ocfs2: fix several issues of append dio

1) Take rw EX lock in case of append dio.
2) Explicitly treat the error code -EIOCBQUEUED as normal.
3) Set di_bh to NULL after brelse if it may be used again later.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Yiwen Jiang <jiangyiwen@huawei.com>
Cc: Weiwei Wang <wangww631@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/file.c

@@ -2271,6 +2271,8 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
 			       OCFS2_MOUNT_COHERENCY_BUFFERED);
 	int unaligned_dio = 0;
 	int dropped_dio = 0;
+	int append_write = ((iocb->ki_pos + count) >=
+			i_size_read(inode) ? 1 : 0);
 
 	trace_ocfs2_file_aio_write(inode, file, file->f_path.dentry,
 		(unsigned long long)OCFS2_I(inode)->ip_blkno,
@@ -2290,8 +2292,9 @@ relock:
 	/*
 	 * Concurrent O_DIRECT writes are allowed with
 	 * mount_option "coherency=buffered".
+	 * For append write, we must take rw EX.
 	 */
-	rw_level = (!direct_io || full_coherency);
+	rw_level = (!direct_io || full_coherency || append_write);
 
 	ret = ocfs2_rw_lock(inode, rw_level);
 	if (ret < 0) {