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.
Signed-off-by: Amol Grover <[email protected]>
---
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
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) <[email protected]>
thanks,
- Joel
>
> Signed-off-by: Amol Grover <[email protected]>
> ---
> 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
>
On Fri, Jan 10, 2020 at 06:53:58PM +0530, Amol Grover wrote:
> +#define subsys_lock_held() \
> + lockdep_is_held(&subsys->lock)
This macro requires "struct nvmet_subsys *subsys" was previously declared
in the function using it, which isn't obvious when looking at the users. I
don't think that's worth the conciseness.
> @@ -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;
On Sat, Jan 11, 2020 at 01:31:34AM +0900, Keith Busch wrote:
> On Fri, Jan 10, 2020 at 06:53:58PM +0530, Amol Grover wrote:
> > +#define subsys_lock_held() \
> > + lockdep_is_held(&subsys->lock)
>
> This macro requires "struct nvmet_subsys *subsys" was previously declared
> in the function using it, which isn't obvious when looking at the users. I
> don't think that's worth the conciseness.
>
Hey Keith,
If I understand correctly, you're saying `*subsys` is always declared in the
function using it, right? I too think, this could cause confusion to the person
going through the code, I'll fix it right away.
Thanks
Amol
> > @@ -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;