[PATCH 0/3] Enable discard on Hyper-V

[Sitsofe Wheeler]

On Thu, Jul 24, 2014 at 08:47:39AM +0100, Sitsofe Wheeler wrote:
> On Wed, Jul 23, 2014 at 09:13:41PM +0100, Sitsofe Wheeler wrote:
> > On Wed, Jul 23, 2014 at 07:15:58AM -0700, Christoph Hellwig wrote:
> > > On Wed, Jul 23, 2014 at 03:10:28PM +0100, Sitsofe Wheeler wrote:
> > > > I'm not sure this alone will work - won't sdev_bflags/bflags have
> > > > already been built at this point?
> > > 
> > > They've been built up, but we can still or new values into it.  It looks
> > > fine to me from review, but if you can test it on an actualy hypverv
> > > setup that would be valueable feedback.
> > 
> > The previous patches didn't work for me with a Windows 2012 R2 host with a
> > 3.16.0-rc6.x86_64-00076-g2f7d2ec-dirty guest. After applying
> > 
> > > term project, this late in the 3.17 cycle I'd just like to merge
> > > something that gets discards on hyperv to work.
> 
> OK how about the following patches:
> 
> Sitsofe Wheeler (3):
>   [SCSI] Add quirk for forcing logical block provisioning tests
>   [SCSI] storvsc: Add Hyper-V logical block provisioning quirk
>   [SCSI] Make LBP quirk skip lbpme checks

With the updated "Make LBP quirk skip lbpme checks" the above patches
enable discard on all Hyper-V disks (both VHDXs and passthrough SSDs) on
Windows 2012 R2 running a Linux 3.16.0-rc6.x86_64-00076-g2f7d2ec-dirty
guest.

Adding back the debugging and looking at just the discard messages shows
this:

sd 0:0:0:0: [sda] Discard mode: 2
sd 0:0:0:0: [sda] Entering discard switch via LBP VPD
sd 0:0:0:0: [sda] Discard mode: 1
sd 0:0:0:0: [sda] Discard mode: 2
sd 0:0:0:0: [sda] Entering discard switch via LBP VPD
sd 0:0:0:0: [sda] Discard mode: 1
sd 0:0:0:0: [sda] Discard mode: 2
sd 0:0:0:0: [sda] Entering discard switch via LBP VPD
sd 0:0:0:0: [sda] Discard mode: 1
sd 1:0:0:3: [sdd] Discard mode: 2
sd 1:0:0:1: [sdc] Entering discard switch with NO LBP VPD
sd 1:0:0:1: [sdc] Discard mode: 1
sd 1:0:0:3: [sdd] Entering discard switch via LBP VPD
sd 1:0:0:3: [sdd] Discard mode: 1
sd 1:0:0:0: [sdb] Discard mode: 2
sd 1:0:0:3: [sdd] Discard mode: 2
sd 1:0:0:1: [sdc] Entering discard switch with NO LBP VPD
sd 1:0:0:1: [sdc] Discard mode: 1
sd 1:0:0:3: [sdd] Entering discard switch via LBP VPD
sd 1:0:0:3: [sdd] Discard mode: 1
sd 1:0:0:1: [sdc] Entering discard switch with NO LBP VPD
sd 1:0:0:1: [sdc] Discard mode: 1
sd 1:0:0:0: [sdb] Entering discard switch via LBP VPD
sd 1:0:0:0: [sdb] Discard mode: 1
sd 1:0:0:3: [sdd] Discard mode: 2
sd 1:0:0:0: [sdb] Discard mode: 2
sd 1:0:0:0: [sdb] Entering discard switch via LBP VPD
sd 1:0:0:0: [sdb] Discard mode: 1
sd 1:0:0:0: [sdb] Discard mode: 2
sd 1:0:0:0: [sdb] Entering discard switch via LBP VPD
sd 1:0:0:0: [sdb] Discard mode: 1
sd 1:0:0:3: [sdd] Entering discard switch via LBP VPD
sd 1:0:0:3: [sdd] Discard mode: 1

All devices eventually end up using discard mode 1 (SD_LBP_UNMAP) but
it's a bit strange the VHDX devices (which set lbpme) flip back and
forth between discard mode 1 and discard mode 2 (SD_LBP_WS16)...

-- 
Sitsofe | http://sucs.org/~sits/