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

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Message-ID: <CA+CK2bDmfuqnR4SuMSgLS43e=wqM9ovu_VBCYDCzdcBaFJW8+g@mail.gmail.com>
Date: Tue, 13 Jan 2026 11:21:26 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: ranxiaokai627@....com
Cc: graf@...zon.com, rppt@...nel.org, pratyush@...nel.org, 
	akpm@...ux-foundation.org, surenb@...gle.com, kexec@...ts.infradead.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, ran.xiaokai@....com.cn
Subject: Re: [PATCH v2] kho: init alloc tags when restoring pages from
 reserved memory

On Mon, Jan 12, 2026 at 10:34 PM <ranxiaokai627@....com> wrote:
>
> From: Ran Xiaokai <ran.xiaokai@....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@....com.cn>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>

Reviewed-by: Pasha Tatashin <pasha.tatashin@...een.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);
>         adjust_managed_page_count(page, nr_pages);
>         return page;
>  }
> --
> 2.25.1