[S390] rework of channel measurement facility.

Fixes for several channel measurement facility bugs:
* Blocks copied from the hardware might not be consistent. Solve this
  by moving the copying into idle state and repeating the copying.
* avg_sample_interval changed with every read, even though no new block
  was available. Solve this by storing a timestamp when the last new
  block was received.
* Several locking issues.
* Measurements were not reenabled after a disconnected device became
  available again.
* Remove #defines for ioctls that were never implemented.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 468 insertions, 177 deletions

diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c
index 07ef3f640f4a..1c3e8e9012b0 100644
--- a/drivers/s390/cio/cmf.c
+++ b/drivers/s390/cio/cmf.c
@@ -3,9 +3,10 @@
  *
  * Linux on zSeries Channel Measurement Facility support
  *
- * Copyright 2000,2003 IBM Corporation
+ * Copyright 2000,2006 IBM Corporation
  *
- * Author: Arnd Bergmann <arndb@de.ibm.com>
+ * Authors: Arnd Bergmann <arndb@de.ibm.com>
+ *          Cornelia Huck <cornelia.huck@de.ibm.com>
  *
  * original idea from Natarajan Krishnaswami <nkrishna@us.ibm.com>
  *
@@ -96,9 +97,9 @@ module_param(format, bool, 0444);
 /**
  * struct cmb_operations - functions to use depending on cmb_format
  *
- * all these functions operate on a struct cmf_device. There is only
- * one instance of struct cmb_operations because all cmf_device
- * objects are guaranteed to be of the same type.
+ * Most of these functions operate on a struct ccw_device. There is only
+ * one instance of struct cmb_operations because the format of the measurement
+ * data is guaranteed to be the same for every ccw_device.
  *
  * @alloc:      allocate memory for a channel measurement block,
  *              either with the help of a special pool or with kmalloc
@@ -107,6 +108,7 @@ module_param(format, bool, 0444);
  * @readall:    read a measurement block in a common format
  * @reset:      clear the data in the associated measurement block and
  *              reset its time stamp
+ * @align:      align an allocated block so that the hardware can use it
  */
 struct cmb_operations {
         int (*alloc)  (struct ccw_device*);
@@ -115,11 +117,19 @@ struct cmb_operations {
         u64 (*read)   (struct ccw_device*, int);
         int (*readall)(struct ccw_device*, struct cmbdata *);
         void (*reset) (struct ccw_device*);
+        void * (*align) (void *);
 
         struct attribute_group *attr_group;
 };
 static struct cmb_operations *cmbops;
 
+struct cmb_data {
+        void *hw_block;   /* Pointer to block updated by hardware */
+        void *last_block; /* Last changed block copied from hardware block */
+        int size;         /* Size of hw_block and last_block */
+        unsigned long long last_update;  /* when last_block was updated */
+};
+
 /* our user interface is designed in terms of nanoseconds,
  * while the hardware measures total times in its own
  * unit.*/
@@ -226,63 +236,229 @@ struct set_schib_struct {
         unsigned long address;
         wait_queue_head_t wait;
         int ret;
+        struct kref kref;
 };
 
+static void cmf_set_schib_release(struct kref *kref)
+{
+        struct set_schib_struct *set_data;
+
+        set_data = container_of(kref, struct set_schib_struct, kref);
+        kfree(set_data);
+}
+
+#define CMF_PENDING 1
+
 static int set_schib_wait(struct ccw_device *cdev, u32 mme,
                                 int mbfc, unsigned long address)
 {
-        struct set_schib_struct s = {
-                .mme = mme,
-                .mbfc = mbfc,
-                .address = address,
-                .wait = __WAIT_QUEUE_HEAD_INITIALIZER(s.wait),
-        };
+        struct set_schib_struct *set_data;
+        int ret;
 
         spin_lock_irq(cdev->ccwlock);
-        s.ret = set_schib(cdev, mme, mbfc, address);
-        if (s.ret != -EBUSY) {
-                goto out_nowait;
+        if (!cdev->private->cmb) {
+                ret = -ENODEV;
+                goto out;
         }
+        set_data = kzalloc(sizeof(struct set_schib_struct), GFP_ATOMIC);
+        if (!set_data) {
+                ret = -ENOMEM;
+                goto out;
+        }
+        init_waitqueue_head(&set_data->wait);
+        kref_init(&set_data->kref);
+        set_data->mme = mme;
+        set_data->mbfc = mbfc;
+        set_data->address = address;
+
+        ret = set_schib(cdev, mme, mbfc, address);
+        if (ret != -EBUSY)
+                goto out_put;
 
         if (cdev->private->state != DEV_STATE_ONLINE) {
-                s.ret = -EBUSY;
                 /* if the device is not online, don't even try again */
-                goto out_nowait;
+                ret = -EBUSY;
+                goto out_put;
         }
+
         cdev->private->state = DEV_STATE_CMFCHANGE;
-        cdev->private->cmb_wait = &s;
-        s.ret = 1;
+        set_data->ret = CMF_PENDING;
+        cdev->private->cmb_wait = set_data;
 
         spin_unlock_irq(cdev->ccwlock);
-        if (wait_event_interruptible(s.wait, s.ret != 1)) {
+        if (wait_event_interruptible(set_data->wait,
+                                     set_data->ret != CMF_PENDING)) {
                 spin_lock_irq(cdev->ccwlock);
-                if (s.ret == 1) {
-                        s.ret = -ERESTARTSYS;
-                        cdev->private->cmb_wait = 0;
+                if (set_data->ret == CMF_PENDING) {
+                        set_data->ret = -ERESTARTSYS;
                         if (cdev->private->state == DEV_STATE_CMFCHANGE)
                                 cdev->private->state = DEV_STATE_ONLINE;
                 }
                 spin_unlock_irq(cdev->ccwlock);
         }
-        return s.ret;
-
-out_nowait:
+        spin_lock_irq(cdev->ccwlock);
+        cdev->private->cmb_wait = NULL;
+        ret = set_data->ret;
+out_put:
+        kref_put(&set_data->kref, cmf_set_schib_release);
+out:
         spin_unlock_irq(cdev->ccwlock);
-        return s.ret;
+        return ret;
 }
 
 void retry_set_schib(struct ccw_device *cdev)
 {
-        struct set_schib_struct *s;
+        struct set_schib_struct *set_data;
+
+        set_data = cdev->private->cmb_wait;
+        if (!set_data) {
+                WARN_ON(1);
+                return;
+        }
+        kref_get(&set_data->kref);
+        set_data->ret = set_schib(cdev, set_data->mme, set_data->mbfc,
+                                  set_data->address);
+        wake_up(&set_data->wait);
+        kref_put(&set_data->kref, cmf_set_schib_release);
+}
+
+static int cmf_copy_block(struct ccw_device *cdev)
+{
+        struct subchannel *sch;
+        void *reference_buf;
+        void *hw_block;
+        struct cmb_data *cmb_data;
+
+        sch = to_subchannel(cdev->dev.parent);
+
+        if (stsch(sch->schid, &sch->schib))
+                return -ENODEV;
+
+        if (sch->schib.scsw.fctl & SCSW_FCTL_START_FUNC) {
+                /* Don't copy if a start function is in progress. */
+                if ((!sch->schib.scsw.actl & SCSW_ACTL_SUSPENDED) &&
+                    (sch->schib.scsw.actl &
+                     (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)) &&
+                    (!sch->schib.scsw.stctl & SCSW_STCTL_SEC_STATUS))
+                        return -EBUSY;
+        }
+        cmb_data = cdev->private->cmb;
+        hw_block = cmbops->align(cmb_data->hw_block);
+        if (!memcmp(cmb_data->last_block, hw_block, cmb_data->size))
+                /* No need to copy. */
+                return 0;
+        reference_buf = kzalloc(cmb_data->size, GFP_ATOMIC);
+        if (!reference_buf)
+                return -ENOMEM;
+        /* Ensure consistency of block copied from hardware. */
+        do {
+                memcpy(cmb_data->last_block, hw_block, cmb_data->size);
+                memcpy(reference_buf, hw_block, cmb_data->size);
+        } while (memcmp(cmb_data->last_block, reference_buf, cmb_data->size));
+        cmb_data->last_update = get_clock();
+        kfree(reference_buf);
+        return 0;
+}
+
+struct copy_block_struct {
+        wait_queue_head_t wait;
+        int ret;
+        struct kref kref;
+};
+
+static void cmf_copy_block_release(struct kref *kref)
+{
+        struct copy_block_struct *copy_block;
+
+        copy_block = container_of(kref, struct copy_block_struct, kref);
+        kfree(copy_block);
+}
+
+static int cmf_cmb_copy_wait(struct ccw_device *cdev)
+{
+        struct copy_block_struct *copy_block;
+        int ret;
+        unsigned long flags;
+
+        spin_lock_irqsave(cdev->ccwlock, flags);
+        if (!cdev->private->cmb) {
+                ret = -ENODEV;
+                goto out;
+        }
+        copy_block = kzalloc(sizeof(struct copy_block_struct), GFP_ATOMIC);
+        if (!copy_block) {
+                ret = -ENOMEM;
+                goto out;
+        }
+        init_waitqueue_head(&copy_block->wait);
+        kref_init(&copy_block->kref);
+
+        ret = cmf_copy_block(cdev);
+        if (ret != -EBUSY)
+                goto out_put;
+
+        if (cdev->private->state != DEV_STATE_ONLINE) {
+                ret = -EBUSY;
+                goto out_put;
+        }
+
+        cdev->private->state = DEV_STATE_CMFUPDATE;
+        copy_block->ret = CMF_PENDING;
+        cdev->private->cmb_wait = copy_block;
+
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        if (wait_event_interruptible(copy_block->wait,
+                                     copy_block->ret != CMF_PENDING)) {
+                spin_lock_irqsave(cdev->ccwlock, flags);
+                if (copy_block->ret == CMF_PENDING) {
+                        copy_block->ret = -ERESTARTSYS;
+                        if (cdev->private->state == DEV_STATE_CMFUPDATE)
+                                cdev->private->state = DEV_STATE_ONLINE;
+                }
+                spin_unlock_irqrestore(cdev->ccwlock, flags);
+        }
+        spin_lock_irqsave(cdev->ccwlock, flags);
+        cdev->private->cmb_wait = NULL;
+        ret = copy_block->ret;
+out_put:
+        kref_put(&copy_block->kref, cmf_copy_block_release);
+out:
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        return ret;
+}
+
+void cmf_retry_copy_block(struct ccw_device *cdev)
+{
+        struct copy_block_struct *copy_block;
 
-        s = cdev->private->cmb_wait;
-        cdev->private->cmb_wait = 0;
-        if (!s) {
+        copy_block = cdev->private->cmb_wait;
+        if (!copy_block) {
                 WARN_ON(1);
                 return;
         }
-        s->ret = set_schib(cdev, s->mme, s->mbfc, s->address);
-        wake_up(&s->wait);
+        kref_get(&copy_block->kref);
+        copy_block->ret = cmf_copy_block(cdev);
+        wake_up(&copy_block->wait);
+        kref_put(&copy_block->kref, cmf_copy_block_release);
+}
+
+static void cmf_generic_reset(struct ccw_device *cdev)
+{
+        struct cmb_data *cmb_data;
+
+        spin_lock_irq(cdev->ccwlock);
+        cmb_data = cdev->private->cmb;
+        if (cmb_data) {
+                memset(cmb_data->last_block, 0, cmb_data->size);
+                /*
+                 * Need to reset hw block as well to make the hardware start
+                 * from 0 again.
+                 */
+                memset(cmbops->align(cmb_data->hw_block), 0, cmb_data->size);
+                cmb_data->last_update = 0;
+        }
+        cdev->private->cmb_start_time = get_clock();
+        spin_unlock_irq(cdev->ccwlock);
 }
 
 /**
@@ -343,8 +519,8 @@ struct cmb {
 /* insert a single device into the cmb_area list
  * called with cmb_area.lock held from alloc_cmb
  */
-static inline int
-alloc_cmb_single (struct ccw_device *cdev)
+static inline int alloc_cmb_single (struct ccw_device *cdev,
+                                    struct cmb_data *cmb_data)
 {
         struct cmb *cmb;
         struct ccw_device_private *node;
@@ -358,10 +534,12 @@ alloc_cmb_single (struct ccw_device *cdev)
 
         /* find first unused cmb in cmb_area.mem.
          * this is a little tricky: cmb_area.list
-         * remains sorted by ->cmb pointers */
+         * remains sorted by ->cmb->hw_data pointers */
         cmb = cmb_area.mem;
         list_for_each_entry(node, &cmb_area.list, cmb_list) {
-                if ((struct cmb*)node->cmb > cmb)
+                struct cmb_data *data;
+                data = node->cmb;
+                if ((struct cmb*)data->hw_block > cmb)
                         break;
                 cmb++;
         }
@@ -372,7 +550,8 @@ alloc_cmb_single (struct ccw_device *cdev)
 
         /* insert new cmb */
         list_add_tail(&cdev->private->cmb_list, &node->cmb_list);
-        cdev->private->cmb = cmb;
+        cmb_data->hw_block = cmb;
+        cdev->private->cmb = cmb_data;
         ret = 0;
 out:
         spin_unlock_irq(cdev->ccwlock);
@@ -385,7 +564,19 @@ alloc_cmb (struct ccw_device *cdev)
         int ret;
         struct cmb *mem;
         ssize_t size;
+        struct cmb_data *cmb_data;
+
+        /* Allocate private cmb_data. */
+        cmb_data = kzalloc(sizeof(struct cmb_data), GFP_KERNEL);
+        if (!cmb_data)
+                return -ENOMEM;
 
+        cmb_data->last_block = kzalloc(sizeof(struct cmb), GFP_KERNEL);
+        if (!cmb_data->last_block) {
+                kfree(cmb_data);
+                return -ENOMEM;
+        }
+        cmb_data->size = sizeof(struct cmb);
         spin_lock(&cmb_area.lock);
 
         if (!cmb_area.mem) {
@@ -414,29 +605,36 @@ alloc_cmb (struct ccw_device *cdev)
         }
 
         /* do the actual allocation */
-        ret = alloc_cmb_single(cdev);
+        ret = alloc_cmb_single(cdev, cmb_data);
 out:
         spin_unlock(&cmb_area.lock);
-
+        if (ret) {
+                kfree(cmb_data->last_block);
+                kfree(cmb_data);
+        }
         return ret;
 }
 
-static void
-free_cmb(struct ccw_device *cdev)
+static void free_cmb(struct ccw_device *cdev)
 {
         struct ccw_device_private *priv;
-
-        priv = cdev->private;
+        struct cmb_data *cmb_data;
 
         spin_lock(&cmb_area.lock);
         spin_lock_irq(cdev->ccwlock);
 
+        priv = cdev->private;
+
         if (list_empty(&priv->cmb_list)) {
                 /* already freed */
                 goto out;
         }
 
+        cmb_data = priv->cmb;
         priv->cmb = NULL;
+        if (cmb_data)
+                kfree(cmb_data->last_block);
+        kfree(cmb_data);
         list_del_init(&priv->cmb_list);
 
         if (list_empty(&cmb_area.list)) {
@@ -451,83 +649,97 @@ out:
         spin_unlock(&cmb_area.lock);
 }
 
-static int
-set_cmb(struct ccw_device *cdev, u32 mme)
+static int set_cmb(struct ccw_device *cdev, u32 mme)
 {
         u16 offset;
+        struct cmb_data *cmb_data;
+        unsigned long flags;
 
-        if (!cdev->private->cmb)
+        spin_lock_irqsave(cdev->ccwlock, flags);
+        if (!cdev->private->cmb) {
+                spin_unlock_irqrestore(cdev->ccwlock, flags);
                 return -EINVAL;
-
-        offset = mme ? (struct cmb *)cdev->private->cmb - cmb_area.mem : 0;
+        }
+        cmb_data = cdev->private->cmb;
+        offset = mme ? (struct cmb *)cmb_data->hw_block - cmb_area.mem : 0;
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
 
         return set_schib_wait(cdev, mme, 0, offset);
 }
 
-static u64
-read_cmb (struct ccw_device *cdev, int index)
+static u64 read_cmb (struct ccw_device *cdev, int index)
 {
-        /* yes, we have to put it on the stack
-         * because the cmb must only be accessed
-         * atomically, e.g. with mvc */
-        struct cmb cmb;
-        unsigned long flags;
+        struct cmb *cmb;
         u32 val;
+        int ret;
+        unsigned long flags;
+
+        ret = cmf_cmb_copy_wait(cdev);
+        if (ret < 0)
+                return 0;
 
         spin_lock_irqsave(cdev->ccwlock, flags);
         if (!cdev->private->cmb) {
-                spin_unlock_irqrestore(cdev->ccwlock, flags);
-                return 0;
+                ret = 0;
+                goto out;
         }
-
-        cmb = *(struct cmb*)cdev->private->cmb;
-        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        cmb = ((struct cmb_data *)cdev->private->cmb)->last_block;
 
         switch (index) {
         case cmb_ssch_rsch_count:
-                return cmb.ssch_rsch_count;
+                ret = cmb->ssch_rsch_count;
+                goto out;
         case cmb_sample_count:
-                return cmb.sample_count;
+                ret = cmb->sample_count;
+                goto out;
         case cmb_device_connect_time:
-                val = cmb.device_connect_time;
+                val = cmb->device_connect_time;
                 break;
         case cmb_function_pending_time:
-                val = cmb.function_pending_time;
+                val = cmb->function_pending_time;
                 break;
         case cmb_device_disconnect_time:
-                val = cmb.device_disconnect_time;
+                val = cmb->device_disconnect_time;
                 break;
         case cmb_control_unit_queuing_time:
-                val = cmb.control_unit_queuing_time;
+                val = cmb->control_unit_queuing_time;
                 break;
         case cmb_device_active_only_time:
-                val = cmb.device_active_only_time;
+                val = cmb->device_active_only_time;
                 break;
         default:
-                return 0;
+                ret = 0;
+                goto out;
         }
-        return time_to_avg_nsec(val, cmb.sample_count);
+        ret = time_to_avg_nsec(val, cmb->sample_count);
+out:
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        return ret;
 }
 
-static int
-readall_cmb (struct ccw_device *cdev, struct cmbdata *data)
+static int readall_cmb (struct ccw_device *cdev, struct cmbdata *data)
 {
-        /* yes, we have to put it on the stack
-         * because the cmb must only be accessed
-         * atomically, e.g. with mvc */
-        struct cmb cmb;
-        unsigned long flags;
+        struct cmb *cmb;
+        struct cmb_data *cmb_data;
         u64 time;
+        unsigned long flags;
+        int ret;
 
+        ret = cmf_cmb_copy_wait(cdev);
+        if (ret < 0)
+                return ret;
         spin_lock_irqsave(cdev->ccwlock, flags);
-        if (!cdev->private->cmb) {
-                spin_unlock_irqrestore(cdev->ccwlock, flags);
-                return -ENODEV;
+        cmb_data = cdev->private->cmb;
+        if (!cmb_data) {
+                ret = -ENODEV;
+                goto out;
         }
-
-        cmb = *(struct cmb*)cdev->private->cmb;
-        time = get_clock() - cdev->private->cmb_start_time;
-        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        if (cmb_data->last_update == 0) {
+                ret = -EAGAIN;
+                goto out;
+        }
+        cmb = cmb_data->last_block;
+        time = cmb_data->last_update - cdev->private->cmb_start_time;
 
         memset(data, 0, sizeof(struct cmbdata));
 
@@ -538,31 +750,32 @@ readall_cmb (struct ccw_device *cdev, struct cmbdata *data)
         data->elapsed_time = (time * 1000) >> 12;
 
         /* copy data to new structure */
-        data->ssch_rsch_count = cmb.ssch_rsch_count;
-        data->sample_count = cmb.sample_count;
+        data->ssch_rsch_count = cmb->ssch_rsch_count;
+        data->sample_count = cmb->sample_count;
 
         /* time fields are converted to nanoseconds while copying */
-        data->device_connect_time = time_to_nsec(cmb.device_connect_time);
-        data->function_pending_time = time_to_nsec(cmb.function_pending_time);
-        data->device_disconnect_time = time_to_nsec(cmb.device_disconnect_time);
+        data->device_connect_time = time_to_nsec(cmb->device_connect_time);
+        data->function_pending_time = time_to_nsec(cmb->function_pending_time);
+        data->device_disconnect_time =
+                time_to_nsec(cmb->device_disconnect_time);
         data->control_unit_queuing_time
-                = time_to_nsec(cmb.control_unit_queuing_time);
+                = time_to_nsec(cmb->control_unit_queuing_time);
         data->device_active_only_time
-                = time_to_nsec(cmb.device_active_only_time);
+                = time_to_nsec(cmb->device_active_only_time);
+        ret = 0;
+out:
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        return ret;
+}
 
-        return 0;
+static void reset_cmb(struct ccw_device *cdev)
+{
+        cmf_generic_reset(cdev);
 }
 
-static void
-reset_cmb(struct ccw_device *cdev)
+static void * align_cmb(void *area)
 {
-        struct cmb *cmb;
-        spin_lock_irq(cdev->ccwlock);
-        cmb = cdev->private->cmb;
-        if (cmb)
-                memset (cmb, 0, sizeof (*cmb));
-        cdev->private->cmb_start_time = get_clock();
-        spin_unlock_irq(cdev->ccwlock);
+        return area;
 }
 
 static struct attribute_group cmf_attr_group;
@@ -574,6 +787,7 @@ static struct cmb_operations cmbops_basic = {
         .read   = read_cmb,
         .readall    = readall_cmb,
         .reset      = reset_cmb,
+        .align      = align_cmb,
         .attr_group = &cmf_attr_group,
 };
 
@@ -610,22 +824,34 @@ static inline struct cmbe* cmbe_align(struct cmbe *c)
         return (struct cmbe*)addr;
 }
 
-static int
-alloc_cmbe (struct ccw_device *cdev)
+static int alloc_cmbe (struct ccw_device *cdev)
 {
         struct cmbe *cmbe;
-        cmbe = kmalloc (sizeof (*cmbe) * 2, GFP_KERNEL);
+        struct cmb_data *cmb_data;
+        int ret;
+
+        cmbe = kzalloc (sizeof (*cmbe) * 2, GFP_KERNEL);
         if (!cmbe)
                 return -ENOMEM;
-
+        cmb_data = kzalloc(sizeof(struct cmb_data), GFP_KERNEL);
+        if (!cmb_data) {
+                ret = -ENOMEM;
+                goto out_free;
+        }
+        cmb_data->last_block = kzalloc(sizeof(struct cmbe), GFP_KERNEL);
+        if (!cmb_data->last_block) {
+                ret = -ENOMEM;
+                goto out_free;
+        }
+        cmb_data->size = sizeof(struct cmbe);
         spin_lock_irq(cdev->ccwlock);
         if (cdev->private->cmb) {
-                kfree(cmbe);
                 spin_unlock_irq(cdev->ccwlock);
-                return -EBUSY;
+                ret = -EBUSY;
+                goto out_free;
         }
-
-        cdev->private->cmb = cmbe;
+        cmb_data->hw_block = cmbe;
+        cdev->private->cmb = cmb_data;
         spin_unlock_irq(cdev->ccwlock);
 
         /* activate global measurement if this is the first channel */
@@ -636,14 +862,24 @@ alloc_cmbe (struct ccw_device *cdev)
         spin_unlock(&cmb_area.lock);
 
         return 0;
+out_free:
+        if (cmb_data)
+                kfree(cmb_data->last_block);
+        kfree(cmb_data);
+        kfree(cmbe);
+        return ret;
 }
 
-static void
-free_cmbe (struct ccw_device *cdev)
+static void free_cmbe (struct ccw_device *cdev)
 {
+        struct cmb_data *cmb_data;
+
         spin_lock_irq(cdev->ccwlock);
-        kfree(cdev->private->cmb);
+        cmb_data = cdev->private->cmb;
         cdev->private->cmb = NULL;
+        if (cmb_data)
+                kfree(cmb_data->last_block);
+        kfree(cmb_data);
         spin_unlock_irq(cdev->ccwlock);
 
         /* deactivate global measurement if this is the last channel */
@@ -654,89 +890,105 @@ free_cmbe (struct ccw_device *cdev)
         spin_unlock(&cmb_area.lock);
 }
 
-static int
-set_cmbe(struct ccw_device *cdev, u32 mme)
+static int set_cmbe(struct ccw_device *cdev, u32 mme)
 {
         unsigned long mba;
+        struct cmb_data *cmb_data;
+        unsigned long flags;
 
-        if (!cdev->private->cmb)
+        spin_lock_irqsave(cdev->ccwlock, flags);
+        if (!cdev->private->cmb) {
+                spin_unlock_irqrestore(cdev->ccwlock, flags);
                 return -EINVAL;
-        mba = mme ? (unsigned long) cmbe_align(cdev->private->cmb) : 0;
+        }
+        cmb_data = cdev->private->cmb;
+        mba = mme ? (unsigned long) cmbe_align(cmb_data->hw_block) : 0;
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
 
         return set_schib_wait(cdev, mme, 1, mba);
 }
 
 
-u64
-read_cmbe (struct ccw_device *cdev, int index)
+static u64 read_cmbe (struct ccw_device *cdev, int index)
 {
-        /* yes, we have to put it on the stack
-         * because the cmb must only be accessed
-         * atomically, e.g. with mvc */
-        struct cmbe cmb;
-        unsigned long flags;
+        struct cmbe *cmb;
+        struct cmb_data *cmb_data;
         u32 val;
+        int ret;
+        unsigned long flags;
 
-        spin_lock_irqsave(cdev->ccwlock, flags);
-        if (!cdev->private->cmb) {
-                spin_unlock_irqrestore(cdev->ccwlock, flags);
+        ret = cmf_cmb_copy_wait(cdev);
+        if (ret < 0)
                 return 0;
-        }
 
-        cmb = *cmbe_align(cdev->private->cmb);
-        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        spin_lock_irqsave(cdev->ccwlock, flags);
+        cmb_data = cdev->private->cmb;
+        if (!cmb_data) {
+                ret = 0;
+                goto out;
+        }
+        cmb = cmb_data->last_block;
 
         switch (index) {
         case cmb_ssch_rsch_count:
-                return cmb.ssch_rsch_count;
+                ret = cmb->ssch_rsch_count;
+                goto out;
         case cmb_sample_count:
-                return cmb.sample_count;
+                ret = cmb->sample_count;
+                goto out;
         case cmb_device_connect_time:
-                val = cmb.device_connect_time;
+                val = cmb->device_connect_time;
                 break;
         case cmb_function_pending_time:
-                val = cmb.function_pending_time;
+                val = cmb->function_pending_time;
                 break;
         case cmb_device_disconnect_time:
-                val = cmb.device_disconnect_time;
+                val = cmb->device_disconnect_time;
                 break;
         case cmb_control_unit_queuing_time:
-                val = cmb.control_unit_queuing_time;
+                val = cmb->control_unit_queuing_time;
                 break;
         case cmb_device_active_only_time:
-                val = cmb.device_active_only_time;
+                val = cmb->device_active_only_time;
                 break;
         case cmb_device_busy_time:
-                val = cmb.device_busy_time;
+                val = cmb->device_busy_time;
                 break;
         case cmb_initial_command_response_time:
-                val = cmb.initial_command_response_time;
+                val = cmb->initial_command_response_time;
                 break;
         default:
-                return 0;
+                ret = 0;
+                goto out;
         }
-        return time_to_avg_nsec(val, cmb.sample_count);
+        ret = time_to_avg_nsec(val, cmb->sample_count);
+out:
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        return ret;
 }
 
-static int
-readall_cmbe (struct ccw_device *cdev, struct cmbdata *data)
+static int readall_cmbe (struct ccw_device *cdev, struct cmbdata *data)
 {
-        /* yes, we have to put it on the stack
-         * because the cmb must only be accessed
-         * atomically, e.g. with mvc */
-        struct cmbe cmb;
-        unsigned long flags;
+        struct cmbe *cmb;
+        struct cmb_data *cmb_data;
         u64 time;
+        unsigned long flags;
+        int ret;
 
+        ret = cmf_cmb_copy_wait(cdev);
+        if (ret < 0)
+                return ret;
         spin_lock_irqsave(cdev->ccwlock, flags);
-        if (!cdev->private->cmb) {
-                spin_unlock_irqrestore(cdev->ccwlock, flags);
-                return -ENODEV;
+        cmb_data = cdev->private->cmb;
+        if (!cmb_data) {
+                ret = -ENODEV;
+                goto out;
         }
-
-        cmb = *cmbe_align(cdev->private->cmb);
-        time = get_clock() - cdev->private->cmb_start_time;
-        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        if (cmb_data->last_update == 0) {
+                ret = -EAGAIN;
+                goto out;
+        }
+        time = cmb_data->last_update - cdev->private->cmb_start_time;
 
         memset (data, 0, sizeof(struct cmbdata));
 
@@ -746,35 +998,38 @@ readall_cmbe (struct ccw_device *cdev, struct cmbdata *data)
         /* conver to nanoseconds */
         data->elapsed_time = (time * 1000) >> 12;
 
+        cmb = cmb_data->last_block;
         /* copy data to new structure */
-        data->ssch_rsch_count = cmb.ssch_rsch_count;
-        data->sample_count = cmb.sample_count;
+        data->ssch_rsch_count = cmb->ssch_rsch_count;
+        data->sample_count = cmb->sample_count;
 
         /* time fields are converted to nanoseconds while copying */
-        data->device_connect_time = time_to_nsec(cmb.device_connect_time);
-        data->function_pending_time = time_to_nsec(cmb.function_pending_time);
-        data->device_disconnect_time = time_to_nsec(cmb.device_disconnect_time);
+        data->device_connect_time = time_to_nsec(cmb->device_connect_time);
+        data->function_pending_time = time_to_nsec(cmb->function_pending_time);
+        data->device_disconnect_time =
+                time_to_nsec(cmb->device_disconnect_time);
         data->control_unit_queuing_time
-                = time_to_nsec(cmb.control_unit_queuing_time);
+                = time_to_nsec(cmb->control_unit_queuing_time);
         data->device_active_only_time
-                = time_to_nsec(cmb.device_active_only_time);
-        data->device_busy_time = time_to_nsec(cmb.device_busy_time);
+                = time_to_nsec(cmb->device_active_only_time);
+        data->device_busy_time = time_to_nsec(cmb->device_busy_time);
         data->initial_command_response_time
-                = time_to_nsec(cmb.initial_command_response_time);
+                = time_to_nsec(cmb->initial_command_response_time);
 
-        return 0;
+        ret = 0;
+out:
+        spin_unlock_irqrestore(cdev->ccwlock, flags);
+        return ret;
 }
 
-static void
-reset_cmbe(struct ccw_device *cdev)
+static void reset_cmbe(struct ccw_device *cdev)
 {
-        struct cmbe *cmb;
-        spin_lock_irq(cdev->ccwlock);
-        cmb = cmbe_align(cdev->private->cmb);
-        if (cmb)
-                memset (cmb, 0, sizeof (*cmb));
-        cdev->private->cmb_start_time = get_clock();
-        spin_unlock_irq(cdev->ccwlock);
+        cmf_generic_reset(cdev);
+}
+
+static void * align_cmbe(void *area)
+{
+        return cmbe_align(area);
 }
 
 static struct attribute_group cmf_attr_group_ext;
@@ -786,6 +1041,7 @@ static struct cmb_operations cmbops_extended = {
         .read       = read_cmbe,
         .readall    = readall_cmbe,
         .reset      = reset_cmbe,
+        .align      = align_cmbe,
         .attr_group = &cmf_attr_group_ext,
 };
 
@@ -803,14 +1059,19 @@ cmb_show_avg_sample_interval(struct device *dev, struct device_attribute *attr,
         struct ccw_device *cdev;
         long interval;
         unsigned long count;
+        struct cmb_data *cmb_data;
 
         cdev = to_ccwdev(dev);
-        interval  = get_clock() - cdev->private->cmb_start_time;
         count = cmf_read(cdev, cmb_sample_count);
-        if (count)
+        spin_lock_irq(cdev->ccwlock);
+        cmb_data = cdev->private->cmb;
+        if (count) {
+                interval = cmb_data->last_update -
+                        cdev->private->cmb_start_time;
                 interval /= count;
-        else
+        } else
                 interval = -1;
+        spin_unlock_irq(cdev->ccwlock);
         return sprintf(buf, "%ld\n", interval);
 }
 
@@ -823,7 +1084,10 @@ cmb_show_avg_utilization(struct device *dev, struct device_attribute *attr, char
         int ret;
 
         ret = cmf_readall(to_ccwdev(dev), &data);
-        if (ret)
+        if (ret == -EAGAIN || ret == -ENODEV)
+                /* No data (yet/currently) available to use for calculation. */
+                return sprintf(buf, "n/a\n");
+        else if (ret)
                 return ret;
 
         utilization = data.device_connect_time +
@@ -982,6 +1246,13 @@ cmf_readall(struct ccw_device *cdev, struct cmbdata *data)
         return cmbops->readall(cdev, data);
 }
 
+/* Reenable cmf when a disconnected device becomes available again. */
+int cmf_reenable(struct ccw_device *cdev)
+{
+        cmbops->reset(cdev);
+        return cmbops->set(cdev, 2);
+}
+
 static int __init
 init_cmf(void)
 {
diff --git a/drivers/s390/cio/device.h b/drivers/s390/cio/device.h
index 8e0d1db3dd4e..00be9a5b4acd 100644
--- a/drivers/s390/cio/device.h
+++ b/drivers/s390/cio/device.h
@@ -27,6 +27,7 @@ enum dev_state {
         DEV_STATE_DISCONNECTED,
         DEV_STATE_DISCONNECTED_SENSE_ID,
         DEV_STATE_CMFCHANGE,
+        DEV_STATE_CMFUPDATE,
         /* last element! */
         NR_DEV_STATES
 };
@@ -118,5 +119,8 @@ int ccw_device_stlck(struct ccw_device *);
 void ccw_device_set_timeout(struct ccw_device *, int);
 extern struct subchannel_id ccw_device_get_subchannel_id(struct ccw_device *);
 
+/* Channel measurement facility related */
 void retry_set_schib(struct ccw_device *cdev);
+void cmf_retry_copy_block(struct ccw_device *);
+int cmf_reenable(struct ccw_device *);
 #endif
diff --git a/drivers/s390/cio/device_fsm.c b/drivers/s390/cio/device_fsm.c
index 5ec8ef1df9fa..7d0dd72635eb 100644
--- a/drivers/s390/cio/device_fsm.c
+++ b/drivers/s390/cio/device_fsm.c
@@ -336,8 +336,11 @@ ccw_device_oper_notify(void *data)
         if (!ret)
                 /* Driver doesn't want device back. */
                 ccw_device_do_unreg_rereg((void *)cdev);
-        else
+        else {
+                /* Reenable channel measurements, if needed. */
+                cmf_reenable(cdev);
                 wake_up(&cdev->private->wait_q);
+        }
 }
 
 /*
@@ -1095,6 +1098,13 @@ ccw_device_change_cmfstate(struct ccw_device *cdev, enum dev_event dev_event)
         dev_fsm_event(cdev, dev_event);
 }
 
+static void ccw_device_update_cmfblock(struct ccw_device *cdev,
+                                       enum dev_event dev_event)
+{
+        cmf_retry_copy_block(cdev);
+        cdev->private->state = DEV_STATE_ONLINE;
+        dev_fsm_event(cdev, dev_event);
+}
 
 static void
 ccw_device_quiesce_done(struct ccw_device *cdev, enum dev_event dev_event)
@@ -1249,6 +1259,12 @@ fsm_func_t *dev_jumptable[NR_DEV_STATES][NR_DEV_EVENTS] = {
                 [DEV_EVENT_TIMEOUT]     = ccw_device_change_cmfstate,
                 [DEV_EVENT_VERIFY]      = ccw_device_change_cmfstate,
         },
+        [DEV_STATE_CMFUPDATE] = {
+                [DEV_EVENT_NOTOPER]     = ccw_device_update_cmfblock,
+                [DEV_EVENT_INTERRUPT]   = ccw_device_update_cmfblock,
+                [DEV_EVENT_TIMEOUT]     = ccw_device_update_cmfblock,
+                [DEV_EVENT_VERIFY]      = ccw_device_update_cmfblock,
+        },
 };
 
 /*