Re: [PATCH 6.18.y] kho: init alloc tags when restoring pages from reserved memory

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Feb 03, 2026 at 07:26:54PM -0500, Sasha Levin wrote:
> From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> 
> [ Upstream commit e86436ad0ad2a9aaf88802d69b68f02cbd1f04a9 ]
> 
> 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.
> 
> Link: https://lkml.kernel.org/r/20260122132740.176468-1-ranxiaokai627@163.com
> Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation")
> Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
> Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Cc: Alexander Graf <graf@amazon.com>
> Cc: Kent Overstreet <kent.overstreet@linux.dev>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  kernel/kexec_handover.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
> index 03d12e27189fc..db08c1a2e1f80 100644
> --- a/kernel/kexec_handover.c
> +++ b/kernel/kexec_handover.c
> @@ -260,6 +260,14 @@ static struct page *kho_restore_page(phys_addr_t phys)
>  	if (info.order > 0)
>  		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);
> +	}
> +

Breaks the build :(