Commit d7f53518 authored by Atsushi Kumagai's avatar Atsushi Kumagai Committed by Linus Torvalds

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 1c290f64
("mm: sanitize page->mapping for tail pages").

If makedumpfile checks page->mapping of a 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.

The problem is that unnecessary hugepages won't be removed from a dump
file in kernels 4.5.x and later.  This means that extra disk space would
be consumed.  It's a problem, but not critical.
Signed-off-by: default avatarAtsushi Kumagai <>
Acked-by: default avatarDave Young <>
Cc: "Eric W. Biederman" <>
Cc: Vivek Goyal <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 8639a847
......@@ -1417,6 +1417,7 @@ 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);
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