From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932389AbcHOTN1 (ORCPT ); Mon, 15 Aug 2016 15:13:27 -0400 Received: from mga02.intel.com ([134.134.136.20]:36178 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753313AbcHOTLJ (ORCPT ); Mon, 15 Aug 2016 15:11:09 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,526,1464678000"; d="scan'208";a="749052623" From: Ross Zwisler To: linux-kernel@vger.kernel.org Cc: Ross Zwisler , "Theodore Ts'o" , Alexander Viro , Andreas Dilger , Andrew Morton , Dan Williams , Dave Chinner , Jan Kara , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org Subject: [PATCH 1/7] ext2: tell DAX the size of allocation holes Date: Mon, 15 Aug 2016 13:09:12 -0600 Message-Id: <20160815190918.20672-2-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160815190918.20672-1-ross.zwisler@linux.intel.com> References: <20160815190918.20672-1-ross.zwisler@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When DAX calls ext2_get_block() and the file offset points to a hole we currently don't set bh_result->b_size. When we re-enable PMD faults DAX will need bh_result->b_size to tell it the size of the hole so it can decide whether to fault in a 4 KiB zero page or a 2 MiB zero page. For ext2 we always want DAX to use 4 KiB zero pages, so we just tell DAX that all holes are 4 KiB in size. Signed-off-by: Ross Zwisler --- fs/ext2/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c index d5c7d09..c6d9763 100644 --- a/fs/ext2/inode.c +++ b/fs/ext2/inode.c @@ -773,6 +773,12 @@ int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_ if (ret > 0) { bh_result->b_size = (ret << inode->i_blkbits); ret = 0; + } else if (ret == 0 && IS_DAX(inode)) { + /* + * We have hit a hole. Tell DAX it is 4k in size so that it + * uses PTE faults. + */ + bh_result->b_size = PAGE_SIZE; } return ret; -- 2.9.0