On Wed, 2014-07-16 at 04:01 -0700, h...@infradead.org wrote: > On Sun, Jul 13, 2014 at 08:58:34AM -0400, Martin K. Petersen wrote: > > >>>>> "KY" == KY Srinivasan <k...@microsoft.com> writes: > > > > KY> Windows hosts do support UNMAP and set the field in the > > KY> EVPD. However, since the host advertises SPC-2 compliance, Linux > > KY> does not even query the VPD page. > > > > >> If we want to enable UNMAP in this case I'd prefer a blacklist entry > > >> than trying UNMAP despite the device not advertising it. > > > > I agree with that. We could do something like the patch below. > > > > However, I do think it's a good idea that you guys are looking into > > reporting SPC-3. > > KY mentioned that they have a prototype for that now. > > Btw, I looked over sd.c a bit more, and I think I understand why they > get the WRITE SAME commands now: > > read_capacity_16 calls sd_config_discard(sdkp, SD_LBP_WS16) if the LPBME > bit is set. At least older SBC drafts left it wide open if a target > supports WRITE SAME with UNMAP or UNMAP in this case. So I think we'd > still want a patch to use UNMAP instead of WRITE SAME for this case, > which should also fix hyperv. Below is the quick hack version of that > that just checks the host no_write_same flag, as the one on the device > isn't set yet - I guess we need to refactor some of that logic. > > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c > index 87566b5..4480fdf 100644 > --- a/drivers/scsi/sd.c > +++ b/drivers/scsi/sd.c > @@ -2035,7 +2035,10 @@ static int read_capacity_16(struct scsi_disk *sdkp, > struct scsi_device *sdp, > if (buffer[14] & 0x40) /* LBPRZ */ > sdkp->lbprz = 1; > > - sd_config_discard(sdkp, SD_LBP_WS16); > + if (sdp->host->no_write_same) > + sd_config_discard(sdkp, SD_LBP_UNMAP); > + else > + sd_config_discard(sdkp, SD_LBP_WS16);
Right, I already said this was the problem: that was the reason for my patch. However, there are a couple of other cases (including the /sys entry) which is why I patched sd_config_discard instead. James
