diff options
| -rw-r--r-- | mm/mmap.c | 76 |
1 files changed, 74 insertions, 2 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 5485f18e6631..43c4955535aa 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -33,6 +33,8 @@ #include <linux/uprobes.h> #include <linux/rbtree_augmented.h> #include <linux/sched/sysctl.h> +#include <linux/notifier.h> +#include <linux/memory.h> #include <asm/uaccess.h> #include <asm/cacheflush.h> @@ -3110,7 +3112,7 @@ void __init mmap_init(void) * The default value is min(3% of free memory, 128MB) * 128MB is enough to recover with sshd/login, bash, and top/kill. */ -static int __meminit init_user_reserve(void) +static int init_user_reserve(void) { unsigned long free_kbytes; @@ -3131,7 +3133,7 @@ module_init(init_user_reserve) * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will * only reserve 3% of free pages by default. */ -static int __meminit init_admin_reserve(void) +static int init_admin_reserve(void) { unsigned long free_kbytes; @@ -3141,3 +3143,73 @@ static int __meminit init_admin_reserve(void) return 0; } module_init(init_admin_reserve) + +/* + * Reinititalise user and admin reserves if memory is added or removed. + * + * The default user reserve max is 128MB, and the default max for the + * admin reserve is 8MB. These are usually, but not always, enough to + * enable recovery from a memory hogging process using login/sshd, a shell, + * and tools like top. It may make sense to increase or even disable the + * reserve depending on the existence of swap or variations in the recovery + * tools. So, the admin may have changed them. + * + * If memory is added and the reserves have been eliminated or increased above + * the default max, then we'll trust the admin. + * + * If memory is removed and there isn't enough free memory, then we + * need to reset the reserves. + * + * Otherwise keep the reserve set by the admin. + */ +static int reserve_mem_notifier(struct notifier_block *nb, + unsigned long action, void *data) +{ + unsigned long tmp, free_kbytes; + + switch (action) { + case MEM_ONLINE: + /* Default max is 128MB. Leave alone if modified by operator. */ + tmp = sysctl_user_reserve_kbytes; + if (0 < tmp && tmp < (1UL << 17)) + init_user_reserve(); + + /* Default max is 8MB. Leave alone if modified by operator. */ + tmp = sysctl_admin_reserve_kbytes; + if (0 < tmp && tmp < (1UL << 13)) + init_admin_reserve(); + + break; + case MEM_OFFLINE: + free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10); + + if (sysctl_user_reserve_kbytes > free_kbytes) { + init_user_reserve(); + pr_info("vm.user_reserve_kbytes reset to %lu\n", + sysctl_user_reserve_kbytes); + } + + if (sysctl_admin_reserve_kbytes > free_kbytes) { + init_admin_reserve(); + pr_info("vm.admin_reserve_kbytes reset to %lu\n", + sysctl_admin_reserve_kbytes); + } + break; + default: + break; + } + return NOTIFY_OK; +} + +static struct notifier_block reserve_mem_nb = { + .notifier_call = reserve_mem_notifier, +}; + +static int __meminit init_reserve_notifier(void) +{ + if (register_hotmemory_notifier(&reserve_mem_nb)) + printk("Failed registering memory add/remove notifier for admin reserve"); + + return 0; +} +module_init(init_reserve_notifier) |