diff options
Diffstat (limited to 'drivers/scsi/scsi_scan.c')
-rw-r--r-- | drivers/scsi/scsi_scan.c | 99 |
1 files changed, 60 insertions, 39 deletions
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 307a81137607..5fad646ee6e5 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -371,6 +371,31 @@ static struct scsi_target *__scsi_find_target(struct device *parent, } /** + * scsi_target_reap_ref_release - remove target from visibility + * @kref: the reap_ref in the target being released + * + * Called on last put of reap_ref, which is the indication that no device + * under this target is visible anymore, so render the target invisible in + * sysfs. Note: we have to be in user context here because the target reaps + * should be done in places where the scsi device visibility is being removed. + */ +static void scsi_target_reap_ref_release(struct kref *kref) +{ + struct scsi_target *starget + = container_of(kref, struct scsi_target, reap_ref); + + transport_remove_device(&starget->dev); + device_del(&starget->dev); + starget->state = STARGET_DEL; + scsi_target_destroy(starget); +} + +static void scsi_target_reap_ref_put(struct scsi_target *starget) +{ + kref_put(&starget->reap_ref, scsi_target_reap_ref_release); +} + +/** * scsi_alloc_target - allocate a new or find an existing target * @parent: parent of the target (need not be a scsi host) * @channel: target channel number (zero if no channels) @@ -392,7 +417,7 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, + shost->transportt->target_size; struct scsi_target *starget; struct scsi_target *found_target; - int error; + int error, ref_got; starget = kzalloc(size, GFP_KERNEL); if (!starget) { @@ -401,7 +426,7 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, } dev = &starget->dev; device_initialize(dev); - starget->reap_ref = 1; + kref_init(&starget->reap_ref); dev->parent = get_device(parent); dev_set_name(dev, "target%d:%d:%d", shost->host_no, channel, id); dev->bus = &scsi_bus_type; @@ -441,29 +466,36 @@ static struct scsi_target *scsi_alloc_target(struct device *parent, return starget; found: - found_target->reap_ref++; + /* + * release routine already fired if kref is zero, so if we can still + * take the reference, the target must be alive. If we can't, it must + * be dying and we need to wait for a new target + */ + ref_got = kref_get_unless_zero(&found_target->reap_ref); + spin_unlock_irqrestore(shost->host_lock, flags); - if (found_target->state != STARGET_DEL) { + if (ref_got) { put_device(dev); return found_target; } - /* Unfortunately, we found a dying target; need to - * wait until it's dead before we can get a new one */ + /* + * Unfortunately, we found a dying target; need to wait until it's + * dead before we can get a new one. There is an anomaly here. We + * *should* call scsi_target_reap() to balance the kref_get() of the + * reap_ref above. However, since the target being released, it's + * already invisible and the reap_ref is irrelevant. If we call + * scsi_target_reap() we might spuriously do another device_del() on + * an already invisible target. + */ put_device(&found_target->dev); - flush_scheduled_work(); + /* + * length of time is irrelevant here, we just want to yield the CPU + * for a tick to avoid busy waiting for the target to die. + */ + msleep(1); goto retry; } -static void scsi_target_reap_usercontext(struct work_struct *work) -{ - struct scsi_target *starget = - container_of(work, struct scsi_target, ew.work); - - transport_remove_device(&starget->dev); - device_del(&starget->dev); - scsi_target_destroy(starget); -} - /** * scsi_target_reap - check to see if target is in use and destroy if not * @starget: target to be checked @@ -474,28 +506,11 @@ static void scsi_target_reap_usercontext(struct work_struct *work) */ void scsi_target_reap(struct scsi_target *starget) { - struct Scsi_Host *shost = dev_to_shost(starget->dev.parent); - unsigned long flags; - enum scsi_target_state state; - int empty = 0; - - spin_lock_irqsave(shost->host_lock, flags); - state = starget->state; - if (--starget->reap_ref == 0 && list_empty(&starget->devices)) { - empty = 1; - starget->state = STARGET_DEL; - } - spin_unlock_irqrestore(shost->host_lock, flags); - - if (!empty) - return; - - BUG_ON(state == STARGET_DEL); - if (state == STARGET_CREATED) + BUG_ON(starget->state == STARGET_DEL); + if (starget->state == STARGET_CREATED) scsi_target_destroy(starget); else - execute_in_process_context(scsi_target_reap_usercontext, - &starget->ew); + scsi_target_reap_ref_put(starget); } /** @@ -1532,6 +1547,10 @@ struct scsi_device *__scsi_add_device(struct Scsi_Host *shost, uint channel, } mutex_unlock(&shost->scan_mutex); scsi_autopm_put_target(starget); + /* + * paired with scsi_alloc_target(). Target will be destroyed unless + * scsi_probe_and_add_lun made an underlying device visible + */ scsi_target_reap(starget); put_device(&starget->dev); @@ -1612,8 +1631,10 @@ static void __scsi_scan_target(struct device *parent, unsigned int channel, out_reap: scsi_autopm_put_target(starget); - /* now determine if the target has any children at all - * and if not, nuke it */ + /* + * paired with scsi_alloc_target(): determine if the target has + * any children at all and if not, nuke it + */ scsi_target_reap(starget); put_device(&starget->dev); |