sysv: drop lock/unlock super

Removed lock/unlock super. Added a new private s_lock mutex.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/sysv/inode.c b/fs/sysv/inode.c
index d33e506..c327d4e 100644
--- a/fs/sysv/inode.c
+++ b/fs/sysv/inode.c
@@ -36,7 +36,7 @@
 	struct sysv_sb_info *sbi = SYSV_SB(sb);
 	unsigned long time = get_seconds(), old_time;
 
-	lock_super(sb);
+	mutex_lock(&sbi->s_lock);
 
 	/*
 	 * If we are going to write out the super block,
@@ -51,7 +51,7 @@
 		mark_buffer_dirty(sbi->s_bh2);
 	}
 
-	unlock_super(sb);
+	mutex_unlock(&sbi->s_lock);
 
 	return 0;
 }