From e4fcf07cca6a3b6c4be00df16f08be894325eaa3 Mon Sep 17 00:00:00 2001 From: Solganik Alexander Date: Sun, 30 Oct 2016 10:35:15 +0200 Subject: [PATCH] nvmet: Fix possible infinite loop triggered on hot namespace removal When removing a namespace we delete it from the subsystem namespaces list with list_del_init which allows us to know if it is enabled or not. The problem is that list_del_init initialize the list next and does not respect the RCU list-traversal we do on the IO path for locating a namespace. Instead we need to use list_del_rcu which is allowed to run concurrently with the _rcu list-traversal primitives (keeps list next intact) and guarantees concurrent nvmet_find_naespace forward progress. By changing that, we cannot rely on ns->dev_link for knowing if the namspace is enabled, so add enabled indicator entry to nvmet_ns for that. Signed-off-by: Sagi Grimberg Signed-off-by: Solganik Alexander Cc: # v4.8+ --- drivers/nvme/target/configfs.c | 6 +++--- drivers/nvme/target/core.c | 14 ++++++++------ drivers/nvme/target/nvmet.h | 6 +----- 3 files changed, 12 insertions(+), 14 deletions(-) diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c index af5e2dc4a3d5..011f88e5663e 100644 --- a/drivers/nvme/target/configfs.c +++ b/drivers/nvme/target/configfs.c @@ -271,7 +271,7 @@ static ssize_t nvmet_ns_device_path_store(struct config_item *item, mutex_lock(&subsys->lock); ret = -EBUSY; - if (nvmet_ns_enabled(ns)) + if (ns->enabled) goto out_unlock; kfree(ns->device_path); @@ -307,7 +307,7 @@ static ssize_t nvmet_ns_device_nguid_store(struct config_item *item, int ret = 0; mutex_lock(&subsys->lock); - if (nvmet_ns_enabled(ns)) { + if (ns->enabled) { ret = -EBUSY; goto out_unlock; } @@ -339,7 +339,7 @@ CONFIGFS_ATTR(nvmet_ns_, device_nguid); static ssize_t nvmet_ns_enable_show(struct config_item *item, char *page) { - return sprintf(page, "%d\n", nvmet_ns_enabled(to_nvmet_ns(item))); + return sprintf(page, "%d\n", to_nvmet_ns(item)->enabled); } static ssize_t nvmet_ns_enable_store(struct config_item *item, diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index c232552be2d8..8b627e2a55c6 100644 --- a/drivers/nvme/target/core.c +++ b/drivers/nvme/target/core.c @@ -264,7 +264,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns) int ret = 0; mutex_lock(&subsys->lock); - if (!list_empty(&ns->dev_link)) + if (ns->enabled) goto out_unlock; ns->bdev = blkdev_get_by_path(ns->device_path, FMODE_READ | FMODE_WRITE, @@ -309,6 +309,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns) list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) nvmet_add_async_event(ctrl, NVME_AER_TYPE_NOTICE, 0, 0); + ns->enabled = true; ret = 0; out_unlock: mutex_unlock(&subsys->lock); @@ -325,11 +326,11 @@ void nvmet_ns_disable(struct nvmet_ns *ns) struct nvmet_ctrl *ctrl; mutex_lock(&subsys->lock); - if (list_empty(&ns->dev_link)) { - mutex_unlock(&subsys->lock); - return; - } - list_del_init(&ns->dev_link); + if (!ns->enabled) + goto out_unlock; + + ns->enabled = false; + list_del_rcu(&ns->dev_link); mutex_unlock(&subsys->lock); /* @@ -351,6 +352,7 @@ void nvmet_ns_disable(struct nvmet_ns *ns) if (ns->bdev) blkdev_put(ns->bdev, FMODE_WRITE|FMODE_READ); +out_unlock: mutex_unlock(&subsys->lock); } diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h index f9c76441e8c9..23d5eb1c944f 100644 --- a/drivers/nvme/target/nvmet.h +++ b/drivers/nvme/target/nvmet.h @@ -47,6 +47,7 @@ struct nvmet_ns { loff_t size; u8 nguid[16]; + bool enabled; struct nvmet_subsys *subsys; const char *device_path; @@ -61,11 +62,6 @@ static inline struct nvmet_ns *to_nvmet_ns(struct config_item *item) return container_of(to_config_group(item), struct nvmet_ns, group); } -static inline bool nvmet_ns_enabled(struct nvmet_ns *ns) -{ - return !list_empty_careful(&ns->dev_link); -} - struct nvmet_cq { u16 qid; u16 size; -- GitLab