linux-kernel - [PATCH 3.10 046/139] scsi: zfcp: fix queuecommand for scsi

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Message-Id: <1509571578-4803-2-git-send-email-w@1wt.eu>
Date:   Wed,  1 Nov 2017 22:26:15 +0100
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Steffen Maier <maier@...ux.vnet.ibm.com>,
        Benjamin Block <bblock@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 046/139] scsi: zfcp: fix queuecommand for scsi_eh commands when DIX enabled

From: Steffen Maier <maier@...ux.vnet.ibm.com>

commit 71b8e45da51a7b64a23378221c0a5868bd79da4f upstream.

Since commit db007fc5e20c ("[SCSI] Command protection operation"),
scsi_eh_prep_cmnd() saves scmd->prot_op and temporarily resets it to
SCSI_PROT_NORMAL.
Other FCP LLDDs such as qla2xxx and lpfc shield their queuecommand()
to only access any of scsi_prot_sg...() if
(scsi_get_prot_op(cmd) != SCSI_PROT_NORMAL).

Do the same thing for zfcp, which introduced DIX support with
commit ef3eb71d8ba4 ("[SCSI] zfcp: Introduce experimental support for
DIF/DIX").

Otherwise, TUR SCSI commands as part of scsi_eh likely fail in zfcp,
because the regular SCSI command with DIX protection data, that scsi_eh
re-uses in scsi_send_eh_cmnd(), of course still has
(scsi_prot_sg_count() != 0) and so zfcp sends down bogus requests to the
FCP channel hardware.

This causes scsi_eh_test_devices() to have (finish_cmds == 0)
[not SCSI device is online or not scsi_eh_tur() failed]
so regular SCSI commands, that caused / were affected by scsi_eh,
are moved to work_q and scsi_eh_test_devices() itself returns false.
In turn, it unnecessarily escalates in our case in scsi_eh_ready_devs()
beyond host reset to finally scsi_eh_offline_sdevs()
which sets affected SCSI devices offline with the following kernel message:

"kernel: sd H:0:T:L: Device offlined - not ready after error recovery"

Signed-off-by: Steffen Maier <maier@...ux.vnet.ibm.com>
Fixes: ef3eb71d8ba4 ("[SCSI] zfcp: Introduce experimental support for DIF/DIX")
Cc: <stable@...r.kernel.org> 
Reviewed-by: Benjamin Block <bblock@...ux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bblock@...ux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/s390/scsi/zfcp_fsf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index ad57184..d27b491 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -2286,7 +2286,8 @@ int zfcp_fsf_fcp_cmnd(struct scsi_cmnd *scsi_cmnd)
 	fcp_cmnd = (struct fcp_cmnd *) &req->qtcb->bottom.io.fcp_cmnd;
 	zfcp_fc_scsi_to_fcp(fcp_cmnd, scsi_cmnd, 0);

-	if (scsi_prot_sg_count(scsi_cmnd)) {
+	if ((scsi_get_prot_op(scsi_cmnd) != SCSI_PROT_NORMAL) &&
+	    scsi_prot_sg_count(scsi_cmnd)) {
 		zfcp_qdio_set_data_div(qdio, &req->qdio_req,
 				       scsi_prot_sg_count(scsi_cmnd));
 		retval = zfcp_qdio_sbals_from_sg(qdio, &req->qdio_req,
-- 
2.8.0.rc2.1.gbe9624a