linux-kernel - [PATCH 3/4] introduce sb_lockdep

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Date:	Mon, 13 Jul 2015 23:25:55 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Daniel Wagner <daniel.wagner@...-carit.de>,
	Davidlohr Bueso <dave@...olabs.net>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] introduce sb_lockdep_release()

Move the "fool the lockdep" code from sb_wait_write() into the new
simple helper, sb_lockdep_release().

This makes sense in any case afaics, this way s_op->freeze_fs(sb) is
called with these write locks held as it seen by lockdep.
---
 fs/super.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index c23bafc..94303fc 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1229,12 +1229,7 @@ static void sb_wait_write(struct super_block *sb, int level)
 {
 	s64 writers;
 
-	/*
-	 * We just cycle-through lockdep here so that it does not complain
-	 * about returning with lock to userspace
-	 */
 	rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
-	rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
 
 	do {
 		DEFINE_WAIT(wait);
@@ -1254,6 +1249,16 @@ static void sb_wait_write(struct super_block *sb, int level)
 	} while (writers);
 }
 
+/* Avoid the warning from lockdep_sys_exit() */
+static void sb_lockdep_release(struct super_block *sb)
+{
+	int level;
+
+	for (level = 0; level < SB_FREEZE_LEVELS; ++level) {
+		rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
+	}
+}
+
 static void sb_unlock_frozen(struct super_block *sb)
 {
 	smp_wmb();
@@ -1356,6 +1361,7 @@ int freeze_super(struct super_block *sb)
 	 * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
 	 */
 	sb->s_writers.frozen = SB_FREEZE_COMPLETE;
+	sb_lockdep_release(sb);
 	up_write(&sb->s_umount);
 	return 0;
 }
-- 
1.5.5.1

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