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Fri, 30 Jan 2026 18:20:59 +0000 (GMT) From: Nilay Shroff To: linux-nvme@lists.infradead.org Cc: kbusch@kernel.org, axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, hare@suse.de, dwagner@suse.de, wenxiong@linux.ibm.com, gjoyce@ibm.com, Nilay Shroff Subject: [PATCH 4/7] nvme: export I/O requeue count when no path is available via sysfs Date: Fri, 30 Jan 2026 23:50:21 +0530 Message-ID: <20260130182028.885089-5-nilay@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260130182028.885089-1-nilay@linux.ibm.com> References: <20260130182028.885089-1-nilay@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: yLd9zbpUIDkKCphlLpvCOBD0OlW8UPDJ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTMwMDE1MCBTYWx0ZWRfXxIIpWUjDCCMY ZqNlUiS2CQrnrbz0UxGtPTndSSjxvkkrQTDpK70XQMsIhc5dAqYtQyJseIbl3ucwVKIbSPx4r8G NoKmsS/izRPL/kDUIqk9bM394J6jmjsqGdpASFvQD6cuPliqUY5ztskHHJNJveKHN5uXEmUqq5l BN7GiHkR2D3Kw3mtHzwRr/CPJHGiRPHpL+lrjKyTbCgwni5oK4+P92r0mzdzzTBAo0Hxa+OE0jR qS3gTeg3CNoZkQVI7ddT9dp6pNXuu03D1TWDP7aFQtfm4ydfsZUKUP0ISe+QUHV9JcarZ3PGZd9 X2EzOYf0ekaRKIk7DnWIiWF0eveX3kH9zhB6Y/uYJzvZ2afKJEgTsDeSx8pK5BKBxCCjD4hqPgG LdWgPB8wMKfIV5FlfZusFIl5dD6MG6/bdCNUuwQFsFb6qspqJvzve28MY/C+MDC2ohdxa2acL+B 0CNB4G1Svc08ID1BklQ== X-Authority-Analysis: v=2.4 cv=Zs3g6t7G c=1 sm=1 tr=0 ts=697cf693 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=vUbySO9Y5rIA:10 a=sWKEhP36mHoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=OdKbmu6maCxnhc5y6U8A:9 X-Proofpoint-ORIG-GUID: yLd9zbpUIDkKCphlLpvCOBD0OlW8UPDJ 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=2026-01-30_02,2026-01-30_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 adultscore=0 phishscore=0 suspectscore=0 bulkscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601300150 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260130_102114_325023_28A3E1F2 X-CRM114-Status: GOOD ( 18.18 ) 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 When the NVMe namespace head determines that there is no currently available path to handle I/O (for example, while a controller is resetting/connecting or due to a transient link failure), incoming I/Os are added to the requeue list. Currently, there is no visibility into how many I/Os have been requeued in this situation. Add a new sysfs counter, requeue_no_available_path, to expose the number of I/Os that were requeued due to the absence of an available path. This statistic can help users understand I/O slowdowns or stalls caused by temporary path unavailability, and can be consumed by monitoring tools such as nvme-top for real-time observability. Signed-off-by: Nilay Shroff --- drivers/nvme/host/multipath.c | 11 +++++++++++ drivers/nvme/host/nvme.h | 2 ++ drivers/nvme/host/sysfs.c | 5 +++++ 3 files changed, 18 insertions(+) diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index 366b820e654a..4e5f8523ca40 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -539,6 +539,7 @@ static void nvme_ns_head_submit_bio(struct bio *bio) spin_lock_irq(&head->requeue_lock); bio_list_add(&head->requeue_list, bio); spin_unlock_irq(&head->requeue_lock); + head->requeue_no_usable_path++; } else { dev_warn_ratelimited(dev, "no available path - failing I/O\n"); @@ -1178,6 +1179,16 @@ static ssize_t multipath_failover_count_show(struct device *dev, } DEVICE_ATTR_RO(multipath_failover_count); +static ssize_t requeue_no_usable_path_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct gendisk *disk = dev_to_disk(dev); + struct nvme_ns_head *head = disk->private_data; + + return sysfs_emit(buf, "%llu\n", head->requeue_no_usable_path); +} +DEVICE_ATTR_RO(requeue_no_usable_path); + static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl, struct nvme_ana_group_desc *desc, void *data) { diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h index b7e46bdd2d59..5836e4c557a2 100644 --- a/drivers/nvme/host/nvme.h +++ b/drivers/nvme/host/nvme.h @@ -509,6 +509,7 @@ struct nvme_ns_head { unsigned long flags; struct delayed_work remove_work; unsigned int delayed_removal_secs; + u64 requeue_no_usable_path; #define NVME_NSHEAD_DISK_LIVE 0 #define NVME_NSHEAD_QUEUE_IF_NO_PATH 1 struct nvme_ns __rcu *current_path[]; @@ -1005,6 +1006,7 @@ extern struct device_attribute dev_attr_queue_depth; extern struct device_attribute dev_attr_numa_nodes; extern struct device_attribute dev_attr_delayed_removal_secs; extern struct device_attribute dev_attr_multipath_failover_count; +extern struct device_attribute dev_attr_requeue_no_usable_path; extern struct device_attribute subsys_attr_iopolicy; static inline bool nvme_disk_is_ns_head(struct gendisk *disk) diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c index 41218fa5081f..84d33445a578 100644 --- a/drivers/nvme/host/sysfs.c +++ b/drivers/nvme/host/sysfs.c @@ -284,6 +284,7 @@ static struct attribute *nvme_ns_attrs[] = { &dev_attr_numa_nodes.attr, &dev_attr_delayed_removal_secs.attr, &dev_attr_multipath_failover_count.attr, + &dev_attr_requeue_no_usable_path.attr, #endif &dev_attr_io_passthru_err_log_enabled.attr, &dev_attr_io_command_retries.attr, @@ -344,6 +345,10 @@ static umode_t nvme_ns_attrs_are_visible(struct kobject *kobj, if (nvme_disk_is_ns_head(dev_to_disk(dev))) return 0; } + if (a == &dev_attr_requeue_no_usable_path.attr) { + if (!nvme_disk_is_ns_head(dev_to_disk(dev))) + return 0; + } #endif return a->mode; } -- 2.52.0