[PATCH v3 10/10] scsi: add support for user-meta interface

[Christoph Hellwig]

> Add support for sending user-meta buffer. Set tags to be checked
> using flags specified by user/block-layer user and underlying DIF/DIX
> configuration. Introduce BLK_INTEGRITY_APP_TAG to specify apptag.
> This provides a way for upper layers to specify apptag checking.

We'll also need that flag for nvme, don't we?  It should also be
added in a block layer patch and not as part of a driver patch.

> +/*
> + * Can't check reftag alone or apptag alone
> + */
> +static bool sd_prot_flags_valid(struct scsi_cmnd *scmd)
> +{
> +	struct request *rq = scsi_cmd_to_rq(scmd);
> +	struct bio *bio = rq->bio;
> +
> +	if (bio_integrity_flagged(bio, BIP_CHECK_REFTAG) &&
> +	    !bio_integrity_flagged(bio, BIP_CHECK_APPTAG))
> +		return false;
> +	if (!bio_integrity_flagged(bio, BIP_CHECK_REFTAG) &&
> +	    bio_integrity_flagged(bio, BIP_CHECK_APPTAG))
> +		return false;
> +	return true;
> +}

We'll need to advertise this limitations to the application or in-kernel
user somehow..

> +		if ((bio_integrity_flagged(bio, BIP_CTRL_NOCHECK) == false) &&
> +			(!dix || bio_integrity_flagged(bio, BIP_CHECK_REFTAG)))

Incorrect formatting.  This is better:

		if (!bio_integrity_flagged(bio, BIP_CTRL_NOCHECK) &&
		    (!dix || bio_integrity_flagged(bio, BIP_CHECK_REFTAG)))