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Wed, 12 Mar 2025 15:27:00 +0000 (GMT) Message-ID: Date: Wed, 12 Mar 2025 20:56:58 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] nvme: remove multipath module parameter To: John Meneghini , Keith Busch Cc: Christoph Hellwig , Hannes Reinecke , Sagi Grimberg , bmarzins@redhat.com, Bryan Gurney , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Marco Patalano , axboe@kernel.dk, Randy Jennings References: <20250305235119.GB896@lst.de> <20250306000348.GA1233@lst.de> <1ffebf60-5672-4cd0-bb5a-934376c16694@suse.de> <20250306141837.GA21353@lst.de> <20250306151654.GA22810@lst.de> <69cdaf9d-2fb4-4ee0-9c32-cc946405a23a@linux.ibm.com> <01d799d1-fc93-4285-aa8f-89ac2d01478b@redhat.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <01d799d1-fc93-4285-aa8f-89ac2d01478b@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: r6vJbcw2bvB4WlR3SZtMe9f1qxIekOde X-Proofpoint-GUID: r6vJbcw2bvB4WlR3SZtMe9f1qxIekOde X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-12_05,2025-03-11_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 spamscore=0 mlxlogscore=999 malwarescore=0 impostorscore=0 bulkscore=0 suspectscore=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2503120105 On 3/12/25 9:17 AM, John Meneghini wrote: > On 3/9/25 1:23 PM, Nilay Shroff wrote: >>> It honestly has potential to solve some real problems, like >>> re-enumeration triggered by a link reset on an in-use drive. You'd >>> currently need to close the old handle and open a new on, even though >>> it's the same device. It may not even be possible to do that if that >>> device contains your root partition, and then you can only power cycle. >>> >>> The downside is we wouldn't get the short cut to blk_mq_submit_bio. We'd >>> instead stack that atop an indirect call, so it's not free. >>> >> Yes agreed however it seems advantages of using an indirect call outweighs >> using the short cut to blk_mq_submit_bio. Moreover it seems the cost of >> indirect call is trivial because we already cache the nexthop. >> >> I integrated your proposed patch (with few trivial additional changes on top) >> and I see that it's coming out nicely. I ran few tests and confirmed it's >> working well. However, in the proposed patch we*always* delay (~10 sec) the > Have you tested this with a NVMe-oF controller... yet? Not on real target. But tested it against blktests which has few NVMeOF test cases though it uses loopback interface. > > Where did the number 10 seconds come from? That was probably used as hard coded value for POC. However, we shall be able to configure that. > >> removal of multipath head node. That means that even while removing the >> nvme module (rmmod nvme) or if user delete/detache the namespace, we delay >> the removal of head node but that may not be what we want. So I'd suggest >> instead, delayed removal of multipath head not shall be configurable using a >> sysfs attribute. With this attribute then we shall let user opt for pinning >> the head node (with optional delayed time as well?). And it's only when user > > So be aware the TP-4129 is adding a CQT parameter which does almost exactly this. > >> shows the intent to pin the node we should delay its removal. This is what >> exactly (pinning of head node) Christoph's proposed patch implements. So I'd >> suggest a bit of amalgamation of yours as well as Christoph patch to implement >> this change. > > Please cc: me on your patches Nilay, I'd like to test them with my NVMe-oF testbed. > Sure, I will keep you in Cc when I send the patch. Thanks, --Nilay