With lockdep enabled, when trigger nvme_remove, suspicious RCU
usage warning will be printed out.
Fix it with adding srcu_read_lock/unlock in it.
Signed-off-by: Jianchao Wang <[email protected]>
---
drivers/nvme/host/nvme.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 061fecf..d326c23 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -446,9 +446,14 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head);
static inline void nvme_mpath_clear_current_path(struct nvme_ns *ns)
{
struct nvme_ns_head *head = ns->head;
+ int srcu_idx;
- if (head && ns == srcu_dereference(head->current_path, &head->srcu))
- rcu_assign_pointer(head->current_path, NULL);
+ if (head) {
+ srcu_idx = srcu_read_lock(&head->srcu);
+ if (ns == srcu_dereference(head->current_path, &head->srcu))
+ rcu_assign_pointer(head->current_path, NULL);
+ srcu_read_unlock(&head->srcu, srcu_idx);
+ }
}
struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);
--
2.7.4
On Wed, Apr 18, 2018 at 03:32:47PM +0800, Jianchao Wang wrote:
> With lockdep enabled, when trigger nvme_remove, suspicious RCU
> usage warning will be printed out.
> Fix it with adding srcu_read_lock/unlock in it.
Looks fine,
Reviewed-by: Christoph Hellwig <[email protected]>
On Wed, Apr 18, 2018 at 03:32:47PM +0800, Jianchao Wang wrote:
> With lockdep enabled, when trigger nvme_remove, suspicious RCU
> usage warning will be printed out.
> Fix it with adding srcu_read_lock/unlock in it.
>
> Signed-off-by: Jianchao Wang <[email protected]>
> ---
> drivers/nvme/host/nvme.h | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 061fecf..d326c23 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -446,9 +446,14 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head);
> static inline void nvme_mpath_clear_current_path(struct nvme_ns *ns)
> {
> struct nvme_ns_head *head = ns->head;
> + int srcu_idx;
>
> - if (head && ns == srcu_dereference(head->current_path, &head->srcu))
> - rcu_assign_pointer(head->current_path, NULL);
> + if (head) {
> + srcu_idx = srcu_read_lock(&head->srcu);
> + if (ns == srcu_dereference(head->current_path, &head->srcu))
> + rcu_assign_pointer(head->current_path, NULL);
> + srcu_read_unlock(&head->srcu, srcu_idx);
> + }
> }
> struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);
Nothing against this patch. This just doesn't look correct even from
before since nvme_find_path can set head->current_path right back to
this namespace that we're trying to clear.
Christoph, am I missing something here or does this need additional
checks/synchronization?
On Wed, Apr 18, 2018 at 08:45:25AM -0600, Keith Busch wrote:
> Nothing against this patch. This just doesn't look correct even from
> before since nvme_find_path can set head->current_path right back to
> this namespace that we're trying to clear.
>
> Christoph, am I missing something here or does this need additional
> checks/synchronization?
Yes, we should probably call it after removing the namespace from
the ns_head list, instead of right before.