Re: [PATCH] mm/swapfile: skip HugeTLB pages for unuse_vma

[Muchun Song]

> On Oct 15, 2024, at 09:45, Liu Shixin <liushixin2@xxxxxxxxxx> wrote:
> 
> I got a bad pud error and lost a 1GB HugeTLB when calling swapoff.
> The problem can be reproduced by the following steps:
> 
> 1. Allocate an anonymous 1GB HugeTLB and some other anonymous memory.
> 2. Swapout the above anonymous memory.
> 3. run swapoff and we will get a bad pud error in kernel message:
> 
>  mm/pgtable-generic.c:42: bad pud 00000000743d215d(84000001400000e7)
> 
> We can tell that pud_clear_bad is called by pud_none_or_clear_bad
> in unuse_pud_range() by ftrace. And therefore the HugeTLB pages will
> never be freed because we lost it from page table. We can skip
> HugeTLB pages for unuse_vma to fix it.
> 
> Fixes: 0fe6e20b9c4c ("hugetlb, rmap: add reverse mapping for hugepage")
> Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>

Acked-by: Muchun Song <muchun.song@xxxxxxxxx>

Thanks.