On Wed, 2014-07-16 at 13:47 -0400, Martin K. Petersen wrote: > >>>>> "Christoph" == hch@infradead org <hch@xxxxxxxxxxxxx> writes: > > Christoph> Oh, we actually have devices that support WRITE SAME with > Christoph> unmap, but not without? That's defintively a little strange. > > Yep :( > > There were several SSDs that did not want to support wearing out flash > by writing gobs of zeroes and only support the UNMAP case. > > Christoph> Yes, and it did this intentionally. I really wouldn't expect > Christoph> devices to support WRITE SAME with UNMAP but blow up on a > Christoph> WRITE SAME without it (and not just simple fail it in an > Christoph> orderly way). > > *sigh* > > Christoph> It definitively seems odd to default to trying WRITE SAME for > Christoph> unmap for a device that explicitly tells us that it doesn't > Christoph> support WRITE SAME. > > Maybe it's just a naming thing. I was really trying to convey > no_req_write_same support, not no_write_same_10_or_16. > > Christoph> Note that I'm not against your patch - I suspect forcing us > Christoph> to read EVPD pages even for devices that claim to be SPC-2 > Christoph> will come in useful in various scenarios. > > I don't have a problem with a BLIST_PREFER_UNMAP flag or something like > that. But BLIST_TRY_VPD_PAGES seems more generally useful and it does > fix the problem at hand. That's why I went that route. Hang on ... unless we apply Christoph or my fix, we'll get the same issue with every raid driver (that's about 10 I think) that set no_write_same when they hit a >2TB RAID volume, so I think we need both fixes. 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
