Commit 32eec68d authored Feb 08, 2012 by Alex Elder

rbd: don't drop the rbd_id too early

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@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>

parent 593a9e7b

drivers/block/rbd.c

+9 −5

Original line number	Diff line number	Diff line
		@@ -2421,7 +2421,12 @@ 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;
		@@ -2433,8 +2438,6 @@ 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);
		@@ -2492,6 +2495,9 @@ 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 */
		@@ -2524,8 +2530,6 @@ 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);

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