> -----Original Message----- > From: hch@xxxxxxxxxxxxx [mailto:hch@xxxxxxxxxxxxx] > Sent: Thursday, July 10, 2014 11:32 PM > To: James Bottomley > Cc: KY Srinivasan; linux-kernel@xxxxxxxxxxxxxxx; mkp@xxxxxxx; > hch@xxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx; > stable@xxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; ohering@xxxxxxxx; > jasowang@xxxxxxxxxx > Subject: Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16 > > On Wed, Jul 09, 2014 at 10:27:24PM +0000, James Bottomley wrote: > > If we fix it at source, why would there be any need to filter? That's > > the reason the no_write_same flag was introduced. If we can find and > > fix the bug, it can go back into the stable trees as a bug fix, hence > > nothing should ever emit write_same(10 or 16) and additional driver > > code is redundant (and counter productive, since if this ever breaks > > again you're our best canary). > > > > This looks like it might be the problem but Martin should confirm (I > > think the problem comes to us from the RC16 code which unconditionally > > sets WS16). > > I think the problem is a differnet one. If we have the logical provisioning > EVPD it configures what method to use, but if we don't have one we simply > check for a max unmap blocks field, and if that's not present use WRITE > SAME. > > The patch checks the no_write_same flag before doing that, for which we > also have to do the write_same setup before the discard setup in > sd_revalidate_disk. > > Ky: does hyperv support UNMAP? If so any idea why it doesn't set the > maximum unmap block count field in the EVPD? Windows hosts do support UNMAP and set the field in the EVPD. However, since the host advertises SPC-2 compliance, Linux 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. > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index ba756b1..fbccfd2 100644 > --- a/drivers/scsi/sd.c > +++ b/drivers/scsi/sd.c > @@ -2614,9 +2614,10 @@ static void sd_read_block_limits(struct scsi_disk > *sdkp) > > if (sdkp->max_unmap_blocks) > sd_config_discard(sdkp, SD_LBP_UNMAP); > - else > + else if (!sdkp->device->no_write_same) > sd_config_discard(sdkp, SD_LBP_WS16); > - > + else > + sd_config_discard(sdkp, SD_LBP_DISABLE); > } else { /* LBP VPD page tells us what to use */ > > if (sdkp->lbpu && sdkp->max_unmap_blocks) @@ - > 2766,6 +2767,7 @@ static int sd_revalidate_disk(struct gendisk *disk) > */ > if (sdkp->media_present) { > sd_read_capacity(sdkp, buffer); > + sd_read_write_same(sdkp, buffer); > > if (sd_try_extended_inquiry(sdp)) { > sd_read_block_provisioning(sdkp); > @@ -2776,7 +2778,6 @@ static int sd_revalidate_disk(struct gendisk *disk) > sd_read_write_protect_flag(sdkp, buffer); > sd_read_cache_type(sdkp, buffer); > sd_read_app_tag_own(sdkp, buffer); > - sd_read_write_same(sdkp, buffer); > } > > sdkp->first_scan = 0; -- 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
