ocfs2: Remove EXIT from masklog.

mlog_exit is used to record the exit status of a function.
But because it is added in so many functions, if we enable it,
the system logs get filled up quickly and cause too much I/O.
So actually no one can open it for a production system or even
for a test.

This patch just try to remove it or change it. So:
1. if all the error paths already use mlog_errno, it is just removed.
   Otherwise, it will be replaced by mlog_errno.
2. if it is used to print some return value, it is replaced with
   mlog(0,...).
mlog_exit_ptr is changed to mlog(0.
All those mlog(0,...) will be replaced with trace events later.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
index 024bd45..c23846d 100644
--- a/fs/ocfs2/buffer_head_io.c
+++ b/fs/ocfs2/buffer_head_io.c
@@ -66,6 +66,7 @@
 	 * can get modified during recovery even if read-only. */
 	if (ocfs2_is_hard_readonly(osb)) {
 		ret = -EROFS;
+		mlog_errno(ret);
 		goto out;
 	}
 
@@ -91,11 +92,11 @@
 		 * uptodate. */
 		ret = -EIO;
 		put_bh(bh);
+		mlog_errno(ret);
 	}
 
 	ocfs2_metadata_cache_io_unlock(ci);
 out:
-	mlog_exit(ret);
 	return ret;
 }
 
@@ -374,7 +375,6 @@
 
 bail:
 
-	mlog_exit(status);
 	return status;
 }
 
@@ -413,6 +413,7 @@
 
 	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb)) {
 		ret = -EROFS;
+		mlog_errno(ret);
 		goto out;
 	}
 
@@ -432,9 +433,9 @@
 	if (!buffer_uptodate(bh)) {
 		ret = -EIO;
 		put_bh(bh);
+		mlog_errno(ret);
 	}
 
 out:
-	mlog_exit(ret);
 	return ret;
 }