mm: introduce page reference manipulation functions
The success of CMA allocation largely depends on the success of
migration and key factor of it is page reference count. Until now, page
reference is manipulated by direct calling atomic functions so we cannot
follow up who and where manipulate it. Then, it is hard to find actual
reason of CMA allocation failure. CMA allocation should be guaranteed
to succeed so finding offending place is really important.
In this patch, call sites where page reference is manipulated are
converted to introduced wrapper function. This is preparation step to
add tracepoint to each page reference manipulation function. With this
facility, we can easily find reason of CMA allocation failure. There is
no functional change in this patch.
In addition, this patch also converts reference read sites. It will
help a second step that renames page._count to something else and
prevents later attempt to direct access to it (Suggested by Andrew).
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 183b15e..1ebd65c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -165,7 +165,7 @@
* SMP requires.
*/
VM_BUG_ON_PAGE(page_count(page) == 0, page);
- atomic_inc(&page->_count);
+ page_ref_inc(page);
#else
if (unlikely(!get_page_unless_zero(page))) {
@@ -194,10 +194,10 @@
VM_BUG_ON(!in_atomic());
# endif
VM_BUG_ON_PAGE(page_count(page) == 0, page);
- atomic_add(count, &page->_count);
+ page_ref_add(page, count);
#else
- if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
+ if (unlikely(!page_ref_add_unless(page, count, 0)))
return 0;
#endif
VM_BUG_ON_PAGE(PageCompound(page) && page != compound_head(page), page);
@@ -205,19 +205,6 @@
return 1;
}
-static inline int page_freeze_refs(struct page *page, int count)
-{
- return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
-}
-
-static inline void page_unfreeze_refs(struct page *page, int count)
-{
- VM_BUG_ON_PAGE(page_count(page) != 0, page);
- VM_BUG_ON(count == 0);
-
- atomic_set(&page->_count, count);
-}
-
#ifdef CONFIG_NUMA
extern struct page *__page_cache_alloc(gfp_t gfp);
#else