From patchwork Fri Jan 10 19:29:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ira Weiny X-Patchwork-Id: 11328377 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6B0BD138D for ; Fri, 10 Jan 2020 19:31:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5104620880 for ; Fri, 10 Jan 2020 19:31:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728814AbgAJTbQ (ORCPT ); Fri, 10 Jan 2020 14:31:16 -0500 Received: from mga14.intel.com ([192.55.52.115]:10924 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728566AbgAJT35 (ORCPT ); Fri, 10 Jan 2020 14:29:57 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Jan 2020 11:29:56 -0800 X-IronPort-AV: E=Sophos;i="5.69,418,1571727600"; d="scan'208";a="272503818" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.157]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Jan 2020 11:29:56 -0800 From: ira.weiny@intel.com To: linux-kernel@vger.kernel.org Cc: Ira Weiny , 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: [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute Date: Fri, 10 Jan 2020 11:29:31 -0800 Message-Id: <20200110192942.25021-2-ira.weiny@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200110192942.25021-1-ira.weiny@intel.com> References: <20200110192942.25021-1-ira.weiny@intel.com> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 Reviewed-by: Jan Kara Reviewed-by: Darrick J. Wong --- 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 */