svn commit: r332385 - head/sys/dev/hyperv/storvsc

[Dexuan Cui]

Author: dexuan
Date: Tue Apr 10 18:05:02 2018
New Revision: 332385
URL: https://svnweb.freebsd.org/changeset/base/332385

Log:
  hyperv/storvsc: storvsc_io_done(): do not use CAM_SEL_TIMEOUT
  
  CAM_SEL_TIMEOUT was introduced in
  https://reviews.freebsd.org/D7521 (r304251), which claimed:
  
  "VM shall response to CAM layer with CAM_SEL_TIMEOUT to filter those
  invalid LUNs. Never use CAM_DEV_NOT_THERE which will block LUN scan
  for LUN number higher than 7."
  
  But it turns out this is not correct:
  
  I think what really filters the invalid LUNs in r304251 is that:
  before r304251, we could set the CAM_REQ_CMP without checking
  vm_srb->srb_status at all:
  ccb->ccb_h.status |= CAM_REQ_CMP.
  
  r304251 checks vm_srb->srb_status and sets ccb->ccb_h.status properly,
  so the invalid LUNs are filtered.
  
  I changed my code version to r304251 but replaced the CAM_SEL_TIMEOUT
  with CAM_DEV_NOT_THERE, and I confirmed the invalid LUNs can also be
  filtered, and I successfully hot-added and hot-removed 8 disks to/from
  the VM without any issue.
  
  CAM_SEL_TIMEOUT has an unwanted side effect -- see cam_periph_error():
  For a selection timeout, we consider all of the LUNs on
  the target to be gone. If the status is CAM_DEV_NOT_THERE,
  then we only get rid of the device(s) specified by the
  path in the original CCB.
  
  This means: for a VM with a valid LUN on 3:0:0:0, when the VM inquires
  3:0:0:1 and the host reports 3:0:0:1 doesn't exist and storvsc returns
  CAM_SEL_TIMEOUT to the CAM layer, CAM will detech 3:0:0:0 as well: this
  is the bug I reported recently:
  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=226583
  
  PR:	226583
  Reviewed by:	mav
  MFC after:	1 week
  Sponsored by:	Microsoft
  Differential Revision:	https://reviews.freebsd.org/D14690

Modified:
  head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c

Modified: head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
==============================================================================
--- head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c	Tue Apr 10 17:40:44 2018	(r332384)
+++ head/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c	Tue Apr 10 18:05:02 2018	(r332385)
@@ -2173,20 +2173,7 @@ storvsc_io_done(struct hv_storvsc_request *reqp)
 					    scsi_op_desc(cmd->opcode, NULL));
 				}
 			}
-
-			/*
-			 * XXX For a selection timeout, all of the LUNs
-			 * on the target will be gone.  It works for SCSI
-			 * disks, but does not work for IDE disks.
-			 *
-			 * For CAM_DEV_NOT_THERE, CAM will only get
-			 * rid of the device(s) specified by the path.
-			 */
-			if (storvsc_get_storage_type(sc->hs_dev) ==
-			    DRIVER_STORVSC)
-				ccb->ccb_h.status |= CAM_SEL_TIMEOUT;
-			else
-				ccb->ccb_h.status |= CAM_DEV_NOT_THERE;
+			ccb->ccb_h.status |= CAM_DEV_NOT_THERE;
 		} else {
 			ccb->ccb_h.status |= CAM_REQ_CMP;
 		}