[XFS] Flush and invalidate dirty pages at the start of a direct read also,

else we can hit a delalloc-extents-via-direct-io BUG.

SGI-PV: 949916
SGI-Modid: xfs-linux-melb:xfs-kern:25483a
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/linux-2.6/xfs_lrw.c

@@ -270,6 +270,10 @@ xfs_read(
 		}
 	}
 
+	if (unlikely((ioflags & IO_ISDIRECT) && VN_CACHED(vp)))
+		VOP_FLUSHINVAL_PAGES(vp, ctooff(offtoct(*offset)),
+						-1, FI_REMAPF_LOCKED);
+
 	xfs_rw_enter_trace(XFS_READ_ENTER, &ip->i_iocore,
 				(void *)iovp, segs, *offset, ioflags);
 	ret = __generic_file_aio_read(iocb, iovp, segs, offset);