Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Christoph Hellwig <hch@infradead.org>]

On Sun, Mar 26, 2023 at 07:06:33PM +0800, Qu Wenruo wrote:
> +	/* Caller should ensure the @bbio doesn't cross stripe boundary. */
> +	ASSERT(map_length >= length);
> +	if (btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE && btrfs_is_zoned(fs_info)) {
> +		bbio->bio.bi_opf &= ~REQ_OP_WRITE;
> +		bbio->bio.bi_opf |= REQ_OP_ZONE_APPEND;
> +	}

Not crossing the stripe boundary is not enough, for zone append it
also must not cross the zone append limit, which (at least in theory)
can be arbitrarily small.

> +	if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
> +		int data_stripes = (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5) ?
> +				    bioc->num_stripes - 1 : bioc->num_stripes - 2;

This calculation feels like it should be in a well document simple
helper.

> +		smap.physical = bioc->stripes[i].physical +
> +				((logical - bioc->full_stripe_logical) &
> +				 BTRFS_STRIPE_LEN_MASK);

This calculation feels like another candidate for a self contained
a well documented helper.


> +		goto submit;
> +	}
> +	ASSERT(mirror_num <= bioc->num_stripes);
> +	smap.dev = bioc->stripes[mirror_num - 1].dev;
> +	smap.physical = bioc->stripes[mirror_num - 1].physical;
> +submit:

Why no else instead of the goto here?  That would read a lot easier.