[PATCH -next v6 2/2] mm/zswap: delay the initializaton of zswap

Liu Shixin
2023-03-22T09:30:05Z

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 | 51 +++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 09fa956920fa..3aed3b26524a 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 *,
@@ -220,6 +222,9 @@ static bool zswap_init_started;
/* fatal error during init */
static bool zswap_init_failed;

+/* 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;

@@ -272,13 +277,13 @@ static void zswap_update_total_size(void)
**********************************/
static struct kmem_cache *zswap_entry_cache;

-static int __init zswap_entry_cache_create(void)
+static int zswap_entry_cache_create(void)
{
zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
return zswap_entry_cache == NULL;
}

-static void __init zswap_entry_cache_destroy(void)
+static void zswap_entry_cache_destroy(void)
{
kmem_cache_destroy(zswap_entry_cache);
}
@@ -663,7 +668,7 @@ 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;

@@ -784,8 +789,15 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
/* if this is load-time (pre-init) param setting,
* don't create a pool; that's done during init.
*/
- if (!zswap_init_started)
- return param_set_charp(s, kp);
+ if (!zswap_init_started) {
+ mutex_lock(&zswap_init_lock);
+ if (!zswap_init_started) {
+ ret = param_set_charp(s, kp);
+ mutex_unlock(&zswap_init_lock);
+ return ret;
+ }
+ mutex_unlock(&zswap_init_lock);
+ }

if (!type) {
if (!zpool_has_pool(s)) {
@@ -884,6 +896,15 @@ static int zswap_enabled_param_set(const char *val,
if (res == *(bool *)kp->arg)
return 0;

+ if (!zswap_init_started && (system_state == SYSTEM_RUNNING)) {
+ mutex_lock(&zswap_init_lock);
+ if (zswap_setup()) {
+ mutex_unlock(&zswap_init_lock);
+ return -ENODEV;
+ }
+ mutex_unlock(&zswap_init_lock);
+ }
+
if (zswap_init_failed) {
pr_err("can't enable, initialization failed\n");
return -ENODEV;
@@ -1451,7 +1472,7 @@ 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;
@@ -1482,7 +1503,7 @@ 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;
}
@@ -1491,12 +1512,13 @@ 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;

- zswap_init_started = true;
+ if (zswap_init_started)
+ return 0;

if (zswap_entry_cache_create()) {
pr_err("entry cache creation failed\n");
@@ -1537,6 +1559,7 @@ static int __init init_zswap(void)
goto destroy_wq;
if (zswap_debugfs_init())
pr_warn("debugfs initialization failed\n");
+ zswap_init_started = true;
return 0;

destroy_wq:
@@ -1551,11 +1574,19 @@ static int __init init_zswap(void)
cache_fail:
/* if built-in, we aren't unloaded on failure; don't allow use */
zswap_init_failed = true;
+ zswap_init_started = true;
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