From 06a7f711246b081afc21fff859f1003f1f2a0fbc Mon Sep 17 00:00:00 2001 From: Amerigo Wang Date: Tue, 15 Dec 2009 16:47:46 -0800 Subject: [PATCH] kexec: premit reduction of the reserved memory size Implement shrinking the reserved memory for crash kernel, if it is more than enough. For example, if you have already reserved 128M, now you just want 100M, you can do: # echo $((100*1024*1024)) > /sys/kernel/kexec_crash_size Note, you can only do this before loading the crash kernel. Signed-off-by: WANG Cong Cc: Neil Horman Acked-by: Eric W. Biederman Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kexec.h | 2 ++ kernel/kexec.c | 59 +++++++++++++++++++++++++++++++++++++++++++ kernel/ksysfs.c | 21 +++++++++++++++ 3 files changed, 82 insertions(+) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index adc34f2c6eff..c356b6914ffd 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -206,6 +206,8 @@ extern size_t vmcoreinfo_max_size; int __init parse_crashkernel(char *cmdline, unsigned long long system_ram, unsigned long long *crash_size, unsigned long long *crash_base); +int crash_shrink_memory(unsigned long new_size); +size_t crash_get_memory_size(void); #else /* !CONFIG_KEXEC */ struct pt_regs; diff --git a/kernel/kexec.c b/kernel/kexec.c index f336e2107f98..433e9fcc1fc5 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include @@ -1082,6 +1083,64 @@ void crash_kexec(struct pt_regs *regs) } } +size_t crash_get_memory_size(void) +{ + size_t size; + mutex_lock(&kexec_mutex); + size = crashk_res.end - crashk_res.start + 1; + mutex_unlock(&kexec_mutex); + return size; +} + +static void free_reserved_phys_range(unsigned long begin, unsigned long end) +{ + unsigned long addr; + + for (addr = begin; addr < end; addr += PAGE_SIZE) { + ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT)); + init_page_count(pfn_to_page(addr >> PAGE_SHIFT)); + free_page((unsigned long)__va(addr)); + totalram_pages++; + } +} + +int crash_shrink_memory(unsigned long new_size) +{ + int ret = 0; + unsigned long start, end; + + mutex_lock(&kexec_mutex); + + if (kexec_crash_image) { + ret = -ENOENT; + goto unlock; + } + start = crashk_res.start; + end = crashk_res.end; + + if (new_size >= end - start + 1) { + ret = -EINVAL; + if (new_size == end - start + 1) + ret = 0; + goto unlock; + } + + start = roundup(start, PAGE_SIZE); + end = roundup(start + new_size, PAGE_SIZE); + + free_reserved_phys_range(end, crashk_res.end); + + if (start == end) { + crashk_res.end = end; + release_resource(&crashk_res); + } else + crashk_res.end = end - 1; + +unlock: + mutex_unlock(&kexec_mutex); + return ret; +} + static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data, size_t data_len) { diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 528dd78e7e7e..3feaf5a74514 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -100,6 +100,26 @@ static ssize_t kexec_crash_loaded_show(struct kobject *kobj, } KERNEL_ATTR_RO(kexec_crash_loaded); +static ssize_t kexec_crash_size_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%zu\n", crash_get_memory_size()); +} +static ssize_t kexec_crash_size_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long cnt; + int ret; + + if (strict_strtoul(buf, 0, &cnt)) + return -EINVAL; + + ret = crash_shrink_memory(cnt); + return ret < 0 ? ret : count; +} +KERNEL_ATTR_RW(kexec_crash_size); + static ssize_t vmcoreinfo_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { @@ -147,6 +167,7 @@ static struct attribute * kernel_attrs[] = { #ifdef CONFIG_KEXEC &kexec_loaded_attr.attr, &kexec_crash_loaded_attr.attr, + &kexec_crash_size_attr.attr, &vmcoreinfo_attr.attr, #endif NULL -- 2.20.1