Re: linux-next: build failure after merge of the xarray tree

Jason Gunthorpe
2019-02-12T16:23:31Z

On Tue, Feb 12, 2019 at 08:15:28AM -0800, Matthew Wilcox wrote:
> On Tue, Feb 12, 2019 at 04:20:03PM +1100, Stephen Rothwell wrote:
> > Caused by commit
> >
> > a3e4d3f97ec8 ("XArray: Redesign xa_alloc API")
> >
> > interacting with commits
> >
> > e59178d895af ("RDMA/devices: Use xarray to store the clients")
> > 0df91bb67334 ("RDMA/devices: Use xarray to store the client_data")
> >
> > from the rdma tree.
> >
> > Its a bit of a pain modifying a published API like this :-(
>
> Yes, it is. I wasn't expecting people to actually start using it ;-)
>
> Seriously, there are several defects in the published API which do
> warrant a change. The most severe one is that it's really easy to
> forget to initialise the start index. And while I'm making that change,
> I should fix smaller things like the errno at the same time.

I hope you will send your tree in the 2nd week of the merge window
with all these merge fixes in it..

I think Linus will not like it if he has to fix this when merging
rdma.

> > I have added the following merge fixup patch for today (I assume some
> > of the assignments are also now redundant).
>
> I think the first of these should be using the alloc_cyclic API, like this:

Yes, it is waiting for you :)

> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> index 283ecc2aee89..d0b56c70a553 100644
> +++ b/drivers/infiniband/core/device.c
> @@ -586,20 +586,8 @@ static int assign_name(struct ib_device *device, const char *name)
> }
> strlcpy(device->name, dev_name(&device->dev), IB_DEVICE_NAME_MAX);
>
> - /* Cyclically allocate a user visible ID for the device */
> - device->index = last_id;
> - ret = xa_alloc(&devices, &device->index, device,
> - XA_LIMIT(last_id, INT_MAX), GFP_KERNEL);
> - if (ret == -ENOSPC) {
> - device->index = 0;
> - ret = xa_alloc(&devices, &device->index, device,
> - XA_LIMIT(0, INT_MAX), GFP_KERNEL);
> - }
> - if (ret)
> - goto out;
> - last_id = device->index + 1;
> -
> - ret = 0;
> + ret = xa_alloc_cyclic(&devices, &device->index, device, xa_limit_31b,
> + &last_id, GFP_KERNEL);
>
> out:
> up_write(&devices_rwsem);
> @@ -750,7 +738,7 @@ int ib_register_device(struct ib_device *device, const char *name)
> int ret;
>
> ret = assign_name(device, name);
> - if (ret)
> + if (ret < 0)
> return ret;

This <0 should be near the xa_alloc_cyclic, I don't want the unusual
'1' to propogate.. Far too likely that someone will forget about
the special case.

Jason