Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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.
Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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.
Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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> --- > 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, >srcu)) > - rcu_assign_pointer(head->current_path, NULL); > + if (head) { > + srcu_idx = srcu_read_lock(>srcu); > + if (ns == srcu_dereference(head->current_path, >srcu)) > + rcu_assign_pointer(head->current_path, NULL); > + srcu_read_unlock(>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?
Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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 > --- > 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, >srcu)) > - rcu_assign_pointer(head->current_path, NULL); > + if (head) { > + srcu_idx = srcu_read_lock(>srcu); > + if (ns == srcu_dereference(head->current_path, >srcu)) > + rcu_assign_pointer(head->current_path, NULL); > + srcu_read_unlock(>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?
Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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
Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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
[PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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--- 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, >srcu)) - rcu_assign_pointer(head->current_path, NULL); + if (head) { + srcu_idx = srcu_read_lock(>srcu); + if (ns == srcu_dereference(head->current_path, >srcu)) + rcu_assign_pointer(head->current_path, NULL); + srcu_read_unlock(>srcu, srcu_idx); + } } struct nvme_ns *nvme_find_path(struct nvme_ns_head *head); -- 2.7.4
[PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
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 --- 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, >srcu)) - rcu_assign_pointer(head->current_path, NULL); + if (head) { + srcu_idx = srcu_read_lock(>srcu); + if (ns == srcu_dereference(head->current_path, >srcu)) + rcu_assign_pointer(head->current_path, NULL); + srcu_read_unlock(>srcu, srcu_idx); + } } struct nvme_ns *nvme_find_path(struct nvme_ns_head *head); -- 2.7.4