Date: Tue, 24 Apr 2018 03:06:05 +0000 (UTC) From: Dexuan Cui <dexuan@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r332903 - stable/11/sys/dev/hyperv/storvsc Message-ID: <201804240306.w3O365pm006301@repo.freebsd.org>
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Author: dexuan Date: Tue Apr 24 03:06:05 2018 New Revision: 332903 URL: https://svnweb.freebsd.org/changeset/base/332903 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/11/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c ============================================================================== --- stable/11/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c Tue Apr 24 01:22:57 2018 (r332902) +++ stable/11/sys/dev/hyperv/storvsc/hv_storvsc_drv_freebsd.c Tue Apr 24 03:06:05 2018 (r332903) @@ -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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