Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751201AbdFDHyf (ORCPT ); Sun, 4 Jun 2017 03:54:35 -0400 Received: from mail-ua0-f175.google.com ([209.85.217.175]:35124 "EHLO mail-ua0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbdFDHya (ORCPT ); Sun, 4 Jun 2017 03:54:30 -0400 MIME-Version: 1.0 In-Reply-To: References: <1491613030-11599-1-git-send-email-deepa.kernel@gmail.com> <1491613030-11599-5-git-send-email-deepa.kernel@gmail.com> From: "Yan, Zheng" Date: Sun, 4 Jun 2017 15:54:27 +0800 Message-ID: Subject: Re: [PATCH 04/12] fs: ceph: CURRENT_TIME with ktime_get_real_ts() To: Arnd Bergmann Cc: Deepa Dinamani , John Stultz , Linux Kernel Mailing List , Andrew Morton , Thomas Gleixner , Al Viro , gregkh , "Dilger, Andreas" , "J. Bruce Fields" , Chris Mason , David Miller , David Sterba , Evgeniy Dushistov , Eric Paris , Jaegeuk Kim , Josef Bacik , Jeff Layton , James Simmons , Ingo Molnar , "Drokin, Oleg" , Paul Moore , Steven Rostedt , yuchao0@huawei.com, ceph-devel , devel@driverdev.osuosl.org, linux-audit@redhat.com, linux-btrfs , linux-cifs@vger.kernel.org, "Linux F2FS DEV, Mailing List" , Linux FS-devel Mailing List , linux-mtd , LSM List , Lustre Development List , Networking , samba-technical@lists.samba.org, y2038 Mailman List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2621 Lines: 56 On Fri, Jun 2, 2017 at 10:18 PM, Arnd Bergmann wrote: > On Fri, Jun 2, 2017 at 2:18 PM, Yan, Zheng wrote: >> On Fri, Jun 2, 2017 at 7:33 PM, Arnd Bergmann wrote: >>> On Fri, Jun 2, 2017 at 1:18 PM, Yan, Zheng wrote: >>> What I meant is another related problem in ceph_mkdir() where the >>> i_ctime field of the parent inode is different between the persistent >>> representation in the mds and the in-memory representation. >>> >> >> I don't see any problem in mkdir case. Parent inode's i_ctime in mds is set to >> r_stamp. When client receives request reply, it set its in-memory inode's ctime >> to the same time stamp. > > Ok, I see it now, thanks for the clarification. Most other file systems do this > the other way round and update all fields in the in-memory inode structure > first and then write that to persistent storage, so I was getting confused about > the order of events here. > > If I understand it all right, we have three different behaviors in ceph now, > though the differences are very minor and probably don't ever matter: > > - in setattr(), we update ctime in the in-memory inode first and then send > the same time to the mds, and expect to set it again when the reply comes. > > - in ceph_write_iter write() and mmap/page_mkwrite(), we call > file_update_time() to set i_mtime and i_ctime to the same > timestamp first once a write is observed by the fs and then take > two other timestamps that we send to the mds, and update the > in-memory inode a second time when the reply comes. ctime > is never older than mtime here, as far as I can tell, but it may > be newer when the timer interrupt happens between taking the > two stamps. We don't use request to send i_mtime/i_ctime to mds in this case. Instead, we use cap flush message. i_mtime/i_ctime are directly encoded in cap flush message. When mds receives the cap flush message, it writes i_mtime/i_ctime to persistent storage and sends a cap flush ack message to client. (when client receives the cap flush ack message, it does not update i_mtime/i_ctime). There is no issue as you described. > > - in all other calls, we only update the inode (and/or parent inode) > after the reply arrives. There are two cases. 1. Client updates in-memory inode's ctime, it sends the new ctime to mds through cap flush message. 2. client set mds request's r_stamp and send the request to mds. MDS updates relavent inodes' ctime and sends reply to client. Client updates in-memory inodes' ctime according to the reply. Regards Yan, Zheng > > Arnd