From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CC67C2D0EC for ; Tue, 7 Apr 2020 23:47:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6432520719 for ; Tue, 7 Apr 2020 23:47:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726528AbgDGXr5 (ORCPT ); Tue, 7 Apr 2020 19:47:57 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:46950 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726416AbgDGXr5 (ORCPT ); Tue, 7 Apr 2020 19:47:57 -0400 Received: from dread.disaster.area (pa49-180-164-3.pa.nsw.optusnet.com.au [49.180.164.3]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id D3CF43A34BE; Wed, 8 Apr 2020 09:47:50 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1jLxwb-0005aM-BR; Wed, 08 Apr 2020 09:47:49 +1000 Date: Wed, 8 Apr 2020 09:47:49 +1000 From: Dave Chinner To: ira.weiny@intel.com Cc: linux-kernel@vger.kernel.org, Jan Kara , "Darrick J . Wong" , Dan Williams , Christoph Hellwig , "Theodore Y. Ts'o" , Jeff Moyer , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH V6 3/8] fs/stat: Define DAX statx attribute Message-ID: <20200407234749.GE24067@dread.disaster.area> References: <20200407182958.568475-1-ira.weiny@intel.com> <20200407182958.568475-4-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407182958.568475-4-ira.weiny@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=X6os11be c=1 sm=1 tr=0 a=K0+o7W9luyMo1Ua2eXjR1w==:117 a=K0+o7W9luyMo1Ua2eXjR1w==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=cl8xLZFz6L8A:10 a=QyXUC8HyAAAA:8 a=yPCof4ZbAAAA:8 a=20KFwNOVAAAA:8 a=7-415B0cAAAA:8 a=luxjZY3Et4Z6tp6Ed88A:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 07, 2020 at 11:29:53AM -0700, ira.weiny@intel.com wrote: > From: Ira Weiny > > In order for users to determine if a file is currently operating in DAX > state (effective DAX). Define a statx attribute value and set that > attribute if the effective DAX flag is set. > > To go along with this we propose the following addition to the statx man > page: > > STATX_ATTR_DAX > > The file is in the DAX (cpu direct access) state. DAX state > attempts to minimize software cache effects for both I/O and > memory mappings of this file. It requires a file system which > has been configured to support DAX. > > DAX generally assumes all accesses are via cpu load / store > instructions which can minimize overhead for small accesses, but > may adversely affect cpu utilization for large transfers. > > File I/O is done directly to/from user-space buffers and memory > mapped I/O may be performed with direct memory mappings that > bypass kernel page cache. > > While the DAX property tends to result in data being transferred > synchronously, it does not give the same guarantees of O_SYNC > where data and the necessary metadata are transferred together. > > A DAX file may support being mapped with the MAP_SYNC flag, > which enables a program to use CPU cache flush instructions to > persist CPU store operations without an explicit fsync(2). See > mmap(2) for more information. > > Reviewed-by: Jan Kara > Reviewed-by: Darrick J. Wong > Signed-off-by: Ira Weiny > > --- > Changes from V2: > Update man page text with comments from Darrick, Jan, Dan, and > Dave. > --- > fs/stat.c | 3 +++ > include/uapi/linux/stat.h | 1 + > 2 files changed, 4 insertions(+) > > diff --git a/fs/stat.c b/fs/stat.c > index 030008796479..894699c74dde 100644 > --- a/fs/stat.c > +++ b/fs/stat.c > @@ -79,6 +79,9 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat, > if (IS_AUTOMOUNT(inode)) > stat->attributes |= STATX_ATTR_AUTOMOUNT; > > + if (IS_DAX(inode)) > + stat->attributes |= STATX_ATTR_DAX; > + > if (inode->i_op->getattr) > return inode->i_op->getattr(path, stat, request_mask, > query_flags); > diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h > index ad80a5c885d5..e5f9d5517f6b 100644 > --- a/include/uapi/linux/stat.h > +++ b/include/uapi/linux/stat.h > @@ -169,6 +169,7 @@ struct statx { > #define STATX_ATTR_ENCRYPTED 0x00000800 /* [I] File requires key to decrypt in fs */ > #define STATX_ATTR_AUTOMOUNT 0x00001000 /* Dir: Automount trigger */ > #define STATX_ATTR_VERITY 0x00100000 /* [I] Verity protected file */ > +#define STATX_ATTR_DAX 0x00002000 /* [I] File is DAX */ > > > #endif /* _UAPI_LINUX_STAT_H */ Looks fine. Man page text seems ok, too. Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com