tree 4fdd506ffcbf64fb211c70e8bce92c251af903cf
parent 8639a847b0e11f8d2daa3eafe15a9609c91fd357
author Atsushi Kumagai <ats-kumagai@wm.jp.nec.com> 1461885501 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1461897244 -0700

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 1c290f642101
("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>