From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id 046FB6B0003 for ; Fri, 2 Mar 2018 17:21:42 -0500 (EST) Received: by mail-oi0-f71.google.com with SMTP id x21so5597060oie.5 for ; Fri, 02 Mar 2018 14:21:42 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id q131sor2918826oia.255.2018.03.02.14.21.40 for (Google Transport Security); Fri, 02 Mar 2018 14:21:40 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20180302221020.GA30722@lst.de> References: <151996281307.28483.12343847096989509127.stgit@dwillia2-desk3.amr.corp.intel.com> <20180302221020.GA30722@lst.de> From: Dan Williams Date: Fri, 2 Mar 2018 14:21:40 -0800 Message-ID: Subject: Re: [PATCH v5 00/12] vfio, dax: prevent long term filesystem-dax pins and other fixes Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: linux-nvdimm , linux-xfs , "Darrick J. Wong" , KVM list , Haozhong Zhang , Jane Chu , Alexander Viro , Gerd Rausch , stable , Jan Kara , Michal Hocko , Andreas Dilger , Ross Zwisler , Matthew Wilcox , linux-fsdevel , Alex Williamson , Theodore Ts'o , Linux MM , Linux Kernel Mailing List On Fri, Mar 2, 2018 at 2:10 PM, Christoph Hellwig wrote: > I really don't like these IS_DEVDAX and IS_FSDAX flags. We should > stop pretending DAX is a global per-inode choice and get rid of these > magic flags entirely. So please convert the instances inside the > various file systems to checking the file system mount options instead. > > For the core ones we'll need to differentiate: > > - the checks in generic_file_read_iter and __generic_file_write_iter > seem to not be needed anymore at all since we stopped abusing the > direct I/O code for DAX, so they should probably be removed. > - io_is_direct is a weird check and should probably just go away, > as there is not point in always setting IOCB_DIRECT for DAX I/O > - fadvise should either become a file op, or a flag on the inode that > fadvice is supported instead of the nasty noop_backing_dev_info or > DAX check. > - Ditto for madvise > - vma_is_dax should probably be replaced with a VMA flag. > - thp_get_unmapped_area I don't really understand why we have a dax > check there. > - dax_mapping will be much harder to sort out. > > But all these DAX flags certainly look like a major hodge podge to me. They are indeed a hodge-podge. The problem is that the current IS_DAX() is broken. So I'd like to propose fixing IS_DAX() with IS_FSDAX() + IS_DEVDAX() for 4.16-rc4 and queue up these wider reworks you propose for the next merge window. Acceptable? -- 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