linux-kernel - Re: [PATCH v6 0/2] uio_hv_generic: Fix ring buffer sysfs creation path

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Message-ID: <2173d71c-301d-4b6c-b839-0e747d0d0a4b@linux.microsoft.com>
Date: Fri, 2 May 2025 11:31:03 +0530
From: Naman Jain <namjain@...ux.microsoft.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "K . Y . Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>,
 Stephen Hemminger <stephen@...workplumber.org>,
 linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...nel.org, Saurabh Sengar <ssengar@...ux.microsoft.com>,
 Michael Kelley <mhklinux@...look.com>
Subject: Re: [PATCH v6 0/2] uio_hv_generic: Fix ring buffer sysfs creation
 path



On 5/1/2025 9:35 PM, Greg Kroah-Hartman wrote:
> On Mon, Apr 28, 2025 at 02:37:22PM +0530, Naman Jain wrote:
>>
>>
>> On 4/25/2025 7:30 PM, Greg Kroah-Hartman wrote:
>>> On Thu, Apr 24, 2025 at 11:05:22AM +0530, Naman Jain wrote:
>>>> Hi,
>>>> This patch series aims to address the sysfs creation issue for the ring
>>>> buffer by reorganizing the code. Additionally, it updates the ring sysfs
>>>> size to accurately reflect the actual ring buffer size, rather than a
>>>> fixed static value.
>>>>
>>>> PFB change logs:
>>>>
>>>> Changes since v5:
>>>> https://lore.kernel.org/all/20250415164452.170239-1-namjain@linux.microsoft.com/
>>>> * Added Reviewed-By tags from Dexuan. Also, addressed minor comments in
>>>>     commit msg of both patches.
>>>> * Missed to remove check for "primary_channel->device_obj->channels_kset" in
>>>>     hv_create_ring_sysfs in earlier patch, as suggested by Michael. Did it
>>>>     now.
>>>> * Changed type for declaring bin_attrs due to changes introduced by
>>>>     commit 9bec944506fa ("sysfs: constify attribute_group::bin_attrs") which
>>>>     merged recently. Did not use bin_attrs_new since another change is in
>>>>     the queue to change usage of bin_attrs_new to bin_attrs
>>>>     (sysfs: finalize the constification of 'struct bin_attribute').
>>>
>>> Please fix up to apply cleanly without build warnings:
>>>
>>> drivers/hv/vmbus_drv.c:1893:15: error: initializing 'struct bin_attribute **' with an expression of type 'const struct bin_attribute *const[2]' discards qualifiers in nested pointer types [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>>>    1893 |         .bin_attrs = vmbus_chan_bin_attrs,
>>>         |                      ^~~~~~~~~~~~~~~~~~~~
>>> 1 error generated.
>>
>> Hi Greg,
>> I tried reproducing this error but could not see it. Should I rebase the
>> change to some other tree or use some specific config option, gcc version,
>> compilation flag etc.?
>>
>> I tried the following:
>> * Rebased to latest linux-next tip with below base commit:
>> 393d0c54cae31317deaa9043320c5fd9454deabc
>> * Regular compilation with gcc: make -j8
>> * extra flags:
>>    make -j8  EXTRA_CFLAGS="-Wall -O2"
>>    make -j8 EXTRA_CFLAGS="-Wincompatible-pointer-types-discards-qualifiers
>> -Werror"
>> * Tried gcc 11.4, 13.3
>> * Tried clang/LLVM with version 18.1.3 : make LLVM=1
> 
> I tried this against my char-misc-linus branch (which is pretty much
> just 6.15.0-rc4 plus some iio patches), and it fails with that error
> above.
> 
>> BTW I had to edit the type for bin_attrs as this change got merged recently:
>> 9bec944506fa ("sysfs: constify attribute_group::bin_attrs")
>>
>> diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
>> index 576b8b3c60af..f418aae4f113 100644
>> --- a/include/linux/sysfs.h
>> +++ b/include/linux/sysfs.h
>> @@ -107,7 +107,7 @@ struct attribute_group {
>>                                              int);
>>          struct attribute        **attrs;
>>          union {
>> -               struct bin_attribute            **bin_attrs;
>> +               const struct bin_attribute      *const *bin_attrs;
>>                  const struct bin_attribute      *const *bin_attrs_new;
>>          };
>>   };
> 
> That commit is not in my char-misc branches, that's coming from
> somewhere else.
> 
> thanks,
> 
> greg k-h

Hi Greg,

I can send a patch based on char-misc/6.15.0-rc4 which does not have 
this patch, but I am worried that it will cause compilation issues when 
your branch is merged with linux-next since this change is already there 
in linux-next. Do you want me to proceed with sending a patch on 6.15.0-rc4?

Here are more details of that patch:

"""
sysfs: constify attribute_group::bin_attrs
All users of this field have been migrated to bin_attrs_new.
It can now be constified.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
Link: 
https://lore.kernel.org/r/20250313-sysfs-const-bin_attr-final-v2-2-96284e1e88ce@weissschuh.net
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

"""

Regards,
Naman