linux-kernel - Re: [PATCH v2 0/8] slab: provide and use krealloc

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Message-ID: <CAMRc=Me4-4Cmoq3UdpYEEhERP6fvt97bEJsZYhrcFSQf+a_voA@mail.gmail.com>
Date:   Tue, 3 Nov 2020 11:12:02 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Joe Perches <joe@...ches.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Christian König <christian.koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Robert Richter <rric@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
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        Linux-ALSA <alsa-devel@...a-project.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 0/8] slab: provide and use krealloc_array()

On Tue, Nov 3, 2020 at 5:14 AM Joe Perches <joe@...ches.com> wrote:
>
> On Mon, 2020-11-02 at 16:20 +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > Andy brought to my attention the fact that users allocating an array of
> > equally sized elements should check if the size multiplication doesn't
> > overflow. This is why we have helpers like kmalloc_array().
> >
> > However we don't have krealloc_array() equivalent and there are many
> > users who do their own multiplication when calling krealloc() for arrays.
> >
> > This series provides krealloc_array() and uses it in a couple places.
>
> My concern about this is a possible assumption that __GFP_ZERO will
> work, and as far as I know, it will not.
>

Yeah so I had this concern for devm_krealloc() and even sent a patch
that extended it to honor __GFP_ZERO before I noticed that regular
krealloc() silently ignores __GFP_ZERO. I'm not sure if this is on
purpose. Maybe we should either make krealloc() honor __GFP_ZERO or
explicitly state in its documentation that it ignores it?

This concern isn't really related to this patch as such - it's more of
a general krealloc() inconsistency.

Bartosz