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

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Message-ID: <752c5b1c-ef67-4644-95d4-712cdba6ad2b@linux.microsoft.com>
Date: Mon, 28 Apr 2025 14:37:22 +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 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



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;
         };
  };


Regards,
Naman