Hi Yi,
On Fri, Sep 04, 2020 at 04:52:10PM +0800, Yi Wang wrote:
> From: zhanglin <zhang.lin16@xxxxxxxxxx>
>
> Add max_num_devices to limit dynamic zram device creation to prevent
> potential OOM
>
> Signed-off-by: zhanglin <zhang.lin16@xxxxxxxxxx>
> Signed-off-by: Yi Wang <wang.yi59@xxxxxxxxxx>
> ---
> v1->v2:
> change hard-coded initial max_num_devices into configurable way.
>
> drivers/block/zram/Kconfig | 7 +++++++
> drivers/block/zram/zram_drv.c | 28 +++++++++++++++++++++-------
> 2 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
> index fe7a4b7d30cf..54a369932417 100644
> --- a/drivers/block/zram/Kconfig
> +++ b/drivers/block/zram/Kconfig
> @@ -37,3 +37,10 @@ config ZRAM_MEMORY_TRACKING
> /sys/kernel/debug/zram/zramX/block_state.
>
> See Documentation/admin-guide/blockdev/zram.rst for more information.
> +
> +config ZRAM_DEV_MAX_COUNT
> + int "Number of zram devices to be created"
> + depends on ZRAM
> + default 256
> + help
> + This option specifies the maximum number of zram devices.
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 36d49159140f..d1022f3c04c4 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -43,8 +43,9 @@ static DEFINE_MUTEX(zram_index_mutex);
> static int zram_major;
> static const char *default_compressor = "lzo-rle";
>
> -/* Module params (documentation at end) */
> static unsigned int num_devices = 1;
> +/* Module params (documentation at end) */
> +static unsigned int max_num_devices = CONFIG_ZRAM_DEV_MAX_COUNT;
> /*
> * Pages that compress to sizes equals or greater than this are stored
> * uncompressed in memory.
> @@ -2013,10 +2014,16 @@ static ssize_t hot_add_show(struct class *class,
> struct class_attribute *attr,
> char *buf)
> {
> - int ret;
> + int ret = -ENOSPC;
>
> mutex_lock(&zram_index_mutex);
> + if (num_devices >= max_num_devices) {
> + mutex_unlock(&zram_index_mutex);
> + return ret;
> + }
> ret = zram_add();
> + if (ret >= 0)
> + num_devices += 1;
Let's have the num_devices inc/dec in zram_add/zram_remove so any caller
doesn't need to take care of it.
> mutex_unlock(&zram_index_mutex);
>
> if (ret < 0)
> @@ -2046,8 +2053,10 @@ static ssize_t hot_remove_store(struct class *class,
> zram = idr_find(&zram_index_idr, dev_id);
> if (zram) {
> ret = zram_remove(zram);
> - if (!ret)
> + if (!ret) {
> idr_remove(&zram_index_idr, dev_id);
> + num_devices -= 1;
> + }
> } else {
> ret = -ENODEV;
> }
> @@ -2089,6 +2098,7 @@ static void destroy_devices(void)
> static int __init zram_init(void)
> {
> int ret;
> + unsigned int i;
>
> ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare",
> zcomp_cpu_up_prepare, zcomp_cpu_dead);
> @@ -2111,13 +2121,17 @@ static int __init zram_init(void)
> return -EBUSY;
> }
>
> - while (num_devices != 0) {
> + if (num_devices > max_num_devices) {
> + pr_err("Number of pre-created zram devices over limit\n");
> + goto out_error;
> + }
> +
> + for (i = 0; i < num_devices; i++) {
> mutex_lock(&zram_index_mutex);
> ret = zram_add();
> mutex_unlock(&zram_index_mutex);
> if (ret < 0)
> goto out_error;
> - num_devices--;
> }
>
> return 0;
> @@ -2135,8 +2149,8 @@ static void __exit zram_exit(void)
> module_init(zram_init);
> module_exit(zram_exit);
>
> -module_param(num_devices, uint, 0);
> -MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
> +module_param(max_num_devices, uint, 0);
> +MODULE_PARM_DESC(max_num_devices, "Max number of created zram devices");
How about this?
"Max number of zram devices to be created"
>
> MODULE_LICENSE("Dual BSD/GPL");
> MODULE_AUTHOR("Nitin Gupta <ngupta@xxxxxxxxxx>");
> --
> 2.17.1
>
