linux-kernel - Re: -next regression: "driver cohandle -EPROBE_DEFER from bus

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Message-ID: <CAOxpaSW=t6WCLrZryBE4j91nnWdT9ckiV_L9ZRsxS8NuOgcVrQ@mail.gmail.com>
Date:	Thu, 17 Dec 2015 10:50:48 -0700
From:	Ross Zwisler <zwisler@...il.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Russell King <rmk+kernel@....linux.org.uk>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	tomeu.vizoso@...labora.com,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, m.szyprowski@...sung.com
Subject: Re: -next regression: "driver cohandle -EPROBE_DEFER from bus_type.match()"

On Thu, Dec 17, 2015 at 8:51 AM, Dan Williams <dan.j.williams@...el.com> wrote:
> The commit below causes the libnvdimm sub-system to stop loading.
> This is due to the fact that nvdimm_bus_match() returns the result of
> test_bit() which may be negative.  If there are any other bus match
> functions using test_bit they may be similarly impacted.
>
> Can we queue a fixup like the following to libnvdimm, and maybe
> others, ahead of this driver core change?
>
> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
> index 7e2c43f701bc..2b2181cdeb63 100644
> --- a/drivers/nvdimm/bus.c
> +++ b/drivers/nvdimm/bus.c
> @@ -62,7 +62,7 @@ static int nvdimm_bus_match(struct device *dev,
> struct device_driver *drv)
> {
>        struct nd_device_driver *nd_drv = to_nd_device_driver(drv);
>
> -       return test_bit(to_nd_device_type(dev), &nd_drv->type);
> +       return !!test_bit(to_nd_device_type(dev), &nd_drv->type);

How is this call to test_bit() returning a negative value?  That can
only happen if the bit number we supply is 63, correct?  I only see
to_nd_device_type() returning 1-6 for the defines ND_DEVICE_DIMM thru
ND_DEVICE_NAMESPACE_BLK?
--
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