From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f70.google.com (mail-pa0-f70.google.com [209.85.220.70]) by kanga.kvack.org (Postfix) with ESMTP id 7199E6B0262 for ; Mon, 15 Aug 2016 15:09:55 -0400 (EDT) Received: by mail-pa0-f70.google.com with SMTP id ag5so116550309pad.2 for ; Mon, 15 Aug 2016 12:09:55 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id p4si19115744paz.202.2016.08.15.12.09.53 for ; Mon, 15 Aug 2016 12:09:54 -0700 (PDT) From: Ross Zwisler 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> In-Reply-To: <20160815190918.20672-1-ross.zwisler@linux.intel.com> References: <20160815190918.20672-1-ross.zwisler@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: 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@lists.01.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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org