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[192.55.52.43]) by mx.google.com with ESMTPS id m1si1815345pjr.47.2019.06.07.07.51.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 07:51:01 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.43 as permitted sender) client-ip=192.55.52.43; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jun 2019 07:51:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,563,1557212400"; d="scan'208";a="182683628" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga002.fm.intel.com with ESMTP; 07 Jun 2019 07:51:00 -0700 Date: Fri, 7 Jun 2019 07:52:13 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Jan Kara , Dan Williams , Theodore Ts'o , Jeff Layton , Dave Chinner , Matthew Wilcox , linux-xfs@vger.kernel.org, Andrew Morton , John Hubbard , =?iso-8859-1?B?Suly9G1l?= Glisse , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal Message-ID: <20190607145213.GB14559@iweiny-DESK2.sc.intel.com> References: <20190606014544.8339-1-ira.weiny@intel.com> <20190606104203.GF7433@quack2.suse.cz> <20190606195114.GA30714@ziepe.ca> <20190606222228.GB11698@iweiny-DESK2.sc.intel.com> <20190607103636.GA12765@quack2.suse.cz> <20190607121729.GA14802@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190607121729.GA14802@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 Fri, Jun 07, 2019 at 09:17:29AM -0300, Jason Gunthorpe wrote: > On Fri, Jun 07, 2019 at 12:36:36PM +0200, Jan Kara wrote: > > > Because the pins would be invisible to sysadmin from that point on. > > It is not invisible, it just shows up in a rdma specific kernel > interface. You have to use rdma netlink to see the kernel object > holding this pin. > > If this visibility is the main sticking point I suggest just enhancing > the existing MR reporting to include the file info for current GUP > pins and teaching lsof to collect information from there as well so it > is easy to use. > > If the ownership of the lease transfers to the MR, and we report that > ownership to userspace in a way lsof can find, then I think all the > concerns that have been raised are met, right? I was contemplating some new lsof feature yesterday. But what I don't think we want is sysadmins to have multiple tools for multiple subsystems. Or even have to teach lsof something new for every potential new subsystem user of GUP pins. I was thinking more along the lines of reporting files which have GUP pins on them directly somewhere (dare I say procfs?) and teaching lsof to report that information. That would cover any subsystem which does a longterm pin. > > > ugly to live so we have to come up with something better. The best I can > > currently come up with is to have a method associated with the lease that > > would invalidate the RDMA context that holds the pins in the same way that > > a file close would do it. > > This is back to requiring all RDMA HW to have some new behavior they > currently don't have.. > > The main objection to the current ODP & DAX solution is that very > little HW can actually implement it, having the alternative still > require HW support doesn't seem like progress. > > I think we will eventually start seein some HW be able to do this > invalidation, but it won't be universal, and I'd rather leave it > optional, for recovery from truely catastrophic errors (ie my DAX is > on fire, I need to unplug it). Agreed. I think software wise there is not much some of the devices can do with such an "invalidate". Ira