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

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Message-ID: <20260121143430.175294-1-ranxiaokai627@163.com>
Date: Wed, 21 Jan 2026 14:34:30 +0000
From: ranxiaokai627@....com
To: pratyush@...nel.org,
	surenb@...gle.com,
	akpm@...ux-foundation.org
Cc: pasha.tatashin@...een.com,
	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,
	ranxiaokai627@....com
Subject: [PATCH v3] kho: init alloc tags when restoring pages from reserved memory

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.

Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
---
It is based on linux-next 20260120. I dont konw whether this base is ok ?

 kernel/liveupdate/kexec_handover.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 43d9d2661163..8f7e09d67e1b 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -219,8 +219,11 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
 /* For physically contiguous 0-order pages. */
 static void kho_init_pages(struct page *page, unsigned long nr_pages)
 {
-	for (unsigned long i = 0; i < nr_pages; i++)
+	for (unsigned long i = 0; i < nr_pages; i++) {
 		set_page_count(page + i, 1);
+		/* Mark the codetag as empty to avoid accounting mismatch */
+		clear_page_tag_ref(page + i);
+	}
 }
 
 static void kho_init_folio(struct page *page, unsigned int order)
@@ -236,6 +239,9 @@ static void kho_init_folio(struct page *page, unsigned int order)
 
 	if (order > 0)
 		prep_compound_page(page, order);
+
+	/* Mark the codetag as empty to avoid accounting mismatch */
+	clear_page_tag_ref(page);
 }
 
 static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
@@ -265,7 +271,6 @@ 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