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

Will Deacon
2023-06-20T09:43:25Z

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;