Re: [PATCH 2/2] libsas: Enhance libsas hotplug

John Garry
2017-05-25T09:05:30Z

Hi,

There are some comments, inline.

In general, if it works, it looks ok.

Other reviews would be greatly appreciated - Hannes, Christoph,
Johannes, Dan - please.

> Libsas complete a hotplug event notified by LLDD in several works,
> for example, if libsas receive a PHYE_LOSS_OF_SIGNAL, we process it
> in following steps:
>
> notify_phy_event [interrupt context]
> sas_queue_event [queue work on shost->work_q]
> sas_phye_loss_of_signal [running in shost->work_q]
> sas_deform_port [remove sas port]
> sas_unregister_dev
> sas_discover_event [queue destruct work on
shost->work_q tail]
>
> In above case, complete whole hotplug in two works, remove sas port
first, then
> put the destruction of device in another work and queue it on in the
tail of
> workqueue, since sas port is the parent of the children rphy device,
so if remove
> sas port first, the children rphy device would also be deleted, when
the destruction
> work coming, it would find the target has been removed already, and
report a
> sysfs warning calltrace.
>
> queue tail queue head
> DISCE_DESTRUCT----> PORTE_BYTES_DMAED event
----->PHYE_LOSS_OF_SIGNAL[running]
>
> There are other hotplug issues in current framework, in above case,
if there is
> hotadd sas event queued between hotremove works, the hotplug order
would be broken
> and unexpected issues would happen.
>
> In this patch, we try to solve these issues in following steps:
> 1. create a new workqueue used to run sas event work, instead of scsi
host workqueue,
> because we may block sas event work, we cannot block the normal
scsi works.

What do we block the event work for?

> 2. create a new workqueue used to run sas discovery events work,
instead of scsi host
> workqueue, because in some cases, eg. in revalidate domain event,
we may unregister
> a sas device and discover new one, we must sync the execution,
wait the remove process
> finish, then start a new discovery. So we must put the probe and
destruct discovery
> events in a new workqueue to avoid deadlock.
> 3. introudce a asd_sas_port level wait-complete and a sas_discovery
level wait-complete
> we use former wait-complete to achieve a sas event atomic process
and use latter to
> make a sas discovery sync.
> 4. remove disco_mutex in sas_revalidate_domain, since now
sas_revalidate_domain sync
> the destruct discovery event execution, it's no need to lock disco
mutex there.
>
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> ---
> drivers/scsi/libsas/sas_discover.c | 58
++++++++++++++++++++++++++++----------
> drivers/scsi/libsas/sas_event.c | 2 +-
> drivers/scsi/libsas/sas_expander.c | 9 +++++-
> drivers/scsi/libsas/sas_init.c | 31 +++++++++++++++++++-
> drivers/scsi/libsas/sas_internal.h | 50 ++++++++++++++++++++++++++++++++
> drivers/scsi/libsas/sas_port.c | 4 +++
> include/scsi/libsas.h | 11 +++++++-
> 7 files changed, 146 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_discover.c
b/drivers/scsi/libsas/sas_discover.c
> index 60de662..43e8a1e 100644
> --- a/drivers/scsi/libsas/sas_discover.c
> +++ b/drivers/scsi/libsas/sas_discover.c
> @@ -503,11 +503,10 @@ static void sas_revalidate_domain(struct
work_struct *work)
> struct domain_device *ddev = port->port_dev;
>
> /* prevent revalidation from finding sata links in recovery */
> - mutex_lock(&ha->disco_mutex);
> if (test_bit(SAS_HA_ATA_EH_ACTIVE, &ha->state)) {
> SAS_DPRINTK("REVALIDATION DEFERRED on port %d, pid:%d\n",
> port->id, task_pid_nr(current));
> - goto out;
> + return;
> }
>
> clear_bit(DISCE_REVALIDATE_DOMAIN, &port->disc.pending);
> @@ -521,20 +520,57 @@ static void sas_revalidate_domain(struct
work_struct *work)
>
> SAS_DPRINTK("done REVALIDATING DOMAIN on port %d, pid:%d, res
0x%x\n",
> port->id, task_pid_nr(current), res);
> - out:
> - mutex_unlock(&ha->disco_mutex);
> +}
> +
> +static const work_func_t sas_event_fns[DISC_NUM_EVENTS] = {
> + [DISCE_DISCOVER_DOMAIN] = sas_discover_domain,
> + [DISCE_REVALIDATE_DOMAIN] = sas_revalidate_domain,
> + [DISCE_PROBE] = sas_probe_devices,
> + [DISCE_SUSPEND] = sas_suspend_devices,
> + [DISCE_RESUME] = sas_resume_devices,
> + [DISCE_DESTRUCT] = sas_destruct_devices,
> +};
> +
> +/* a simple wrapper for sas discover event funtions */
> +static void sas_discover_common_fn(struct work_struct *work)
> +{
> + struct sas_discovery_event *ev = to_sas_discovery_event(work);
> + struct asd_sas_port *port = ev->port;
> +
> + sas_event_fns[ev->type](work);
> + sas_unbusy_port(port);
> }
>
> /* ---------- Events ---------- */
>
> static void sas_chain_work(struct sas_ha_struct *ha, struct sas_work
*sw)
> {
> + int ret;
> + struct sas_discovery_event *ev = to_sas_discovery_event(&sw->work);
> + struct asd_sas_port *port = ev->port;
> +
> /* chained work is not subject to SA_HA_DRAINING or
> * SAS_HA_REGISTERED, because it is either submitted in the
> * workqueue, or known to be submitted from a context that is
> * not racing against draining
> */

Is this comment still valid (even if you have not touched the drain
logic work)?

> - scsi_queue_work(ha->core.shost, &sw->work);
> + sas_busy_port(port);
> +
> + /*
> + * discovery event probe and destruct would be called in other
> + * discovery event like discover domain and revalidate domain
> + * events, in some cases, we need to sync execute probe and destruct
> + * events, so run discover events except probe/destruct in a new
> + * workqueue.
> + */
> + if (ev->type == DISCE_PROBE || ev->type == DISCE_DESTRUCT)
> + ret = scsi_queue_work(ha->core.shost, &sw->work);
> + else
> + ret = queue_work(ha->disc_q, &sw->work);
> +
> + if (ret != 1)
> + /* queue a work fail, unbusy the ha before return */
> + sas_unbusy_port(port);

Do we really need to check for this error case, since we have dynamic
work structs (I think queue_work only fails if we try requeuing a work
item)?

> }
>
> static void sas_chain_event(int event, unsigned long *pending,
> @@ -575,18 +611,10 @@ void sas_init_disc(struct sas_discovery *disc,
struct asd_sas_port *port)
> {
> int i;
>
> - static const work_func_t sas_event_fns[DISC_NUM_EVENTS] = {
> - [DISCE_DISCOVER_DOMAIN] = sas_discover_domain,
> - [DISCE_REVALIDATE_DOMAIN] = sas_revalidate_domain,
> - [DISCE_PROBE] = sas_probe_devices,
> - [DISCE_SUSPEND] = sas_suspend_devices,
> - [DISCE_RESUME] = sas_resume_devices,
> - [DISCE_DESTRUCT] = sas_destruct_devices,
> - };
> -
> disc->pending = 0;
> for (i = 0; i < DISC_NUM_EVENTS; i++) {
> - INIT_SAS_WORK(&disc->disc_work[i].work, sas_event_fns[i]);
> + INIT_SAS_WORK(&disc->disc_work[i].work, sas_discover_common_fn);
> disc->disc_work[i].port = port;
> + disc->disc_work[i].type = i;
> }
> }
> diff --git a/drivers/scsi/libsas/sas_event.c
b/drivers/scsi/libsas/sas_event.c
> index 06c5c4b..c0fc07d 100644
> --- a/drivers/scsi/libsas/sas_event.c
> +++ b/drivers/scsi/libsas/sas_event.c
> @@ -41,7 +41,7 @@ void sas_queue_work(struct sas_ha_struct *ha,
struct sas_work *sw)
> if (list_empty(&sw->drain_node))
> list_add(&sw->drain_node, &ha->defer_q);
> } else
> - scsi_queue_work(ha->core.shost, &sw->work);
> + queue_work(ha->event_q, &sw->work);
> }
>
> static void sas_queue_event(int event, struct sas_work *work,
> diff --git a/drivers/scsi/libsas/sas_expander.c
b/drivers/scsi/libsas/sas_expander.c
> index 570b2cb..a8c8ae1 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -822,7 +822,9 @@ static struct domain_device *sas_ex_discover_end_dev(
>
> list_add_tail(&child->disco_list_node,
&parent->port->disco_list);
>
> + wait_discover_event_init(child->port);
> res = sas_discover_sata(child);
> + wait_for_discover_event_finish(child->port);
> if (res) {
> SAS_DPRINTK("sas_discover_sata() for device %16llx at "
> "%016llx:0x%x returned 0x%x\n",
> @@ -847,7 +849,9 @@ static struct domain_device *sas_ex_discover_end_dev(
>
> list_add_tail(&child->disco_list_node,
&parent->port->disco_list);
>
> + wait_discover_event_init(child->port);
> res = sas_discover_end_dev(child);

In sas_discover_end_dev(), we may return before sending the queue event
(if LLDD notify dev found returns error), we please take care of this.

> + wait_for_discover_event_finish(child->port);
> if (res) {
> SAS_DPRINTK("sas_discover_end_dev() for device %16llx "
> "at %016llx:0x%x returned 0x%x\n",
> @@ -1890,8 +1894,11 @@ static void
sas_unregister_devs_sas_addr(struct domain_device *parent,
> if (child->dev_type == SAS_EDGE_EXPANDER_DEVICE ||
> child->dev_type == SAS_FANOUT_EXPANDER_DEVICE)
> sas_unregister_ex_tree(parent->port, child);
> - else
> + else {
> + wait_discover_event_init(parent->port);
> sas_unregister_dev(parent->port, child);
> + wait_for_discover_event_finish(parent->port);
> + }
> found = child;
> break;
> }
> diff --git a/drivers/scsi/libsas/sas_init.c
b/drivers/scsi/libsas/sas_init.c
> index 79f95d0..1c49483 100644
> --- a/drivers/scsi/libsas/sas_init.c
> +++ b/drivers/scsi/libsas/sas_init.c
> @@ -38,6 +38,8 @@
>
> #include "../scsi_sas_internal.h"
>
> +static DEFINE_IDA(sas_ida);
> +
> static struct kmem_cache *sas_task_cache;
>
> struct sas_task *sas_alloc_task(gfp_t flags)
> @@ -116,6 +118,7 @@ void sas_hae_reset(struct work_struct *work)
> int sas_register_ha(struct sas_ha_struct *sas_ha)
> {
> int error = 0;
> + char name[64];
>
> mutex_init(&sas_ha->disco_mutex);
> spin_lock_init(&sas_ha->phy_port_lock);
> @@ -146,6 +149,30 @@ int sas_register_ha(struct sas_ha_struct *sas_ha)
> goto Undo_ports;
> }
>
> + sas_ha->id = ida_simple_get(&sas_ida, 0, 0, GFP_KERNEL);
> + if(sas_ha->id < 0)
> + goto Undo_ports;
> +
> + memset(name, 0, 64);

Why memset and then sprintf?

> + snprintf(name, 64, "sas-event-%d", sas_ha->id);

Can you just use unique dev_name(sas_ha->dev) to help form this name, so
that you don't have to introduce IDR?

> + sas_ha->event_q = create_singlethread_workqueue(name);
> +
> + /*
> + * sas-disc-xx workqueue run the discover work except
> + * probe and destruct.
> + */
> + snprintf(name, 64, "sas-disc-%d", sas_ha->id);
> + sas_ha->disc_q = create_singlethread_workqueue(name);
> + if(!sas_ha->event_q || !sas_ha->disc_q) {
> + ida_simple_remove(&sas_ida, sas_ha->id);
> + if (sas_ha->event_q)
> + destroy_workqueue(sas_ha->event_q);
> + if (sas_ha->disc_q)
> + destroy_workqueue(sas_ha->disc_q);

Can this error handling be a bit more concise?

> + goto Undo_ports;
> + }
> +
> +
> INIT_LIST_HEAD(&sas_ha->eh_done_q);
> INIT_LIST_HEAD(&sas_ha->eh_ata_q);
>
> @@ -181,6 +208,9 @@ int sas_unregister_ha(struct sas_ha_struct *sas_ha)
> __sas_drain_work(sas_ha);
> mutex_unlock(&sas_ha->drain_mutex);
>
> + destroy_workqueue(sas_ha->event_q);
> + destroy_workqueue(sas_ha->disc_q);
> + ida_simple_remove(&sas_ida, sas_ha->id);
> return 0;
> }
>
> @@ -568,7 +598,6 @@ void sas_domain_release_transport(struct
scsi_transport_template *stt)
> EXPORT_SYMBOL_GPL(sas_domain_release_transport);
>
> /* ---------- SAS Class register/unregister ---------- */
> -
> static int __init sas_class_init(void)
> {
> sas_task_cache = KMEM_CACHE(sas_task, SLAB_HWCACHE_ALIGN);
> diff --git a/drivers/scsi/libsas/sas_internal.h
b/drivers/scsi/libsas/sas_internal.h
> index 33ce7e5..276df8e 100644
> --- a/drivers/scsi/libsas/sas_internal.h
> +++ b/drivers/scsi/libsas/sas_internal.h
> @@ -100,6 +100,56 @@ void sas_free_device(struct kref *kref);
> extern const work_func_t sas_phy_event_fns[PHY_NUM_EVENTS];
> extern const work_func_t sas_port_event_fns[PORT_NUM_EVENTS];
>
> +static inline void wait_discover_event_init(struct asd_sas_port *port)

You need to change function names to have "sas" prefix. Actually these
functions are all a bit messy.

> +{
> + if (port) {

This init and wait function are currently act ask bookend wrappers. I
think it may be better to put them in the wrapped function (if
possible), as:
a. probably then we don't need port NULL check
b. handles situations where event is possibly not queued, like the
suspected sas_discover_end_dev()

> + init_completion(&port->disc.completion);
> + port->disc.wait = 1;
> + }
> +}
> +
> +static inline void wait_for_discover_event_finish(
> + struct asd_sas_port *port)
> +{
> + if (port && port->disc.wait == 1)

Can you just use completion_done() instead of introducing another
variable in discovery_event.wait?

> + wait_for_completion(&port->disc.completion);
> +}
> +
> +static inline void wait_sas_event_init(struct asd_sas_port *port)
> +{
> + if (port) {
> + init_completion(&port->completion);
> + port->busy = 0;
> + }
> +}
> +
> +static inline void wait_for_sas_event_finish(
> + struct asd_sas_port *port)
> +{
> + if (port && port->busy)
> + wait_for_completion(&port->completion);
> +}
> +
> +static inline void sas_busy_port(struct asd_sas_port *port)
> +{
> + if (port)
> + port->busy++;

Why not use kref?

> +}
> +
> +static inline void sas_unbusy_port(struct asd_sas_port *port)
> +{
> + if (port && (port->busy > 0)) {
> + port->busy--;
> + if (!port->busy)
> + complete(&port->completion);
> + }
> +
> + if (port && (port->disc.wait == 1)) {

Why check port twice?

> + complete(&port->disc.completion);
> + port->disc.wait = 0;
> + }
> +}
> +
> #ifdef CONFIG_SCSI_SAS_HOST_SMP
> extern int sas_smp_host_handler(struct Scsi_Host *shost, struct
request *req,
> struct request *rsp);
> diff --git a/drivers/scsi/libsas/sas_port.c
b/drivers/scsi/libsas/sas_port.c
> index 9326628..8d8b38c 100644
> --- a/drivers/scsi/libsas/sas_port.c
> +++ b/drivers/scsi/libsas/sas_port.c
> @@ -191,7 +191,9 @@ static void sas_form_port(struct asd_sas_phy *phy)
> if (si->dft->lldd_port_formed)
> si->dft->lldd_port_formed(phy);
>
> + wait_sas_event_init(port);
> sas_discover_event(phy->port, DISCE_DISCOVER_DOMAIN);
> + wait_for_sas_event_finish(port);

Is it neater to put these calls inside sas_discover_event()?

> }
>
> /**
> @@ -218,7 +220,9 @@ void sas_deform_port(struct asd_sas_phy *phy, int
gone)
> dev->pathways--;
>
> if (port->num_phys == 1) {
> + wait_sas_event_init(port);
> sas_unregister_domain_devices(port, gone);
> + wait_for_sas_event_finish(port);
> sas_port_delete(port->port);
> port->port = NULL;
> } else {
> diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
> index c4444ad..4b931d4 100644
> --- a/include/scsi/libsas.h
> +++ b/include/scsi/libsas.h
> @@ -240,6 +240,9 @@ static inline void INIT_SAS_WORK(struct sas_work
*sw, void (*fn)(struct work_str
> struct sas_discovery_event {
> struct sas_work work;
> struct asd_sas_port *port;
> + enum discover_event type;
> + int wait;
> + struct completion completion;
> };
>
> static inline struct sas_discovery_event
*to_sas_discovery_event(struct work_struct *work)
> @@ -256,6 +259,8 @@ struct sas_discovery {
> u8 eeds_a[8];
> u8 eeds_b[8];
> int max_level;
> + int wait;
> + struct completion completion;

Again, does completion_done() do the same job as wait element?

> };
>
> /* The port struct is Class:RW, driver:RO */
> @@ -276,7 +281,8 @@ struct asd_sas_port {
>
> /* public: */
> int id;
> -
> + int busy;
> + struct completion completion;

I think public means LLDD can access, which is not the case

> enum sas_class class;
> u8 sas_addr[SAS_ADDR_SIZE];
> u8 attached_sas_addr[SAS_ADDR_SIZE];
> @@ -387,6 +393,7 @@ struct sas_ha_struct {
> int eh_active;
> wait_queue_head_t eh_wait_q;
> struct list_head eh_dev_q;
> + int id; /* for create workqueue */
>
> struct mutex disco_mutex;
>
> @@ -396,6 +403,8 @@ struct sas_ha_struct {
> char *sas_ha_name;
> struct device *dev; /* should be set */
> struct module *lldd_module; /* should be set */
> + struct workqueue_struct *event_q;
> + struct workqueue_struct *disc_q;
>
> u8 *sas_addr; /* must be set */
> u8 hashed_sas_addr[HASHED_SAS_ADDR_SIZE];
>