[PATCH V2] ia64/mm: fix a bad_page bug when crash kernel booting

Xishi Qiu
2013-02-07T02:32:40Z

On 2013/2/5 0:32, Matt Fleming wrote:

> On Tue, 2013-01-29 at 11:52 +0800, Xishi Qiu wrote:
>> On ia64 platform, I set "crashkernel\x1024M-:600M", and dmesg shows 128M-728M
>> memory is reserved for crash kernel. Then "echo c > /proc/sysrq-trigger" to
>> test kdump.
>>
>> When crash kernel booting, efi_init() will aligns the memory address in
>> IA64_GRANULE_SIZE(16M), so 720M-728M memory will be dropped, It means
>> crash kernel only manage 128M-720M memory.
>>
>> But initrd start and end are fixed in boot loader, it is before efi_init(),
>> so initrd size maybe overflow when free_initrd_mem().
>
> [...]
>
>> diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
>> index b755ea9..cfdb1eb 100644
>> --- a/arch/ia64/mm/init.c
>> +++ b/arch/ia64/mm/init.c
>> @@ -207,6 +207,17 @@ free_initrd_mem (unsigned long start, unsigned long end)
>> start = PAGE_ALIGN(start);
>> end = end & PAGE_MASK;
>>
>> + /*
>> + * Initrd size is fixed in boot loader, but kernel parameter max_addr
>> + * which aligns in granules is fixed after boot loader, so initrd size
>> + * maybe overflow.
>> + */
>> + if (max_addr != ~0UL) {
>> + end = GRANULEROUNDDOWN(end);
>> + if (start > end)
>> + start = end;
>> + }
>> +
>> if (start < end)
>> printk(KERN_INFO "Freeing initrd memory: %ldkB freed\n", (end - start) >> 10);
>
> I don't think this is the correct fix.
>
> Now, my ia64-fu is weak, but could it be that there's actually a bug in
> efi_init() and that the following patch would be the best way to fix
> this?
>
> ---
>
> diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
> index f034563..8d579f1 100644
> --- a/arch/ia64/kernel/efi.c
> +++ b/arch/ia64/kernel/efi.c
> @@ -482,7 +482,7 @@ efi_init (void)
> if (memcmp(cp, "mem=", 4) = 0) {
> mem_limit = memparse(cp + 4, &cp);
> } else if (memcmp(cp, "max_addr=", 9) = 0) {
> - max_addr = GRANULEROUNDDOWN(memparse(cp + 9, &cp));
> + max_addr = GRANULEROUNDUP(memparse(cp + 9, &cp));
> } else if (memcmp(cp, "min_addr=", 9) = 0) {
> min_addr = GRANULEROUNDDOWN(memparse(cp + 9, &cp));
> } else {
>
>

Sorry, this bug will be happen when use Sparse-Memory(section is valid, but last
several pages are invalid). If use Flat-Memory, crash kernel will boot successfully.
I think the following patch would be better.

Hi Andrew, will you just ignore the earlier patch and consider the following one? :>

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
---
arch/ia64/mm/init.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 082e383..23f2ee3 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -213,6 +213,8 @@ free_initrd_mem (unsigned long start, unsigned long end)
for (; start < end; start += PAGE_SIZE) {
if (!virt_addr_valid(start))
continue;
+ if ((start >> PAGE_SHIFT) >= max_low_pfn)
+ continue;
page = virt_to_page(start);
ClearPageReserved(page);
init_page_count(page);
--
1.7.6.1