>>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes: >> That is 0x7fffff (over 8 million) blocks (4 GB) being unmapped in one >> operation! That may exceed the "maximum unmap lba count" field in the >> Block Limits VPD page. The latest SBC draft (sbc3r22.pdf) says that >> field applies to the SCSI UNMAP command and does not mention the >> WRITE SAME (16) command but that is probably an oversight. Maximum Unmap LBA Count > 0 (in combination with the descriptor count) are what indicate that the device server supports UNMAP. You could argue, then, that a Maximum Unmap LBA Count > 0 but a Maximum Unmap Descriptor Count of 0 would provide means to indicate the maximum range for WRITE SAME. But the T10 people I have talked to all agree that the LBA count for WRITE SAME is gated by the command's LBA count and nothing else. So no special casing for when the UNMAP bit is set. I.e. the max for WRITE SAME(16) is 32-bits times logical_block_size. Mike> # cat /sys/block/sda/queue/discard_granularity Mike> 512 Mike> # cat /sys/block/sda/queue/discard_max_bytes Mike> 4294966784 Mike> I'll look to understand why 'discard_max_bytes' is so large for Mike> this LUN despite the standard Block limits VPD page not reflecting Mike> this. discard_max_bytes is 0xFFFFFFFF for WRITE SAME(16). -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
