Re: [Libguestfs] [libnbd PATCH] api: Add LIBNBD_SHUTDOWN_IMMEDIATE flag

On Fri, Sep 11, 2020 at 09:31:11AM -0500, Eric Blake wrote: > As mentioned in commits 176fc4ea and 609c25f0, our original plan in > adding a flags argument to nbd_shutdown was to let us specify > different behaviors at the libnbd level, rather than NBD protocol > flags (for that, the user has nbd_aio_disconnect). But when we later > parameterized OFlags to accept various bitmasks (commit f891340b), we > failed to mark nbd_shutdown as using a different bitmask than > NBD_CMD_FLAG. > > I've finally found a use for such a flag. By itself, > nbd_aio_disconnect merely queues itself at the back of all pending > commands. But if the server is processing responses slowly, it can be > desirable to elevate a disconnect request to the front of the queue, > intentionally abandoning all subsequent commands that have not already > started on their way to the server. > > Fortunately, we have been rejecting all flag values, so changing the > type of the OFlags argument now has no impact to either the C API or > the ABI. Other language bindings that are more strongly-typed will > see a different enum, but we don't promise compatibility there, and > even then, languages that permit omitting the flags argument in favor > of a default don't see any difference for client that were omitting > the argument in favor of the default. I think for the reasons you've outlined here it's fine to change this from cmd_flags to shutdown_flags. And the new flag looks useful. Patch looks good, so ACK.