On 2023/5/31 17:53, Baoquan He wrote:
> On 05/27/23 at 08:34pm, Zhen Lei wrote:
>> The crashk_low_res should be considered by /sys/kernel/kexec_crash_size
>> to support two crash kernel regions. Since crashk_res manages the memory
>> with high address and crashk_low_res manages the memory with low address,
>> crashk_low_res is shrunken only when all crashk_res is shrunken. And
>> because when there is only one crash kernel region, crashk_res is always
>> used. Therefore, if all crashk_res is shrunken and crashk_low_res still
>> exists, swap them.
>
> This looks good, otherwise someone else won't stop attempting to add
> support of crashk_low_res shrinking. Not sure if this will bring corner
> case issue in testing, let's see. For the patch log, I tried to
> rephrase, feel free to refer to.
>
> =====
> The crashk_low_res should be considered by /sys/kernel/kexec_crash_size
> to support two crash kernel regions shrinking if existing.
>
> While doing it, crashk_low_res will only be shrunk when the entire
> crashk_res is empty; and if the crashk_res is empty and crahk_low_res
> is not, change crashk_low_res to be crashk_res.
> =====
>
> With the log updated, you can add:
>
> Acked-by: Baoquan He <bhe@xxxxxxxxxx>
OK, I will update the log and add Acked-by in v2.
>
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>> kernel/kexec_core.c | 43 ++++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 38 insertions(+), 5 deletions(-)
>>
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index e82bc6d6634136a..c1d50f6566300d9 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -1091,6 +1091,11 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs)
>> }
>> }
>>
>> +static inline resource_size_t crash_resource_size(const struct resource *res)
>> +{
>> + return !res->end ? 0 : resource_size(res);
>> +}
>> +
>> ssize_t crash_get_memory_size(void)
>> {
>> ssize_t size = 0;
>> @@ -1098,8 +1103,8 @@ ssize_t crash_get_memory_size(void)
>> if (!kexec_trylock())
>> return -EBUSY;
>>
>> - if (crashk_res.end != crashk_res.start)
>> - size = resource_size(&crashk_res);
>> + size += crash_resource_size(&crashk_res);
>> + size += crash_resource_size(&crashk_low_res);
>>
>> kexec_unlock();
>> return size;
>> @@ -1135,7 +1140,7 @@ int __crash_shrink_memory(struct resource *old_res, unsigned long new_size)
>> int crash_shrink_memory(unsigned long new_size)
>> {
>> int ret = 0;
>> - unsigned long old_size;
>> + unsigned long old_size, low_size;
>>
>> if (!kexec_trylock())
>> return -EBUSY;
>> @@ -1144,14 +1149,42 @@ int crash_shrink_memory(unsigned long new_size)
>> ret = -ENOENT;
>> goto unlock;
>> }
>> - old_size = !crashk_res.end ? 0 : resource_size(&crashk_res);
>> +
>> + low_size = crash_resource_size(&crashk_low_res);
>> + old_size = crash_resource_size(&crashk_res) + low_size;
>> new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
>> if (new_size >= old_size) {
>> ret = (new_size == old_size) ? 0 : -EINVAL;
>> goto unlock;
>> }
>>
>> - ret = __crash_shrink_memory(&crashk_res, new_size);
>> + /*
>> + * (low_size > new_size) implies that low_size is greater than zero.
>> + * This also means that if low_size is zero, the else branch is taken.
>> + *
>> + * If low_size is greater than 0, (low_size > new_size) indicates that
>> + * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res
>> + * needs to be shrunken.
>> + */
>> + if (low_size > new_size) {
>> + ret = __crash_shrink_memory(&crashk_res, 0);
>> + if (ret)
>> + goto unlock;
>> +
>> + ret = __crash_shrink_memory(&crashk_low_res, new_size);
>> + } else {
>> + ret = __crash_shrink_memory(&crashk_res, new_size - low_size);
>> + }
>> +
>> + /* Swap crashk_res and crashk_low_res if needed */
>> + if (!crashk_res.end && crashk_low_res.end) {
>> + crashk_res.start = crashk_low_res.start;
>> + crashk_res.end = crashk_low_res.end;
>> + release_resource(&crashk_low_res);
>> + crashk_low_res.start = 0;
>> + crashk_low_res.end = 0;
>> + insert_resource(&iomem_resource, &crashk_res);
>> + }
>>
>> unlock:
>> kexec_unlock();
>> --
>> 2.25.1
>>
>
> .
>
--
Regards,
Zhen Lei
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