linux-kernel - Re: [PATCH 6.12] Drivers: hv: Make the sysfs node size for the ring buffer dynamic

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Message-ID: <5e7f02ee-6007-417b-b234-a70cec30c385@linux.microsoft.com>
Date: Mon, 4 Aug 2025 11:19:34 +0530
From: Naman Jain <namjain@...ux.microsoft.com>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Michael Kelley <mhklinux@...look.com>,
 "stable@...r.kernel.org" <stable@...r.kernel.org>,
 Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
 "K . Y . Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Long Li <longli@...rosoft.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6.12] Drivers: hv: Make the sysfs node size for the ring
 buffer dynamic

On 8/1/2025 4:22 PM, Thomas Weißschuh wrote:
> Hi Naman,
> 
> On 2025-07-31 21:13:27+0530, Naman Jain wrote:
>> On 7/30/2025 1:15 AM, Michael Kelley wrote:
>>> From: Thomas Weißschuh <linux@...ssschuh.net> Sent: Tuesday, July 29, 2025 11:47 AM
>>>> On 2025-07-29 18:39:45+0000, Michael Kelley wrote:
>>>>> From: Naman Jain <namjain@...ux.microsoft.com> Sent: Wednesday, July 23, 2025 12:02 AM
> <snip>
> 
>>>>> Unfortunately, I don't see a fix, short of backporting support for the
>>>>> .bin_size function, as this is exactly the problem that function solves.
>>>>
>>>> It should work out in practice. (I introduced the .bin_size function)
>>>
>>> The race I describe is unlikely, particularly if attribute groups are created
>>> once and then not disturbed. But note that the Hyper-V fcopy group can
>>> get updated in a running VM via update_sysfs_group(), which also calls
>>> create_files(). Such an update might marginally increase the potential for
>>> the race and for getting the wrong size. Still, I agree it should work out
>>> in practice.
>>>
>>> Michael
>>>
>>>>
>>>> Thomas
>>
>> hi Thomas,
>> Would it be possible to port your changes on 6.12 kernel, to avoid such
>> race conditions?
> 
> Possible, surely. But Greg has to accept it.
> And you will need to do the backports.
> 
>> Or if it has a lot of dependencies, or if you have a
>> follow-up advice, please let us us know.
> 
> Not more than mentioned before.
> 
> 
> Thomas

Acked. Thanks.

Regards,
Naman