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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 00A88C61DA4 for ; Tue, 14 Feb 2023 16:17:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=7sVd9vKytytEoka1VMQqCQsd7uad8oiIXImy6lOhW+c=; b=BI8Loh7E0lZz/YDu6pxmy2vCj3 QLW8LzeGfPnaon8p5OYglc1gZGvxrewtiWeQO99KiLJIaWMsuoLNttdL31pEfAgKVEycT/QO18epH Hdj7cuZ9WvSV5RY7TsvjVKVe7k5BpeEMWnQwlC8/Ewcb6uRAn88JG4swfqfbbb7g8neqCIqDog9th w+yMxeX89V3duX/d2gSEmgc3kZqUnGbcN7BFZMqLmrwlwV18kuq60dF5vnRcTTc8AVU0fnaiQsNNf kYs0HwvIfzisjAdTdc1RqzVwitVQK4OdTifRUHb229ksELKkHv6ddvfzBt1GPJTUuHAER74+KB7HA ErQ3egRA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pRxzl-002lHt-GF; Tue, 14 Feb 2023 16:17:29 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pRxzc-002lCe-9i for linux-nvme@lists.infradead.org; Tue, 14 Feb 2023 16:17:21 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9C4E06171A; Tue, 14 Feb 2023 16:17:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F180C4339B; Tue, 14 Feb 2023 16:17:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1676391439; bh=9g24emceslv08x9zeyMzV7S+L43JTRSvmFyneogox2o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WAk6cgoteryFw/0034wUEjSgjkiZrFuSOEMO24uw5oPb1VfNLChMH2agu8MnKD8d7 vN5X/z8ghbJ5HpAut4Pp+TsH2w8dX5z9gRzRnZdxWSQWnBdKR3HrGsdGJS+nmAOlhZ 1TWBkSn7GznAdd0OZYWumCzkMzMz8HxVva4fj2lXqeEYCHfWlLuf0+/j7euXtkfTM9 Va1SEwwUvqhzYpSxP5SiurZ60RYKoU6iWuCBaACpuznzgYQw/SZ88F+klWKgljf1c7 xPKzdcpWbjDZCTujm7njnKGQwMhvbOfYD+FdGVQwispISNME+WQN4msCaX6emEjqJC 3X/1I7KawdJFA== Date: Tue, 14 Feb 2023 09:17:15 -0700 From: Keith Busch To: Ming Lei Cc: Sagi Grimberg , Christoph Hellwig , John Meneghini , "linux-nvme@lists.infradead.org" Subject: Re: nvme/pcie hot plug results in /dev name change Message-ID: References: <2205fb9d-f887-dedc-04c1-06190dc51413@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230214_081720_416634_8863E510 X-CRM114-Status: GOOD ( 26.63 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Feb 14, 2023 at 08:04:22AM +0800, Ming Lei wrote: > On Mon, Feb 13, 2023 at 09:32:35AM -0700, Keith Busch wrote: > > On Mon, Feb 13, 2023 at 04:01:03PM +0200, Sagi Grimberg wrote: > > > > Also not sure if this is going to work out, but it looks like a good start to > > > > me. > > > > > > > > Instead of user pinning the virtual device so that it never goes away though, I > > > > considered a user tunable "device missing delay" parameter to debounce link > > > > events. New IOs would be deferred to the requeue_list while the timer is > > > > active, and then EIO'ed if the timer expires without a successful LIVE > > > > controller attachment. The use cases I'm considering are short bounces from > > > > transient link resets, so I'd expect timers to be from a few seconds to maybe a > > > > minute. > > > > > > Isn't this equivalent to dm-mpath queue_if_no_path or no_path_timeout ? > > > > Similiar, but generic to non-multipath devices. > > > > > We can keep the mpath device around, but if not, what is the desired > > > behavior from the upper layers? > > > > I don't think we're looking for any behavioral changes in the upper layers. > > That also means no matter if the nvme mpath layer is added or not, upper > layer still has to handle this kind of failure, so what is the > difference made from the added nvme-mpath? I don't understand. There's no difference here for the upper layers. It's just a different timing from when a disconnect starts failing IO. The upper layers can keep doing what they're already doing in either case.