Re: [PATCH V2] block: add bio_truncate to fix guard_bio_eod

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

> +void bio_truncate(struct bio *bio, unsigned new_size)

This function really needs a kerneldoc or similar comment describing
what it does in detail.

> +	if (bio_data_dir(bio) != READ)
> +		goto exit;

This really should check the passed in op for REQ_OP_READ directly instead
of just the direction on the potentially not fully set up bio.