The patch titled
Subject: kexec: export OFFSET(page.compound_head) to find out compound tail page
has been removed from the -mm tree. Its filename was
kexec-export-offsetpagecompound_head-to-find-out-compound-tail-page.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Atsushi Kumagai <ats-kumagai@xxxxxxxxxxxxx>
Subject: 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 1c290f642101e6 ("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@xxxxxxxxxxxxx>
Acked-by: Dave Young <dyoung@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kexec_core.c | 1 +
1 file changed, 1 insertion(+)
diff -puN kernel/kexec_core.c~kexec-export-offsetpagecompound_head-to-find-out-compound-tail-page kernel/kexec_core.c
--- a/kernel/kexec_core.c~kexec-export-offsetpagecompound_head-to-find-out-compound-tail-page
+++ a/kernel/kexec_core.c
@@ -1417,6 +1417,7 @@ static int __init crash_save_vmcoreinfo_
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
_
Patches currently in -mm which might be from ats-kumagai@xxxxxxxxxxxxx are
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