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>
>
> 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
>
_______________________________________________
kexec mailing list
kexec@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/kexec
