On 7/24/2018 4:55 PM, Christoph Hellwig wrote:

quoted

+/*
+ * The virtual start sector is the one that was originally submitted
+ * by the block layer.	Due to partitioning, MD/DM cloning, etc. the
+ * actual physical start sector is likely to be different.  Remap
+ * protection information to match the physical LBA.
+ *
+ * From SCSI protocol perspective there's a slight difference between
+ * Type 1 and 2.  The latter uses command's 32-byte exclusively, and the
+ * reference tag is seeded in the command.  This gives us the potential to
+ * avoid virt->phys remapping during write.  However, at read time we
+ * don't know whether the virt sector is the same as when we wrote it
+ * (we could be reading from real disk as opposed to MD/DM device.  So
+ * we always remap Type 2 making it identical to Type 1.
+ *
+ * Type 3 does not have a reference tag so no remapping is required.
+ */

Please convert the comments for  t10_pi_prepare/t10_pi_complete to
kerneldoc format, and remove the mention of 32-byte CDBs, which
are SCSI specific.

something like this:

/**
  * t10_pi_prepare() - prepate PI prior submitting request to device
  * @rq:               request with PI that should be prepared
  * @protection_type:  PI type (Type 1/Type 2/Type 3)
  *
  * Description:
  *    For Type 1/Type 2, the virtual start sector is the one that was
  *    originally submitted by the block layer for the ref_tag usage. Due to
  *    partitioning, MD/DM cloning, etc. the actual physical start sector is
  *    likely to be different. Remap protection information to match the
  *    physical LBA.
  *
  *    Type 3 does not have a reference tag so no remapping is required.
  */

Otherwise this looks good to me.

Note that after this patch only sd_dif_config_host is left in sd_dif.c,
at which point it might be worth merging into sd.c as a separate patch.