From 09f40f98bfa2ac22a332a713629a2f8f92896834 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Fri, 2 Sep 2011 17:04:10 -0600
Subject: [PATCH] mm: Add comment explaining task state setting in
 bdi_forker_thread()

CC: Wu Fengguang <fengguang.wu@intel.com>
CC: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
---
 mm/backing-dev.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 94a047bb6c39..a87da524a4a0 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -401,6 +401,13 @@ static int bdi_forker_thread(void *ptr)
 		}
 
 		spin_lock_bh(&bdi_lock);
+		/*
+		 * In the following loop we are going to check whether we have
+		 * some work to do without any synchronization with tasks
+		 * waking us up to do work for them. So we have to set task
+		 * state already here so that we don't miss wakeups coming
+		 * after we verify some condition.
+		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 
 		list_for_each_entry(bdi, &bdi_list, bdi_list) {