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 a flags entry to nvmet_ns and use atomic
updates on NVMET_NS_ENABLED.
Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Signed-off-by: Solganik Alexander <sashas@xxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.8+
---
drivers/nvme/target/core.c | 29 +++++++++++++----------------
drivers/nvme/target/nvmet.h | 5 +++++
2 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index bbb6bba45e3c..efb78f23b0e7 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -261,11 +261,10 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
{
struct nvmet_subsys *subsys = ns->subsys;
struct nvmet_ctrl *ctrl;
- int ret = 0;
+ int ret;
- mutex_lock(&subsys->lock);
- if (!list_empty(&ns->dev_link))
- goto out_unlock;
+ if (test_and_set_bit(NVMET_NS_ENABLED, &ns->flags))
+ return 0;
ns->bdev = blkdev_get_by_path(ns->device_path, FMODE_READ | FMODE_WRITE,
NULL);
@@ -274,7 +273,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
ns->device_path, PTR_ERR(ns->bdev));
ret = PTR_ERR(ns->bdev);
ns->bdev = NULL;
- goto out_unlock;
+ goto out;
}
ns->size = i_size_read(ns->bdev->bd_inode);
@@ -292,6 +291,7 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
* The namespaces list needs to be sorted to simplify the implementation
* of the Identify Namepace List subcommand.
*/
+ mutex_lock(&subsys->lock);
if (list_empty(&subsys->namespaces)) {
list_add_tail_rcu(&ns->dev_link, &subsys->namespaces);
} else {
@@ -308,15 +308,15 @@ 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);
-
- ret = 0;
-out_unlock:
mutex_unlock(&subsys->lock);
- return ret;
+
+ return 0;
+
out_blkdev_put:
blkdev_put(ns->bdev, FMODE_WRITE|FMODE_READ);
ns->bdev = NULL;
- goto out_unlock;
+out:
+ return ret;
}
void nvmet_ns_disable(struct nvmet_ns *ns)
@@ -324,13 +324,10 @@ void nvmet_ns_disable(struct nvmet_ns *ns)
struct nvmet_subsys *subsys = ns->subsys;
struct nvmet_ctrl *ctrl;
- mutex_lock(&subsys->lock);
- if (list_empty(&ns->dev_link)) {
- mutex_unlock(&subsys->lock);
+ if (!test_and_clear_bit(NVMET_NS_ENABLED, &ns->flags))
return;
- }
- list_del_init(&ns->dev_link);
- mutex_unlock(&subsys->lock);
+
+ list_del_rcu(&ns->dev_link);
/*
* Now that we removed the namespaces from the lookup list, we
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 76b6eedccaf9..f5db4b6a85c3 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -38,6 +38,10 @@
#define IPO_IATTR_CONNECT_SQE(x) \
(cpu_to_le32(offsetof(struct nvmf_connect_command, x)))
+enum nvmet_ns_flags {
+ NVMET_NS_ENABLED = (1 << 0),
+};
+
struct nvmet_ns {
struct list_head dev_link;
struct percpu_ref ref;
@@ -47,6 +51,7 @@ struct nvmet_ns {
loff_t size;
u8 nguid[16];
+ unsigned long flags;
struct nvmet_subsys *subsys;
const char *device_path;
--
2.7.4
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