On Thu, Mar 10, 2022 at 03:44:49PM +0100, Christoph Hellwig wrote: > On Thu, Mar 10, 2022 at 01:57:58PM +0100, Pankaj Raghav wrote: > > Yes, these drives are intended for Linux users that would use the zoned > > block device. Append is supported but holes in the LBA space (due to > > diff in zone cap and zone size) is still a problem for these users. > > I'd really like to hear from the users. Because really, either they > should use a proper file system abstraction (including zonefs if that is > all they need), That requires access to at least the block device and without PO2 emulation that is not possible. Using zonefs is not possible today for !PO2 devices. > or raw nvme passthrough which will alredy work for this > case. This effort is not upstream yet, however, once and if this does land upstream it does mean something other than zonefs must be used since !PO2 devices are not supported by zonefs. So although the goal with the zonefs was to provide a unified interface for raw access for applications, the PO2 requirement will essentially create fragmenetation. > But adding a whole bunch of crap because people want to use the > block device special file for something it is not designed for just > does not make any sense. Using Linux requires PO2. And so on behalf of Damien's request the logical thing to do was to upkeep that requirement and to avoid any performance regressions. That "crap" was done to slowly pave the way forward to then later remove the PO2 requirement. I think we'll all acknowledge that doing emulation just means adding more software for something that is not a NAND requirement, but a requirement imposed by the inheritance of zoned software designed for SMR HDDs. I think we may also all acknowledge now that keeping this emulation code *forever* seems like complete insanity. Since the PO2 requirement imposed on Linux today seems to be now sending us down a dubious effort we'd need to support, let me then try to get folks who have been saying that we must keep this requirement to answer the following question: Are you 100% sure your ZNS hardware team and firmware team will always be happy you have caked in a PO2 requirement for ZNS drives on Linux and are you ready to deal with those consequences on Linux forever? Really? NAND has no PO2 requirement. The emulation effort was only done to help add support for !PO2 devices because there is no alternative. If we however are ready instead to go down the avenue of removing those restrictions well let's go there then instead. If that's not even something we are willing to consider I'd really like folks who stand behind the PO2 requirement to stick their necks out and clearly say that their hw/fw teams are happy to deal with this requirement forever on ZNS.
