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nvmet: Fix possible infinite loop triggered on hot namespace removal

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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 <sagi@grimberg.me>
Signed-off-by: Solganik Alexander <sashas@lightbitslabs.com>
Cc: <stable@vger.kernel.org> # v4.8+
This commit is contained in:
Solganik Alexander 2016-10-30 10:35:15 +02:00 committed by Sagi Grimberg
parent f3116d8f1e
commit e4fcf07cca
3 changed files with 12 additions and 14 deletions
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6
drivers/nvme/target/configfs.c
View File

@ -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,

14
drivers/nvme/target/core.c
View File

@ -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);
}

6
drivers/nvme/target/nvmet.h
View File

@ -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;