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Subject[PATCH 3.10 096/129] rbd: protect against concurrent unmaps
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alex Elder <elder@inktank.com>

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>

---
drivers/block/rbd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -5108,6 +5108,7 @@ static ssize_t rbd_remove(struct bus_typ
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_typ
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);



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