Re: [PATCH v2] kho: init alloc tags when restoring pages from reserved memory

[Pratyush Yadav <pratyush@kernel.org>]

Hi Ran,

On Tue, Jan 13 2026, ranxiaokai627@163.com wrote:

> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
>
> Memblock pages (including reserved memory) should have their allocation
> tags initialized to CODETAG_EMPTY via clear_page_tag_ref() before being
> released to the page allocator. When kho restores pages through
> kho_restore_page(), missing this call causes mismatched
> allocation/deallocation tracking and below warning message:
> alloc_tag was not set
> WARNING: include/linux/alloc_tag.h:164 at ___free_pages+0xb8/0x260, CPU#1: swapper/0/1
> RIP: 0010:___free_pages+0xb8/0x260
>  kho_restore_vmalloc+0x187/0x2e0
>  kho_test_init+0x3c4/0xa30
>  do_one_initcall+0x62/0x2b0
>  kernel_init_freeable+0x25b/0x480
>  kernel_init+0x1a/0x1c0
>  ret_from_fork+0x2d1/0x360
>
> Add missing clear_page_tag_ref() annotation in kho_restore_page() to
> fix this.
>
> Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation")
> Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Reviewed-by: Suren Baghdasaryan <surenb@google.com>
> ---
>  kernel/liveupdate/kexec_handover.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index cd6b3fb9dcae..2d47f2c50bd8 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -268,6 +268,7 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
>  	else
>  		kho_init_pages(page, nr_pages);
>  
> +	clear_page_tag_ref(page);

You are only clearing the tag for the head page. The tail pages are
still un-initialized. Is that intentional?

What about non-compound pages (the ones you get from
kho_restore_pages(), aka when is_folio is false)? Do we need to clear
the tag on all pages in that case?

>  	adjust_managed_page_count(page, nr_pages);
>  	return page;
>  }