Re: [PATCH] drivers: nvme: target: core: Pass lockdep expression to RCU lists

[Joel Fernandes]

On Fri, Jan 10, 2020 at 06:53:58PM +0530, Amol Grover wrote:
> ctrl->subsys->namespaces and subsys->namespaces are traversed with
> hlist_for_each_entry_rcu outside an RCU read-side critical section
> but under the protection of subsys->lock.
> 
> Hence, add the corresponding lockdep expression to the list traversal
> primitive to silence false-positive lockdep warnings, and
> harden RCU lists.
> 
> Add macro for the corresponding lockdep expression to make the code
> clean and concise.

Amol, thanks. Could you fix this checkpatch warnings? hint: Use --fix-inplace

CHECK: Alignment should match open parenthesis
#50: FILE: drivers/nvme/target/core.c:562:
+               list_for_each_entry_rcu(old, &subsys->namespaces, dev_link,
+                                                       subsys_lock_held()) {

CHECK: Alignment should match open parenthesis
#60: FILE: drivers/nvme/target/core.c:1180:
+       list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link,
+                                                       subsys_lock_held())

Otherwise,

Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>

thanks,

 - Joel


> 
> Signed-off-by: Amol Grover <frextrite@xxxxxxxxx>
> ---
>  drivers/nvme/target/core.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 28438b833c1b..7caab4ba6a04 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -15,6 +15,9 @@
>  
>  #include "nvmet.h"
>  
> +#define subsys_lock_held() \
> +	lockdep_is_held(&subsys->lock)
> +
>  struct workqueue_struct *buffered_io_wq;
>  static const struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
>  static DEFINE_IDA(cntlid_ida);
> @@ -555,7 +558,8 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
>  	} else {
>  		struct nvmet_ns *old;
>  
> -		list_for_each_entry_rcu(old, &subsys->namespaces, dev_link) {
> +		list_for_each_entry_rcu(old, &subsys->namespaces, dev_link,
> +							subsys_lock_held()) {
>  			BUG_ON(ns->nsid == old->nsid);
>  			if (ns->nsid < old->nsid)
>  				break;
> @@ -1172,7 +1176,8 @@ static void nvmet_setup_p2p_ns_map(struct nvmet_ctrl *ctrl,
>  
>  	ctrl->p2p_client = get_device(req->p2p_client);
>  
> -	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link)
> +	list_for_each_entry_rcu(ns, &ctrl->subsys->namespaces, dev_link,
> +							subsys_lock_held())
>  		nvmet_p2pmem_ns_add_p2p(ctrl, ns);
>  }
>  
> -- 
> 2.24.1
>