Mikulas, > If you create the integrity tag at or above device mapper level, you > will run into problems because the same device can be accessed using > device mapper and using physical volume /dev/sd*. If you create > integrity tags at device mapper level, they will contain device > mapper's logical sector number and the sector number won't match if > you access the device directly using /dev/sd*. For writes, the bip seed value is adjusted every time a bio is cloned, sliced and diced as it traverses partitioning/MD/DM. And then at the bottom of the stack, the ref tag values in the protection information buffer are verified against the adjusted seed value and remapped according to the starting logical block number. The reverse is taking place for reads. This is much faster than doing a remapping of the actual protection buffer values every time the I/O transitions from one address space to the other. In addition, some HBA hardware allows us to program the PI engine with the seed value. So the submitter value to LBA conversion can be done on the fly in hardware. -- Martin K. Petersen Oracle Linux Engineering -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
