* [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
@ 2018-04-18 7:32 ` Jianchao Wang
0 siblings, 0 replies; 8+ messages in thread
From: Jianchao Wang @ 2018-04-18 7:32 UTC (permalink / raw)
To: keith.busch, axboe, hch, sagi, linux-nvme, linux-kernel
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 <jianchao.w.wang@oracle.com>
---
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
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
@ 2018-04-18 7:32 ` Jianchao Wang
0 siblings, 0 replies; 8+ messages in thread
From: Jianchao Wang @ 2018-04-18 7:32 UTC (permalink / raw)
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 <jianchao.w.wang at oracle.com>
---
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
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
2018-04-18 7:32 ` Jianchao Wang
@ 2018-04-18 10:19 ` Christoph Hellwig
-1 siblings, 0 replies; 8+ messages in thread
From: Christoph Hellwig @ 2018-04-18 10:19 UTC (permalink / raw)
To: Jianchao Wang; +Cc: keith.busch, axboe, hch, sagi, linux-nvme, linux-kernel
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 <hch@lst.de>
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
@ 2018-04-18 10:19 ` Christoph Hellwig
0 siblings, 0 replies; 8+ messages in thread
From: Christoph Hellwig @ 2018-04-18 10:19 UTC (permalink / raw)
On Wed, Apr 18, 2018@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 <hch at lst.de>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
2018-04-18 7:32 ` Jianchao Wang
@ 2018-04-18 14:45 ` Keith Busch
-1 siblings, 0 replies; 8+ messages in thread
From: Keith Busch @ 2018-04-18 14:45 UTC (permalink / raw)
To: Jianchao Wang; +Cc: axboe, hch, sagi, linux-nvme, linux-kernel
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 <jianchao.w.wang@oracle.com>
> ---
> 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?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
@ 2018-04-18 14:45 ` Keith Busch
0 siblings, 0 replies; 8+ messages in thread
From: Keith Busch @ 2018-04-18 14:45 UTC (permalink / raw)
On Wed, Apr 18, 2018@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 <jianchao.w.wang at oracle.com>
> ---
> 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?
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
2018-04-18 14:45 ` Keith Busch
@ 2018-04-18 15:07 ` Christoph Hellwig
-1 siblings, 0 replies; 8+ messages in thread
From: Christoph Hellwig @ 2018-04-18 15:07 UTC (permalink / raw)
To: Keith Busch; +Cc: Jianchao Wang, axboe, hch, sagi, linux-nvme, linux-kernel
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.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path
@ 2018-04-18 15:07 ` Christoph Hellwig
0 siblings, 0 replies; 8+ messages in thread
From: Christoph Hellwig @ 2018-04-18 15:07 UTC (permalink / raw)
On Wed, Apr 18, 2018@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.
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2018-04-18 15:07 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-04-18 7:32 [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path Jianchao Wang
2018-04-18 7:32 ` Jianchao Wang
2018-04-18 10:19 ` Christoph Hellwig
2018-04-18 10:19 ` Christoph Hellwig
2018-04-18 14:45 ` Keith Busch
2018-04-18 14:45 ` Keith Busch
2018-04-18 15:07 ` Christoph Hellwig
2018-04-18 15:07 ` Christoph Hellwig
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