linux-kernel - Re: [PATCH 0/2] btrfs: Prevent open-coded arithmetic on kmalloc

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Message-ID: <87plbh4qe9.fsf@>
Date: Tue, 23 Sep 2025 08:46:54 +0200
From: Miquel Sabaté Solà <mssola@...ola.com>
To: David Sterba <dsterba@...e.cz>
Cc: linux-btrfs@...r.kernel.org,  clm@...com,  dsterba@...e.com,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] btrfs: Prevent open-coded arithmetic on kmalloc

David Sterba @ 2025-09-23 08:11 +02:

> On Mon, Sep 22, 2025 at 02:51:15PM +0200, Miquel Sabaté Solà wrote:
>> > On Fri, Sep 19, 2025 at 04:58:14PM +0200, Miquel Sabaté Solà wrote:
>> >> The second patch is a small cleanup after fixing up my first patch, in
>> >> which I realized that the __free(kfree) attribute would come in handy in a
>> >> couple of particularly large functions with multiple exit points. This
>> >> second patch is probably more of a cosmetic thing, and it's not an
>> >> exhaustive exercise by any means. All of this to say that even if I feel
>> >> like it should be included, I don't mind if it has to be dropped.
>> >
>> > Yes there are many candidates for the __free() cleanup annotation and
>> > we'll want to fix them all systematically. We already have the automatic
>> > cleaning for struct btrfs_path (BTRFS_PATH_AUTO_FREE). For the
>> > kfree/kvfree I'd like to something similar:
>> >
>> > #define AUTO_KFREE(name)       *name __free(kfree) = NULL
>> > #define AUTO_KVFREE(name)      *name __free(kvfree) = NULL
>> >
>> > This wraps the name and initializes it to NULL so it's not accidentally
>> > forgotten.
>>
>> Makes sense! I can take a look at this if nobody else is working on it,
>> even if I think it should go into a new patch series.
>
> Thanks, it's yours. Yes this should be in a separate patchset.

Great, will do!

>
>> Hence, if it sounds good to you, we can merge this patch as it is right
>> now, and in parallel I work on this proposed AUTO_KFREE and AUTO_KVFREE
>> macros in a new patch series (which will take more time to prepare).
>
> I'd rather see all the changes done the same way so it's not __free and
> then converted to AUTO_KFREE. Also the development branch is frozen
> before 6.18 pull request so all that will be in the 6.19 cycle anyway.

Got it. Then in v2 I will drop this in favor of the later patchset.

Greetings,
Miquel

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