* [PATCH] zram: add restriction on dynamic zram device creation
@ 2020-09-01 6:42 Yi Wang
2020-09-03 19:53 ` Minchan Kim
0 siblings, 1 reply; 2+ messages in thread
From: Yi Wang @ 2020-09-01 6:42 UTC (permalink / raw)
To: minchan
Cc: ngupta, sergey.senozhatsky.work, axboe, linux-kernel,
linux-block, xue.zhihong, wang.yi59, jiang.xuexin, zhanglin
From: zhanglin <zhang.lin16@zte.com.cn>
Add max_num_devices to limit dynamic zram device creation to prevent
potential OOM
Signed-off-by: zhanglin <zhang.lin16@zte.com.cn>
---
drivers/block/zram/zram_drv.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 36d49159140f..4f2c4eef5051 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 = 8;
/*
* 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;
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 +2121,15 @@ static int __init zram_init(void)
return -EBUSY;
}
- while (num_devices != 0) {
+ if (num_devices > max_num_devices)
+ num_devices = max_num_devices;
+
+ 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 +2147,8 @@ 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");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] zram: add restriction on dynamic zram device creation
2020-09-01 6:42 [PATCH] zram: add restriction on dynamic zram device creation Yi Wang
@ 2020-09-03 19:53 ` Minchan Kim
0 siblings, 0 replies; 2+ messages in thread
From: Minchan Kim @ 2020-09-03 19:53 UTC (permalink / raw)
To: Yi Wang
Cc: ngupta, sergey.senozhatsky.work, axboe, linux-kernel,
linux-block, xue.zhihong, jiang.xuexin, zhanglin
Hello, Yi,
On Tue, Sep 01, 2020 at 02:42:47PM +0800, Yi Wang wrote:
> From: zhanglin <zhang.lin16@zte.com.cn>
>
> Add max_num_devices to limit dynamic zram device creation to prevent
> potential OOM
>
> Signed-off-by: zhanglin <zhang.lin16@zte.com.cn>
> ---
> drivers/block/zram/zram_drv.c | 26 +++++++++++++++++++-------
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 36d49159140f..4f2c4eef5051 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 = 8;
It seems 8 is too small to me by default. How about 256?
Furthemore, I think it would be worth to have in Kconfig.
config ZRAM_DEV_MAX_COUNT
int "Number of zram devices to be created"
depends on ZRAM
default 256
help
blah blah
> /*
> * 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;
> 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 +2121,15 @@ static int __init zram_init(void)
> return -EBUSY;
> }
>
> - while (num_devices != 0) {
> + if (num_devices > max_num_devices)
> + num_devices = max_num_devices;
I am not sure the overriding is a good idea.
Just leave it but just return error if user wanted to pre-create
exceeding max size in configuration.
Thanks.
> +
> + 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 +2147,8 @@ 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");
>
> MODULE_LICENSE("Dual BSD/GPL");
> MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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