Return-Path: Received: from fieldses.org ([173.255.197.46]:40702 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639AbdFTTYu (ORCPT ); Tue, 20 Jun 2017 15:24:50 -0400 Date: Tue, 20 Jun 2017 15:24:49 -0400 To: Christoph Hellwig Cc: Chuck Lever , linux-rdma@vger.kernel.org, Linux NFS Mailing List Subject: Re: [PATCH v2 19/19] sunrpc: Disable splice for krb5i Message-ID: <20170620192449.GB13008@fieldses.org> References: <20170616151535.14210.34926.stgit@klimt.1015granger.net> <20170616152254.14210.48071.stgit@klimt.1015granger.net> <20170617150705.GA27917@infradead.org> <20170618073438.GA15358@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170618073438.GA15358@infradead.org> From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sun, Jun 18, 2017 at 12:34:38AM -0700, Christoph Hellwig wrote: > On Sat, Jun 17, 2017 at 01:23:24PM -0400, Chuck Lever wrote: > > > > > On Jun 17, 2017, at 11:07 AM, Christoph Hellwig wrote: > > > > > > On Fri, Jun 16, 2017 at 11:22:54AM -0400, Chuck Lever wrote: > > >> Running a multi-threaded 8KB fio test (70/30 mix), three or four out > > >> of twelve of the jobs fail when using krb5i. The failure is an EIO > > >> on a read. > > > > > > Just curious: what is the backing fs that you tested with? I'd be > > > curious if you see this on XFS for example. > > > > I was able to reproduce this with a tmpfs share and > > with an XFS share on NVMe LUNs. > > Interesting. XFS actually locks out all writes while doing a buffered > read, so we end up with two different read instance for the hash vs > the data, which does indeed sound dangerous. In the bad case Chuck was seeing, we were going through splice_direct_to_actor(), is that a buffered read for the purposes of the above statement? --b.