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Thu, 8 May 2025 15:11:21 +0000 (GMT) Message-ID: <346f2e71-e406-4ac4-b15d-3b19dafa6561@linux.ibm.com> Date: Thu, 8 May 2025 20:41:19 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCHv3 1/3] nvme-multipath: introduce delayed removal of the multipath head node To: Christoph Hellwig Cc: Hannes Reinecke , linux-nvme@lists.infradead.org, kbusch@kernel.org, sagi@grimberg.me, jmeneghi@redhat.com, axboe@kernel.dk, martin.petersen@oracle.com, gjoyce@ibm.com References: <20250504175051.2208162-1-nilay@linux.ibm.com> <20250504175051.2208162-2-nilay@linux.ibm.com> <20250507065050.GA31543@lst.de> <6fa58716-8995-43b9-b01e-3bbcf2cc6b2f@linux.ibm.com> <20250508053303.GA27661@lst.de> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20250508053303.GA27661@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=NLnV+16g c=1 sm=1 tr=0 ts=681cc99e cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=MffHSR8OajMSlqoAl5IA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: BAqoVvH7DvUK8fW3h0LNsLoyr8ZO-CFU X-Proofpoint-GUID: BAqoVvH7DvUK8fW3h0LNsLoyr8ZO-CFU X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTA4MDEzMCBTYWx0ZWRfX44j6Dy1KqrpN Dfg2eNAViaW8l6qh1rMb3tP0xLHECv4hs7Zar02k8BSr2TgiYZPnANkdLhVlSedM1OSDogcBIHI T0nh/qatyE844dWDGMpOrVXqzrctlZ3dL29s1Dd3oQZ2hDVgTACZMfAXWdL2QWET2FCw7r/xIA4 GiPZDY+rraF/2hQXn4BIUcMgd+1DPBfWeUEnQThZY7IqyLcsmTXqgBxlvFQ4FsqbZFyavmHOWSA L3IcV6CphHoHjzypD6k4n7y/dPxS25eRm6r/kU2mkJNBGuXHbivUg04ITjdIn98PstTIL1Nb6N0 B/s4U8pBDGIl+Jd2YmfojlDricfZ7wbcQeSHDfFPKBI1Wg+f//lQ/3Ri6z+2W8ex0EgdIfNmM5s Bt88LIZWHyQKvKi8wpUWS43xUfSfK8Yh7oc+m2AsnlzVklxgBhI4lInciRjnaXthlKEvBppz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-08_05,2025-05-07_02,2025-02-21_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 suspectscore=0 mlxlogscore=838 phishscore=0 mlxscore=0 impostorscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 malwarescore=0 priorityscore=1501 adultscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2504070000 definitions=main-2505080130 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250508_081148_462423_01B4BD28 X-CRM114-Status: GOOD ( 14.93 ) 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 5/8/25 11:03 AM, Christoph Hellwig wrote: > On Thu, May 08, 2025 at 01:26:16AM +0530, Nilay Shroff wrote: >> That's a possible approach; however, the challenge arises when the head node >> points to multiple namespace paths, each associated with different fabric >> controllers. > > That's generally a good point. Especially PCIe vs fabrics will be > fun to test. We really need a PCI loop device for nvmet to be able > to test it. > >> As we know, max_reconnects is a per-controller attribute. So, if only one of >> the fabric controllers has max_reconnects set to a non-zero value, but others >> do not, how do we decide whether to implicitly disable head->delayed_removal_secs? > > Well, as soon as something in the subsystems can't reconnect we want to > delay the removal, right? > Hmm, okay I agree (as you earlier suggested) lets not make any difference between pcie vs fabric setup and unify both. If PCIe/fabric link fails to reconnect and we lost all paths to a namespace then we'd start the head node's delayed_removal_secs timer. This way we'd not further complicate the logic and we also don't need to learn whether head node points to a fabric setup. I will spin a new patchset with this change and send upstream. Thanks, --Nilay