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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 26772C33CB2 for ; Wed, 15 Jan 2020 11:37:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 042AE2073A for ; Wed, 15 Jan 2020 11:37:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730092AbgAOLhW (ORCPT ); Wed, 15 Jan 2020 06:37:22 -0500 Received: from mx2.suse.de ([195.135.220.15]:39188 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729900AbgAOLhT (ORCPT ); Wed, 15 Jan 2020 06:37:19 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 10DC6AEEE; Wed, 15 Jan 2020 11:37:16 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 5B5171E0D08; Wed, 15 Jan 2020 12:37:15 +0100 (CET) Date: Wed, 15 Jan 2020 12:37:15 +0100 From: Jan Kara To: ira.weiny@intel.com Cc: linux-kernel@vger.kernel.org, Alexander Viro , "Darrick J. Wong" , Dan Williams , Dave Chinner , Christoph Hellwig , "Theodore Y. Ts'o" , Jan Kara , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute Message-ID: <20200115113715.GB2595@quack2.suse.cz> References: <20200110192942.25021-1-ira.weiny@intel.com> <20200110192942.25021-2-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200110192942.25021-2-ira.weiny@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 10-01-20 11:29:31, ira.weiny@intel.com wrote: > From: Ira Weiny > > In order for users to determine if a file is currently operating in DAX > mode (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 > > DAX (cpu direct access) is a file mode that attempts to minimize > software cache effects for both I/O and memory mappings of this > file. It requires a capable device, a compatible filesystem > block size, and filesystem opt-in. It generally assumes all > accesses are via cpu load / store instructions which can > minimize overhead for small accesses, but adversely affect cpu > utilization for large transfers. File I/O is done directly > to/from user-space buffers. While the DAX property tends to > result in data being transferred synchronously it does not give > the guarantees of synchronous I/O that data and necessary > metadata are transferred. Memory mapped I/O may be performed > with direct mappings that bypass system memory buffering. Again > while memory-mapped I/O tends to result in data being > transferred synchronously it does not guarantee synchronous > metadata updates. A dax file may optionally support being mapped > with the MAP_SYNC flag which does allow cpu store operations to > be considered synchronous modulo cpu cache effects. > > Signed-off-by: Ira Weiny This looks good to me. You can add: Reviewed-by: Jan Kara Honza > --- > 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 */ > -- > 2.21.0 > -- Jan Kara SUSE Labs, CR