[PATCH] USB: ub 03 Oops with CFQ

The blk_cleanup_queue does not necesserily destroy the queue. When we
destroy the corresponding ub_dev, it may leave the queue spinlock pointer
dangling.

This patch moves spinlocks from ub_dev to static memory. The locking
scheme is not changed. These spinlocks are still separate from the ub_lock.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 45 insertions, 23 deletions

diff --git a/drivers/block/ub.c b/drivers/block/ub.c
index a05fe5843e6c..db4943c53d36 100644
--- a/drivers/block/ub.c
+++ b/drivers/block/ub.c
@@ -355,7 +355,7 @@ struct ub_lun {
  * The USB device instance.
  */
 struct ub_dev {
-        spinlock_t lock;
+        spinlock_t *lock;
         atomic_t poison;                /* The USB device is disconnected */
         int openc;                      /* protected by ub_lock! */
                                         /* kref is too implicit for our taste */
@@ -452,6 +452,10 @@ MODULE_DEVICE_TABLE(usb, ub_usb_ids);
 #define UB_MAX_HOSTS  26
 static char ub_hostv[UB_MAX_HOSTS];
 
+#define UB_QLOCK_NUM 5
+static spinlock_t ub_qlockv[UB_QLOCK_NUM];
+static int ub_qlock_next = 0;
+
 static DEFINE_SPINLOCK(ub_lock);        /* Locks globals and ->openc */
 
 /*
@@ -531,7 +535,7 @@ static ssize_t ub_diag_show(struct device *dev, struct device_attribute *attr,
                 return 0;
 
         cnt = 0;
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
 
         cnt += sprintf(page + cnt,
             "poison %d reset %d\n",
@@ -579,7 +583,7 @@ static ssize_t ub_diag_show(struct device *dev, struct device_attribute *attr,
                 if (++nc == SCMD_TRACE_SZ) nc = 0;
         }
 
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
         return cnt;
 }
 
@@ -627,6 +631,24 @@ static void ub_id_put(int id)
 }
 
 /*
+ * This is necessitated by the fact that blk_cleanup_queue does not
+ * necesserily destroy the queue. Instead, it may merely decrease q->refcnt.
+ * Since our blk_init_queue() passes a spinlock common with ub_dev,
+ * we have life time issues when ub_cleanup frees ub_dev.
+ */
+static spinlock_t *ub_next_lock(void)
+{
+        unsigned long flags;
+        spinlock_t *ret;
+
+        spin_lock_irqsave(&ub_lock, flags);
+        ret = &ub_qlockv[ub_qlock_next];
+        ub_qlock_next = (ub_qlock_next + 1) % UB_QLOCK_NUM;
+        spin_unlock_irqrestore(&ub_lock, flags);
+        return ret;
+}
+
+/*
  * Downcount for deallocation. This rides on two assumptions:
  *  - once something is poisoned, its refcount cannot grow
  *  - opens cannot happen at this time (del_gendisk was done)
@@ -1083,9 +1105,9 @@ static void ub_urb_timeout(unsigned long arg)
         struct ub_dev *sc = (struct ub_dev *) arg;
         unsigned long flags;
 
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         usb_unlink_urb(&sc->work_urb);
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 }
 
 /*
@@ -1108,10 +1130,10 @@ static void ub_scsi_action(unsigned long _dev)
         struct ub_dev *sc = (struct ub_dev *) _dev;
         unsigned long flags;
 
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         del_timer(&sc->work_timer);
         ub_scsi_dispatch(sc);
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 }
 
 static void ub_scsi_dispatch(struct ub_dev *sc)
@@ -1754,7 +1776,7 @@ static void ub_reset_task(void *arg)
          * queues of resets or anything. We do need a spinlock though,
          * to interact with block layer.
          */
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         sc->reset = 0;
         tasklet_schedule(&sc->tasklet);
         list_for_each(p, &sc->luns) {
@@ -1762,7 +1784,7 @@ static void ub_reset_task(void *arg)
                 blk_start_queue(lun->disk->queue);
         }
         wake_up(&sc->reset_wait);
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 }
 
 /*
@@ -1990,11 +2012,11 @@ static int ub_sync_tur(struct ub_dev *sc, struct ub_lun *lun)
         cmd->done = ub_probe_done;
         cmd->back = &compl;
 
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         cmd->tag = sc->tagcnt++;
 
         rc = ub_submit_scsi(sc, cmd);
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 
         if (rc != 0) {
                 printk("ub: testing ready: submit error (%d)\n", rc); /* P3 */
@@ -2052,11 +2074,11 @@ static int ub_sync_read_cap(struct ub_dev *sc, struct ub_lun *lun,
         cmd->done = ub_probe_done;
         cmd->back = &compl;
 
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         cmd->tag = sc->tagcnt++;
 
         rc = ub_submit_scsi(sc, cmd);
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 
         if (rc != 0) {
                 printk("ub: reading capacity: submit error (%d)\n", rc); /* P3 */
@@ -2333,7 +2355,7 @@ static int ub_probe(struct usb_interface *intf,
         if ((sc = kmalloc(sizeof(struct ub_dev), GFP_KERNEL)) == NULL)
                 goto err_core;
         memset(sc, 0, sizeof(struct ub_dev));
-        spin_lock_init(&sc->lock);
+        sc->lock = ub_next_lock();
         INIT_LIST_HEAD(&sc->luns);
         usb_init_urb(&sc->work_urb);
         tasklet_init(&sc->tasklet, ub_scsi_action, (unsigned long)sc);
@@ -2483,7 +2505,7 @@ static int ub_probe_lun(struct ub_dev *sc, int lnum)
         disk->driverfs_dev = &sc->intf->dev;
 
         rc = -ENOMEM;
-        if ((q = blk_init_queue(ub_request_fn, &sc->lock)) == NULL)
+        if ((q = blk_init_queue(ub_request_fn, sc->lock)) == NULL)
                 goto err_blkqinit;
 
         disk->queue = q;
@@ -2554,7 +2576,7 @@ static void ub_disconnect(struct usb_interface *intf)
          * and the whole queue drains. So, we just use this code to
          * print warnings.
          */
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         {
                 struct ub_scsi_cmd *cmd;
                 int cnt = 0;
@@ -2571,7 +2593,7 @@ static void ub_disconnect(struct usb_interface *intf)
                             "%d was queued after shutdown\n", sc->name, cnt);
                 }
         }
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 
         /*
          * Unregister the upper layer.
@@ -2590,19 +2612,15 @@ static void ub_disconnect(struct usb_interface *intf)
         }
 
         /*
-         * Taking a lock on a structure which is about to be freed
-         * is very nonsensual. Here it is largely a way to do a debug freeze,
-         * and a bracket which shows where the nonsensual code segment ends.
-         *
          * Testing for -EINPROGRESS is always a bug, so we are bending
          * the rules a little.
          */
-        spin_lock_irqsave(&sc->lock, flags);
+        spin_lock_irqsave(sc->lock, flags);
         if (sc->work_urb.status == -EINPROGRESS) {      /* janitors: ignore */
                 printk(KERN_WARNING "%s: "
                     "URB is active after disconnect\n", sc->name);
         }
-        spin_unlock_irqrestore(&sc->lock, flags);
+        spin_unlock_irqrestore(sc->lock, flags);
 
         /*
          * There is virtually no chance that other CPU runs times so long
@@ -2636,6 +2654,10 @@ static struct usb_driver ub_driver = {
 static int __init ub_init(void)
 {
         int rc;
+        int i;
+
+        for (i = 0; i < UB_QLOCK_NUM; i++)
+                spin_lock_init(&ub_qlockv[i]);
 
         if ((rc = register_blkdev(UB_MAJOR, DRV_NAME)) != 0)
                 goto err_regblkdev;