[dm-devel] [PATCH 3/6] block: open code blk_max_size_offset in blk_rq_get_max_sectors

[Bart Van Assche]

On 6/14/22 02:09, Christoph Hellwig wrote:
> blk_rq_get_max_sectors always uses q->limits.chunk_sectors as the
> chunk_sectors argument, and already checks for max_sectors through the
> call to blk_queue_get_max_sectors.  That means much of
> blk_max_size_offset is not needed and open coding it simplifies the code.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>   block/blk-merge.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index db2e03c8af7f4..df003ecfbd474 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -566,17 +566,18 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
>   						  sector_t offset)
>   {
>   	struct request_queue *q = rq->q;
> +	unsigned int max_sectors;
>   
>   	if (blk_rq_is_passthrough(rq))
>   		return q->limits.max_hw_sectors;
>   
> +	max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
>   	if (!q->limits.chunk_sectors ||
>   	    req_op(rq) == REQ_OP_DISCARD ||
>   	    req_op(rq) == REQ_OP_SECURE_ERASE)
> -		return blk_queue_get_max_sectors(q, req_op(rq));
> -
> -	return min(blk_max_size_offset(q, offset, 0),
> -			blk_queue_get_max_sectors(q, req_op(rq)));
> +		return max_sectors;
> +	return min(max_sectors,
> +		   blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
>   }

blk_set_default_limits() initializes chunk_sectors to zero and 
blk_chunk_sectors_left() triggers a division by zero if a zero is passed 
as the second argument. What am I missing?

Thanks,

Bart.