linux-kernel - [PATCH 2/2] kexec: export OFFSET(page.compound

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Message-ID: <0910DD04CBD6DE4193FCF86B9C00BE9701E25FD3@BPXM01GP.gisp.nec.co.jp>
Date:	Tue, 1 Mar 2016 06:14:38 +0000
From:	Atsushi Kumagai <ats-kumagai@...jp.nec.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: [PATCH 2/2] kexec: export OFFSET(page.compound_head) to find out
 compound tail page

PageAnon() always look at head page to check PAGE_MAPPING_ANON and
tail page's page->mapping has just a poisoned data since commit
1c290f642101e6.

If makedumpfile checks page->mapping of an compound tail page to
distinguish anonymous page as usual, it must fail in newer kernel.
So it's necessary to export OFFSET(page.compound_head) to
avoid checking compound tail pages.

Signed-off-by: Atsushi Kumagai <ats-kumagai@...jp.nec.com>
---
 kernel/kexec_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 7c0b61d..4726999 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1415,6 +1415,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 	VMCOREINFO_OFFSET(page, private);
 	VMCOREINFO_OFFSET(page, compound_dtor);
 	VMCOREINFO_OFFSET(page, compound_order);
+	VMCOREINFO_OFFSET(page, compound_head);
 	VMCOREINFO_OFFSET(pglist_data, node_zones);
 	VMCOREINFO_OFFSET(pglist_data, nr_zones);
 #ifdef CONFIG_FLAT_NODE_MEM_MAP
-- 
2.7.2