From: Alex Elder <elder@inktank.com>
Date: Fri, 31 May 2013 22:40:44 +0000 (-0500)
Subject: rbd: protect against concurrent unmaps
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=7aa73ee13251af1534de166ea5379f32a6bf7793;p=linux-edison.git

rbd: protect against concurrent unmaps

commit 82a442d239695a242c4d584464c9606322cd02aa upstream.

Make sure two concurrent unmap operations on the same rbd device
won't collide, by only proceeding with the removal and cleanup of a
device if is not already underway.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index afdbd558485..8326b39b057 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -5108,6 +5108,7 @@ static ssize_t rbd_remove(struct bus_type *bus,
 	struct list_head *tmp;
 	int dev_id;
 	unsigned long ul;
+	bool already = false;
 	int ret;
 
 	ret = strict_strtoul(buf, 10, &ul);
@@ -5135,11 +5136,12 @@ static ssize_t rbd_remove(struct bus_type *bus,
 		if (rbd_dev->open_count)
 			ret = -EBUSY;
 		else
-			set_bit(RBD_DEV_FLAG_REMOVING, &rbd_dev->flags);
+			already = test_and_set_bit(RBD_DEV_FLAG_REMOVING,
+							&rbd_dev->flags);
 		spin_unlock_irq(&rbd_dev->lock);
 	}
 	spin_unlock(&rbd_dev_list_lock);
-	if (ret < 0)
+	if (ret < 0 || already)
 		goto done;
 
 	rbd_bus_del_dev(rbd_dev);