Am 10.12.2010 16:00, schrieb Christoph Hellwig: > This patchset adds support for the ATA TRIM and SCSI WRITE SAME with > unmap commands, which allow reclaiming free space from a backing image. > > The user facing implementation is pretty complete, but not really > efficient because the underlying bdrv_discard implementation doesn't > use the aio implementation yet. The reason for that is that the SCSI > layer doesn't really allow any asynchronous commands except for > READ/WRITE by design, and implementing the ATA TRIM command with it's > multiple ranges is rather painful, and combined with the SCSI limitation > I didn't bother yet. The only backend support so far is the XFS hole > punching ioctl, but others can be added easily when they become > available. A virtio implementation for a discard command would also > be pretty easy, but until we actually support a better backend then > a plain sparse file it's not worth using for production enviroments > anyway, but more for playing with the thin provisioning infrastructure, > or observing guest behaviour when TRIM / unmap is supported. > > If the support is enabled and the backend doesn't support hole punching > the TRIM / WRITE SAME commands become no-ops so that migration from > hosts supporting or not supporting it works. > > Version 3: > - refactor IDE dma support code > - proper brace obsfucation > - fix compile without xfs headers > - use bool instead of int for a one-byte flag > > Version 2: > - replace tabs with spaces > - return -ENOMEDIUM from bdrv_discard if there's no driver > assigned > - actually list the TP EVPD page as supported when querying > for supported EVPD pages
The SCSI changes seem to apply, but the rest conflicts with recent changes, most notably AHCI. Can you rebase on top of the block branch? I also found some minor things in the SCSI code, so I'll take the chance to comment on them. Kevin
