On 05/31/23 at 09:16am, Leizhen (ThunderTown) wrote:
>
>
> 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?
OK, I misread your log. You are saying the new_size is close to
crashk_res.end but has a tiny difference in your example, I
thought the new_size is smaller than KEXEC_CRASH_MEM_ALIGN which is just
in the opposite direction.
Yea, it does have the possibility to waste a ram_res but does nothing
even though the chance is very small.
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
>
> 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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