linux-kernel - Re: [PATCH] devres: zero the memory in devm

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Message-ID: <CAMRc=MfuejMqpcfOedPMMTR3EY6s2K+4whoWyk7RmJYPaB176w@mail.gmail.com>
Date:   Fri, 30 Oct 2020 10:03:50 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] devres: zero the memory in devm_krealloc() if needed

On Thu, Oct 29, 2020 at 9:05 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Mon, Oct 26, 2020 at 01:27:28PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > If we're returning the same pointer (when new size is smaller or equal
> > to the old size) we need to check if the user wants the memory zeroed
> > and memset() it manually if so.
>
> Any use case? Because to me it sounds contradictory to the whole idea of [k]realloc().
>

This is kind of a gray area in original krealloc() too and I want to
submit a patch for mm too. Right now krealloc ignores the __GFP_ZERO
flag if new_size <= old_size but zeroes the memory if new_size >
old_size. This should be consistent - either ignore __GFP_ZERO or
don't ignore it in both cases. I think that not ignoring it is better
- if user passes it then it's for a reason.

Bartosz