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Mon, 2 Mar 2026 12:57:12 +0000 (GMT) Message-ID: Date: Mon, 2 Mar 2026 18:27:11 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 19/19] nvme-multipath: switch to use libmultipath To: John Garry , hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, axboe@fb.com, martin.petersen@oracle.com, james.bottomley@hansenpartnership.com, hare@suse.com Cc: jmeneghi@redhat.com, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, michael.christie@oracle.com, snitzer@kernel.org, bmarzins@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260225154007.1033735-1-john.g.garry@oracle.com> <20260225154007.1033735-20-john.g.garry@oracle.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20260225154007.1033735-20-john.g.garry@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAyMDEwNiBTYWx0ZWRfX08ZG4mfYdE6+ Pgtc0Q/jGKa+jDQNE0D+GrQjHKgMnFzoHCqSu1ifqjMpkeREbPJtmEaIO9GDdlyqoix0A4iKnHM cWPTqmGukRD+IAgnETbDg4A6HsMmzcl3mFPG7whALYPLnrPwsfSmk1d1HmZsuB3/sJnjvrcC+ws jrR24Dv2Nb41sT1mxJEx7tjCxkwzHlmsRf/oGegnyhGZfHMj7tY/ZXlIJfTJgNj+4eYSdTHnN23 VToJkQiBTVF7qOd756gghV+boAmuRDWm+lRlynZeh1XKhyAQJZ4pBkmcVgZ7y/gwxByv15H44fi ih3mFr+3mKU1Jx+t5maDc4pBFEK1wLhsR/5WxfDXr+lGl9dlfVYLVIU354rQFSrtrdOF+X+vi1s /jrdGPpTmejHF9fPkuh+jbj3TYi0P2fTwTjgcFf7fs9l9egIJER25DB/fhJCYN66PvOFOO/v2yQ I6RLWIDDP3LRYFqC9Xw== X-Proofpoint-ORIG-GUID: 9hUb9hBF3IRM0ca70u5en9RE3Z-TTG7C X-Proofpoint-GUID: 9hUb9hBF3IRM0ca70u5en9RE3Z-TTG7C X-Authority-Analysis: v=2.4 cv=AobjHe9P c=1 sm=1 tr=0 ts=69a58930 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=CpEX-UuAubdY51wu2XgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-02_03,2026-02-27_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 clxscore=1015 suspectscore=0 adultscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603020106 On 2/25/26 9:10 PM, John Garry wrote: > void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl) > @@ -277,30 +279,35 @@ void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl) > srcu_idx = srcu_read_lock(&ctrl->srcu); > list_for_each_entry_srcu(ns, &ctrl->namespaces, list, > srcu_read_lock_held(&ctrl->srcu)) { > + struct nvme_ns_head *head = ns->head; > + struct mpath_disk *mpath_disk = head->mpath_disk; > + > + if (!mpath_disk) > + continue; > + > nvme_mpath_clear_current_path(ns); > - kblockd_schedule_work(&ns->head->requeue_work); > + kblockd_schedule_work(&mpath_disk->mpath_head->requeue_work); > } > srcu_read_unlock(&ctrl->srcu, srcu_idx); > } > > +static void nvme_mpath_revalidate_paths_cb(struct mpath_device *mpath_device, > + sector_t capacity) > +{ > + struct nvme_ns *ns = nvme_mpath_to_ns(mpath_device); > + > + if (capacity != get_capacity(ns->disk)) > + clear_bit(NVME_NS_READY, &ns->flags); > +} > + I don't quite understand the intent of the above function. Here I see that we compare mpath_disk capacity with per-path disk. Do we really have sectors allocated for mpath_disk? Overall, IMO abstracting out common multipath function into a separate library is a good move. But then I just want to understand layering here with libmultipath. Does it sit above the driver or below? I see in some places we have back and forth callbacks from driver to libmultipath and then back to the driver, for instance: nvme_mpath_add_disk => driver -> mpath_device_set_live => libmultipath -> mpath_head_add_cdev => libmultipath -> nvme_mpath_add_cdev => driver Does this intentional? Or am I missing overall picture... Thanks, --Nilay