On 2023/5/31 8:13, Baoquan He wrote:
> On 05/27/23 at 08:34pm, Zhen Lei wrote:
>> If the value of parameter 'new_size' is in the semi-open and semi-closed
>> interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
>> calculation result of ram_res is:
>> ram_res->start = crashk_res.end + 1
>> ram_res->end = crashk_res.end
>
> If the new_size is smaller than KEXEC_CRASH_MEM_ALIGN, does it make
> any sense except of testing purpose? Do we need to fail this kind of
> shrinking, or just shrink all the left crash memory?
We can't give a fixed value, that is, how much crash memory is reserved to
ensure that the capture kernel runs. The size of KEXEC_CRASH_MEM_ALIGN is
only one page on non-s390 platforms. So, it's better to keep the code simple,
and let the user(administrator) shrink the crash memory reasonably.
include/linux/kexec.h
#define KEXEC_CRASH_MEM_ALIGN PAGE_SIZE
>
>> The operation of function insert_resource() fails, and ram_res is not
>> added to iomem_resource. As a result, the memory of the control block
>> ram_res is leaked.
>>
>> In fact, on all architectures, the start address and size of crashk_res
>> are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to
>> round up crashk_res.start again. Instead, we should round up 'new_size'
>> in advance.
>>
>> Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
>> Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>> kernel/kexec_core.c | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 3d578c6fefee385..22acee18195a591 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size)
>> start = crashk_res.start;
>> end = crashk_res.end;
>> old_size = (end == 0) ? 0 : end - start + 1;
>> + new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
>> if (new_size >= old_size) {
>> ret = (new_size == old_size) ? 0 : -EINVAL;
>> goto unlock;
>> @@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size)
>> goto unlock;
>> }
>>
>> - start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
>> - end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
>> -
>> + end = start + new_size;
>> crash_free_reserved_phys_range(end, crashk_res.end);
>>
>> if ((start == end) && (crashk_res.parent != NULL))
>> --
>> 2.25.1
>>
>
> .
>
--
Regards,
Zhen Lei
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