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

Joel Fernandes
2020-01-10T15:47:26Z

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@joelfernandes.org>

thanks,

- Joel

>
> Signed-off-by: Amol Grover <frextrite@gmail.com>
> ---
> 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
>