nvme: don't hold nvmf_transports_rwsem for more than transport lookups

Only take nvmf_transports_rwsem when doing a lookup of registered
transports, so that a blocking ->create_ctrl doesn't prevent other
actions on /dev/nvme-fabrics.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
[hch: increased lock hold time a bit to be safe, added a comment
 and updated the changelog]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 5 insertions, 1 deletions

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 5f5f7067c41d..fa32c1216409 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -952,6 +952,7 @@ nvmf_create_ctrl(struct device *dev, const char *buf, size_t count)
                 ret = -EBUSY;
                 goto out_unlock;
         }
+        up_read(&nvmf_transports_rwsem);
 
         ret = nvmf_check_required_opts(opts, ops->required_opts);
         if (ret)
@@ -968,11 +969,11 @@ nvmf_create_ctrl(struct device *dev, const char *buf, size_t count)
         }
 
         module_put(ops->module);
-        up_read(&nvmf_transports_rwsem);
         return ctrl;
 
 out_module_put:
         module_put(ops->module);
+        goto out_free_opts;
 out_unlock:
         up_read(&nvmf_transports_rwsem);
 out_free_opts:
diff --git a/drivers/nvme/host/fabrics.h b/drivers/nvme/host/fabrics.h
index 0cf0460a5c92..7491a0bbf711 100644
--- a/drivers/nvme/host/fabrics.h
+++ b/drivers/nvme/host/fabrics.h
@@ -124,6 +124,9 @@ struct nvmf_ctrl_options {
  *      1. At minimum, 'required_opts' and 'allowed_opts' should
  *         be set to the same enum parsing options defined earlier.
  *      2. create_ctrl() must be defined (even if it does nothing)
+ *      3. struct nvmf_transport_ops must be statically allocated in the
+ *         modules .bss section so that a pure module_get on @module
+ *         prevents the memory from beeing freed.
  */
 struct nvmf_transport_ops {
         struct list_head        entry;