[S390] cio: replace subchannel evaluation queue with bitmap

Use a bitmap for indicating which subchannels require evaluation
instead of allocating memory for each evaluation request. This
approach reduces memory consumption during recovery in case of
massive evaluation request occurrence and removes the need for
memory allocation failure handling.

Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

11 files changed, 235 insertions, 236 deletions

diff --git a/drivers/s390/cio/Makefile b/drivers/s390/cio/Makefile
index fe7b3ffa1ea..cfaf77b320f 100644
--- a/drivers/s390/cio/Makefile
+++ b/drivers/s390/cio/Makefile
@@ -2,7 +2,7 @@
 # Makefile for the S/390 common i/o drivers
 #
 
-obj-y += airq.o blacklist.o chsc.o cio.o css.o chp.o
+obj-y += airq.o blacklist.o chsc.o cio.o css.o chp.o idset.o
 ccw_device-objs += device.o device_fsm.o device_ops.o
 ccw_device-objs += device_id.o device_pgid.o device_status.o
 obj-y += ccw_device.o cmf.o
diff --git a/drivers/s390/cio/chp.c b/drivers/s390/cio/chp.c
index 0e92c8c8986..ac289e6eadf 100644
--- a/drivers/s390/cio/chp.c
+++ b/drivers/s390/cio/chp.c
@@ -491,7 +491,7 @@ void *chp_get_chp_desc(struct chp_id chpid)
  * Handle channel-report-words indicating that the status of a channel-path
  * has changed.
  */
-int chp_process_crw(int id, int status)
+void chp_process_crw(int id, int status)
 {
 	struct chp_id chpid;
 
@@ -500,11 +500,9 @@ int chp_process_crw(int id, int status)
 	if (status) {
 		if (!chp_is_registered(chpid))
 			chp_new(chpid);
-		return chsc_chp_online(chpid);
-	} else {
+		chsc_chp_online(chpid);
+	} else
 		chsc_chp_offline(chpid);
-		return 0;
-	}
 }
 
 static inline int info_bit_num(struct chp_id id)
diff --git a/drivers/s390/cio/chp.h b/drivers/s390/cio/chp.h
index 862af69d970..65286563c59 100644
--- a/drivers/s390/cio/chp.h
+++ b/drivers/s390/cio/chp.h
@@ -42,7 +42,7 @@ int chp_get_status(struct chp_id chpid);
 u8 chp_get_sch_opm(struct subchannel *sch);
 int chp_is_registered(struct chp_id chpid);
 void *chp_get_chp_desc(struct chp_id chpid);
-int chp_process_crw(int id, int available);
+void chp_process_crw(int id, int available);
 void chp_remove_cmg_attr(struct channel_path *chp);
 int chp_add_cmg_attr(struct channel_path *chp);
 int chp_new(struct chp_id chpid);
diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c
index 02615eb4398..89a130a6265 100644
--- a/drivers/s390/cio/chsc.c
+++ b/drivers/s390/cio/chsc.c
@@ -195,12 +195,8 @@ static void terminate_internal_io(struct subchannel *sch)
 	if (cio_clear(sch)) {
 		/* Recheck device in case clear failed. */
 		sch->lpm = 0;
-		if (device_trigger_verify(sch) != 0) {
-			if(css_enqueue_subchannel_slow(sch->schid)) {
-				css_clear_subchannel_slow_list();
-				need_rescan = 1;
-			}
-		}
+		if (device_trigger_verify(sch) != 0)
+			css_schedule_eval(sch->schid);
 		return;
 	}
 	/* Request retry of internal operation. */
@@ -262,11 +258,8 @@ s390_subchannel_remove_chpid(struct device *dev, void *data)
 
 out_unreg:
 	sch->lpm = 0;
-	if (css_enqueue_subchannel_slow(sch->schid)) {
-		css_clear_subchannel_slow_list();
-		need_rescan = 1;
-	}
 	spin_unlock_irq(sch->lock);
+	css_schedule_eval(sch->schid);
 	return 0;
 }
 
@@ -281,9 +274,6 @@ void chsc_chp_offline(struct chp_id chpid)
 		return;
 	bus_for_each_dev(&css_bus_type, NULL, &chpid,
 			 s390_subchannel_remove_chpid);
-
-	if (need_rescan || css_slow_subchannels_exist())
-		queue_work(slow_path_wq, &slow_path_work);
 }
 
 struct res_acc_data {
@@ -331,7 +321,6 @@ static int
 s390_process_res_acc_new_sch(struct subchannel_id schid)
 {
 	struct schib schib;
-	int ret;
 	/*
 	 * We don't know the device yet, but since a path
 	 * may be available now to the device we'll have
@@ -342,15 +331,10 @@ s390_process_res_acc_new_sch(struct subchannel_id schid)
 	 */
 	if (stsch_err(schid, &schib))
 		/* We're through */
-		return need_rescan ? -EAGAIN : -ENXIO;
+		return -ENXIO;
 
 	/* Put it on the slow path. */
-	ret = css_enqueue_subchannel_slow(schid);
-	if (ret) {
-		css_clear_subchannel_slow_list();
-		need_rescan = 1;
-		return -EAGAIN;
-	}
+	css_schedule_eval(schid);
 	return 0;
 }
 
@@ -392,10 +376,8 @@ __s390_process_res_acc(struct subchannel_id schid, void *data)
 }
 
 
-static int
-s390_process_res_acc (struct res_acc_data *res_data)
+static void s390_process_res_acc (struct res_acc_data *res_data)
 {
-	int rc;
 	char dbf_txt[15];
 
 	sprintf(dbf_txt, "accpr%x.%02x", res_data->chpid.cssid,
@@ -413,12 +395,7 @@ s390_process_res_acc (struct res_acc_data *res_data)
 	 * The more information we have (info), the less scanning
 	 * will we have to do.
 	 */
-	rc = for_each_subchannel(__s390_process_res_acc, res_data);
-	if (css_slow_subchannels_exist())
-		rc = -EAGAIN;
-	else if (rc != -EAGAIN)
-		rc = 0;
-	return rc;
+	for_each_subchannel(__s390_process_res_acc, res_data);
 }
 
 static int
@@ -470,7 +447,7 @@ struct chsc_sei_area {
 	/* ccdf has to be big enough for a link-incident record */
 } __attribute__ ((packed));
 
-static int chsc_process_sei_link_incident(struct chsc_sei_area *sei_area)
+static void chsc_process_sei_link_incident(struct chsc_sei_area *sei_area)
 {
 	struct chp_id chpid;
 	int id;
@@ -478,7 +455,7 @@ static int chsc_process_sei_link_incident(struct chsc_sei_area *sei_area)
 	CIO_CRW_EVENT(4, "chsc: link incident (rs=%02x, rs_id=%04x)\n",
 		      sei_area->rs, sei_area->rsid);
 	if (sei_area->rs != 4)
-		return 0;
+		return;
 	id = __get_chpid_from_lir(sei_area->ccdf);
 	if (id < 0)
 		CIO_CRW_EVENT(4, "chsc: link incident - invalid LIR\n");
@@ -487,21 +464,18 @@ static int chsc_process_sei_link_incident(struct chsc_sei_area *sei_area)
 		chpid.id = id;
 		chsc_chp_offline(chpid);
 	}
-
-	return 0;
 }
 
-static int chsc_process_sei_res_acc(struct chsc_sei_area *sei_area)
+static void chsc_process_sei_res_acc(struct chsc_sei_area *sei_area)
 {
 	struct res_acc_data res_data;
 	struct chp_id chpid;
 	int status;
-	int rc;
 
 	CIO_CRW_EVENT(4, "chsc: resource accessibility event (rs=%02x, "
 		      "rs_id=%04x)\n", sei_area->rs, sei_area->rsid);
 	if (sei_area->rs != 4)
-		return 0;
+		return;
 	chp_id_init(&chpid);
 	chpid.id = sei_area->rsid;
 	/* allocate a new channel path structure, if needed */
@@ -509,7 +483,7 @@ static int chsc_process_sei_res_acc(struct chsc_sei_area *sei_area)
 	if (status < 0)
 		chp_new(chpid);
 	else if (!status)
-		return 0;
+		return;
 	memset(&res_data, 0, sizeof(struct res_acc_data));
 	res_data.chpid = chpid;
 	if ((sei_area->vf & 0xc0) != 0) {
@@ -521,9 +495,7 @@ static int chsc_process_sei_res_acc(struct chsc_sei_area *sei_area)
 			/* link address */
 			res_data.fla_mask = 0xff00;
 	}
-	rc = s390_process_res_acc(&res_data);
-
-	return rc;
+	s390_process_res_acc(&res_data);
 }
 
 struct chp_config_data {
@@ -532,7 +504,7 @@ struct chp_config_data {
 	u8 pc;
 };
 
-static int chsc_process_sei_chp_config(struct chsc_sei_area *sei_area)
+static void chsc_process_sei_chp_config(struct chsc_sei_area *sei_area)
 {
 	struct chp_config_data *data;
 	struct chp_id chpid;
@@ -540,7 +512,7 @@ static int chsc_process_sei_chp_config(struct chsc_sei_area *sei_area)
 
 	CIO_CRW_EVENT(4, "chsc: channel-path-configuration notification\n");
 	if (sei_area->rs != 0)
-		return 0;
+		return;
 	data = (struct chp_config_data *) &(sei_area->ccdf);
 	chp_id_init(&chpid);
 	for (num = 0; num <= __MAX_CHPID; num++) {
@@ -561,52 +533,44 @@ static int chsc_process_sei_chp_config(struct chsc_sei_area *sei_area)
 			break;
 		}
 	}
-
-	return 0;
 }
 
-static int chsc_process_sei(struct chsc_sei_area *sei_area)
+static void chsc_process_sei(struct chsc_sei_area *sei_area)
 {
-	int rc;
-
 	/* Check if we might have lost some information. */
-	if (sei_area->flags & 0x40)
+	if (sei_area->flags & 0x40) {
 		CIO_CRW_EVENT(2, "chsc: event overflow\n");
+		css_schedule_eval_all();
+	}
 	/* which kind of information was stored? */
-	rc = 0;
 	switch (sei_area->cc) {
 	case 1: /* link incident*/
-		rc = chsc_process_sei_link_incident(sei_area);
+		chsc_process_sei_link_incident(sei_area);
 		break;
 	case 2: /* i/o resource accessibiliy */
-		rc = chsc_process_sei_res_acc(sei_area);
+		chsc_process_sei_res_acc(sei_area);
 		break;
 	case 8: /* channel-path-configuration notification */
-		rc = chsc_process_sei_chp_config(sei_area);
+		chsc_process_sei_chp_config(sei_area);
 		break;
 	default: /* other stuff */
 		CIO_CRW_EVENT(4, "chsc: unhandled sei content code %d\n",
 			      sei_area->cc);
 		break;
 	}
-
-	return rc;
 }
 
-int chsc_process_crw(void)
+void chsc_process_crw(void)
 {
 	struct chsc_sei_area *sei_area;
-	int ret;
-	int rc;
 
 	if (!sei_page)
-		return 0;
+		return;
 	/* Access to sei_page is serialized through machine check handler
 	 * thread, so no need for locking. */
 	sei_area = sei_page;
 
 	CIO_TRACE_EVENT( 2, "prcss");
-	ret = 0;
 	do {
 		memset(sei_area, 0, sizeof(*sei_area));
 		sei_area->request.length = 0x0010;
@@ -616,37 +580,26 @@ int chsc_process_crw(void)
 
 		if (sei_area->response.code == 0x0001) {
 			CIO_CRW_EVENT(4, "chsc: sei successful\n");
-			rc = chsc_process_sei(sei_area);
-			if (rc)
-				ret = rc;
+			chsc_process_sei(sei_area);
 		} else {
 			CIO_CRW_EVENT(2, "chsc: sei failed (rc=%04x)\n",
 				      sei_area->response.code);
-			ret = 0;
 			break;
 		}
 	} while (sei_area->flags & 0x80);
-
-	return ret;
 }
 
 static int
 __chp_add_new_sch(struct subchannel_id schid)
 {
 	struct schib schib;
-	int ret;
 
 	if (stsch_err(schid, &schib))
 		/* We're through */
-		return need_rescan ? -EAGAIN : -ENXIO;
+		return -ENXIO;
 
 	/* Put it on the slow path. */
-	ret = css_enqueue_subchannel_slow(schid);
-	if (ret) {
-		css_clear_subchannel_slow_list();
-		need_rescan = 1;
-		return -EAGAIN;
-	}
+	css_schedule_eval(schid);
 	return 0;
 }
 
@@ -693,22 +646,15 @@ __chp_add(struct subchannel_id schid, void *data)
 	return 0;
 }
 
-int chsc_chp_online(struct chp_id chpid)
+void chsc_chp_online(struct chp_id chpid)
 {
-	int rc;
 	char dbf_txt[15];
 
 	sprintf(dbf_txt, "cadd%x.%02x", chpid.cssid, chpid.id);
 	CIO_TRACE_EVENT(2, dbf_txt);
 
-	if (chp_get_status(chpid) == 0)
-		return 0;
-	rc = for_each_subchannel(__chp_add, &chpid);
-	if (css_slow_subchannels_exist())
-		rc = -EAGAIN;
-	if (rc != -EAGAIN)
-		rc = 0;
-	return rc;
+	if (chp_get_status(chpid) != 0)
+		for_each_subchannel(__chp_add, &chpid);
 }
 
 static void __s390_subchannel_vary_chpid(struct subchannel *sch,
@@ -749,12 +695,8 @@ static void __s390_subchannel_vary_chpid(struct subchannel *sch,
 					sch->driver->verify(&sch->dev);
 			}
 		} else if (!sch->lpm) {
-			if (device_trigger_verify(sch) != 0) {
-				if (css_enqueue_subchannel_slow(sch->schid)) {
-					css_clear_subchannel_slow_list();
-					need_rescan = 1;
-				}
-			}
+			if (device_trigger_verify(sch) != 0)
+				css_schedule_eval(sch->schid);
 		} else if (sch->driver && sch->driver->verify)
 			sch->driver->verify(&sch->dev);
 		break;
@@ -801,11 +743,7 @@ __s390_vary_chpid_on(struct subchannel_id schid, void *data)
 		/* We're through */
 		return -ENXIO;
 	/* Put it on the slow path. */
-	if (css_enqueue_subchannel_slow(schid)) {
-		css_clear_subchannel_slow_list();
-		need_rescan = 1;
-		return -EAGAIN;
-	}
+	css_schedule_eval(schid);
 	return 0;
 }
 
@@ -826,8 +764,6 @@ int chsc_chp_vary(struct chp_id chpid, int on)
 	if (on)
 		/* Scan for new devices on varied on path. */
 		for_each_subchannel(__s390_vary_chpid_on, NULL);
-	if (need_rescan || css_slow_subchannels_exist())
-		queue_work(slow_path_wq, &slow_path_work);
 	return 0;
 }
 
diff --git a/drivers/s390/cio/chsc.h b/drivers/s390/cio/chsc.h
index 322586f27cc..742ef57d2c5 100644
--- a/drivers/s390/cio/chsc.h
+++ b/drivers/s390/cio/chsc.h
@@ -36,7 +36,7 @@ struct channel_path_desc {
 struct channel_path;
 
 extern int css_get_ssd_info(struct subchannel *);
-extern int chsc_process_crw(void);
+extern void chsc_process_crw(void);
 
 struct css_general_char {
 	u64 : 41;
@@ -79,7 +79,7 @@ extern int chsc_secm(struct channel_subsystem *, int);
 int chsc_chp_vary(struct chp_id chpid, int on);
 int chsc_determine_channel_path_description(struct chp_id chpid,
 					    struct channel_path_desc *desc);
-int chsc_chp_online(struct chp_id chpid);
+void chsc_chp_online(struct chp_id chpid);
 void chsc_chp_offline(struct chp_id chpid);
 int chsc_get_channel_measurement_chars(struct channel_path *chp);
 
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index fe0ace7aece..fcc641e578f 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -20,8 +20,8 @@
 #include "ioasm.h"
 #include "chsc.h"
 #include "device.h"
+#include "idset.h"
 
-int need_rescan = 0;
 int css_init_done = 0;
 static int need_reprobe = 0;
 static int max_ssid = 0;
@@ -306,7 +306,7 @@ static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
 	return css_probe_device(schid);
 }
 
-static int css_evaluate_subchannel(struct subchannel_id schid, int slow)
+static void css_evaluate_subchannel(struct subchannel_id schid, int slow)
 {
 	struct subchannel *sch;
 	int ret;
@@ -317,53 +317,66 @@ static int css_evaluate_subchannel(struct subchannel_id schid, int slow)
 		put_device(&sch->dev);
 	} else
 		ret = css_evaluate_new_subchannel(schid, slow);
-
-	return ret;
+	if (ret == -EAGAIN)
+		css_schedule_eval(schid);
 }
 
-static int
-css_rescan_devices(struct subchannel_id schid, void *data)
+static struct idset *slow_subchannel_set;
+static spinlock_t slow_subchannel_lock;
+
+static int __init slow_subchannel_init(void)
 {
-	return css_evaluate_subchannel(schid, 1);
+	spin_lock_init(&slow_subchannel_lock);
+	slow_subchannel_set = idset_sch_new();
+	if (!slow_subchannel_set) {
+		printk(KERN_WARNING "cio: could not allocate slow subchannel "
+		       "set\n");
+		return -ENOMEM;
+	}
+	return 0;
 }
 
-struct slow_subchannel {
-	struct list_head slow_list;
-	struct subchannel_id schid;
-};
-
-static LIST_HEAD(slow_subchannels_head);
-static DEFINE_SPINLOCK(slow_subchannel_lock);
+subsys_initcall(slow_subchannel_init);
 
-static void
-css_trigger_slow_path(struct work_struct *unused)
+static void css_slow_path_func(struct work_struct *unused)
 {
-	CIO_TRACE_EVENT(4, "slowpath");
-
-	if (need_rescan) {
-		need_rescan = 0;
-		for_each_subchannel(css_rescan_devices, NULL);
-		return;
-	}
+	struct subchannel_id schid;
 
+	CIO_TRACE_EVENT(4, "slowpath");
 	spin_lock_irq(&slow_subchannel_lock);
-	while (!list_empty(&slow_subchannels_head)) {
-		struct slow_subchannel *slow_sch =
-			list_entry(slow_subchannels_head.next,
-				   struct slow_subchannel, slow_list);
-
-		list_del_init(slow_subchannels_head.next);
+	init_subchannel_id(&schid);
+	while (idset_sch_get_first(slow_subchannel_set, &schid)) {
+		idset_sch_del(slow_subchannel_set, schid);
 		spin_unlock_irq(&slow_subchannel_lock);
-		css_evaluate_subchannel(slow_sch->schid, 1);
+		css_evaluate_subchannel(schid, 1);
 		spin_lock_irq(&slow_subchannel_lock);
-		kfree(slow_sch);
 	}
 	spin_unlock_irq(&slow_subchannel_lock);
 }
 
-DECLARE_WORK(slow_path_work, css_trigger_slow_path);
+static DECLARE_WORK(slow_path_work, css_slow_path_func);
 struct workqueue_struct *slow_path_wq;
 
+void css_schedule_eval(struct subchannel_id schid)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&slow_subchannel_lock, flags);
+	idset_sch_add(slow_subchannel_set, schid);
+	queue_work(slow_path_wq, &slow_path_work);
+	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
+}
+
+void css_schedule_eval_all(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&slow_subchannel_lock, flags);
+	idset_fill(slow_subchannel_set);
+	queue_work(slow_path_wq, &slow_path_work);
+	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
+}
+
 /* Reprobe subchannel if unregistered. */
 static int reprobe_subchannel(struct subchannel_id schid, void *data)
 {
@@ -426,33 +439,14 @@ void css_schedule_reprobe(void)
 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
 
 /*
- * Rescan for new devices. FIXME: This is slow.
- * This function is called when we have lost CRWs due to overflows and we have
- * to do subchannel housekeeping.
- */
-void
-css_reiterate_subchannels(void)
-{
-	css_clear_subchannel_slow_list();
-	need_rescan = 1;
-}
-
-/*
  * Called from the machine check handler for subchannel report words.
  */
-int
-css_process_crw(int rsid1, int rsid2)
+void css_process_crw(int rsid1, int rsid2)
 {
-	int ret;
 	struct subchannel_id mchk_schid;
 
 	CIO_CRW_EVENT(2, "source is subchannel %04X, subsystem id %x\n",
 		      rsid1, rsid2);
-
-	if (need_rescan)
-		/* We need to iterate all subchannels anyway. */
-		return -EAGAIN;
-
 	init_subchannel_id(&mchk_schid);
 	mchk_schid.sch_no = rsid1;
 	if (rsid2 != 0)
@@ -463,14 +457,7 @@ css_process_crw(int rsid1, int rsid2)
 	 * use stsch() to find out if the subchannel in question has come
 	 * or gone.
 	 */
-	ret = css_evaluate_subchannel(mchk_schid, 0);
-	if (ret == -EAGAIN) {
-		if (css_enqueue_subchannel_slow(mchk_schid)) {
-			css_clear_subchannel_slow_list();
-			need_rescan = 1;
-		}
-	}
-	return ret;
+	css_evaluate_subchannel(mchk_schid, 0);
 }
 
 static int __init
@@ -745,47 +732,6 @@ struct bus_type css_bus_type = {
 
 subsys_initcall(init_channel_subsystem);
 
-int
-css_enqueue_subchannel_slow(struct subchannel_id schid)
-{
-	struct slow_subchannel *new_slow_sch;
-	unsigned long flags;
-
-	new_slow_sch = kzalloc(sizeof(struct slow_subchannel), GFP_ATOMIC);
-	if (!new_slow_sch)
-		return -ENOMEM;
-	new_slow_sch->schid = schid;
-	spin_lock_irqsave(&slow_subchannel_lock, flags);
-	list_add_tail(&new_slow_sch->slow_list, &slow_subchannels_head);
-	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
-	return 0;
-}
-
-void
-css_clear_subchannel_slow_list(void)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&slow_subchannel_lock, flags);
-	while (!list_empty(&slow_subchannels_head)) {
-		struct slow_subchannel *slow_sch =
-			list_entry(slow_subchannels_head.next,
-				   struct slow_subchannel, slow_list);
-
-		list_del_init(slow_subchannels_head.next);
-		kfree(slow_sch);
-	}
-	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
-}
-
-
-
-int
-css_slow_subchannels_exist(void)
-{
-	return (!list_empty(&slow_subchannels_head));
-}
-
 MODULE_LICENSE("GPL");
 EXPORT_SYMBOL(css_bus_type);
 EXPORT_SYMBOL_GPL(css_characteristics_avail);
diff --git a/drivers/s390/cio/css.h b/drivers/s390/cio/css.h
index b2b1a265c60..4b3133a7bae 100644
--- a/drivers/s390/cio/css.h
+++ b/drivers/s390/cio/css.h
@@ -146,7 +146,7 @@ extern void css_sch_device_unregister(struct subchannel *);
 extern struct subchannel * get_subchannel_by_schid(struct subchannel_id);
 extern int css_init_done;
 extern int for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *);
-extern int css_process_crw(int, int);
+extern void css_process_crw(int, int);
 extern void css_reiterate_subchannels(void);
 
 #define __MAX_SUBCHANNEL 65535
@@ -186,16 +186,12 @@ int device_trigger_verify(struct subchannel *sch);
 void device_kill_pending_timer(struct subchannel *);
 
 /* Helper functions to build lists for the slow path. */
-extern int css_enqueue_subchannel_slow(struct subchannel_id schid);
-void css_walk_subchannel_slow_list(void (*fn)(unsigned long));
-void css_clear_subchannel_slow_list(void);
-int css_slow_subchannels_exist(void);
-extern int need_rescan;
+void css_schedule_eval(struct subchannel_id schid);
+void css_schedule_eval_all(void);
 
 int sch_is_pseudo_sch(struct subchannel *);
 
 extern struct workqueue_struct *slow_path_wq;
-extern struct work_struct slow_path_work;
 
 int subchannel_add_files (struct device *);
 extern struct attribute_group *subch_attr_groups[];
diff --git a/drivers/s390/cio/device_fsm.c b/drivers/s390/cio/device_fsm.c
index d6226881d0d..898ec3b2beb 100644
--- a/drivers/s390/cio/device_fsm.c
+++ b/drivers/s390/cio/device_fsm.c
@@ -222,10 +222,8 @@ __recover_lost_chpids(struct subchannel *sch, int old_lpm)
 		if (old_lpm & mask)
 			continue;
 		chpid.id = sch->schib.pmcw.chpid[i];
-		if (!chp_is_registered(chpid)) {
-			need_rescan = 1;
-			queue_work(slow_path_wq, &slow_path_work);
-		}
+		if (!chp_is_registered(chpid))
+			css_schedule_eval_all();
 	}
 }
 
diff --git a/drivers/s390/cio/idset.c b/drivers/s390/cio/idset.c
new file mode 100644
index 00000000000..16ea828e99f
--- /dev/null
+++ b/drivers/s390/cio/idset.c
@@ -0,0 +1,112 @@
+/*
+ *  drivers/s390/cio/idset.c
+ *
+ *    Copyright IBM Corp. 2007
+ *    Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
+ */
+
+#include <linux/slab.h>
+#include <asm/bitops.h>
+#include "idset.h"
+#include "css.h"
+
+struct idset {
+	int num_ssid;
+	int num_id;
+	unsigned long bitmap[0];
+};
+
+static inline unsigned long bitmap_size(int num_ssid, int num_id)
+{
+	return __BITOPS_WORDS(num_ssid * num_id) * sizeof(unsigned long);
+}
+
+static struct idset *idset_new(int num_ssid, int num_id)
+{
+	struct idset *set;
+
+	set = kzalloc(sizeof(struct idset) + bitmap_size(num_ssid, num_id),
+		      GFP_KERNEL);
+	if (set) {
+		set->num_ssid = num_ssid;
+		set->num_id = num_id;
+	}
+	return set;
+}
+
+void idset_free(struct idset *set)
+{
+	kfree(set);
+}
+
+void idset_clear(struct idset *set)
+{
+	memset(set->bitmap, 0, bitmap_size(set->num_ssid, set->num_id));
+}
+
+void idset_fill(struct idset *set)
+{
+	memset(set->bitmap, 0xff, bitmap_size(set->num_ssid, set->num_id));
+}
+
+static inline void idset_add(struct idset *set, int ssid, int id)
+{
+	set_bit(ssid * set->num_id + id, set->bitmap);
+}
+
+static inline void idset_del(struct idset *set, int ssid, int id)
+{
+	clear_bit(ssid * set->num_id + id, set->bitmap);
+}
+
+static inline int idset_contains(struct idset *set, int ssid, int id)
+{
+	return test_bit(ssid * set->num_id + id, set->bitmap);
+}
+
+static inline int idset_get_first(struct idset *set, int *ssid, int *id)
+{
+	int bitnum;
+
+	bitnum = find_first_bit(set->bitmap, set->num_ssid * set->num_id);
+	if (bitnum >= set->num_ssid * set->num_id)
+		return 0;
+	*ssid = bitnum / set->num_id;
+	*id = bitnum % set->num_id;
+	return 1;
+}
+
+struct idset *idset_sch_new(void)
+{
+	return idset_new(__MAX_SSID + 1, __MAX_SUBCHANNEL + 1);
+}
+
+void idset_sch_add(struct idset *set, struct subchannel_id schid)
+{
+	idset_add(set, schid.ssid, schid.sch_no);
+}
+
+void idset_sch_del(struct idset *set, struct subchannel_id schid)
+{
+	idset_del(set, schid.ssid, schid.sch_no);
+}
+
+int idset_sch_contains(struct idset *set, struct subchannel_id schid)
+{
+	return idset_contains(set, schid.ssid, schid.sch_no);
+}
+
+int idset_sch_get_first(struct idset *set, struct subchannel_id *schid)
+{
+	int ssid = 0;
+	int id = 0;
+	int rc;
+
+	rc = idset_get_first(set, &ssid, &id);
+	if (rc) {
+		init_subchannel_id(schid);
+		schid->ssid = ssid;
+		schid->sch_no = id;
+	}
+	return rc;
+}
diff --git a/drivers/s390/cio/idset.h b/drivers/s390/cio/idset.h
new file mode 100644
index 00000000000..144466ab8c1
--- /dev/null
+++ b/drivers/s390/cio/idset.h
@@ -0,0 +1,25 @@
+/*
+ *  drivers/s390/cio/idset.h
+ *
+ *    Copyright IBM Corp. 2007
+ *    Author(s): Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
+ */
+
+#ifndef S390_IDSET_H
+#define S390_IDSET_H S390_IDSET_H
+
+#include "schid.h"
+
+struct idset;
+
+void idset_free(struct idset *set);
+void idset_clear(struct idset *set);
+void idset_fill(struct idset *set);
+
+struct idset *idset_sch_new(void);
+void idset_sch_add(struct idset *set, struct subchannel_id id);
+void idset_sch_del(struct idset *set, struct subchannel_id id);
+int idset_sch_contains(struct idset *set, struct subchannel_id id);
+int idset_sch_get_first(struct idset *set, struct subchannel_id *id);
+
+#endif /* S390_IDSET_H */
diff --git a/drivers/s390/s390mach.c b/drivers/s390/s390mach.c
index afd8a3c0f8d..644a06eba82 100644
--- a/drivers/s390/s390mach.c
+++ b/drivers/s390/s390mach.c
@@ -45,14 +45,13 @@ static int
 s390_collect_crw_info(void *param)
 {
 	struct crw crw[2];
-	int ccode, ret, slow;
+	int ccode;
 	struct semaphore *sem;
 	unsigned int chain;
 
 	sem = (struct semaphore *)param;
 repeat:
 	down_interruptible(sem);
-	slow = 0;
 	chain = 0;
 	while (1) {
 		if (unlikely(chain > 1)) {
@@ -85,9 +84,8 @@ repeat:
 		/* Check for overflows. */
 		if (crw[chain].oflw) {
 			pr_debug("%s: crw overflow detected!\n", __FUNCTION__);
-			css_reiterate_subchannels();
+			css_schedule_eval_all();
 			chain = 0;
-			slow = 1;
 			continue;
 		}
 		switch (crw[chain].rsc) {
@@ -95,10 +93,7 @@ repeat:
 			if (crw[0].chn && !chain)
 				break;
 			pr_debug("source is subchannel %04X\n", crw[0].rsid);
-			ret = css_process_crw (crw[0].rsid,
-					       chain ? crw[1].rsid : 0);
-			if (ret == -EAGAIN)
-				slow = 1;
+			css_process_crw(crw[0].rsid, chain ? crw[1].rsid : 0);
 			break;
 		case CRW_RSC_MONITOR:
 			pr_debug("source is monitoring facility\n");
@@ -117,28 +112,23 @@ repeat:
 			}
 			switch (crw[0].erc) {
 			case CRW_ERC_IPARM: /* Path has come. */
-				ret = chp_process_crw(crw[0].rsid, 1);
+				chp_process_crw(crw[0].rsid, 1);
 				break;
 			case CRW_ERC_PERRI: /* Path has gone. */
 			case CRW_ERC_PERRN:
-				ret = chp_process_crw(crw[0].rsid, 0);
+				chp_process_crw(crw[0].rsid, 0);
 				break;
 			default:
 				pr_debug("Don't know how to handle erc=%x\n",
 					 crw[0].erc);
-				ret = 0;
 			}
-			if (ret == -EAGAIN)
-				slow = 1;
 			break;
 		case CRW_RSC_CONFIG:
 			pr_debug("source is configuration-alert facility\n");
 			break;
 		case CRW_RSC_CSS:
 			pr_debug("source is channel subsystem\n");
-			ret = chsc_process_crw();
-			if (ret == -EAGAIN)
-				slow = 1;
+			chsc_process_crw();
 			break;
 		default:
 			pr_debug("unknown source\n");
@@ -147,8 +137,6 @@ repeat:
 		/* chain is always 0 or 1 here. */
 		chain = crw[chain].chn ? chain + 1 : 0;
 	}
-	if (slow)
-		queue_work(slow_path_wq, &slow_path_work);
 	goto repeat;
 	return 0;
 }