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>

1 files changed, 5 insertions, 5 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index fdaf0818fb30..577c94b8e959 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -349,7 +349,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
                 return -EAGAIN;
         }
 
-        if (!page_freeze_refs(page, expected_count)) {
+        if (!page_ref_freeze(page, expected_count)) {
                 spin_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
         }
@@ -363,7 +363,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
          */
         if (mode == MIGRATE_ASYNC && head &&
                         !buffer_migrate_lock_buffers(head, mode)) {
-                page_unfreeze_refs(page, expected_count);
+                page_ref_unfreeze(page, expected_count);
                 spin_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
         }
@@ -397,7 +397,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
          * to one less reference.
          * We know this isn't the last reference.
          */
-        page_unfreeze_refs(page, expected_count - 1);
+        page_ref_unfreeze(page, expected_count - 1);
 
         spin_unlock(&mapping->tree_lock);
         /* Leave irq disabled to prevent preemption while updating stats */
@@ -451,7 +451,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
                 return -EAGAIN;
         }
 
-        if (!page_freeze_refs(page, expected_count)) {
+        if (!page_ref_freeze(page, expected_count)) {
                 spin_unlock_irq(&mapping->tree_lock);
                 return -EAGAIN;
         }
@@ -463,7 +463,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 
         radix_tree_replace_slot(pslot, newpage);
 
-        page_unfreeze_refs(page, expected_count - 1);
+        page_ref_unfreeze(page, expected_count - 1);
 
         spin_unlock_irq(&mapping->tree_lock);