reiserfs: convert j_lock to mutex

j_lock is a semaphore but uses it as if it were a mutex.  This patch converts
it to a mutex.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Edward Shishkin <edward.shishkin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/reiserfs_fs_sb.h b/include/linux/reiserfs_fs_sb.h
index 336ee43..49b639b 100644
--- a/include/linux/reiserfs_fs_sb.h
+++ b/include/linux/reiserfs_fs_sb.h
@@ -193,7 +193,7 @@
 	struct buffer_head *j_header_bh;
 
 	time_t j_trans_start_time;	/* time this transaction started */
-	struct semaphore j_lock;
+	struct mutex j_mutex;
 	struct semaphore j_flush_sem;
 	wait_queue_head_t j_join_wait;	/* wait for current transaction to finish before starting new one */
 	atomic_t j_jlock;	/* lock for j_join_wait */