Commit d26ab06e authored by Swen Schillig's avatar Swen Schillig Committed by James Bottomley
Browse files

[SCSI] zfcp: receiving an unsolicted status can lead to I/O stall 



Processing of an unsolicted status request can lead to a locking race
of the request_queue's queue_lock during the recreation of the
used up status read request while still in interrupt context
of the response handler.

Detaching the 'refill' of the long running status read requests from
the handler to a scheduled work is solving this issue.

In addition, each refill-run is trying to re-establish the full amount
of status read requests, which might have failed in earlier runs.

Signed-off-by: default avatarSwen Schillig <swen@vnet.ibm.com>
Signed-off-by: default avatarChristof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 15424921

drivers/s390/scsi/zfcp_aux.c

+23 −0
Original line number Diff line number Diff line
@@ -970,6 +970,27 @@ static void zfcp_dummy_release(struct device *dev) 
	return;

}



int zfcp_status_read_refill(struct zfcp_adapter *adapter)

{

	while (atomic_read(&adapter->stat_miss) > 0)

		if (zfcp_fsf_status_read(adapter, ZFCP_WAIT_FOR_SBAL))

			break;

	else

		atomic_dec(&adapter->stat_miss);



	if (ZFCP_STATUS_READS_RECOM <= atomic_read(&adapter->stat_miss)) {

		zfcp_erp_adapter_reopen(adapter, 0, 103, NULL);

		return 1;

	}

	return 0;

}



static void _zfcp_status_read_scheduler(struct work_struct *work)

{

	zfcp_status_read_refill(container_of(work, struct zfcp_adapter,

					     stat_work));

}



/*

 * Enqueues an adapter at the end of the adapter list in the driver data.

 * All adapter internal structures are set up.
@@ -1063,6 +1084,7 @@ zfcp_adapter_enqueue(struct ccw_device *ccw_device) 


	/* initialize lock of associated request queue */

	rwlock_init(&adapter->request_queue.queue_lock);

	INIT_WORK(&adapter->stat_work, _zfcp_status_read_scheduler);



	/* mark adapter unusable as long as sysfs registration is not complete */

	atomic_set_mask(ZFCP_STATUS_COMMON_REMOVE, &adapter->status);
@@ -1123,6 +1145,7 @@ zfcp_adapter_dequeue(struct zfcp_adapter *adapter) 
	int retval = 0;

	unsigned long flags;



	cancel_work_sync(&adapter->stat_work);

	zfcp_adapter_scsi_unregister(adapter);

	device_unregister(&adapter->generic_services);

	zfcp_sysfs_adapter_remove_files(&adapter->ccw_device->dev);

drivers/s390/scsi/zfcp_dbf.c

+1 −1
Original line number Diff line number Diff line
@@ -268,7 +268,7 @@ void zfcp_hba_dbf_event_fsf_unsol(const char *tag, struct zfcp_adapter *adapter, 
	strncpy(rec->tag, "stat", ZFCP_DBF_TAG_SIZE);

	strncpy(rec->tag2, tag, ZFCP_DBF_TAG_SIZE);



	rec->u.status.failed = adapter->status_read_failed;

	rec->u.status.failed = atomic_read(&adapter->stat_miss);

	if (status_buffer != NULL) {

		rec->u.status.status_type = status_buffer->status_type;

		rec->u.status.status_subtype = status_buffer->status_subtype;

drivers/s390/scsi/zfcp_def.h

+2 −2
Original line number Diff line number Diff line
@@ -136,7 +136,6 @@ zfcp_address_to_sg(void *address, struct scatterlist *list, unsigned int size) 
#define ZFCP_QTCB_VERSION	FSF_QTCB_CURRENT_VERSION

/* ATTENTION: value must not be used by hardware */

#define FSF_QTCB_UNSOLICITED_STATUS		0x6305

#define ZFCP_STATUS_READ_FAILED_THRESHOLD	3

#define ZFCP_STATUS_READS_RECOM		        FSF_STATUS_READS_RECOM



/* Do 1st retry in 1 second, then double the timeout for each following retry */
@@ -759,7 +758,8 @@ struct zfcp_adapter { 
	rwlock_t		abort_lock;        /* Protects against SCSI

						      stack abort/command

						      completion races */

	u16			status_read_failed; /* # failed status reads */

	atomic_t		stat_miss;	   /* # missing status reads*/

	struct work_struct	stat_work;

	atomic_t		status;	           /* status of this adapter */

	struct list_head	erp_ready_head;	   /* error recovery for this

						      adapter/devices */

drivers/s390/scsi/zfcp_erp.c

+2 −17
Original line number Diff line number Diff line
@@ -2139,25 +2139,10 @@ static int 
zfcp_erp_adapter_strategy_open_fsf_statusread(struct zfcp_erp_action

					      *erp_action)

{

	int retval = ZFCP_ERP_SUCCEEDED;

	int temp_ret;

	struct zfcp_adapter *adapter = erp_action->adapter;

	int i;



	adapter->status_read_failed = 0;

	for (i = 0; i < ZFCP_STATUS_READS_RECOM; i++) {

		temp_ret = zfcp_fsf_status_read(adapter, ZFCP_WAIT_FOR_SBAL);

		if (temp_ret < 0) {

			ZFCP_LOG_INFO("error: set-up of unsolicited status "

				      "notification failed on adapter %s\n",

				      zfcp_get_busid_by_adapter(adapter));

			retval = ZFCP_ERP_FAILED;

			i--;

			break;

		}

	}



	return retval;

	atomic_set(&adapter->stat_miss, 16);

	return zfcp_status_read_refill(adapter);

}



/*

drivers/s390/scsi/zfcp_ext.h

+1 −0
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ extern void zfcp_fsf_start_timer(struct zfcp_fsf_req *, unsigned long); 
extern void zfcp_erp_start_timer(struct zfcp_fsf_req *);

extern void zfcp_fsf_req_dismiss_all(struct zfcp_adapter *);

extern int  zfcp_fsf_status_read(struct zfcp_adapter *, int);

extern int zfcp_status_read_refill(struct zfcp_adapter *adapter);

extern int zfcp_fsf_req_create(struct zfcp_adapter *, u32, int, mempool_t *,

			       unsigned long *, struct zfcp_fsf_req **);

extern int zfcp_fsf_send_ct(struct zfcp_send_ct *, mempool_t *,

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