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Subject[PATCH v2 1/2] kexec: Introduce "/sys/kernel/kexec_crash_low_size"
Date
"/sys/kernel/kexec_crash_size" only handles crashk_res, it
is fine in most cases, but sometimes we have crashk_low_res.
For example, when "crashkernel=size[KMG],high" combined with
"crashkernel=size[KMG],low" is used for 64-bit x86.

Like crashk_res, we introduce the corresponding sysfs file
"/sys/kernel/kexec_crash_low_size" for crashk_low_res.

So, the exact total reserved memory is the sum of the two.

crashk_low_res can also be shrunk via this new interface,
and users should be aware of what they are doing.

Suggested-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
include/linux/kexec.h | 4 ++--
kernel/kexec_core.c | 23 ++++++++++++-----------
kernel/ksysfs.c | 25 +++++++++++++++++++++++--
3 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d743777..4f271fc 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -304,8 +304,8 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
int parse_crashkernel_low(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);
+int crash_shrink_memory(struct resource *res, unsigned long new_size);
+size_t crash_get_memory_size(struct resource *res);
void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);

int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 5616755..707d18e 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -925,13 +925,13 @@ void crash_kexec(struct pt_regs *regs)
}
}

-size_t crash_get_memory_size(void)
+size_t crash_get_memory_size(struct resource *res)
{
size_t size = 0;

mutex_lock(&kexec_mutex);
- if (crashk_res.end != crashk_res.start)
- size = resource_size(&crashk_res);
+ if (res->end != res->start)
+ size = resource_size(res);
mutex_unlock(&kexec_mutex);
return size;
}
@@ -945,7 +945,7 @@ void __weak crash_free_reserved_phys_range(unsigned long begin,
free_reserved_page(boot_pfn_to_page(addr >> PAGE_SHIFT));
}

-int crash_shrink_memory(unsigned long new_size)
+int crash_shrink_memory(struct resource *res, unsigned long new_size)
{
int ret = 0;
unsigned long start, end;
@@ -958,8 +958,9 @@ int crash_shrink_memory(unsigned long new_size)
ret = -ENOENT;
goto unlock;
}
- start = crashk_res.start;
- end = crashk_res.end;
+
+ start = res->start;
+ end = res->end;
old_size = (end == 0) ? 0 : end - start + 1;
if (new_size >= old_size) {
ret = (new_size == old_size) ? 0 : -EINVAL;
@@ -975,17 +976,17 @@ int crash_shrink_memory(unsigned long new_size)
start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);

- crash_free_reserved_phys_range(end, crashk_res.end);
+ crash_free_reserved_phys_range(end, res->end);

- if ((start == end) && (crashk_res.parent != NULL))
- release_resource(&crashk_res);
+ if ((start == end) && (res->parent != NULL))
+ release_resource(res);

ram_res->start = end;
- ram_res->end = crashk_res.end;
+ ram_res->end = res->end;
ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
ram_res->name = "System RAM";

- crashk_res.end = end - 1;
+ res->end = end - 1;

insert_resource(&iomem_resource, ram_res);

diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index ee1bc1b..3336fd5 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -105,10 +105,30 @@ static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(kexec_crash_loaded);

+static ssize_t kexec_crash_low_size_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%zu\n", crash_get_memory_size(&crashk_low_res));
+}
+static ssize_t kexec_crash_low_size_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long cnt;
+ int ret;
+
+ if (kstrtoul(buf, 0, &cnt))
+ return -EINVAL;
+
+ ret = crash_shrink_memory(&crashk_low_res, cnt);
+ return ret < 0 ? ret : count;
+}
+KERNEL_ATTR_RW(kexec_crash_low_size);
+
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());
+ return sprintf(buf, "%zu\n", crash_get_memory_size(&crashk_res));
}
static ssize_t kexec_crash_size_store(struct kobject *kobj,
struct kobj_attribute *attr,
@@ -120,7 +140,7 @@ static ssize_t kexec_crash_size_store(struct kobject *kobj,
if (kstrtoul(buf, 0, &cnt))
return -EINVAL;

- ret = crash_shrink_memory(cnt);
+ ret = crash_shrink_memory(&crashk_res, cnt);
return ret < 0 ? ret : count;
}
KERNEL_ATTR_RW(kexec_crash_size);
@@ -218,6 +238,7 @@ static struct attribute * kernel_attrs[] = {
#ifdef CONFIG_KEXEC_CORE
&kexec_loaded_attr.attr,
&kexec_crash_loaded_attr.attr,
+ &kexec_crash_low_size_attr.attr,
&kexec_crash_size_attr.attr,
&vmcoreinfo_attr.attr,
#endif
--
1.8.3.1
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