Re: [PATCH v4 1/3] devres: provide devm_krealloc()

[Andy Shevchenko]

On Mon, Jul 13, 2020 at 04:59:32PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxx>
> ---
>  .../driver-api/driver-model/devres.rst        |  1 +
>  drivers/base/devres.c                         | 67 +++++++++++++++++++
>  include/linux/device.h                        |  2 +
>  3 files changed, 70 insertions(+)
> 
> diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
> index eaaaafc21134f..f318a5c0033c1 100644
> --- a/Documentation/driver-api/driver-model/devres.rst
> +++ b/Documentation/driver-api/driver-model/devres.rst
> @@ -354,6 +354,7 @@ MEM
>    devm_kmalloc()
>    devm_kmalloc_array()
>    devm_kmemdup()
> +  devm_krealloc()
>    devm_kstrdup()
>    devm_kvasprintf()
>    devm_kzalloc()
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index ed615d3b9cf15..1775d35462300 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -837,6 +837,73 @@ void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp)
>  }
>  EXPORT_SYMBOL_GPL(devm_kmalloc);
>  
> +/**
> + * devm_krealloc - Resource-managed krealloc()
> + * @dev: Device to re-allocate memory for
> + * @ptr: Pointer to the memory chunk to re-allocate
> + * @new_size: New allocation size
> + * @gfp: Allocation gfp flags
> + *
> + * Managed krealloc(). Resizes the memory chunk allocated with devm_kmalloc().
> + * Behaves similarly to regular krealloc(): if @ptr is NULL or ZERO_SIZE_PTR,
> + * it's the equivalent of devm_kmalloc(). If new_size is zero, it returns

'it frees the previously allocated memory and returns'

> + * ZERO_SIZE_PTR. This function doesn't change the order in which the release
> + * callback for the re-alloc'ed devres will be called (except when falling back
> + * to devm_kmalloc()

'or when freeing resources when new_size is zero'

> ). The contents of the memory are preserved up to the
> + * lesser of new and old sizes.
> + */
> +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;
> +	size_t total_size;
> +	void *ret = NULL;
> +
> +	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, &total_size))
> +		return NULL;
> +
> +	spin_lock_irqsave(&dev->devres_lock, flags);
> +
> +	old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> +	if (!old_dr) {
> +		spin_unlock_irqrestore(&dev->devres_lock, flags);
> +		WARN(1, "Memory chunk not managed or managed by a different device.");
> +		return NULL;
> +	}
> +
> +	old_head = old_dr->node.entry;
> +
> +	new_dr = krealloc(old_dr, total_size, gfp);
> +	if (!new_dr) {
> +		spin_unlock_irqrestore(&dev->devres_lock, flags);
> +		return NULL;
> +	}
> +
> +	if (new_dr != old_dr)
> +		list_replace(&old_head, &new_dr->node.entry);
> +
> +	ret = new_dr->data;
> +	spin_unlock_irqrestore(&dev->devres_lock, flags);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(devm_krealloc);
> +
>  /**
>   * devm_kstrdup - Allocate resource managed space and
>   *                copy an existing string into that.
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 7322c51e9c0c7..f64f408431593 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -206,6 +206,8 @@ int devres_release_group(struct device *dev, void *id);
>  
>  /* managed devm_k.alloc/kfree for device drivers */
>  void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp) __malloc;

> +void *devm_krealloc(struct device *dev, void *ptr, size_t size,
> +		    gfp_t gfp) __must_check;

Strange indentation, also you can move __must_check to the beginning of the
declaration.


>  __printf(3, 0) char *devm_kvasprintf(struct device *dev, gfp_t gfp,
>  				     const char *fmt, va_list ap) __malloc;
>  __printf(3, 4) char *devm_kasprintf(struct device *dev, gfp_t gfp,
> -- 
> 2.26.1
> 

-- 
With Best Regards,
Andy Shevchenko