blkfront: don't access freed struct xenbus_device

Unfortunately commit "blkfront: fixes for 'xm block-detach ... --force'"
still wasn't quite right - there was a reference to freed memory left
from blkfront_closing().

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 22091e4..60006b7 100644 (file)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -981,13 +981,11 @@ static void blkfront_connect(struct blkfront_info *info)
  * the backend.  Once is this done, we can switch to Closed in
  * acknowledgement.
  */
-static void blkfront_closing(struct xenbus_device *dev)
+static void blkfront_closing(struct blkfront_info *info)
 {
-       struct blkfront_info *info = dev_get_drvdata(&dev->dev);
        unsigned int minor, nr_minors;
        unsigned long flags;
 
-       dev_dbg(&dev->dev, "blkfront_closing: %s removed\n", dev->nodename);
 
        if (info->rq == NULL)
                goto out;
@@ -1013,7 +1011,8 @@ static void blkfront_closing(struct xenbus_device *dev)
        xlbd_release_minors(minor, nr_minors);
 
  out:
-       xenbus_frontend_closed(dev);
+       if (info->xbdev)
+               xenbus_frontend_closed(info->xbdev);
 }
 
 /**
@@ -1053,7 +1052,7 @@ static void blkback_changed(struct xenbus_device *dev,
                        xenbus_dev_error(dev, -EBUSY,
                                         "Device in use; refusing to close");
                else
-                       blkfront_closing(dev);
+                       blkfront_closing(info);
                mutex_unlock(&bd->bd_mutex);
                bdput(bd);
                break;
@@ -1071,7 +1070,7 @@ static int blkfront_remove(struct xenbus_device *dev)
        if(info->users == 0)
                kfree(info);
        else
-               info->is_ready = -1;
+               info->xbdev = NULL;
 
        return 0;
 }
@@ -1080,22 +1079,21 @@ static int blkfront_is_ready(struct xenbus_device *dev)
 {
        struct blkfront_info *info = dev_get_drvdata(&dev->dev);
 
-       return info->is_ready > 0;
+       return info->is_ready && info->xbdev;
 }
 
 static int blkif_open(struct block_device *bdev, fmode_t mode)
 {
        struct blkfront_info *info = bdev->bd_disk->private_data;
-       int ret = 0;
+
+       if (!info->xbdev)
+               return -ENODEV;
 
        lock_kernel();
-       if (info->is_ready < 0)
-               ret = -ENODEV;
-       else
-               info->users++;
+       info->users++;
        unlock_kernel();
 
-       return ret;
+       return 0;
 }
 
 static int blkif_release(struct gendisk *disk, fmode_t mode)
@@ -1108,13 +1106,13 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
                   have ignored this request initially, as the device was
                   still mounted. */
                struct xenbus_device *dev = info->xbdev;
-               enum xenbus_state state = xenbus_read_driver_state(dev->otherend);
 
-               if(info->is_ready < 0) {
-                       blkfront_closing(dev);
+               if (!dev) {
+                       blkfront_closing(info);
                        kfree(info);
-               } else if (state == XenbusStateClosing && info->is_ready)
-                       blkfront_closing(dev);
+               } else if (xenbus_read_driver_state(dev->otherend)
+                          == XenbusStateClosing && info->is_ready)
+                       blkfront_closing(info);
        }
        unlock_kernel();
        return 0;