[PATCH makedumpfile] Fix wrong exclusion of compound tail pages on Linux 7.1 and later

[HAGIO KAZUHITO(萩尾 一仁)]

From: Kazuhito Hagio <k-hagio-ab at nec.com>

* Required for kernel 7.1

Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the
'struct page' to 'compound_info'), which is contained in Linux 7.1 and
later kernels, renamed its vmcoreinfo entry too.

Without the patch, makedumpfile cannot get the offset of it from the
vmcoreinfo, and cannot determine whether a page is a tail page or not.
As a result, makedumpfile can exclude required tail pages wrongly.

Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
---
 makedumpfile.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/makedumpfile.c b/makedumpfile.c
index 12fb0d816726..80637a7233f3 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -1751,6 +1751,9 @@ get_structure_info(void)
 	OFFSET_INIT(page.compound_dtor, "page", "compound_dtor");
 	OFFSET_INIT(page.compound_order, "page", "compound_order");
 	OFFSET_INIT(page.compound_head, "page", "compound_head");
+	/* Linux 7.1 and later */
+	if (OFFSET(page.compound_head) == NOT_FOUND_STRUCTURE)
+		OFFSET_INIT(page.compound_head, "page", "compound_info");
 	/* Linux 6.3 and later */
 	OFFSET_INIT(folio._folio_dtor, "folio", "_folio_dtor");
 	OFFSET_INIT(folio._folio_order, "folio", "_folio_order");
@@ -2426,6 +2429,10 @@ write_vmcoreinfo_data(void)
 	WRITE_MEMBER_OFFSET("page.private", page.private);
 	WRITE_MEMBER_OFFSET("page.compound_dtor", page.compound_dtor);
 	WRITE_MEMBER_OFFSET("page.compound_order", page.compound_order);
+	/*
+	 * on Linux 7.1 and later, this has page.compound_info's value, but
+	 * it's OK to write it as 'page.compound_head'. See read_vmcoreinfo().
+	 */
 	WRITE_MEMBER_OFFSET("page.compound_head", page.compound_head);
 	/* Linux 6.3 and later */
 	WRITE_MEMBER_OFFSET("folio._folio_dtor", folio._folio_dtor);
@@ -2876,6 +2883,8 @@ read_vmcoreinfo(void)
 	READ_MEMBER_OFFSET("page.compound_dtor", page.compound_dtor);
 	READ_MEMBER_OFFSET("page.compound_order", page.compound_order);
 	READ_MEMBER_OFFSET("page.compound_head", page.compound_head);
+	/* Linux 7.1 and later */
+	READ_MEMBER_OFFSET("page.compound_info", page.compound_head);
 	/* Linux 6.3 and later */
 	READ_MEMBER_OFFSET("folio._folio_dtor", folio._folio_dtor);
 	READ_MEMBER_OFFSET("folio._folio_order", folio._folio_order);
-- 
2.31.1