[PATCH v2] blkfront: don't change to closing if we're busy

[Andrew Jones <drjones@redhat.com>]

We just reported to xenbus that we can't close yet, because we're still
in use. So we shouldn't then immediately tell xenbus that we are
closing. If we do, then we risk bypassing the chance to complain again,
if we're told to close again, and we're still in use. The reason this
code was here was to implement a deferred close. We can still support
this feature by adding a member to our private data, and setting that
instead. Besides being able to complain each time, this patch fixes
a problem when running on hosts with legacy tools that may interpret
the lack of a complaint or state=Closing incorrectly, and then yank
the device out from under the guest.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 drivers/block/xen-blkfront.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 2f22874..d7f2e03 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -103,6 +103,7 @@ struct blkfront_info
 	unsigned int discard_granularity;
 	unsigned int discard_alignment;
 	int is_ready;
+	int closing;
 };
 
 static DEFINE_SPINLOCK(blkif_io_lock);
@@ -1134,7 +1135,7 @@ blkfront_closing(struct blkfront_info *info)
 	if (bdev->bd_openers) {
 		xenbus_dev_error(xbdev, -EBUSY,
 				 "Device in use; refusing to close");
-		xenbus_switch_state(xbdev, XenbusStateClosing);
+		info->closing = 1;
 	} else {
 		xlvbd_release_gendisk(info);
 		xenbus_frontend_closed(xbdev);
@@ -1423,8 +1424,10 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
 	mutex_lock(&info->mutex);
 	xbdev = info->xbdev;
 
-	if (xbdev && xbdev->state == XenbusStateClosing) {
+	if (xbdev && (xbdev->state == XenbusStateClosing || info->closing)) {
 		/* pending switch to state closed */
+		if (xbdev->state != XenbusStateClosing)
+			xenbus_switch_state(xbdev, XenbusStateClosing);
 		dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");
 		xlvbd_release_gendisk(info);
 		xenbus_frontend_closed(info->xbdev);
-- 
1.7.7.5