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[62.219.42.90]) by smtp.gmail.com with ESMTPSA id p14-20020a1c544e000000b003db06493ee7sm20623650wmi.47.2023.02.14.01.04.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Feb 2023 01:04:45 -0800 (PST) Message-ID: <6e532415-e440-c8ba-6bc2-afcf1fccf183@grimberg.me> Date: Tue, 14 Feb 2023 11:04:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: nvme/pcie hot plug results in /dev name change Content-Language: en-US To: Keith Busch Cc: Christoph Hellwig , Ming Lei , John Meneghini , "linux-nvme@lists.infradead.org" References: <472fe309-f0f9-65bf-1ad1-8a92a349e973@redhat.com> <2205fb9d-f887-dedc-04c1-06190dc51413@grimberg.me> From: Sagi Grimberg In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230214_010450_052655_AE8E13C1 X-CRM114-Status: GOOD ( 16.16 ) 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 >>> 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. I'm looking to what Christoph wrote, that in the long term upper layers will need to look for replugged devices. Let's take the simple example of a FS mounted disk that is going away, today the FS may get an error and go into RO or failure, needing a manual remount after the disk came back. What exactly is the proposal for change here?