From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752746AbcBVTEp (ORCPT ); Mon, 22 Feb 2016 14:04:45 -0500 Received: from mga11.intel.com ([192.55.52.93]:9769 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752234AbcBVS7k (ORCPT ); Mon, 22 Feb 2016 13:59:40 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,485,1449561600"; d="scan'208";a="657296574" From: Ross Zwisler To: linux-kernel@vger.kernel.org Cc: Dan Williams , "Theodore Ts'o" , Alexander Viro , Andreas Dilger , Andrew Morton , Dave Chinner , Jan Kara , Jens Axboe , Matthew Wilcox , linux-block@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org, xfs@oss.sgi.com, Jan Kara , Jens Axboe , Matthew Wilcox , Al Viro , Ross Zwisler Subject: [PATCH v4 1/5] block: disable block device DAX by default Date: Mon, 22 Feb 2016 11:59:18 -0700 Message-Id: <1456167562-28576-2-git-send-email-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1456167562-28576-1-git-send-email-ross.zwisler@linux.intel.com> References: <1456167562-28576-1-git-send-email-ross.zwisler@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dan Williams The recent *sync enabling discovered that we are inserting into the block_device pagecache counter to the expectations of the dirty data tracking for dax mappings. This can lead to data corruption. We want to support DAX for block devices eventually, but it requires wider changes to properly manage the pagecache. [] dump_stack+0x85/0xc2 [] dax_writeback_mapping_range+0x60/0xe0 [] blkdev_writepages+0x3f/0x50 [] do_writepages+0x21/0x30 [] __filemap_fdatawrite_range+0xc6/0x100 [] filemap_write_and_wait+0x4a/0xa0 [] set_blocksize+0x70/0xd0 [] sb_set_blocksize+0x1d/0x50 [] ext4_fill_super+0x75b/0x3360 [] ? vsnprintf+0x201/0x4c0 [] ? snprintf+0x49/0x60 [] mount_bdev+0x180/0x1b0 [] ? ext4_calculate_overhead+0x370/0x370 [] ext4_mount+0x15/0x20 [] mount_fs+0x38/0x170 Mark the support broken so its disabled by default, but otherwise still available for testing. Cc: Jan Kara Cc: Jens Axboe Cc: Matthew Wilcox Cc: Al Viro Reported-by: Ross Zwisler Suggested-by: Dave Chinner Signed-off-by: Dan Williams Signed-off-by: Ross Zwisler Reviewed-by: Jan Kara --- block/Kconfig | 13 +++++++++++++ fs/block_dev.c | 6 +++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/block/Kconfig b/block/Kconfig index 161491d..0363cd7 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -88,6 +88,19 @@ config BLK_DEV_INTEGRITY T10/SCSI Data Integrity Field or the T13/ATA External Path Protection. If in doubt, say N. +config BLK_DEV_DAX + bool "Block device DAX support" + depends on FS_DAX + depends on BROKEN + help + When DAX support is available (CONFIG_FS_DAX) raw block + devices can also support direct userspace access to the + storage capacity via MMAP(2) similar to a file on a + DAX-enabled filesystem. However, the DAX I/O-path disables + some standard I/O-statistics, and the MMAP(2) path has some + operational differences due to bypassing the page + cache. If in doubt, say N. + config BLK_DEV_THROTTLING bool "Block layer bio throttling support" depends on BLK_CGROUP=y diff --git a/fs/block_dev.c b/fs/block_dev.c index 39b3a17..31c6d10 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1201,7 +1201,11 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_disk = disk; bdev->bd_queue = disk->queue; bdev->bd_contains = bdev; - bdev->bd_inode->i_flags = disk->fops->direct_access ? S_DAX : 0; + if (IS_ENABLED(CONFIG_BLK_DEV_DAX) && disk->fops->direct_access) + bdev->bd_inode->i_flags = S_DAX; + else + bdev->bd_inode->i_flags = 0; + if (!partno) { ret = -ENXIO; bdev->bd_part = disk_get_part(disk, partno); -- 2.5.0