FAILED: patch "[PATCH] kho: init alloc tags when restoring pages from reserved" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x e86436ad0ad2a9aaf88802d69b68f02cbd1f04a9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026020303-drippy-appliance-a74c@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e86436ad0ad2a9aaf88802d69b68f02cbd1f04a9 Mon Sep 17 00:00:00 2001
From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Date: Thu, 22 Jan 2026 13:27:40 +0000
Subject: [PATCH] kho: init alloc tags when restoring pages from reserved
 memory

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>

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;
 }