linux-kernel - Re: [PATCH] nvdimm: nvdimm_bus_register: Avoid adding device to the unregistered bus

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Message-ID: <641918a2cf2d3_26992942@dwillia2-xfh.jf.intel.com.notmuch>
Date:   Mon, 20 Mar 2023 19:38:26 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "lizhijian@...itsu.com" <lizhijian@...itsu.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "vishal.l.verma@...el.com" <vishal.l.verma@...el.com>,
        "dave.jiang@...el.com" <dave.jiang@...el.com>,
        "ira.weiny@...el.com" <ira.weiny@...el.com>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm: nvdimm_bus_register: Avoid adding device to the
 unregistered bus

lizhijian@...itsu.com wrote:
[..]
> > Now I do think it would be a good idea to fail device_add() if the bus
> > is not registered,
> 
> BTW, below line 369: device_add() didn't fail in practical.
> 

I think that's ok because the device gets added, but never probed due to
this part of that commit I referenced:

@@ -503,20 +517,21 @@ int bus_add_device(struct device *dev)
  */
 void bus_probe_device(struct device *dev)
 {
-       struct bus_type *bus = dev->bus;
+       struct subsys_private *sp = bus_to_subsys(dev->bus);
        struct subsys_interface *sif;
 
-       if (!bus)
+       if (!sp)
                return;
 

...so it does what you want which is disable the libnvdimm subsystem
from binding to any devices without crashing.