From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:59679 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750778AbdGYJfN (ORCPT ); Tue, 25 Jul 2017 05:35:13 -0400 Date: Tue, 25 Jul 2017 11:35:08 +0200 From: Jan Kara Subject: Re: [PATCH v5 1/5] mm: add vm_insert_mixed_mkwrite() Message-ID: <20170725093508.GA19943@quack2.suse.cz> References: <20170724170616.25810-1-ross.zwisler@linux.intel.com> <20170724170616.25810-2-ross.zwisler@linux.intel.com> <20170724221400.pcq5zvke7w2yfkxi@node.shutemov.name> <20170725080158.GA5374@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725080158.GA5374@lst.de> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: "Kirill A. Shutemov" , Ross Zwisler , Andrew Morton , linux-kernel@vger.kernel.org, "Darrick J. Wong" , Theodore Ts'o , Alexander Viro , Andreas Dilger , Dan Williams , Dave Chinner , Ingo Molnar , Jan Kara , Jonathan Corbet , Matthew Wilcox , Steven Rostedt , linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org On Tue 25-07-17 10:01:58, Christoph Hellwig wrote: > On Tue, Jul 25, 2017 at 01:14:00AM +0300, Kirill A. Shutemov wrote: > > I guess it's up to filesystem if it wants to reuse the same spot to write > > data or not. I think your assumptions works for ext4 and xfs. I wouldn't > > be that sure for btrfs or other filesystems with CoW support. > > Or XFS with reflinks for that matter. Which currently can't be > combined with DAX, but I had a somewhat working version a few month > ago. But in cases like COW when the block mapping changes, the process must run unmap_mapping_range() before installing the new PTE so that all processes mapping this file offset actually refault and see the new mapping. So this would go through pte_none() case. Am I missing something? Honza -- Jan Kara SUSE Labs, CR