On Mon, 2008-06-23 at 17:04 -0400, Greg Freemyer wrote: > On Fri, Jun 20, 2008 at 6:41 PM, Jeff Garzik <jeff@xxxxxxxxxx> wrote: > > James Bottomley wrote: > >> > >> On Fri, 2008-06-20 at 13:06 +0900, Tejun Heo wrote: > >>> > >>> The biggest problem is how to keep userland happy. hdX -> sdX > >>> transition was painful enough and I have a strong feeling that > >>> everyone will come after and hunt down us if we try something like sdX > >>> -> bdX now. :-) > > > >> In theory mounting by label or ID should have fixed a lot of this. > >> However, if we need to head off a revolt, the sdX allocation algorithm > >> can be placed into it's own module so both sd and a ULD ata driver could > >> use it ... > > > >> Actually, surely we can mostly dump the SAT layer? > > > > > > I don't see that we can do that for a long time... And it's not just the > > sdX allocation algorithm in question -- SCSI block devices come with their > > own partition limits and set of supported ioctls. > > > > Therefore, my recommended path has always been > > > > * create ata_disk block device driver (ULD, in your terminology) > > > > * make SAT an optional piece, which maintains compatibility with existing > > SCSI blkdevs, ioctls, command sets > > > > > > I just don't see a valid path moving forward that breaks userland /again/... > > we (ATA hackers) would be drummed out of a job I think :) > > > > Another option that's been discussed is > > > > 1) Make SCSI block devices themselves an allocate-able resource (I think > > that's what you meant by "placed into it's own module so both sd and a ULD > > ata driver could use it"?) > > > > 2) Ensure that any ata_disk ULD would support the same partition limits and > > ioctl set, enough to ensure binary compatibility. > > > > Because that's the real need -- maintaining binary compatibility with SCSI > > block devices, so major/minor, ioctl supported set, partition limits, and > > other relevant details need to remain unchanged. > > > > I've seen a lot of end user complaints about libata only supporting > 15(14?) partitions. Will that limit be moved back to the traditional > drivers/ide limit as part of this? Number of partitions is directly related to number of minors, so it can't be changed without a change in the allocation of major/minor space in sd ... that could only be done compatibly by permuting the space. The only other way to do it is incompatibly by changing major (again). James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
