>Support reading atomic write registers to fill in request_queue >properties. >Use following method to calculate limits: >atomic_write_max_bytes = flp2(NAWUPF ?: AWUPF) >atomic_write_unit_min = logical_block_size >atomic_write_unit_max = flp2(NAWUPF ?: AWUPF) >atomic_write_boundary = NABSPF In case the device doesn't support namespace atomic boundary size (i.e. NABSPF is zero) then while merging atomic block-IO we should allow merge. For example, while front/back merging the atomic block IO, we check whether boundary is defined or not. In case if boundary is not-defined (i.e. it's zero) then we simply reject merging ateempt (as implemented in rq_straddles_atomic_write_boundary()). I am quoting this from NVMe spec (Command Set Specification, revision 1.0a, Section 2.1.4.3) : "To ensure backwards compatibility, the values reported for AWUN, AWUPF, and ACWU shall be set such that they are supported even if a write crosses an atomic boundary. If a controller does not guarantee atomicity across atomic boundaries, the controller shall set AWUN, AWUPF, and ACWU to 0h (1 LBA)." Thanks, --Nilay
