mm: task dirty accounting fix

YAMAMOTO-san noticed that task_dirty_inc doesn't seem to be called properly for
cases where set_page_dirty is not used to dirty a page (eg. mark_buffer_dirty).

Additionally, there is some inconsistency about when task_dirty_inc is
called.  It is used for dirty balancing, however it even gets called for
__set_page_dirty_no_writeback.

So rather than increment it in a set_page_dirty wrapper, move it down to
exactly where the dirty page accounting stats are incremented.

Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 10 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 3c84128596ba..74dc57c74349 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -240,7 +240,7 @@ void bdi_writeout_inc(struct backing_dev_info *bdi)
 }
 EXPORT_SYMBOL_GPL(bdi_writeout_inc);
 
-static inline void task_dirty_inc(struct task_struct *tsk)
+void task_dirty_inc(struct task_struct *tsk)
 {
         prop_inc_single(&vm_dirties, &tsk->dirties);
 }
@@ -1230,6 +1230,7 @@ int __set_page_dirty_nobuffers(struct page *page)
                                 __inc_zone_page_state(page, NR_FILE_DIRTY);
                                 __inc_bdi_stat(mapping->backing_dev_info,
                                                 BDI_RECLAIMABLE);
+                                task_dirty_inc(current);
                                 task_io_account_write(PAGE_CACHE_SIZE);
                         }
                         radix_tree_tag_set(&mapping->page_tree,
@@ -1262,7 +1263,7 @@ EXPORT_SYMBOL(redirty_page_for_writepage);
  * If the mapping doesn't provide a set_page_dirty a_op, then
  * just fall through and assume that it wants buffer_heads.
  */
-static int __set_page_dirty(struct page *page)
+int set_page_dirty(struct page *page)
 {
         struct address_space *mapping = page_mapping(page);
 
@@ -1280,14 +1281,6 @@ static int __set_page_dirty(struct page *page)
         }
         return 0;
 }
-
-int set_page_dirty(struct page *page)
-{
-        int ret = __set_page_dirty(page);
-        if (ret)
-                task_dirty_inc(current);
-        return ret;
-}
 EXPORT_SYMBOL(set_page_dirty);
 
 /*