From: Solganik Alexander <sashas@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxx>
Signed-off-by: Solganik Alexander <sashas@xxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.8+
---
Changes from v1:
- Changed enabled from atomic bit to bool and updated it under
the subsys lock in order to protect against enable/disable
running concurrently
- Fixed nvmet_ns_enabled display
drivers/nvme/target/core.c | 15 +++++++++------
drivers/nvme/target/nvmet.h | 3 ++-
2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 6559d5afa7bf..bf36d2486245 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -264,9 +264,11 @@ 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->enabled = true;
+
ns->bdev = blkdev_get_by_path(ns->device_path, FMODE_READ | FMODE_WRITE,
NULL);
if (IS_ERR(ns->bdev)) {
@@ -325,11 +327,11 @@ 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 +353,7 @@ 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 76b6eedccaf9..d440f636f396 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;
@@ -63,7 +64,7 @@ static inline struct nvmet_ns *to_nvmet_ns(struct config_item *item)
static inline bool nvmet_ns_enabled(struct nvmet_ns *ns)
{
- return !list_empty_careful(&ns->dev_link);
+ return ns->enabled;
}
struct nvmet_cq {
--
2.7.4
--
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