linux-kernel - Re: [PATCH RESEND v3] kho: init alloc tags when restoring pages from reserved memory

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Message-ID: <CA+CK2bAMBxZMBGS6DLaEO7M92vutW5UhfJNSwk+okdVu=EYu+g@mail.gmail.com>
Date: Thu, 22 Jan 2026 13:09:06 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: ranxiaokai627@....com
Cc: pratyush@...nel.org, surenb@...gle.com, akpm@...ux-foundation.org, 
	kent.overstreet@...ux.dev, rppt@...nel.org, graf@...zon.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, kexec@...ts.infradead.org, 
	ran.xiaokai@....com.cn, stable@...r.kernel.org
Subject: Re: [PATCH RESEND v3] kho: init alloc tags when restoring pages from
 reserved memory

On Thu, Jan 22, 2026 at 8:28 AM <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")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
> ---
>
> v2 -> v3:
>  - also call clear_page_tag_ref() for non-compound order-0 tail pages
>
>  kernel/liveupdate/kexec_handover.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index d4482b6e3cae..96767b106cac 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -255,6 +255,14 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
>         if (is_folio && info.order)
>                 prep_compound_page(page, info.order);
>
> +       /* Always mark headpage's codetag as empty to avoid accounting mismatch */
> +       clear_page_tag_ref(page);
> +       if (!is_folio) {
> +               /* Also do that for the non-compound tail pages */
> +               for (unsigned int i = 1; i < nr_pages; i++)
> +                       clear_page_tag_ref(page + i);
> +       }
> +

Reviewed-by: Pasha Tatashin <pasha.tatashin@...een.com>

Pasha

>         adjust_managed_page_count(page, nr_pages);
>         return page;
>  }
> --
> 2.25.1
>
>
>