s390/cio: avoid excessive path-verification requests

Currently when removing a device from cio_ignore list, we trigger a
path-verification for all the subchannels available in the system. This
could lead to path-verification requests on subchannels with an online
device, which could cause unwanted delay. Instead of all the
subchannels, trigger the path-verifications to those without an online
device.

Reported-by: Julian Wiedmann <jwi@linux.ibm.com>
Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/drivers/s390/cio/blacklist.c b/drivers/s390/cio/blacklist.c
index f3c656975e054ec5ce0d2ec95ab7ee7d9aae3feb..93695d535380bcc08442c31376d14c4c5084e508 100644 (file)
--- a/drivers/s390/cio/blacklist.c
+++ b/drivers/s390/cio/blacklist.c
@@ -262,10 +262,12 @@ static int blacklist_parse_proc_parameters(char *buf)
 
        if (strcmp("free", parm) == 0) {
                rc = blacklist_parse_parameters(buf, free, 0);
-               /* There could be subchannels without proper devices connected.
-                * evaluate all the entries
+               /*
+                * Evaluate the subchannels without an online device. This way,
+                * no path-verification will be triggered on those subchannels
+                * and it avoids unnecessary delays.
                 */
-               css_schedule_eval_all();
+               css_schedule_eval_cond(CSS_EVAL_NOT_ONLINE, 0);
        } else if (strcmp("add", parm) == 0)
                rc = blacklist_parse_parameters(buf, add, 0);
        else if (strcmp("purge", parm) == 0)

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 3377097e65de68a0f3c9c9422846fde18e444452..44461928aab8afd3b3042a31c2640d39dec931ee 100644 (file)
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -788,27 +788,49 @@ static int __unset_registered(struct device *dev, void *data)
        return 0;
 }
 
-void css_schedule_eval_all_unreg(unsigned long delay)
+static int __unset_online(struct device *dev, void *data)
+{
+       struct idset *set = data;
+       struct subchannel *sch = to_subchannel(dev);
+       struct ccw_device *cdev = sch_get_cdev(sch);
+
+       if (cdev && cdev->online)
+               idset_sch_del(set, sch->schid);
+
+       return 0;
+}
+
+void css_schedule_eval_cond(enum css_eval_cond cond, unsigned long delay)
 {
        unsigned long flags;
-       struct idset *unreg_set;
+       struct idset *set;
 
        /* Find unregistered subchannels. */
-       unreg_set = idset_sch_new();
-       if (!unreg_set) {
+       set = idset_sch_new();
+       if (!set) {
                /* Fallback. */
                css_schedule_eval_all();
                return;
        }
-       idset_fill(unreg_set);
-       bus_for_each_dev(&css_bus_type, NULL, unreg_set, __unset_registered);
+       idset_fill(set);
+       switch (cond) {
+       case CSS_EVAL_UNREG:
+               bus_for_each_dev(&css_bus_type, NULL, set, __unset_registered);
+               break;
+       case CSS_EVAL_NOT_ONLINE:
+               bus_for_each_dev(&css_bus_type, NULL, set, __unset_online);
+               break;
+       default:
+               break;
+       }
+
        /* Apply to slow_subchannel_set. */
        spin_lock_irqsave(&slow_subchannel_lock, flags);
-       idset_add_set(slow_subchannel_set, unreg_set);
+       idset_add_set(slow_subchannel_set, set);
        atomic_set(&css_eval_scheduled, 1);
        queue_delayed_work(cio_work_q, &slow_path_work, delay);
        spin_unlock_irqrestore(&slow_subchannel_lock, flags);
-       idset_free(unreg_set);
+       idset_free(set);
 }
 
 void css_wait_for_slow_path(void)
@@ -820,7 +842,7 @@ void css_wait_for_slow_path(void)
 void css_schedule_reprobe(void)
 {
        /* Schedule with a delay to allow merging of subsequent calls. */
-       css_schedule_eval_all_unreg(1 * HZ);
+       css_schedule_eval_cond(CSS_EVAL_UNREG, 1 * HZ);
 }
 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
 

diff --git a/drivers/s390/cio/css.h b/drivers/s390/cio/css.h
index c98522cbe276f13019f990e03ab015a039e46747..ede0b905bc6ff7c85c592287889c345ce69d3d15 100644 (file)
--- a/drivers/s390/cio/css.h
+++ b/drivers/s390/cio/css.h
@@ -34,6 +34,14 @@
 #define SNID_STATE3_MULTI_PATH    1
 #define SNID_STATE3_SINGLE_PATH           0
 
+/*
+ * Conditions used to specify which subchannels need evaluation
+ */
+enum css_eval_cond {
+       CSS_EVAL_UNREG,         /* unregistered subchannels */
+       CSS_EVAL_NOT_ONLINE     /* sch without an online-device */
+};
+
 struct path_state {
        __u8  state1 : 2;       /* path state value 1 */
        __u8  state2 : 2;       /* path state value 2 */
@@ -136,7 +144,7 @@ static inline struct channel_subsystem *css_by_id(u8 cssid)
 /* Helper functions to build lists for the slow path. */
 void css_schedule_eval(struct subchannel_id schid);
 void css_schedule_eval_all(void);
-void css_schedule_eval_all_unreg(unsigned long delay);
+void css_schedule_eval_cond(enum css_eval_cond, unsigned long delay);
 int css_complete_work(void);
 
 int sch_is_pseudo_sch(struct subchannel *);