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 <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>
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 528dd78..3feaf5a 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -100,6 +100,26 @@
}
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 @@
#ifdef CONFIG_KEXEC
&kexec_loaded_attr.attr,
&kexec_crash_loaded_attr.attr,
+ &kexec_crash_size_attr.attr,
&vmcoreinfo_attr.attr,
#endif
NULL