[PATCH] makedumpfile: support _count -> _refcount rename in struct page

[Vitaly Kuznetsov]

_count member was renamed to _refcount in linux commit commit 0139aa7b7fa12
("mm: rename _count, field of the struct page, to _refcount") and this
broke makedumpfile. The reason for making the change was to find all users
accessing it directly and not through the recommended API. I tried
suggesting to revert the change but failed, I see no other choice than to
start supporting both _count and _refcount in makedumpfile.

Signed-off-by: Vitaly Kuznetsov <vkuznets at redhat.com>
---
- 'crash' tool is now broken as well.
---
 makedumpfile.c | 18 +++++++++++++++++-
 makedumpfile.h |  1 +
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index 853b999..96dfe39 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -1580,6 +1580,13 @@ get_structure_info(void)
 	SIZE_INIT(page, "page");
 	OFFSET_INIT(page.flags, "page", "flags");
 	OFFSET_INIT(page._count, "page", "_count");
+	if (OFFSET(page._count) == NOT_FOUND_STRUCTURE) {
+		info->flag_refcount = TRUE;
+		OFFSET_INIT(page._count, "page", "_refcount");
+	} else {
+		info->flag_refcount = FALSE;
+	}
+
 	OFFSET_INIT(page.mapping, "page", "mapping");
 	OFFSET_INIT(page._mapcount, "page", "_mapcount");
 	OFFSET_INIT(page.private, "page", "private");
@@ -2151,7 +2158,10 @@ write_vmcoreinfo_data(void)
 	 * write the member offset of 1st kernel
 	 */
 	WRITE_MEMBER_OFFSET("page.flags", page.flags);
-	WRITE_MEMBER_OFFSET("page._count", page._count);
+	if (info->flag_refcount)
+		WRITE_MEMBER_OFFSET("page._refcount", page._count);
+	else
+		WRITE_MEMBER_OFFSET("page._count", page._count);
 	WRITE_MEMBER_OFFSET("page.mapping", page.mapping);
 	WRITE_MEMBER_OFFSET("page.lru", page.lru);
 	WRITE_MEMBER_OFFSET("page._mapcount", page._mapcount);
@@ -2492,6 +2502,12 @@ read_vmcoreinfo(void)
 
 	READ_MEMBER_OFFSET("page.flags", page.flags);
 	READ_MEMBER_OFFSET("page._count", page._count);
+	if (OFFSET(page._count) == NOT_FOUND_STRUCTURE) {
+		info->flag_refcount = TRUE;
+		READ_MEMBER_OFFSET("page._refcount", page._count);
+	} else {
+		info->flag_refcount = FALSE;
+	}
 	READ_MEMBER_OFFSET("page.mapping", page.mapping);
 	READ_MEMBER_OFFSET("page.lru", page.lru);
 	READ_MEMBER_OFFSET("page._mapcount", page._mapcount);
diff --git a/makedumpfile.h b/makedumpfile.h
index 251d4bf..3742389 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -1100,6 +1100,7 @@ struct DumpInfo {
 	int		flag_nospace;	     /* the flag of "No space on device" error */
 	int		flag_vmemmap;        /* kernel supports vmemmap address space */
 	int		flag_excludevm;      /* -e - excluding unused vmemmap pages */
+	int		flag_refcount;       /* _count is renamed to _refcount */
 	unsigned long	vaddr_for_vtop;      /* virtual address for debugging */
 	long		page_size;           /* size of page */
 	long		page_shift;
-- 
2.5.5