kexec: premit reduction of the reserved memory size
Amerigo Wang [Wed, 16 Dec 2009 00:47:46 +0000 (16:47 -0800)]
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 <amwang@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kexec.h
kernel/kexec.c
kernel/ksysfs.c

index adc34f2..c356b69 100644 (file)
@@ -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;
index f336e21..433e9fc 100644 (file)
@@ -31,6 +31,7 @@
 #include <linux/cpu.h>
 #include <linux/console.h>
 #include <linux/vmalloc.h>
+#include <linux/swap.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -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)
 {
index 528dd78..3feaf5a 100644 (file)
@@ -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