rbd: avoid a deadlock on header_rwsem when flushing notifies
[ Upstream commit5.4-rM2-2.2.x-imx-squashed0e4e1de5b6
] rbd_unregister_watch() flushes notifies and therefore cannot be called under header_rwsem because a header update notify takes header_rwsem to synchronize with "rbd map". If mapping an image fails after the watch is established and a header update notify sneaks in, we deadlock when erroring out from rbd_dev_image_probe(). Move watch registration and unregistration out of the critical section. The only reason they were put there was to make header_rwsem management slightly more obvious. Fixes:811c668877
("rbd: fix rbd map vs notify races") Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Jason Dillaman <dillaman@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
parent
a362482b23
commit
88a57e387c
|
@ -4636,6 +4636,10 @@ static void cancel_tasks_sync(struct rbd_device *rbd_dev)
|
|||
cancel_work_sync(&rbd_dev->unlock_work);
|
||||
}
|
||||
|
||||
/*
|
||||
* header_rwsem must not be held to avoid a deadlock with
|
||||
* rbd_dev_refresh() when flushing notifies.
|
||||
*/
|
||||
static void rbd_unregister_watch(struct rbd_device *rbd_dev)
|
||||
{
|
||||
cancel_tasks_sync(rbd_dev);
|
||||
|
@ -6942,6 +6946,9 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev)
|
|||
* device. If this image is the one being mapped (i.e., not a
|
||||
* parent), initiate a watch on its header object before using that
|
||||
* object to get detailed information about the rbd image.
|
||||
*
|
||||
* On success, returns with header_rwsem held for write if called
|
||||
* with @depth == 0.
|
||||
*/
|
||||
static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
|
||||
{
|
||||
|
@ -6974,6 +6981,9 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
|
|||
}
|
||||
}
|
||||
|
||||
if (!depth)
|
||||
down_write(&rbd_dev->header_rwsem);
|
||||
|
||||
ret = rbd_dev_header_info(rbd_dev);
|
||||
if (ret)
|
||||
goto err_out_watch;
|
||||
|
@ -7027,6 +7037,8 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth)
|
|||
err_out_probe:
|
||||
rbd_dev_unprobe(rbd_dev);
|
||||
err_out_watch:
|
||||
if (!depth)
|
||||
up_write(&rbd_dev->header_rwsem);
|
||||
if (!depth)
|
||||
rbd_unregister_watch(rbd_dev);
|
||||
err_out_format:
|
||||
|
@ -7085,12 +7097,9 @@ static ssize_t do_rbd_add(struct bus_type *bus,
|
|||
goto err_out_rbd_dev;
|
||||
}
|
||||
|
||||
down_write(&rbd_dev->header_rwsem);
|
||||
rc = rbd_dev_image_probe(rbd_dev, 0);
|
||||
if (rc < 0) {
|
||||
up_write(&rbd_dev->header_rwsem);
|
||||
if (rc < 0)
|
||||
goto err_out_rbd_dev;
|
||||
}
|
||||
|
||||
/* If we are mapping a snapshot it must be marked read-only */
|
||||
if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
|
||||
|
|
Loading…
Reference in New Issue