linux-kernel - Re: [PATCH v2 5/6] devres: provide devm

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Date:   Thu, 2 Jul 2020 14:42:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jonathan Corbet <corbet@....net>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jean Delvare <jdelvare@...e.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 5/6] devres: provide devm_krealloc()

On Mon, Jun 29, 2020 at 08:50:07AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> Implement the managed variant of krealloc(). This function works with
> all memory allocated by devm_kmalloc() (or devres functions using it
> implicitly like devm_kmemdup(), devm_kstrdup() etc.).
> 
> Managed realloc'ed chunks can be manually released with devm_kfree().
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>  .../driver-api/driver-model/devres.rst        |  1 +
>  drivers/base/devres.c                         | 50 +++++++++++++++++++
>  include/linux/device.h                        |  2 +
>  3 files changed, 53 insertions(+)
> 
> diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
> index e0b58c392e4f..0a2572c3813c 100644
> --- a/Documentation/driver-api/driver-model/devres.rst
> +++ b/Documentation/driver-api/driver-model/devres.rst
> @@ -352,6 +352,7 @@ MEM
>    devm_kfree()
>    devm_kmalloc()
>    devm_kmalloc_array()
> +  devm_krealloc()
>    devm_kmemdup()
>    devm_kstrdup()
>    devm_kvasprintf()
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index ed615d3b9cf1..4b8870ef6a3f 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -837,6 +837,56 @@ void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp)
>  }
>  EXPORT_SYMBOL_GPL(devm_kmalloc);
>  
> +void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
> +{
> +	struct devres *old_dr, *new_dr;
> +	struct list_head old_head;
> +	unsigned long flags;
> +	void *ret = NULL;
> +	size_t tot_size;
> +
> +	if (unlikely(!new_size)) {
> +		devm_kfree(dev, ptr);
> +		return ZERO_SIZE_PTR;
> +	}
> +
> +	if (unlikely(ZERO_OR_NULL_PTR(ptr)))
> +		return devm_kmalloc(dev, new_size, gfp);
> +
> +	if (WARN_ON(is_kernel_rodata((unsigned long)ptr)))
> +		/*
> +		 * We cannot reliably realloc a const string returned by
> +		 * devm_kstrdup_const().
> +		 */
> +		return NULL;
> +
> +	if (!check_dr_size(new_size, &tot_size))
> +		return NULL;
> +
> +	spin_lock_irqsave(&dev->devres_lock, flags);
> +
> +	old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> +	if (WARN_ON(!old_dr))
> +		/* Memory chunk not managed or managed by a different device. */
> +		goto out;
> +
> +	old_head = old_dr->node.entry;
> +
> +	new_dr = krealloc(old_dr, tot_size, gfp);
> +	if (!new_dr)
> +		goto out;
> +
> +	if (new_dr != old_dr)
> +		list_replace(&old_head, &new_dr->node.entry);
> +
> +	ret = new_dr->data;
> +
> +out:
> +	spin_unlock_irqrestore(&dev->devres_lock, flags);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(devm_krealloc);

That's a lot of logic that does not seem to match up with the krealloc()
logic in mm/slab_common.c, are you sure we need to do all of that?

Who wants this?

thanks,

greg k-h