kexec: save PG_head_mask in VMCOREINFO

To allow filtering of huge pages, makedumpfile must be able to identify
them in the dump.  This can be done by checking the appropriate page flag,
so communicate its value to makedumpfile through the VMCOREINFO interface.

There's only one small catch.  Depending on how many page flags are
available on a given architecture, this bit can be called PG_head or
PG_compound.

I sent a similar patch back in 2012, but Eric Biederman did not like using
an #ifdef.  So, this time I'm adding a common symbol (PG_head_mask)
instead.

See https://lkml.org/lkml/2012/11/28/91 for the previous version.

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 2093eb72785ea499a32c4ab70d8f20d1715d4530..7baf0fee100fd9a6870333aa2716047f31cd82c3 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -350,6 +350,9 @@ static inline void ClearPageCompound(struct page *page)
        ClearPageHead(page);
 }
 #endif
+
+#define PG_head_mask ((1L << PG_head))
+
 #else
 /*
  * Reduce page flag use as much as possible by overlapping

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 4d7a678782b3920119d02034d8047ff26956c5aa..bf0b929e7f942a5f831a1e7de1e5efa42d7771a1 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1617,6 +1617,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 #ifdef CONFIG_MEMORY_FAILURE
        VMCOREINFO_NUMBER(PG_hwpoison);
 #endif
+       VMCOREINFO_NUMBER(PG_head_mask);
        VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
 
        arch_crash_save_vmcoreinfo();