RDMA/srp: Apply the __packed attribute to members instead of structures

Applying the __packed attribute to an entire data structure results in
suboptimal code on architectures that do not support unaligned accesses.
Hence apply the __packed attribute only to those data members that are
not naturally aligned.

Link: https://lore.kernel.org/r/20210524041211.9480-4-bvanassche@acm.org
Cc: Nicolas Morey-Chaisemartin <nmoreychaisemartin@suse.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

scsi: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare variable-length
types such as these ones is a flexible array member[1][2], introduced in
C99:

struct foo {
int stuff;
struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by this
change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Link: https://lore.kernel.org/r/20200224161406.GA21454@embeddedor
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Satish Kharat <satishkh@cisco.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/scsi/srp.h: Add support for immediate data

Add constants and data structures to support immediate data. These
changes conform to SRP2r04.

Cc: Sergey Gorenko <sergeygo@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/scsi/srp.h: Move response flag definitions into this file

This patch moves all constants that come from the SRP standard into the
include/scsi/srp.h header file.

Cc: Sergey Gorenko <sergeygo@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

IB/srp: Add RDMA/CM support

Since the SRP_LOGIN_REQ defined in the SRP standard is larger than
what fits in the RDMA/CM login request private data, introduce a new
login request format for the RDMA/CM.

Note: since srp_daemon and ibsrpdm rely on the subnet manager and
since there is no equivalent of the IB subnet manager in non-IB
networks, login has to be performed manually for non-IB networks.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

IB/srp: Add 64-bit LUN support

The SCSI standard defines 64-bit values for LUNs. Large arrays
employing large or hierarchical LUN numbers become more and more
common. So update the SRP initiator to use 64-bit LUN numbers.
See also Hannes Reinecke, commit 9cb78c16f5da ("scsi: use 64-bit LUNs"),
June 2014.

The largest LUN number that has been tested is 0xd2003fff00000000.

Checked the following structure sizes with gdb:
* sizeof(struct srp_cmd) = 48
* sizeof(struct srp_tsk_mgmt) = 48
* sizeof(struct srp_aer_req) = 36

The ibmvscsi changes have been compile tested only (on a PPC system).

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

IB/srp: Implement SRP_CRED_REQ and SRP_AER_REQ

This patch adds support for SRP_CRED_REQ to avoid a lockup by targets
that use that mechanism to return credits to the initiator. This
prevents a lockup observed in the field where we would never add the
credits from the SRP_CRED_REQ to our current count, and would therefore
never send another command to the target.

Minimal support for SRP_AER_REQ is also added, as these messages can
also be used to convey additional credits to the initiator.

Based upon extensive debugging and code by Bart Van Assche and a bug
report by Chris Worley.

Signed-off-by: David Dillow <dillowda@ornl.gov>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

[SCSI] srp.h: Add I/O Class values

Add enum values for I/O Class values from rev. 10 and rev. 16a SRP
drafts. The values are used to detect targets that implement obsolete
revisions of SRP, so that the initiator can use the old format for
port identifier when connecting to them.

Signed-off-by: Ramachandra K <rkuchimanchi@silverstorm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

[SCSI] srp.h: avoid padding of structs

Several structs in <scsi/srp.h> get padded to a multiple of 8 bytes on
64-bit architectures and end up with a size that does not match the
definition in the SRP spec:

SRP spec 64-bit
sizeof (struct indirect_buf) 20 24
sizeof (struct srp_login_rsp) 52 56
sizeof (struct srp_rsp) 36 40

Fix this by adding __attribute__((packed)) to the offending structs.

Problem pointed out by Arne Redlich <arne.redlich@xiranet.com>.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

IB: Add SCSI RDMA Protocol (SRP) initiator

Add an InfiniBand SCSI RDMA Protocol (SRP) initiator. This driver is
used to talk talk to InfiniBand SRP targets (storage devices).

Signed-off-by: Roland Dreier <rolandd@cisco.com>