[PATCH v2 1/3] part: add part_get_info_cached() API

[Heinrich Schuchardt]

On 08.04.25 11:13, Neil Armstrong wrote:
> Introduce a new part_get_info_cached() API that's used to
> get the part_info of a blk_desc allowing to use an eventual
> partition scanning cache to avoid rescanning the entire disk
> partition scheme for each partition number.
>
> The part_get_info_cached_free() is also added to hint the
> partition code to flush any cached data from this disk.
>
> The equivalent ops are added that directly maps to those
> added functions.
>
> This API is designed to be used as a direct replacement of
> part_get_info() in codes scanning all partitions for a same
> disk, like in blk-uclass. With this, a lot of unnecessary
> computation is saved, leading to a faster boot time when
> partitions are scanned, especially with storage medias
> with potentially multiple large hardware partitions like
> UFS, NVMe or eMMC.
>
> Signed-off-by: Neil Armstrong <neil.armstrong at linaro.org>
> ---
>   disk/part.c    | 55 ++++++++++++++++++++++++++++++++++++++++++++-----------
>   include/part.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 88 insertions(+), 11 deletions(-)
>
> diff --git a/disk/part.c b/disk/part.c
> index 303178161c083ec6e1b767b4f06ac5773576ca60..1d09c0511c75d457c81cab040c3f5caa924ee945 100644
> --- a/disk/part.c
> +++ b/disk/part.c
> @@ -335,8 +335,8 @@ void part_print(struct blk_desc *desc)
>   		drv->print(desc);
>   }
>
> -int part_get_info_by_type(struct blk_desc *desc, int part, int part_type,
> -			  struct disk_partition *info)

Thank you, Neil, for pushing this forward.

All functions deserve a description.

> +static int _part_get_info_by_type(struct blk_desc *desc, int part, int part_type,
> +				  struct disk_partition *info, bool cached)
>   {
>   	struct part_driver *drv;
>
> @@ -356,24 +356,57 @@ int part_get_info_by_type(struct blk_desc *desc, int part, int part_type,
>   			      desc->part_type);
>   			return -EPROTONOSUPPORT;
>   		}
> -		if (!drv->get_info) {
> -			PRINTF("## Driver %s does not have the get_info() method\n",

Writing to the console creates screen havoc in EFI applications. Please,
use log_debug() instead of PRINTF().

And, please, remove that noisy '## '. It carries no information.

Best regards

Heinrich

> -			       drv->name);
> -			return -ENOSYS;
> -		}
> -		if (drv->get_info(desc, part, info) == 0) {
> -			PRINTF("## Valid %s partition found ##\n", drv->name);
> -			return 0;
> +		if (cached && drv->get_info_cached) {
> +			if (drv->get_info_cached(desc, part, info) == 0) {
> +				PRINTF("## Valid %s partition found ##\n", drv->name);
> +				return 0;
> +			}
> +		} else {
> +			if (!drv->get_info) {
> +				PRINTF("## Driver %s does not have the get_info() method\n",
> +				       drv->name);
> +				return -ENOSYS;
> +			}
> +			if (drv->get_info(desc, part, info) == 0) {
> +				PRINTF("## Valid %s partition found ##\n", drv->name);
> +				return 0;
> +			}
>   		}
>   	}
>
>   	return -ENOENT;
>   }
>
> +int part_get_info_by_type(struct blk_desc *desc, int part, int part_type,
> +			  struct disk_partition *info)
> +{
> +	return _part_get_info_by_type(desc, part, part_type, info, false);
> +}
> +
> +int part_get_info_cached(struct blk_desc *desc, int part,
> +			 struct disk_partition *info)
> +{
> +	return _part_get_info_by_type(desc, part, PART_TYPE_UNKNOWN, info, true);
> +}
> +
>   int part_get_info(struct blk_desc *desc, int part,
>   		  struct disk_partition *info)
>   {
> -	return part_get_info_by_type(desc, part, PART_TYPE_UNKNOWN, info);
> +	return _part_get_info_by_type(desc, part, PART_TYPE_UNKNOWN, info, false);
> +}
> +
> +void part_get_info_cached_free(struct blk_desc *desc)
> +{
> +	struct part_driver *drv;
> +
> +	if (blk_enabled()) {
> +		drv = part_driver_lookup_type(desc);
> +		if (!drv)
> +			return;
> +		if (!drv->get_info_cache_free)
> +			return;
> +		drv->get_info_cache_free(desc);
> +	}
>   }
>
>   int part_get_info_whole_disk(struct blk_desc *desc,
> diff --git a/include/part.h b/include/part.h
> index fcb3c13dea4de6346ad98d6ce320ef36747dda85..8c98865146306fb66509576068c45de01b9cedb6 100644
> --- a/include/part.h
> +++ b/include/part.h
> @@ -216,6 +216,34 @@ struct blk_desc *mg_disk_get_dev(int dev);
>    */
>   int part_get_info_by_type(struct blk_desc *desc, int part, int part_type,
>   			  struct disk_partition *info);
> +
> +/**
> + * part_get_info_cached() - Get partitions from a block device but save the
> + * disk partition map between different partitions.
> + *
> + * Call to part_get_info_cached_free() is required when scanning of the
> + * block device is finished.
> + *
> + * If the partition driver doesn't support cached part_info, the
> + * normal part_info will be called instead.
> + *
> + * @desc:	Block device descriptor
> + * @part:	Partition number to read
> + * @info:	Returned partition information
> + *
> + * Return: 0 on success, negative errno on failure
> + */
> +int part_get_info_cached(struct blk_desc *desc, int part,
> +			 struct disk_partition *info);
> +
> +/**
> + * part_get_info_cached_free() - Free the saved disk partition map
> + * from a previous call of part_get_info_cached().
> + *
> + * @desc:	Block device descriptor
> + */
> +void part_get_info_cached_free(struct blk_desc *desc);
> +
>   int part_get_info(struct blk_desc *desc, int part,
>   		  struct disk_partition *info);
>   /**
> @@ -463,6 +491,22 @@ struct part_driver {
>   	int part_type;
>   	/** @max_entries:	maximum number of partition table entries */
>   	const int max_entries;
> +	/**
> +	 * @cache_free_cache_free:	Free any parsing data stored from get_info_cached()
> +	 *
> +	 * @get_info_cache_free.desc:	Block device descriptor
> +	 */
> +	void (*get_info_cache_free)(struct blk_desc *desc);
> +	/**
> +	 * @get_inf_cachedo:		Get information about a partition, and save
> +	 *				the resulting parsing data for the next partition.
> +	 *
> +	 * @get_info_cached.desc:	Block device descriptor
> +	 * @get_info_cached.part:	Partition number (1 = first)
> +	 * @get_info_cached.info:	Returns partition information
> +	 */
> +	int (*get_info_cached)(struct blk_desc *desc, int part,
> +			       struct disk_partition *info);
>   	/**
>   	 * @get_info:		Get information about a partition
>   	 *
>