Author: dexuan
Date: Tue Apr 24 03:07:49 2018
New Revision: 332904
URL: https://svnweb.freebsd.org/changeset/base/332904
Log:
MFC: 332385
r332385:
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
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D14690
Modified:
stable/10/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c
==============================================================================
--- stable/10/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c Tue Apr 24
03:06:05 2018 (r332903)
+++ stable/10/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c Tue Apr 24
03:07:49 2018 (r332904)
@@ -2172,20 +2172,7 @@ 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;
}
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