From: zhanglin <[email protected]> Add max_num_devices to limit dynamic zram device creation to prevent potential OOM
Signed-off-by: zhanglin <[email protected]> Signed-off-by: Yi Wang <[email protected]> --- 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; 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"); MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("Nitin Gupta <[email protected]>"); -- 2.17.1
