xfs: fix IOCB_NOWAIT handling in xfs_file_dio_aio_read

Direct I/O reads can also be used with RWF_NOWAIT & co.  Fix the inode
locking in xfs_file_dio_aio_read to take IOCB_NOWAIT into account.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_file.c

@@ -187,7 +187,12 @@ xfs_file_dio_aio_read(
 
 	file_accessed(iocb->ki_filp);
 
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
+			return -EAGAIN;
+	} else {
 		xfs_ilock(ip, XFS_IOLOCK_SHARED);
+	}
 	ret = iomap_dio_rw(iocb, to, &xfs_read_iomap_ops, NULL,
 			is_sync_kiocb(iocb));
 	xfs_iunlock(ip, XFS_IOLOCK_SHARED);