linux-kernel - Re: [Xen-devel] [PATCH v3 2/3] xen/pciback: avoid multiple entries in slot list

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Date:   Wed, 28 Sep 2016 19:22:17 +0200
From:   Juergen Gross <jgross@...e.com>
To:     David Vrabel <david.vrabel@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCH v3 2/3] xen/pciback: avoid multiple entries in
 slot list

On 23/09/16 12:15, David Vrabel wrote:
> On 22/09/16 22:02, Boris Ostrovsky wrote:
>> On 09/22/2016 04:45 AM, Juergen Gross wrote:
>>> The Xen pciback driver has a list of all pci devices it is ready to
>>> seize. There is no check whether a to be added entry already exists.
>>> While this might be no problem in the common case it might confuse
>>> those which consume the list via sysfs.
>>>
>>> Modify the handling of this list by not adding an entry which already
>>> exists. As this will be needed later split out the list handling into
>>> a separate function.
>>>
>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>> ---
>>>  drivers/xen/xen-pciback/pci_stub.c | 39 ++++++++++++++++++++++++++++++--------
>>>  1 file changed, 31 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
>>> index 79a9e4d..0179333 100644
>>> --- a/drivers/xen/xen-pciback/pci_stub.c
>>> +++ b/drivers/xen/xen-pciback/pci_stub.c
>>> @@ -478,6 +478,36 @@ static int __init pcistub_init_devices_late(void)
>>>  	return 0;
>>>  }
>>>  
>>> +static void pcistub_device_id_add_list(struct pcistub_device_id *new,
>>> +				       int domain, int bus, unsigned int devfn)
> 
> I think this should allocate the new pcistub_device_id if needed.  You
> can pass in GFP flags if needed.
> 
> Then it can return the newly allocated one, or the existing one.
> 
> static struct pcistub_device_id *pcistub_device_id_add_list(
>     int domain, int bus, unsigned int devfn)

Patch 3 will be very nasty then: in case of an allocation failure
all of the actions done in pcistub_seize() will have to be undone
again. I'd really like to avoid that.


Juergen