[Xen-devel] [PATCH 14/16] blkfront: Lock blockfront_info during xbdev removal

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Daniel Stodden <daniel.stodden@xxxxxxxxxx>

Same approach as blkfront_closing:
 * Grab the bdev safely, holding the info mutex.
 * Zap xbdev safely, holding the info mutex.
 * Try bdev removal safely, holding bd_mutex.

Signed-off-by: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 drivers/block/xen-blkfront.c |   41 +++++++++++++++++++++++++++++++++++------
 1 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 214c92e..96ff225 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1093,18 +1093,47 @@ static void blkback_changed(struct xenbus_device *dev,
        }
 }
 
-static int blkfront_remove(struct xenbus_device *dev)
+static int blkfront_remove(struct xenbus_device *xbdev)
 {
-       struct blkfront_info *info = dev_get_drvdata(&dev->dev);
+       struct blkfront_info *info = dev_get_drvdata(&xbdev->dev);
+       struct block_device *bdev = NULL;
+       struct gendisk *disk;
 
-       dev_dbg(&dev->dev, "blkfront_remove: %s removed\n", dev->nodename);
+       dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
 
        blkif_free(info, 0);
 
-       if(info->users == 0)
+       mutex_lock(&info->mutex);
+
+       disk = info->gd;
+       if (disk)
+               bdev = bdget_disk(disk, 0);
+
+       info->xbdev = NULL;
+       mutex_unlock(&info->mutex);
+
+       if (!bdev) {
+               kfree(info);
+               return 0;
+       }
+
+       /*
+        * The xbdev was removed before we reached the Closed
+        * state. See if it's safe to remove the disk. If the bdev
+        * isn't closed yet, we let release take care of it.
+        */
+
+       mutex_lock(&bdev->bd_mutex);
+       info = disk->private_data;
+
+       if (info && !info->users) {
+               xlvbd_release_gendisk(info);
+               disk->private_data = NULL;
                kfree(info);
-       else
-               info->xbdev = NULL;
+       }
+
+       mutex_unlock(&bdev->bd_mutex);
+       bdput(bdev);
 
        return 0;
 }
-- 
1.7.1.1


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