1 files changed, 197 insertions, 6 deletions

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 94a274645f6f..aa1b1e0e9d22 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -29,7 +29,9 @@
 #include <linux/moduleparam.h>
 #include <linux/init.h>
 #include <linux/blkdev.h>
-#include <asm/semaphore.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/spinlock.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -87,6 +89,11 @@ module_param_named(max_luns, max_scsi_luns, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(max_luns,
                  "last scsi LUN (should be between 1 and 2^32-1)");
 
+static char scsi_scan_type[6] = "sync";
+
+module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
+MODULE_PARM_DESC(scan, "sync, async or none");
+
 /*
  * max_scsi_report_luns: the maximum number of LUNS that will be
  * returned from the REPORT LUNS command. 8 times this value must
@@ -108,6 +115,68 @@ MODULE_PARM_DESC(inq_timeout,
                  "Timeout (in seconds) waiting for devices to answer INQUIRY."
                  " Default is 5. Some non-compliant devices need more.");
 
+static DEFINE_SPINLOCK(async_scan_lock);
+static LIST_HEAD(scanning_hosts);
+
+struct async_scan_data {
+        struct list_head list;
+        struct Scsi_Host *shost;
+        struct completion prev_finished;
+};
+
+/**
+ * scsi_complete_async_scans - Wait for asynchronous scans to complete
+ *
+ * Asynchronous scans add themselves to the scanning_hosts list.  Once
+ * that list is empty, we know that the scans are complete.  Rather than
+ * waking up periodically to check the state of the list, we pretend to be
+ * a scanning task by adding ourselves at the end of the list and going to
+ * sleep.  When the task before us wakes us up, we take ourselves off the
+ * list and return.
+ */
+int scsi_complete_async_scans(void)
+{
+        struct async_scan_data *data;
+
+        do {
+                if (list_empty(&scanning_hosts))
+                        return 0;
+                /* If we can't get memory immediately, that's OK.  Just
+                 * sleep a little.  Even if we never get memory, the async
+                 * scans will finish eventually.
+                 */
+                data = kmalloc(sizeof(*data), GFP_KERNEL);
+                if (!data)
+                        msleep(1);
+        } while (!data);
+
+        data->shost = NULL;
+        init_completion(&data->prev_finished);
+
+        spin_lock(&async_scan_lock);
+        /* Check that there's still somebody else on the list */
+        if (list_empty(&scanning_hosts))
+                goto done;
+        list_add_tail(&data->list, &scanning_hosts);
+        spin_unlock(&async_scan_lock);
+
+        printk(KERN_INFO "scsi: waiting for bus probes to complete ...\n");
+        wait_for_completion(&data->prev_finished);
+
+        spin_lock(&async_scan_lock);
+        list_del(&data->list);
+ done:
+        spin_unlock(&async_scan_lock);
+
+        kfree(data);
+        return 0;
+}
+
+#ifdef MODULE
+/* Only exported for the benefit of scsi_wait_scan */
+EXPORT_SYMBOL_GPL(scsi_complete_async_scans);
+#endif
+
 /**
  * scsi_unlock_floptical - unlock device via a special MODE SENSE command
  * @sdev:       scsi device to send command to
@@ -619,7 +688,7 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
  *     SCSI_SCAN_LUN_PRESENT: a new scsi_device was allocated and initialized
  **/
 static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
-                int *bflags)
+                int *bflags, int async)
 {
         /*
          * XXX do not save the inquiry, since it can change underneath us,
@@ -805,7 +874,7 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
          * register it and tell the rest of the kernel
          * about it.
          */
-        if (scsi_sysfs_add_sdev(sdev) != 0)
+        if (!async && scsi_sysfs_add_sdev(sdev) != 0)
                 return SCSI_SCAN_NO_RESPONSE;
 
         return SCSI_SCAN_LUN_PRESENT;
@@ -974,7 +1043,7 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
                 goto out_free_result;
         }
 
-        res = scsi_add_lun(sdev, result, &bflags);
+        res = scsi_add_lun(sdev, result, &bflags, shost->async_scan);
         if (res == SCSI_SCAN_LUN_PRESENT) {
                 if (bflags & BLIST_KEY) {
                         sdev->lockable = 0;
@@ -1474,6 +1543,9 @@ void scsi_scan_target(struct device *parent, unsigned int channel,
 {
         struct Scsi_Host *shost = dev_to_shost(parent);
 
+        if (!shost->async_scan)
+                scsi_complete_async_scans();
+
         mutex_lock(&shost->scan_mutex);
         if (scsi_host_scan_allowed(shost))
                 __scsi_scan_target(parent, channel, id, lun, rescan);
@@ -1519,6 +1591,9 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel,
                 "%s: <%u:%u:%u>\n",
                 __FUNCTION__, channel, id, lun));
 
+        if (!shost->async_scan)
+                scsi_complete_async_scans();
+
         if (((channel != SCAN_WILD_CARD) && (channel > shost->max_channel)) ||
             ((id != SCAN_WILD_CARD) && (id >= shost->max_id)) ||
             ((lun != SCAN_WILD_CARD) && (lun > shost->max_lun)))
@@ -1539,14 +1614,130 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel,
         return 0;
 }
 
+static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
+{
+        struct scsi_device *sdev;
+        shost_for_each_device(sdev, shost) {
+                if (scsi_sysfs_add_sdev(sdev) != 0)
+                        scsi_destroy_sdev(sdev);
+        }
+}
+
+/**
+ * scsi_prep_async_scan - prepare for an async scan
+ * @shost: the host which will be scanned
+ * Returns: a cookie to be passed to scsi_finish_async_scan()
+ *
+ * Tells the midlayer this host is going to do an asynchronous scan.
+ * It reserves the host's position in the scanning list and ensures
+ * that other asynchronous scans started after this one won't affect the
+ * ordering of the discovered devices.
+ */
+struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
+{
+        struct async_scan_data *data;
+
+        if (strncmp(scsi_scan_type, "sync", 4) == 0)
+                return NULL;
+
+        if (shost->async_scan) {
+                printk("%s called twice for host %d", __FUNCTION__,
+                                shost->host_no);
+                dump_stack();
+                return NULL;
+        }
+
+        data = kmalloc(sizeof(*data), GFP_KERNEL);
+        if (!data)
+                goto err;
+        data->shost = scsi_host_get(shost);
+        if (!data->shost)
+                goto err;
+        init_completion(&data->prev_finished);
+
+        spin_lock(&async_scan_lock);
+        shost->async_scan = 1;
+        if (list_empty(&scanning_hosts))
+                complete(&data->prev_finished);
+        list_add_tail(&data->list, &scanning_hosts);
+        spin_unlock(&async_scan_lock);
+
+        return data;
+
+ err:
+        kfree(data);
+        return NULL;
+}
+
+/**
+ * scsi_finish_async_scan - asynchronous scan has finished
+ * @data: cookie returned from earlier call to scsi_prep_async_scan()
+ *
+ * All the devices currently attached to this host have been found.
+ * This function announces all the devices it has found to the rest
+ * of the system.
+ */
+void scsi_finish_async_scan(struct async_scan_data *data)
+{
+        struct Scsi_Host *shost;
+
+        if (!data)
+                return;
+
+        shost = data->shost;
+        if (!shost->async_scan) {
+                printk("%s called twice for host %d", __FUNCTION__,
+                                shost->host_no);
+                dump_stack();
+                return;
+        }
+
+        wait_for_completion(&data->prev_finished);
+
+        scsi_sysfs_add_devices(shost);
+
+        spin_lock(&async_scan_lock);
+        shost->async_scan = 0;
+        list_del(&data->list);
+        if (!list_empty(&scanning_hosts)) {
+                struct async_scan_data *next = list_entry(scanning_hosts.next,
+                                struct async_scan_data, list);
+                complete(&next->prev_finished);
+        }
+        spin_unlock(&async_scan_lock);
+
+        scsi_host_put(shost);
+        kfree(data);
+}
+
+static int do_scan_async(void *_data)
+{
+        struct async_scan_data *data = _data;
+        scsi_scan_host_selected(data->shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
+                                SCAN_WILD_CARD, 0);
+
+        scsi_finish_async_scan(data);
+        return 0;
+}
+
 /**
  * scsi_scan_host - scan the given adapter
  * @shost:      adapter to scan
  **/
 void scsi_scan_host(struct Scsi_Host *shost)
 {
-        scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
-                                SCAN_WILD_CARD, 0);
+        struct async_scan_data *data;
+
+        if (strncmp(scsi_scan_type, "none", 4) == 0)
+                return;
+
+        data = scsi_prep_async_scan(shost);
+        if (!data) {
+                scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
+                                        SCAN_WILD_CARD, 0);
+                return;
+        }
+        kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
 }
 EXPORT_SYMBOL(scsi_scan_host);