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

[Atsushi Kumagai]

Hello Vitaly,

>_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>

Thanks for your report and fixing it.

>---
>- '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;
>+	}
>+

I prefer to check the new symbol name first since it's likely
from now on.

> 	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;
>+	}

same as OFFSET_INIT.

Thanks,
Atsushi Kumagai

> 	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