,
* don't create a pool; that's done during init.
*/
- return param_set_charp(s, kp);
+ ret = param_set_charp(s, kp);
+ break;
case ZSWAP_INIT_SUCCEED:
- /* no change required */
- if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
- return 0;
+ new_pool = zswap_pool_changed(s, kp);
break;
case ZSWAP_INIT_FAILED:
pr_err("can't set param, initialization failed\n");
- return -ENODEV;
+ ret = -ENODEV;
}
+ mutex_unlock(&zswap_init_lock);
+
+ /* no need to create a new pool, return directly */
+ if (!new_pool)
+ return ret;

if (!type) {
if (!zpool_has_pool(s)) {
@@ -867,19 +886,30 @@ static int zswap_zpool_param_set(const char *val,
static int zswap_enabled_param_set(const char *val,
const struct kernel_param *kp)
{
+ int ret = -ENODEV;
+
+ /* if this is load-time (pre-init) param setting, only set param. */
+ if (system_state != SYSTEM_RUNNING)
+ return param_set_bool(val, kp);
+
+ mutex_lock(&zswap_init_lock);
switch (zswap_init_state) {
case ZSWAP_UNINIT:
- return param_set_bool(val, kp);
+ if (zswap_setup())
+ break;
+ fallthrough;
case ZSWAP_INIT_SUCCEED:
- if (!zswap_has_pool) {
+ if (!zswap_has_pool)
pr_err("can't enable, no pool configured\n");
- return -ENODEV;
- } else
- return param_set_bool(val, kp);
+ else
+ ret = param_set_bool(val, kp);
+ break;
case ZSWAP_INIT_FAILED:
pr_err("can't enable, initialization failed\n");
- return -ENODEV;
}
+ mutex_unlock(&zswap_init_lock);
+
+ return ret;
}

/*********************************
@@ -1437,7 +1467,7 @@ static const struct frontswap_ops zswap_frontswap_ops = {

static struct dentry *zswap_debugfs_root;

-static int __init zswap_debugfs_init(void)
+static int zswap_debugfs_init(void)
{
if (!debugfs_initialized())
return -ENODEV;
@@ -1468,7 +1498,7 @@ static int __init zswap_debugfs_init(void)
return 0;
}
#else
-static int __init zswap_debugfs_init(void)
+static int zswap_debugfs_init(void)
{
return 0;
}
@@ -1477,7 +1507,7 @@ static int __init zswap_debugfs_init(void)
/*********************************
* module init and exit
**********************************/
-static int __init init_zswap(void)
+static int zswap_setup(void)
{
struct zswap_pool *pool;
int ret;
@@ -1540,8 +1570,15 @@ static int __init init_zswap(void)
zswap_enabled = false;
return -ENOMEM;
}
+
+static int __init zswap_init(void)
+{
+ if (!zswap_enabled)
+ return 0;
+ return zswap_setup();
+}
/* must be late so crypto has time to come up */
-late_initcall(init_zswap);
+late_initcall(zswap_init);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
--
2.25.1