Hi Aneesh,

On Thu, Apr 22, 2021 at 11:13:17AM +0530, Aneesh Kumar K.V wrote:
> pmd/pud_populate is the right interface to be used to set the respective
> page table entries. Some architectures like ppc64 do assume that set_pmd/pud_at
> can only be used to set a hugepage PTE. Since we are not setting up a hugepage
> PTE here, use the pmd/pud_populate interface.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  mm/mremap.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/mremap.c b/mm/mremap.c
> index ec8f840399ed..574287f9bb39 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -26,6 +26,7 @@
>  
>  #include <asm/cacheflush.h>
>  #include <asm/tlbflush.h>
> +#include <asm/pgalloc.h>
>  
>  #include "internal.h"
>  
> @@ -257,9 +258,8 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
>  	pmd_clear(old_pmd);
>  
>  	VM_BUG_ON(!pmd_none(*new_pmd));
> +	pmd_populate(mm, new_pmd, (pgtable_t)pmd_page_vaddr(pmd));
>  
> -	/* Set the new pmd */
> -	set_pmd_at(mm, new_addr, new_pmd, pmd);
>  	flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
>  	if (new_ptl != old_ptl)
>  		spin_unlock(new_ptl);
> @@ -306,8 +306,7 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
>  
>  	VM_BUG_ON(!pud_none(*new_pud));
>  
> -	/* Set the new pud */
> -	set_pud_at(mm, new_addr, new_pud, pud);
> +	pud_populate(mm, new_pud, (pmd_t *)pud_page_vaddr(pud));
>  	flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
>  	if (new_ptl != old_ptl)
>  		spin_unlock(new_ptl);
> -- 
> 2.30.2
> 
> 

This commit causes my WSL2 VM to close when compiling something memory
intensive, such as an x86_64_defconfig + CONFIG_LTO_CLANG_FULL=y kernel
or LLVM/Clang. Unfortunately, I do not have much further information to
provide since I do not see any sort of splat in dmesg right before it
closes and I have found zero information about getting the previous
kernel message in WSL2 (custom init so no systemd or anything).

The config file is the stock one from Microsoft:

https://github.com/microsoft/WSL2-Linux-Kernel/blob/a571dc8cedc8e0e56487c0dc93243e0b5db8960a/Microsoft/config-wsl

I have attached my .config anyways, which includes CONFIG_DEBUG_VM,
which does not appear to show anything out of the ordinary. I have also
attached a dmesg just in case anything sticks out. I am happy to provide
any additional information or perform additional debugging steps as
needed.

Cheers,
Nathan

$ git bisect log
# bad: [cd557f1c605fc5a2c0eb0b540610f50dc67dd849] Add linux-next specific files for 20210514
# good: [315d99318179b9cd5077ccc9f7f26a164c9fa998] Merge tag 'pm-5.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
git bisect start 'cd557f1c605fc5a2c0eb0b540610f50dc67dd849' '315d99318179b9cd5077ccc9f7f26a164c9fa998'
# good: [9634d7cb3c506ae886a5136d12b4af696b9cee8a] Merge remote-tracking branch 'drm-misc/for-linux-next'
git bisect good 9634d7cb3c506ae886a5136d12b4af696b9cee8a
# good: [294636a24ae819a7caf0807d05d8eb5b964ec06f] Merge remote-tracking branch 'rcu/rcu/next'
git bisect good 294636a24ae819a7caf0807d05d8eb5b964ec06f
# good: [cb753d0611f912439c8e814f4254d15fa8fa1d75] Merge remote-tracking branch 'gpio-brgl/gpio/for-next'
git bisect good cb753d0611f912439c8e814f4254d15fa8fa1d75
# bad: [b1e7389449084b74a044a70860c6a1c7466781cb] lib/string_helpers: switch to use BIT() macro
git bisect bad b1e7389449084b74a044a70860c6a1c7466781cb
# bad: [bf5570ed0654a21000e5dad9243ea1ba30bfe208] kasan: use dump_stack_lvl(KERN_ERR) to print stacks
git bisect bad bf5570ed0654a21000e5dad9243ea1ba30bfe208
# good: [4a292ff7a819404039588c7a9af272aca22c869e] fixup! mm: gup: pack has_pinned in MMF_HAS_PINNED
git bisect good 4a292ff7a819404039588c7a9af272aca22c869e
# good: [5ed68c90c7fb884c3c493d5529aca79dcf125848] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock
git bisect good 5ed68c90c7fb884c3c493d5529aca79dcf125848
# good: [f96ae2c1e63b71134e216e9940df3f2793a9a4b1] mm/memory.c: fix comment of finish_mkwrite_fault()
git bisect good f96ae2c1e63b71134e216e9940df3f2793a9a4b1
# bad: [5b0a28a7f9f5fdc2fe5a5e2cce7ea17b98e5eaeb] mm/mremap: use range flush that does TLB and page walk cache flush
git bisect bad 5b0a28a7f9f5fdc2fe5a5e2cce7ea17b98e5eaeb
# bad: [dbee97d1f49a2f2f1f5c26bf15151cc998572e89] mm/mremap: use pmd/pud_poplulate to update page table entries
git bisect bad dbee97d1f49a2f2f1f5c26bf15151cc998572e89
# good: [c4c8a76d96a7d38d1ec8732e3f852418d18a7424] selftest/mremap_test: avoid crash with static build
git bisect good c4c8a76d96a7d38d1ec8732e3f852418d18a7424
# first bad commit: [dbee97d1f49a2f2f1f5c26bf15151cc998572e89] mm/mremap: use pmd/pud_poplulate to update page table entries