From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753349AbZHKMHE (ORCPT ); Tue, 11 Aug 2009 08:07:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753018AbZHKMG7 (ORCPT ); Tue, 11 Aug 2009 08:06:59 -0400 Received: from mx2.redhat.com ([66.187.237.31]:38853 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753248AbZHKMGw (ORCPT ); Tue, 11 Aug 2009 08:06:52 -0400 Date: Tue, 11 Aug 2009 06:46:06 -0400 From: Neil Horman To: Amerigo Wang Cc: linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, "Eric W. Biederman" , Andi Kleen , akpm@linux-foundation.org, Ingo Molnar Subject: Re: [RFC Patch 2/2] kexec: allow to shrink reserved memory Message-ID: <20090811104606.GA26587@hmsreliant.think-freely.org> References: <20090811104144.5154.77871.sendpatchset@localhost.localdomain> <20090811104154.5154.78710.sendpatchset@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090811104154.5154.78710.sendpatchset@localhost.localdomain> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 11, 2009 at 06:39:32AM -0400, Amerigo Wang wrote: > > 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 > > Signed-off-by: WANG Cong > Cc: Neil Horman > Cc: Eric W. Biederman > Cc: Andi Kleen > Since the reserved area is also used for heap in the new kernel, isn't this mechanism going to guarantee a non-bootable kernel. It seems like it shrinks the reserved area to the size of the image, leaving no additional memory for heap allocations during the kernels boot. Or am I missing something? Neil > --- > Index: linux-2.6/include/linux/kexec.h > =================================================================== > --- linux-2.6.orig/include/linux/kexec.h > +++ linux-2.6/include/linux/kexec.h > @@ -158,6 +158,8 @@ unsigned long paddr_vmcoreinfo_note(void > > extern struct kimage *kexec_image; > extern struct kimage *kexec_crash_image; > +extern struct resource *kexec_res; > +extern struct resource *kexec_free_res; > > #ifndef kexec_flush_icache_page > #define kexec_flush_icache_page(page) > @@ -206,6 +208,7 @@ 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 start, unsigned long end); > > #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 > @@ -1130,6 +1130,51 @@ void crash_kexec(struct pt_regs *regs) > } > } > > +int shrink_crash_memory(unsigned long start, unsigned long end) > +{ > + struct page **pages; > + int ret = 0; > + int npages, i; > + unsigned long addr; > + void *vaddr; > + > + if (!mutex_trylock(&kexec_mutex)) > + return -EBUSY; > + > + if (!kexec_free_res) { > + ret = -ENOENT; > + goto unlock; > + } > + > + start = roundup(start, PAGE_SIZE); > + end = roundup(end, PAGE_SIZE) - 1; > + npages = (end + 1 - start ) / PAGE_SIZE; > + > + pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL); > + if (!pages) { > + ret = -ENOMEM; > + goto unlock; > + } > + for (i = 0; i < npages; i++) { > + addr = start + i * PAGE_SIZE; > + pages[i] = virt_to_page(addr); > + } > + > + vaddr = vm_map_ram(pages, npages, 0, PAGE_KERNEL); > + if (!vaddr) { > + ret = -ENOMEM; > + goto free; > + } > + kexec_free_res->end = start - 1; > + crashk_res.end = start - 1; > + > +free: > + kfree(pages); > +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 +100,32 @@ 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, "%llu\n", crashk_res.end - crashk_res.start + 1); > +} > +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 (!kexec_res || !kexec_free_res) > + return -ENOENT; > + cnt = simple_strtoul(buf, NULL, 10); > + if (cnt < kexec_res->end - kexec_res->start + 1) > + return -ENOENT; > + if (cnt > kexec_free_res->end - kexec_res->start + 1) > + return -ENOENT; > + cnt -= kexec_res->end - kexec_res->start + 1; > + ret = shrink_crash_memory(kexec_free_res->start + cnt, > + kexec_free_res->end); > + 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 +173,7 @@ 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