zfcp: fix ELS/GS request&response length for hardware data router

This change “zfcp: fix ELS/GS request&response length for hardware data router” in Linux kernel is authored by Steffen Maier <maier [at] linux.vnet.ibm.com> on Wed Aug 10 18:30:45 2016 +0200.

zfcp: fix ELS/GS request&response length for hardware data router

In the hardware data router case, introduced with kernel 3.2
commit 86a9668a8d29 ("[SCSI] zfcp: support for hardware data router")
the ELS/GS request&response length needs to be initialized
as in the chained SBAL case.

Otherwise, the FCP channel rejects ELS requests with
FSF_REQUEST_SIZE_TOO_LARGE.

Such ELS requests can be issued by user space through BSG / HBA API,
or zfcp itself uses ADISC ELS for remote port link test on RSCN.
The latter can cause a short path outage due to
unnecessary remote target port recovery because the always
failing ADISC cannot detect extremely short path interruptions
beyond the local FCP channel.

Below example is decoded with zfcpdbf from s390-tools:

Timestamp      : ...
Area           : SAN
Subarea        : 00
Level          : 1
Exception      : -
CPU id         : ..
Caller         : zfcp_dbf_san_req+0408
Record id      : 1
Tag            : fssels1
Request id     : 0x<reqid>
Destination ID : 0x00<target d_id>
Payload info   : 52000000 00000000 <our wwpn       >           [ADISC]
                 <our wwnn       > 00<s_id> 00000000
                 00000000 00000000 00000000 00000000

Timestamp      : ...
Area           : HBA
Subarea        : 00
Level          : 1
Exception      : -
CPU id         : ..
Caller         : zfcp_dbf_hba_fsf_res+0740
Record id      : 1
Tag            : fs_ferr
Request id     : 0x<reqid>
Request status : 0x00000010
FSF cmnd       : 0x0000000b               [FSF_QTCB_SEND_ELS]
FSF sequence no: 0x...
FSF issued     : ...
FSF stat       : 0x00000061		  [FSF_REQUEST_SIZE_TOO_LARGE]
FSF stat qual  : 00000000 00000000 00000000 00000000
Prot stat      : 0x00000100
Prot stat qual : 00000000 00000000 00000000 00000000

Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Fixes: 86a9668a8d29 ("[SCSI] zfcp: support for hardware data router")
Cc: <stable@vger.kernel.org> # 3.2+
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 70369f8.

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/s390/scsi/zfcp_fsf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index 84353f4..96d35a7 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -984,8 +984,12 @@ static int zfcp_fsf_setup_ct_els_sbals(struct zfcp_fsf_req *req,
 	if (zfcp_adapter_multi_buffer_active(adapter)) {
 		if (zfcp_qdio_sbals_from_sg(qdio, &req->qdio_req, sg_req))
 			return -EIO;
+		qtcb->bottom.support.req_buf_length =
+			zfcp_qdio_real_bytes(sg_req);
 		if (zfcp_qdio_sbals_from_sg(qdio, &req->qdio_req, sg_resp))
 			return -EIO;
+		qtcb->bottom.support.resp_buf_length =
+			zfcp_qdio_real_bytes(sg_resp);
 
 		zfcp_qdio_set_data_div(qdio, &req->qdio_req,
 					zfcp_qdio_sbale_count(sg_req));

The commit for this change in Linux stable tree is 70369f8 (patch).

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