Am 24.09.2016 um 14:27 hat Vladimir Sementsov-Ogievskiy geschrieben: > On 24.09.2016 15:06, Vladimir Sementsov-Ogievskiy wrote: > >On 24.09.2016 00:21, Wouter Verhelst wrote: > >>On Fri, Sep 23, 2016 at 02:00:06PM -0500, Eric Blake wrote: > >>>My preference would be a new flag to the existing commands, with > >>>explicit documentation that 0 offset and 0 length must be used > >>>with that > >>>flag, when requesting a full-device wipe. > >>Alternatively, what about a flag that says "if you use this flag, the > >>size should be left-shifted by X bits before processing"? That allows > >>you to do TRIM or WRITE_ZEROES on much larger chunks, without being > >>limited to "whole disk" commands. We should probably make it an illegal > >>flag for any command that actually sends data over the wire, though. > >> > > > > > >Note: if disk size is not aligned to X we will have to send > >request larger than the disk size to clear the whole disk. > > > > Also, in this case, which realization of bdrv interface in qemu > would be most appropriate? Similar flag (in this case X must be > defined in some very transparent way, as a constant of 64k for > example), or flag BDRV_REQ_WHOLE_DISK, or separate .bdrv_zero_all > and .bdrv_discard_all ?
Maybe the best would be to extend the existing discard/write_zeroes functions to take a 64 bit byte count and then NBD can internally check whether a request clears the whole disk. Kevin