[dm-devel] [PATCH 1/6] block: factor out a chunk_size_left helper

[Mike Snitzer]

On Tue, Jun 14 2022 at  5:09P -0400,
Christoph Hellwig <hch at lst.de> wrote:

> Factor out a helper from blk_max_size_offset so that it can be reused
> independently.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  include/linux/blkdev.h | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 914c613d81da7..e66ad451274ec 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -933,6 +933,17 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
>  	return q->limits.max_sectors;
>  }
>  
> +/*
> + * Return how much of the chunk is left to be used for I/O at a given offset.
> + */
> +static inline unsigned int blk_chunk_sectors_left(sector_t offset,
> +		unsigned int chunk_sectors)
> +{
> +	if (unlikely(!is_power_of_2(chunk_sectors)))
> +		return chunk_sectors - sector_div(offset, chunk_sectors);
> +	return chunk_sectors - (offset & (chunk_sectors - 1));
> +}
> +
>  /*
>   * Return maximum size of a request at given offset. Only valid for
>   * file system requests.
> @@ -948,12 +959,8 @@ static inline unsigned int blk_max_size_offset(struct request_queue *q,
>  			return q->limits.max_sectors;
>  	}
>  
> -	if (likely(is_power_of_2(chunk_sectors)))
> -		chunk_sectors -= offset & (chunk_sectors - 1);
> -	else
> -		chunk_sectors -= sector_div(offset, chunk_sectors);
> -
> -	return min(q->limits.max_sectors, chunk_sectors);
> +	return min(q->limits.max_sectors,
> +			blk_chunk_sectors_left(offset, chunk_sectors));
>  }

While you're at it, any reason not to use queue_max_sectors() here?