Currently an rbd device's id is released when it is removed, but it
is done before the code is run to clean up sysfs-related files (such
as /sys/bus/rbd/devices/1).
It's possible that an rbd is still in use after the rbd_remove()
call has been made. It's essentially the same as an active inode
that stays around after it has been removed--until its final close
operation. This means that the id shows up as free for reuse at a
time it should not be.
The effect of this was seen by Jens Rehpoehler, who:
- had a filesystem mounted on an rbd device
- unmapped that filesystem (without unmounting)
- found that the mount still worked properly
- but hit a panic when he attempted to re-map a new rbd device
This re-map attempt found the previously-unmapped id available.
The subsequent attempt to reuse it was met with a panic while
attempting to (re-)install the sysfs entry for the new mapped
device.
Fix this by holding off "putting" the rbd id, until the rbd_device
release function is called--when the last reference is finally
dropped.
Note: This fixes: http://tracker.newdream.net/issues/1907
Signed-off-by: Alex Elder <elder@xxxxxxxxxxxxx>
---
drivers/block/rbd.c | 14 +++++++++-----
1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index da38804..7cae4a3 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2440,7 +2440,12 @@ static ssize_t rbd_add(struct bus_type *bus,
if (rc)
goto err_out_blkdev;
- /* set up and announce blkdev mapping */
+ /*
+ * At this point cleanup in the event of an error is the job
+ * of the sysfs code (initiated by rbd_bus_del_dev()).
+ *
+ * Set up and announce blkdev mapping.
+ */
rc = rbd_init_disk(rbd_dev);
if (rc)
goto err_out_bus;
@@ -2452,8 +2457,6 @@ static ssize_t rbd_add(struct bus_type *bus,
return count;
err_out_bus:
- rbd_id_put(rbd_dev);
-
/* this will also clean up rest of rbd_dev stuff */
rbd_bus_del_dev(rbd_dev);
@@ -2511,6 +2514,9 @@ static void rbd_dev_release(struct device *dev)
/* clean up and free blkdev */
rbd_free_disk(rbd_dev);
unregister_blkdev(rbd_dev->major, rbd_dev->name);
+
+ /* done with the id, and with the rbd_dev */
+ rbd_id_put(rbd_dev);
kfree(rbd_dev);
/* release module ref */
@@ -2543,8 +2549,6 @@ static ssize_t rbd_remove(struct bus_type *bus,
goto done;
}
- rbd_id_put(rbd_dev);
-
__rbd_remove_all_snaps(rbd_dev);
rbd_bus_del_dev(rbd_dev);
--
1.7.5.4
--
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