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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 1c290f6421
("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: Atsushi Kumagai <ats-kumagai@wm.jp.nec.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Atsushi Kumagai 2016-04-28 16:18:21 -07:00 committed by Linus Torvalds
parent 8639a847b0
commit d7f53518f7
1 changed files with 1 additions and 0 deletions
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kernel/kexec_core.c
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@ -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);
#ifdef CONFIG_FLAT_NODE_MEM_MAP