[PATCHv10 4/9] block: allow ability to limit partition write hints

[Bart Van Assche]

On 10/29/24 8:19 AM, Keith Busch wrote:
> +static ssize_t part_write_hint_mask_store(struct device *dev,
> +					  struct device_attribute *attr,
> +					  const char *buf, size_t count)
> +{
> +	struct block_device *bdev = dev_to_bdev(dev);
> +	unsigned short max_write_hints = bdev_max_write_hints(bdev);
> +	unsigned long *new_mask;
> +
> +	if (!max_write_hints)
> +		return count;
> +
> +	new_mask = bitmap_alloc(max_write_hints, GFP_KERNEL);
> +	if (!new_mask)
> +		return -ENOMEM;
> +
> +	bitmap_parse(buf, count, new_mask, max_write_hints);
> +	bitmap_copy(bdev->write_hint_mask, new_mask, max_write_hints);
> +	bitmap_free(new_mask);
> +
> +	return count;
> +}

bitmap_copy() is not atomic. Shouldn't the bitmap_copy() call be
serialized against the code that tests bits in bdev->write_hint_mask?

Thanks,

Bart.