Re: [PATCH v2 5/6] devres: provide devm_krealloc()

Greg Kroah-Hartman
2020-07-02T12:42:57Z

On Mon, Jun 29, 2020 at 08:50:07AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.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@baylibre.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