From de105068fead55ed5c07ade75e9c8e7f86a00d1d Mon Sep 17 00:00:00 2001 From: Chunguang Xu Date: Mon, 11 Mar 2024 10:09:27 +0800 Subject: nvme: fix reconnection fail due to reserved tag allocation We found a issue on production environment while using NVMe over RDMA, admin_q reconnect failed forever while remote target and network is ok. After dig into it, we found it may caused by a ABBA deadlock due to tag allocation. In my case, the tag was hold by a keep alive request waiting inside admin_q, as we quiesced admin_q while reset ctrl, so the request maked as idle and will not process before reset success. As fabric_q shares tagset with admin_q, while reconnect remote target, we need a tag for connect command, but the only one reserved tag was held by keep alive command which waiting inside admin_q. As a result, we failed to reconnect admin_q forever. In order to fix this issue, I think we should keep two reserved tags for admin queue. Fixes: ed01fee283a0 ("nvme-fabrics: only reserve a single tag") Signed-off-by: Chunguang Xu Reviewed-by: Sagi Grimberg Reviewed-by: Chaitanya Kulkarni Reviewed-by: Christoph Hellwig Signed-off-by: Keith Busch --- drivers/nvme/host/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'drivers/nvme/host/core.c') diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 0dcaf3973dc4..fb55b6ac0385 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -4385,7 +4385,8 @@ int nvme_alloc_admin_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set, set->ops = ops; set->queue_depth = NVME_AQ_MQ_TAG_DEPTH; if (ctrl->ops->flags & NVME_F_FABRICS) - set->reserved_tags = NVMF_RESERVED_TAGS; + /* Reserved for fabric connect and keep alive */ + set->reserved_tags = 2; set->numa_node = ctrl->numa_node; set->flags = BLK_MQ_F_NO_SCHED; if (ctrl->ops->flags & NVME_F_BLOCKING) @@ -4454,7 +4455,8 @@ int nvme_alloc_io_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set, if (ctrl->quirks & NVME_QUIRK_SHARED_TAGS) set->reserved_tags = NVME_AQ_DEPTH; else if (ctrl->ops->flags & NVME_F_FABRICS) - set->reserved_tags = NVMF_RESERVED_TAGS; + /* Reserved for fabric connect */ + set->reserved_tags = 1; set->numa_node = ctrl->numa_node; set->flags = BLK_MQ_F_SHOULD_MERGE; if (ctrl->ops->flags & NVME_F_BLOCKING) -- cgit