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=-2.2 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 03058C3A5A1 for ; Mon, 19 Aug 2019 21:53:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C4B1C22CEC for ; Mon, 19 Aug 2019 21:53:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4B1C22CEC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6551B6B0005; Mon, 19 Aug 2019 17:53:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5DE396B0006; Mon, 19 Aug 2019 17:53:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4CC5D6B0007; Mon, 19 Aug 2019 17:53:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0220.hostedemail.com [216.40.44.220]) by kanga.kvack.org (Postfix) with ESMTP id 2496F6B0005 for ; Mon, 19 Aug 2019 17:53:28 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 91BF3181AC9AE for ; Mon, 19 Aug 2019 21:53:27 +0000 (UTC) X-FDA: 75840529254.29.net37_5845d837b4d5e X-HE-Tag: net37_5845d837b4d5e X-Filterd-Recvd-Size: 3477 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Mon, 19 Aug 2019 21:53:26 +0000 (UTC) X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Aug 2019 14:53:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,406,1559545200"; d="scan'208";a="189658795" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga002.jf.intel.com with ESMTP; 19 Aug 2019 14:53:23 -0700 Date: Mon, 19 Aug 2019 14:53:23 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Dave Chinner , Jan Kara , Andrew Morton , Dan Williams , Matthew Wilcox , Theodore Ts'o , John Hubbard , Michal Hocko , linux-xfs@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Message-ID: <20190819215322.GA2839@iweiny-DESK2.sc.intel.com> References: <20190809225833.6657-1-ira.weiny@intel.com> <20190814101714.GA26273@quack2.suse.cz> <20190814180848.GB31490@iweiny-DESK2.sc.intel.com> <20190815130558.GF14313@quack2.suse.cz> <20190816190528.GB371@iweiny-DESK2.sc.intel.com> <20190817022603.GW6129@dread.disaster.area> <20190819063412.GA20455@quack2.suse.cz> <20190819092409.GM7777@dread.disaster.area> <20190819123841.GC5058@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190819123841.GC5058@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 19, 2019 at 09:38:41AM -0300, Jason Gunthorpe wrote: > On Mon, Aug 19, 2019 at 07:24:09PM +1000, Dave Chinner wrote: > > > So that leaves just the normal close() syscall exit case, where the > > application has full control of the order in which resources are > > released. We've already established that we can block in this > > context. Blocking in an interruptible state will allow fatal signal > > delivery to wake us, and then we fall into the > > fatal_signal_pending() case if we get a SIGKILL while blocking. > > The major problem with RDMA is that it doesn't always wait on close() for the > MR holding the page pins to be destoyed. This is done to avoid a > deadlock of the form: > > uverbs_destroy_ufile_hw() > mutex_lock() > [..] > mmput() > exit_mmap() > remove_vma() > fput(); > file_operations->release() > ib_uverbs_close() > uverbs_destroy_ufile_hw() > mutex_lock() <-- Deadlock > > But, as I said to Ira earlier, I wonder if this is now impossible on > modern kernels and we can switch to making the whole thing > synchronous. That would resolve RDMA's main problem with this. I'm still looking into this... but my bigger concern is that the RDMA FD can be passed to other processes via SCM_RIGHTS. Which means the process holding the pin may _not_ be the one with the open file and layout lease... Ira