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

[ranxiaokai627@163.com]

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")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.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);
+	}
+
 	adjust_managed_page_count(page, nr_pages);
 	return page;
 }
-- 
2.25.1