[PATCH v2] makedumpfile: support _count -> _refcount rename in struct page

[Pratyush Anand]

On 21/06/2016:05:43:29 AM, Atsushi Kumagai wrote:
> Hello Vitaly,
> 
> >_count member was renamed to _refcount in linux 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>
> >---
> >Changes since 'v1':
> >- Make '_refcount' the default [Atsushi Kumagai]

Sorry, I missed this conversation earlier.

> 
> Good fix, I'll merge this into v1.6.1.
> 
> Thanks,
> Atsushi Kumagai
> 
> >---
> > makedumpfile.c | 26 +++++++++++++++++++++-----
> > makedumpfile.h |  3 ++-
> > 2 files changed, 23 insertions(+), 6 deletions(-)
> >
> >diff --git a/makedumpfile.c b/makedumpfile.c
> >index 853b999..fd884d3 100644
> >--- a/makedumpfile.c
> >+++ b/makedumpfile.c
> >@@ -1579,7 +1579,14 @@ get_structure_info(void)
> > 	 */
> > 	SIZE_INIT(page, "page");
> > 	OFFSET_INIT(page.flags, "page", "flags");
> >-	OFFSET_INIT(page._count, "page", "_count");
> >+	OFFSET_INIT(page._refcount, "page", "_refcount");
> >+	if (OFFSET(page._refcount) == NOT_FOUND_STRUCTURE) {
> >+		info->flag_use_count = TRUE;
> >+		OFFSET_INIT(page._refcount, "page", "_count");
> >+	} else {
> >+		info->flag_use_count = FALSE;

Probably we could have avoided this flag and could have solved it same way as we
have solved for other such kernel changes, like that of "module.module_core".
Infact, we do not need to add "_refcount" in makedumpfile's page struct.

See:
https://github.com/pratyushanand/makedumpfile/commit/8c58c177d27d4ac31db2ee42442ef056dbbd2c93

~Pratyush

> >+	}
> >+
> > 	OFFSET_INIT(page.mapping, "page", "mapping");
> > 	OFFSET_INIT(page._mapcount, "page", "_mapcount");
> > 	OFFSET_INIT(page.private, "page", "private");
> >@@ -2044,7 +2051,7 @@ get_mem_type(void)
> >
> > 	if ((SIZE(page) == NOT_FOUND_STRUCTURE)
> > 	    || (OFFSET(page.flags) == NOT_FOUND_STRUCTURE)
> >-	    || (OFFSET(page._count) == NOT_FOUND_STRUCTURE)
> >+	    || (OFFSET(page._refcount) == NOT_FOUND_STRUCTURE)
> > 	    || (OFFSET(page.mapping) == NOT_FOUND_STRUCTURE)) {
> > 		ret = NOT_FOUND_MEMTYPE;
> > 	} else if ((((SYMBOL(node_data) != NOT_FOUND_SYMBOL)
> >@@ -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_use_count)
> >+		WRITE_MEMBER_OFFSET("page._count", page._refcount);
> >+	else
> >+		WRITE_MEMBER_OFFSET("page._refcount", page._refcount);
> > 	WRITE_MEMBER_OFFSET("page.mapping", page.mapping);
> > 	WRITE_MEMBER_OFFSET("page.lru", page.lru);
> > 	WRITE_MEMBER_OFFSET("page._mapcount", page._mapcount);
> >@@ -2491,7 +2501,13 @@ read_vmcoreinfo(void)
> >
> >
> > 	READ_MEMBER_OFFSET("page.flags", page.flags);
> >-	READ_MEMBER_OFFSET("page._count", page._count);
> >+	READ_MEMBER_OFFSET("page._refcount", page._refcount);
> >+	if (OFFSET(page._refcount) == NOT_FOUND_STRUCTURE) {
> >+		info->flag_use_count = TRUE;
> >+		READ_MEMBER_OFFSET("page._count", page._refcount);
> >+	} else {
> >+		info->flag_use_count = FALSE;
> >+	}
> > 	READ_MEMBER_OFFSET("page.mapping", page.mapping);
> > 	READ_MEMBER_OFFSET("page.lru", page.lru);
> > 	READ_MEMBER_OFFSET("page._mapcount", page._mapcount);
> >@@ -5615,7 +5631,7 @@ __exclude_unnecessary_pages(unsigned long mem_map,
> > 		pcache  = page_cache + (index_pg * SIZE(page));
> >
> > 		flags   = ULONG(pcache + OFFSET(page.flags));
> >-		_count  = UINT(pcache + OFFSET(page._count));
> >+		_count  = UINT(pcache + OFFSET(page._refcount));
> > 		mapping = ULONG(pcache + OFFSET(page.mapping));
> >
> > 		if (OFFSET(page.compound_order) != NOT_FOUND_STRUCTURE) {
> >diff --git a/makedumpfile.h b/makedumpfile.h
> >index 251d4bf..533e5b8 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_use_count;      /* _refcount is named _count in struct page */
> > 	unsigned long	vaddr_for_vtop;      /* virtual address for debugging */
> > 	long		page_size;           /* size of page */
> > 	long		page_shift;
> >@@ -1483,7 +1484,7 @@ struct size_table {
> > struct offset_table {
> > 	struct page {
> > 		long	flags;
> >-		long	_count;
> >+		long	_refcount;
> > 		long	mapping;
> > 		long	lru;
> > 		long	_mapcount;
> >--
> >2.5.5
> 
> 
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