Re: linux-next: manual merge of the mm tree with Linus' tree

Jain, Ayush
2023-06-20T15:03:07Z

Hello Will,
On 6/20/2023 3:13 PM, Will Deacon wrote:
> On Mon, Jun 19, 2023 at 02:39:44PM -0700, Andrew Morton wrote:
>> On Mon, 19 Jun 2023 21:43:11 +0100 Will Deacon <will@kernel.org> wrote:
>>
>>>> /*
>>>> * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
>>>> * VM_GROWSUP VMA. Such VMAs can change their size under
>>>
>>> This resolution seems to be causing horrible problems on arm64 with 16k
>>> pages. I see things like the crash below, but the two branches being merged
>>> are fine on their own.
>>
>> I've dropped the mm.git side of this conflict so next -next should
>> be better.
>
> Thanks, Andrew. next-20230620 is still broken, so I came up with the diff
> below in the meantime which seems to resolve the crashes. I don't pretend
> to understand the VMA iterator stuff well enough though, so I may have
> missed something else.
>
> Will
>
> --->8
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 9a93b054148a..4c82e9b36fb3 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2396,6 +2396,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
> if (error)
> goto end_split_failed;
> }
> + mas_set(&mas_detach, count);
> vma_start_write(next);
> if (mas_store_gfp(&mas_detach, next, GFP_KERNEL))
> goto munmap_gather_failed;

Thanks, Will. I have been able to reproduce similar kernel panics on AMD x86 platform
on next-20230619 and next-20230620.
By applying your patch kernel looks to being able to boot now.

Tested-by: Ayush Jain <Ayush.jain3@amd.com>