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

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Pratyush Anand <panand@redhat.com> writes:

> 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@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.
>

Yes, the flag is only needed to do the write. Why do you think we don't
need it?

> 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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-- 
  Vitaly

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