[PATCH 6/6] scsi: zfcp: lift Request Queue tasklet & timer from qdio

Benjamin Block
2021-04-14T17:08:20Z

From: Julian Wiedmann <jwi@linux.ibm.com>

The qdio layer currently provides its own infrastructure to scan for
Request Queue completions & to report them to the device driver.
This comes with several drawbacks - having an async tasklet & timer
construct in qdio introduces additional lifetime complexity, and makes
it harder to integrate them with the rest of the device driver. The
timeouts are also currently hard-coded, and can't be tweaked without
affecting other qdio drivers (ie. qeth).

But due to recent enhancements to the qdio layer, zfcp can actually take
full control of the Request Queue completion processing. It merely needs
to opt-out from the qdio layer mechanisms by setting the scan_threshold
to 0, and then use qdio_inspect_queue() to scan for completions.

So re-implement the tasklet & timer mechanism in zfcp, while initially
copying the scan conditions from qdio's handle_outbound() and
qdio_outbound_tasklet(). One minor behavioural change is that
zfcp_qdio_send() will unconditionally reduce the timeout to 1 HZ, rather
than leaving it at 10 Hz if it was last armed by the tasklet. This just
makes things more consistent. Also note that we can drop a lot of the
accumulated cruft in qdio_outbound_tasklet(), as zfcp doesn't even use
PCI interrupt requests any longer.

This also slightly touches the Response Queue processing, as
qdio_get_next_buffers() will no longer implicitly scan for Request Queue
completions. So complete the migration to qdio_inspect_queue() here as
well and make the tasklet_schedule() visible.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
---
drivers/s390/scsi/zfcp_qdio.c | 68 ++++++++++++++++++++++++++++-------
drivers/s390/scsi/zfcp_qdio.h | 5 +++
2 files changed, 61 insertions(+), 12 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c
index 23ab16d65f2a..16a332d501e7 100644
--- a/drivers/s390/scsi/zfcp_qdio.c
+++ b/drivers/s390/scsi/zfcp_qdio.c
@@ -20,6 +20,9 @@ static bool enable_multibuffer = true;
module_param_named(datarouter, enable_multibuffer, bool, 0400);
MODULE_PARM_DESC(datarouter, "Enable hardware data router support (default on)");

+#define ZFCP_QDIO_REQUEST_RESCAN_MSECS (MSEC_PER_SEC * 10)
+#define ZFCP_QDIO_REQUEST_SCAN_MSECS MSEC_PER_SEC
+
static void zfcp_qdio_handler_error(struct zfcp_qdio *qdio, char *dbftag,
unsigned int qdio_err)
{
@@ -70,15 +73,41 @@ static void zfcp_qdio_int_req(struct ccw_device *cdev, unsigned int qdio_err,
zfcp_qdio_handler_error(qdio, "qdireq1", qdio_err);
return;
}
+}

- /* cleanup all SBALs being program-owned now */
- zfcp_qdio_zero_sbals(qdio->req_q, idx, count);
+static void zfcp_qdio_request_tasklet(struct tasklet_struct *tasklet)
+{
+ struct zfcp_qdio *qdio = from_tasklet(qdio, tasklet, request_tasklet);
+ struct ccw_device *cdev = qdio->adapter->ccw_device;
+ unsigned int start, error;
+ int completed;

- spin_lock_irq(&qdio->stat_lock);
- zfcp_qdio_account(qdio);
- spin_unlock_irq(&qdio->stat_lock);
- atomic_add(count, &qdio->req_q_free);
- wake_up(&qdio->req_q_wq);
+ completed = qdio_inspect_queue(cdev, 0, false, &start, &error);
+ if (completed > 0) {
+ if (error) {
+ zfcp_qdio_handler_error(qdio, "qdreqt1", error);
+ } else {
+ /* cleanup all SBALs being program-owned now */
+ zfcp_qdio_zero_sbals(qdio->req_q, start, completed);
+
+ spin_lock_irq(&qdio->stat_lock);
+ zfcp_qdio_account(qdio);
+ spin_unlock_irq(&qdio->stat_lock);
+ atomic_add(completed, &qdio->req_q_free);
+ wake_up(&qdio->req_q_wq);
+ }
+ }
+
+ if (atomic_read(&qdio->req_q_free) < QDIO_MAX_BUFFERS_PER_Q)
+ timer_reduce(&qdio->request_timer,
+ jiffies + msecs_to_jiffies(ZFCP_QDIO_REQUEST_RESCAN_MSECS));
+}
+
+static void zfcp_qdio_request_timer(struct timer_list *timer)
+{
+ struct zfcp_qdio *qdio = from_timer(qdio, timer, request_timer);
+
+ tasklet_schedule(&qdio->request_tasklet);
}

static void zfcp_qdio_int_resp(struct ccw_device *cdev, unsigned int qdio_err,
@@ -139,8 +168,11 @@ static void zfcp_qdio_irq_tasklet(struct tasklet_struct *tasklet)
unsigned int start, error;
int completed;

- /* Check the Response Queue, and kick off the Request Queue tasklet: */
- completed = qdio_get_next_buffers(cdev, 0, &start, &error);
+ if (atomic_read(&qdio->req_q_free) < QDIO_MAX_BUFFERS_PER_Q)
+ tasklet_schedule(&qdio->request_tasklet);
+
+ /* Check the Response Queue: */
+ completed = qdio_inspect_queue(cdev, 0, true, &start, &error);
if (completed < 0)
return;
if (completed > 0)
@@ -286,7 +318,7 @@ int zfcp_qdio_send(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req)

/*
* This should actually be a spin_lock_bh(stat_lock), to protect against
- * zfcp_qdio_int_req() in tasklet context.
+ * Request Queue completion processing in tasklet context.
* But we can't do so (and are safe), as we always get called with IRQs
* disabled by spin_lock_irq[save](req_q_lock).
*/
@@ -308,6 +340,12 @@ int zfcp_qdio_send(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req)
return retval;
}

+ if (atomic_read(&qdio->req_q_free) <= 2 * ZFCP_QDIO_MAX_SBALS_PER_REQ)
+ tasklet_schedule(&qdio->request_tasklet);
+ else
+ timer_reduce(&qdio->request_timer,
+ jiffies + msecs_to_jiffies(ZFCP_QDIO_REQUEST_SCAN_MSECS));
+
/* account for transferred buffers */
qdio->req_q_idx += sbal_number;
qdio->req_q_idx %= QDIO_MAX_BUFFERS_PER_Q;
@@ -368,6 +406,8 @@ void zfcp_qdio_close(struct zfcp_qdio *qdio)
wake_up(&qdio->req_q_wq);

tasklet_disable(&qdio->irq_tasklet);
+ tasklet_disable(&qdio->request_tasklet);
+ del_timer_sync(&qdio->request_timer);
qdio_stop_irq(adapter->ccw_device);
qdio_shutdown(adapter->ccw_device, QDIO_FLAG_CLEANUP_USING_CLEAR);

@@ -428,8 +468,6 @@ int zfcp_qdio_open(struct zfcp_qdio *qdio)
init_data.int_parm = (unsigned long) qdio;
init_data.input_sbal_addr_array = input_sbals;
init_data.output_sbal_addr_array = output_sbals;
- init_data.scan_threshold =
- QDIO_MAX_BUFFERS_PER_Q - ZFCP_QDIO_MAX_SBALS_PER_REQ * 2;

if (qdio_establish(cdev, &init_data))
goto failed_establish;
@@ -471,6 +509,8 @@ int zfcp_qdio_open(struct zfcp_qdio *qdio)
atomic_set(&qdio->req_q_free, QDIO_MAX_BUFFERS_PER_Q);
atomic_or(ZFCP_STATUS_ADAPTER_QDIOUP, &qdio->adapter->status);

+ /* Enable processing for Request Queue completions: */
+ tasklet_enable(&qdio->request_tasklet);
/* Enable processing for QDIO interrupts: */
tasklet_enable(&qdio->irq_tasklet);
/* This results in a qdio_start_irq(): */
@@ -494,6 +534,7 @@ void zfcp_qdio_destroy(struct zfcp_qdio *qdio)
return;

tasklet_kill(&qdio->irq_tasklet);
+ tasklet_kill(&qdio->request_tasklet);

if (qdio->adapter->ccw_device)
qdio_free(qdio->adapter->ccw_device);
@@ -520,8 +561,11 @@ int zfcp_qdio_setup(struct zfcp_adapter *adapter)

spin_lock_init(&qdio->req_q_lock);
spin_lock_init(&qdio->stat_lock);
+ timer_setup(&qdio->request_timer, zfcp_qdio_request_timer, 0);
tasklet_setup(&qdio->irq_tasklet, zfcp_qdio_irq_tasklet);
+ tasklet_setup(&qdio->request_tasklet, zfcp_qdio_request_tasklet);
tasklet_disable(&qdio->irq_tasklet);
+ tasklet_disable(&qdio->request_tasklet);

adapter->qdio = qdio;
return 0;
diff --git a/drivers/s390/scsi/zfcp_qdio.h b/drivers/s390/scsi/zfcp_qdio.h
index 9c1f310db155..390706867df3 100644
--- a/drivers/s390/scsi/zfcp_qdio.h
+++ b/drivers/s390/scsi/zfcp_qdio.h
@@ -30,6 +30,9 @@
* @req_q_util: used for accounting
* @req_q_full: queue full incidents
* @req_q_wq: used to wait for SBAL availability
+ * @irq_tasklet: used for QDIO interrupt processing
+ * @request_tasklet: used for Request Queue completion processing
+ * @request_timer: used to trigger the Request Queue completion processing
* @adapter: adapter used in conjunction with this qdio structure
* @max_sbale_per_sbal: qdio limit per sbal
* @max_sbale_per_req: qdio limit per request
@@ -46,6 +49,8 @@ struct zfcp_qdio {
atomic_t req_q_full;
wait_queue_head_t req_q_wq;
struct tasklet_struct irq_tasklet;
+ struct tasklet_struct request_tasklet;
+ struct timer_list request_timer;
struct zfcp_adapter *adapter;
u16 max_sbale_per_sbal;
u16 max_sbale_per_req;
--
2.30.2