writeback: fix inode cgroup switching comment

Commit 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb
transaction and use it for stat updates") refers to
inode_switch_wb_work_fn() which never got merged.

Switch the comments to inode_switch_wbs_work_fn().

Link: http://lkml.kernel.org/r/20190305004617.142590-1-gthelen@google.com
Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates")
Signed-off-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fd423fe..08f2604 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2091,7 +2091,7 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
  * I_WB_SWITCH		Cgroup bdi_writeback switching in progress.  Used to
  *			synchronize competing switching instances and to tell
  *			wb stat updates to grab the i_pages lock.  See
- *			inode_switch_wb_work_fn() for details.
+ *			inode_switch_wbs_work_fn() for details.
  *
  * I_OVL_INUSE		Used by overlayfs to get exclusive ownership on upper
  *			and work dirs among overlayfs mounts.