>>>>> "Lukas" == Lukas Czerner <lczerner@xxxxxxxxxx> writes: Lukas, Lukas> So is that documented somewhere ? Because to me it is really not Lukas> obvious whether 0 means that the device does not support discard, Lukas> or the device just does not report discard_max_bytes at all. discard_max_bytes does not necessarily correspond to a single value reported by the device. Not all device types have the notion of such a setting. discard_max_bytes is calculated at the bottom of the stack depending on a combination of heuristics and metrics reported by the device. The same goes for granularity and alignment. So I guess the important thing here is that these values may or may not correspond directly to the underlying device (hopefully they will :). But the topology information *itself* is the interface. That's the whole point. To detach the top of the stack from the intricacies of the hardware. You should never have to ask yourself whether a device supports reporting discard_max_bytes. If a device supports discard then discard_max_bytes will be set. Always. Same goes for granularity and alignment. Regardless of whether the device reports these values or not. We'll fill out the blanks. This is true for the rest of the topology information as well. If the device does not report a physical block size (most don't) we'll set it to match the logical block size. Etc. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
