Re: [PATCH RESEND] libsas: Fixup device_del() inversion

[John Garry <john.garry@huawei.com>]

On 31/08/2017 10:20, Hannes Reinecke wrote:
> (resending to include linux-scsi)
>
> When removing the HBA or port there's a device_del() inversion
> in sas_deform_port().
> If there's only one phy it will call sas_unregister_domain_devices(),
> which in turn might remove any phys and end_devices asynchronously
> via the DISCE_DESTRUCT event.
> But then it goes ahead and calls sas_port_delete() before the DISCE_DESTRUCT
> event had a chance to run.
> Consequently the port is removed before the phy, and we're getting
> nasty kernel WARNING like
>

Hi Hannes,

Your solution looks similar to what Dan tried originally to fix this, here:
https://marc.info/?l=linux-scsi&m=143459794823595&w=2

As I recall, I was getting a NULL dereference with his.

Anyway, have you tried removing a disk from an expander? I don't see how 
this is fixed-up in your patch. I quickly tested and I see the WARN. 
However just removing a directly attached disk looked ok.

BTW, another colleague of mine has taken over the work we were doing on 
this topic. I reviewed internally the candidate patchset yesterday, and 
it still has a few issues; here's that patchset:
https://github.com/JasonYanHuawei/linux-libsas

All the best,
John

> WARNING: CPU: 14 PID: 1592 at fs/sysfs/group.c:237 device_del+0x61/0x2a0()
> sysfs group ffffffff81eff140 not found for kobject '6:0:0:0'
>
> This patch moves the call to sas_port_delete() into the DISCE_DESTRUCT
> handler to ensure that devices are removed in the correct order.
>
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/scsi/libsas/sas_discover.c | 10 +++++++++-
>  drivers/scsi/libsas/sas_port.c     |  6 ++----
>  2 files changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_discover.c b/drivers/scsi/libsas/sas_discover.c
> index 60de662..dc8f789 100644
> --- a/drivers/scsi/libsas/sas_discover.c
> +++ b/drivers/scsi/libsas/sas_discover.c
> @@ -368,6 +368,10 @@ static void sas_destruct_devices(struct work_struct *work)
>  		sas_rphy_delete(dev->rphy);
>  		sas_unregister_common_dev(port, dev);
>  	}
> +	if (!port->port->rphy) {
> +		sas_port_delete(port->port);
> +		port->port = NULL;
> +	}
>  }
>
>  void sas_unregister_dev(struct asd_sas_port *port, struct domain_device *dev)
> @@ -401,8 +405,12 @@ void sas_unregister_domain_devices(struct asd_sas_port *port, int gone)
>  	list_for_each_entry_safe(dev, n, &port->disco_list, disco_list_node)
>  		sas_unregister_dev(port, dev);
>
> +	/*
> +	 * Add another destruct event (or overload the existing one)
> +	 * to trigger port deletion.
> +	 */
>  	port->port->rphy = NULL;
> -
> +	sas_discover_event(port, DISCE_DESTRUCT);
>  }
>
>  void sas_device_set_phy(struct domain_device *dev, struct sas_port *port)
> diff --git a/drivers/scsi/libsas/sas_port.c b/drivers/scsi/libsas/sas_port.c
> index d3c5297..7ee0c0a 100644
> --- a/drivers/scsi/libsas/sas_port.c
> +++ b/drivers/scsi/libsas/sas_port.c
> @@ -217,11 +217,9 @@ void sas_deform_port(struct asd_sas_phy *phy, int gone)
>  	if (dev)
>  		dev->pathways--;
>
> -	if (port->num_phys == 1) {
> +	if (port->num_phys == 1)
>  		sas_unregister_domain_devices(port, gone);
> -		sas_port_delete(port->port);
> -		port->port = NULL;
> -	} else {
> +	else {
>  		sas_port_delete_phy(port->port, phy->phy);
>  		sas_device_set_phy(dev, port->port);
>  	}
>