page_writeback: revive cancel_dirty_page() in a restricted form

cancel_dirty_page() had some issues and b9ea25152e56 ("page_writeback:
clean up mess around cancel_dirty_page()") replaced it with
account_page_cleaned() which makes the caller responsible for clearing
the dirty bit; unfortunately, the planned changes for cgroup writeback
support requires synchronization between dirty bit manipulation and
stat updates.  While we can open-code such synchronization in each
account_page_cleaned() callsite, that's gonna be unnecessarily awkward
and verbose.

This patch revives cancel_dirty_page() but in a more restricted form.
All it does is TestClearPageDirty() followed by account_page_cleaned()
invocation if the page was dirty.  This helper covers all
account_page_cleaned() usages except for __delete_from_page_cache()
which is a special case anyway and left alone.  As this leaves no
module user for account_page_cleaned(), EXPORT_SYMBOL() is dropped
from it.

This patch just revives cancel_dirty_page() as a trivial wrapper to
replace equivalent usages and doesn't introduce any functional
changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index f96173a..f21327d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3232,8 +3232,8 @@ int try_to_free_buffers(struct page *page)
 	 * to synchronise against __set_page_dirty_buffers and prevent the
 	 * dirty bit from being lost.
 	 */
-	if (ret && TestClearPageDirty(page))
-		account_page_cleaned(page, mapping);
+	if (ret)
+		cancel_dirty_page(page);
 	spin_unlock(&mapping->private_lock);
 out:
 	if (buffers_to_free) {