Messages in this thread | | | Subject | Re: [Patch 1/8] kexec: allow to shrink reserved memory | From | (Eric W. Biederman) | Date | Fri, 21 Aug 2009 18:39:43 -0700 |
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Amerigo Wang <amwang@redhat.com> writes:
> This patch implements 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> > Cc: Eric W. Biederman <ebiederm@xmission.com> > Cc: Andi Kleen <andi@firstfloor.org> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > --- > > Index: linux-2.6/include/linux/kexec.h > =================================================================== > --- linux-2.6.orig/include/linux/kexec.h > +++ linux-2.6/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 shrink_crash_memory(unsigned long new_size); > +size_t get_crash_memory_size(void); > > #else /* !CONFIG_KEXEC */ > struct pt_regs; > Index: linux-2.6/kernel/kexec.c > =================================================================== > --- linux-2.6.orig/kernel/kexec.c > +++ linux-2.6/kernel/kexec.c > @@ -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> > @@ -1083,6 +1084,58 @@ void crash_kexec(struct pt_regs *regs) > } > } > > +size_t get_crash_memory_size(void) > +{ > + size_t size; > + mutex_lock(&kexec_mutex); > + size = crashk_res.end - crashk_res.start + 1; > + mutex_unlock(&kexec_mutex); > + return size; > +} > + > +int shrink_crash_memory(unsigned long new_size) > +{ > + int ret = 0; > + unsigned long addr; > + 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); > + > + for (addr = end; addr < crashk_res.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++;
Any chance we can move this inline snippet into a helper function in -mm. To expose what is happening here to the mm developers.
Eric
> + } > + > + 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: linux-2.6/kernel/ksysfs.c > =================================================================== > --- linux-2.6.orig/kernel/ksysfs.c > +++ linux-2.6/kernel/ksysfs.c > @@ -100,6 +100,26 @@ static ssize_t kexec_crash_loaded_show(s > } > 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, "%lu\n", get_crash_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 = shrink_crash_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
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