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Wed, 2 Sep 2026 14:27:48 +0000 (GMT) Received: from [9.61.83.86] (unknown [9.61.83.86]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 2 Sep 2026 14:27:48 +0000 (GMT) Message-ID: <61165430-a724-40d3-a00d-2cbe1ea656b0@linux.ibm.com> Date: Wed, 2 Sep 2026 19:57:47 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] nvme: keep transport module referenced while head node is open To: Christoph Hellwig Cc: linux-nvme@lists.infradead.org, kbusch@kernel.org, sagi@grimberg.me, axboe@fb.com, john.g.garry@oracle.com, wenxiong@linux.ibm.com, gjoyce@linux.ibm.com References: <20260831152006.819471-1-nilay@linux.ibm.com> <20260831152006.819471-2-nilay@linux.ibm.com> <20260902133104.GA20945@lst.de> <20260902141347.GA24385@lst.de> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20260902141347.GA24385@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=PPc/P/qC c=1 sm=1 tr=0 ts=6a983269 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=38FUgixByHOs7A2MsVUA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: zcAHXQHAracm4bHI1_30wT_g9vc85hk5 X-Proofpoint-ORIG-GUID: zcAHXQHAracm4bHI1_30wT_g9vc85hk5 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTAyMDEyNCBTYWx0ZWRfX+4pG6WE9wTAp qoz8WO4eSM2lSCnUqLsJJVgqFds90gkvBoZuFB6uwGX0ZygGXHjjAuyHvkJQF1U1vp186WDY7np zW8jYjqkz/S56maENH7pwEgp5AUPr6o= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTAyMDEyNCBTYWx0ZWRfX77T1YwOsHzT/ iNjCR0IhJ+JMwYj8whxF/elF6Oa3r53EqKaFNMB21TP77CIxTB0p8mBw3IDr6TagDjoekf3VKgj JRBdxC9f9hZzU2ZJERZd99jisoWag0S0dYQQhNTwv8VWyqVjTU757rYKafn1YInQUh23B3NtD2J lLUEqaTgBNBkdAl3jj1jGjAYa1XiyI9gRWUo1ssqXDSCZMYxv5KelWZf5bEGW8rZXLTmoFlA52b srWrLd5QlFM2DjkM1iBMTLFeBcQVoftCyIibljdmxZ1DAXPVapnMySyp2Fxlvjg9t+Aui9fzV+q KRqqBL/BZHTKYR/gFvIOgHanG24cO7yYBIS+xhFV8zYQJ1Ge6+A0EydAIxLfI6SJn/02qVlrZFZ NHRwUhoiWZ5sr61Hohm4KhGnRUm7bpC2OXB0K3eAutSj1d/qUUm7mK2xjUHiVbxH3FyAQr70iIF guq4wtjQW/mQyIYrYSQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-02_03,2026-09-01_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 phishscore=0 adultscore=0 suspectscore=0 bulkscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609020124 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260902_072803_314902_8F21B13C X-CRM114-Status: GOOD ( 18.76 ) 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 9/2/26 7:43 PM, Christoph Hellwig wrote: > On Wed, Sep 02, 2026 at 07:39:32PM +0530, Nilay Shroff wrote: >> So the practical problem is that an open multipath head can continue to >> be used after its underlying transport module has been unloaded. The >> proposed change keeps the transport module referenced while the head >> node is open, preventing the module from being unloaded in this >> scenario. > > But why do you unload it in the first place? > Well, in my view, unloading a module while it is not in use should be a legitimate operation. In the example shown earlier, the NVMe transport module is still being used by the open multipath head. Shouldn't we explicitly reflect that by incrementing its module refcount? We don't explicitly unload the module as part of normal NVMe operation, but in theory I think the transport module should remain referenced for as long as it is being used. That would also prohibit user from unloading module by mistake. Thanks, --Nilay