Re: [PATCH] mm/hugetlb: fix memory offline failure due to hwpoisoned file hugetlb

[Miaohe Lin <linmiaohe@huawei.com>]

On 2026/3/18 10:07, Jinjiang Tu wrote:
> When a file hugetlb folio triggers UCE, me_huge_page() will keep the
> hugetlb folio in pagcahe with refcount increased and PG_hwpoison set. Even
> after the hugetlb file is deleted, the hugetlb folio is still leaked.
> 
> If we want to offline the memory block that the hwpoisoned hugetlb folio
> belongs to, it fails in dissolve_free_hugetlb_folios() due to the
> hwpoisoned hugetlb folio isn't free.
> 
> I can reproduce this issue with the following steps in qemu:
>  1) echo offline >/sys/devices/system/memory/auto_online_blocks
>  2) in qemu monitor:
>        object_add memory-backend-ram,id=mem10,size=1G
>        device_add pc-dimm,id=dimm1,memdev=mem10,node=2
>  3) echo online_movable > /sys/devices/system/node/node2/memory136/state
>  4) echo 5 > /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages
>  5) run ./hugetlb_file. This process will receive SIGBUS.
>  6) remove the hugetlbfs file.
>  7) echo offline > /sys/devices/system/node/node2/memory136/state
> 
> hugetlb_file.c:
>   fd = open("/dev/hugepages/my_hugepage_file", O_CREAT | O_RDWR, 0755);
>   fallocate(fd, 0, 0, HUGEPAGE_SIZE * 2);
>   addr = mmap(NULL, HUGEPAGE_SIZE * 2, PROT_READ | PROT_WRITE,
> 		MAP_SHARED | MAP_HUGETLB, fd, 0);
>   memset(addr, 0xaa, HUGEPAGE_SIZE * 2);
>   madvise(addr, HUGEPAGE_SIZE, MADV_HWPOISON);
> 
> To fix it, when deleting hugetlb folio from pagecache, mark the hugetlb
> folio temporary, and put the refcount increased by memory-failure. After
> the hugetlb folio is deleted from pagecache, the refcount is decreased to
> zero and the hugetlb folio is dissolved.

Thanks for your patch.

> 
> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
> ---
>  fs/hugetlbfs/inode.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 3f70c47981de..6bebe2e67f3e 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -603,6 +603,11 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
>  							index, truncate_op))
>  				freed++;
>  
> +			if (unlikely(folio_test_hwpoison(folio))) {
> +				folio_set_hugetlb_temporary(folio);

I think it is not needed to mark the hugetlb folio as temporary because
offline_pages() will call dissolve_free_hugetlb_folios().

> +				folio_put(folio);

__get_huge_page_for_hwpoison() will always set hwpoison for hugetlb folio
even without page refcnt increased. So this folio_put() might be unexpected.
Please see [1] for detail.

Thanks.
.