On Sat, Aug 27, 2022 at 12:12 PM Liu Shixin <liushixin2@xxxxxxxxxx> wrote:
>
> In the initialization of zswap, about 18MB memory will be allocated for
> zswap_pool in my machine. Since not all users use zswap, the memory may be
> wasted. Save the memory for these users by delaying the initialization of
> zswap to first enablement.
>
> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
Reviewed-by: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
> ---
> mm/zswap.c | 50 ++++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 40 insertions(+), 10 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 84e38300f571..4c476c463035 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 +222,8 @@ static atomic_t zswap_pools_count = ATOMIC_INIT(0);
>
> /* init state */
> static int 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;
> @@ -273,13 +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);
> }
> @@ -664,7 +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;
>
> @@ -782,11 +786,17 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
> if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
> return 0;
>
> - /* if this is load-time (pre-init) param setting,
> + /*
> + * if zswap has not been initialized,
> * don't create a pool; that's done during init.
> */
> - if (zswap_init_state == ZSWAP_UNINIT)
> - return param_set_charp(s, kp);
> + mutex_lock(&zswap_init_lock);
> + if (zswap_init_state == ZSWAP_UNINIT) {
> + 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)) {
> @@ -876,6 +886,14 @@ static int zswap_zpool_param_set(const char *val,
> static int zswap_enabled_param_set(const char *val,
> const struct kernel_param *kp)
> {
> + if (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_state == ZSWAP_INIT_FAILED) {
> pr_err("can't enable, initialization failed\n");
> return -ENODEV;
> @@ -1432,7 +1450,7 @@ 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;
> @@ -1463,7 +1481,7 @@ 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;
> }
> @@ -1472,11 +1490,14 @@ 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;
>
> + if (zswap_init_state != ZSWAP_UNINIT)
> + return 0;
> +
> if (zswap_entry_cache_create()) {
> pr_err("entry cache creation failed\n");
> goto cache_fail;
> @@ -1534,8 +1555,17 @@ static int __init init_zswap(void)
> zswap_enabled = false;
> return -ENOMEM;
> }
> +
> +static int __init zswap_init(void)
> +{
> + /* skip init if zswap is disabled when system startup */
> + 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@xxxxxxxxxxxxxx>");
> --
> 2.25.1
>
