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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 39954C3A59F for ; Mon, 26 Aug 2019 20:51:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14A7D2186A for ; Mon, 26 Aug 2019 20:51:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726787AbfHZUv5 (ORCPT ); Mon, 26 Aug 2019 16:51:57 -0400 Received: from fieldses.org ([173.255.197.46]:46938 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726345AbfHZUv5 (ORCPT ); Mon, 26 Aug 2019 16:51:57 -0400 Received: by fieldses.org (Postfix, from userid 2815) id C5FE41E3B; Mon, 26 Aug 2019 16:51:56 -0400 (EDT) Date: Mon, 26 Aug 2019 16:51:56 -0400 To: Trond Myklebust Cc: "J. Bruce Fields" , linux-nfs@vger.kernel.org Subject: Re: [PATCH 0/3] Handling NFSv3 I/O errors in knfsd Message-ID: <20190826205156.GA27834@fieldses.org> References: <20190826165021.81075-1-trond.myklebust@hammerspace.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190826165021.81075-1-trond.myklebust@hammerspace.com> User-Agent: Mutt/1.5.21 (2010-09-15) From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Mon, Aug 26, 2019 at 12:50:18PM -0400, Trond Myklebust wrote: > Recently, a number of changes went into the kernel to try to ensure > that I/O errors (specifically write errors) are reported to the > application once and only once. The vehicle for ensuring the errors > are reported is the struct file, which uses the 'f_wb_err' field to > track which errors have been reported. > > The problem is that errors are mainly intended to be reported through > fsync(). If the client is doing synchronous writes, then all is well, > but if it is doing unstable writes, then the errors may not be > reported until the client calls COMMIT. If the file cache has > thrown out the struct file, due to memory pressure, or just because > the client took a long while between the last WRITE and the COMMIT, > then the error report may be lost, and the client may just think > its data is safely stored. These were lost before the file caching patches as well, right? Or is there some regression? > Note that the problem is compounded by the fact that NFSv3 is stateless, > so the server never knows that the client may have rebooted, so there > can be no guarantee that a COMMIT will ever be sent. > > The following patch set attempts to remedy the situation using 2 > strategies: > > 1) If the inode is dirty, then avoid garbage collecting the file > from the file cache. > 2) If the file is closed, and we see that it would have reported > an error to COMMIT, then we bump the boot verifier in order to > ensure the client retransmits all its writes. Sounds sensible to me. > Note that if multiple clients were writing to the same file, then > we probably want to bump the boot verifier anyway, since only one > COMMIT will see the error report (because the cached file is also > shared). I'm confused by the "probably should". So that's future work? I guess it'd mean some additional work to identify that case. You can't really even distinguish clients in the NFSv3 case, but I suppose you could use IP address or TCP connection as an approximation. --b. > So in order to implement the above strategy, we first have to do > the following: split up the file cache to act per net namespace, > since the boot verifier is per net namespace. Then add a helper > to update the boot verifier. > > Trond Myklebust (3): > nfsd: nfsd_file cache entries should be per net namespace > nfsd: Support the server resetting the boot verifier > nfsd: Don't garbage collect files that might contain write errors > > fs/nfsd/export.c | 2 +- > fs/nfsd/filecache.c | 76 +++++++++++++++++++++++++++++++++++++-------- > fs/nfsd/filecache.h | 3 +- > fs/nfsd/netns.h | 4 +++ > fs/nfsd/nfs3xdr.c | 13 +++++--- > fs/nfsd/nfs4proc.c | 14 +++------ > fs/nfsd/nfsctl.c | 1 + > fs/nfsd/nfssvc.c | 32 ++++++++++++++++++- > 8 files changed, 115 insertions(+), 30 deletions(-) > > -- > 2.21.0