FAILED: patch "[PATCH] mm/memory_hotplug: use pfn math in place of direct struct" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-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 <[email protected]>.

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-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 1640a0ef80f6d572725f5b0330038c18e98ea168
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023112351-skipping-barman-8e9a@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 1640a0ef80f6d572725f5b0330038c18e98ea168 Mon Sep 17 00:00:00 2001
From: Zi Yan <[email protected]>
Date: Wed, 13 Sep 2023 16:12:46 -0400
Subject: [PATCH] mm/memory_hotplug: use pfn math in place of direct struct
page manipulation

When dealing with hugetlb pages, manipulating struct page pointers directly can get to wrong struct page, since struct page is not guaranteed to be contiguous on SPARSEMEM without VMEMMAP. Use pfn calculation to handle it properly.

Without the fix, a wrong number of page might be skipped. Since skip cannot be negative, scan_movable_page() will end early and might miss a movable page with -ENOENT. This might fail offline_pages(). No bug is reported. The fix comes from code inspection.

index 1b03f4ec6fd2..3b301c4023ff 100644
@@ -1689,7 +1689,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
 		 */
 		if (HPageMigratable(head))
 			goto found;
-		skip = compound_nr(head) - (page - head);
+		skip = compound_nr(head) - (pfn - page_to_pfn(head));
 		pfn += skip - 1;
 	}
 	return -ENOENT;