From b3acc56bfe1287c6b666e80edc70b89eea2a1a80 Mon Sep 17 00:00:00 2001 From: Petr Tesarik Date: Mon, 23 Jun 2014 13:22:03 -0700 Subject: [PATCH] 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 Acked-by: Vivek Goyal Cc: Eric Biederman Cc: Paul Mackerras Cc: Fengguang Wu Cc: Benjamin Herrenschmidt Cc: Shaohua Li Cc: Alexey Kardashevskiy Cc: Sasha Levin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/page-flags.h | 3 +++ kernel/kexec.c | 1 + 2 files changed, 4 insertions(+) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 3c545b48aeab..8304959ad336 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -360,6 +360,9 @@ 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 6748688813d0..369f41a94124 100644 --- 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();