Disabling an SRP target port causes the state of all QPs associated
with a port to be changed into IB_QPS_ERR. Avoid that this causes
one error message per I/O context to be reported.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

At least when running the ib_srpt driver on top of the rdma_rxe
driver it is easy to trigger a zero-length write completion in
the CH_DISCONNECTED state. Hence make the message that reports
this less noisy.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Make the ib_srpt driver use the IPv6 format for GIDs in log messages
to improve consistency of this driver with other RDMA kernel drivers.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Verify whether port numbers are in the expected range before using
these as an array index. Complain if a port number is out of range.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Since the SRQ event message is only useful for debugging purposes,
reduce its severity from "informational" to "debug".
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Rename rsp_size into max_rsp_size and SRPT_RQ_SIZE into MAX_SRPT_RQ_SIZE.
The new names better reflect the role of this member variable and constant.
Since the prefix "srp_" is superfluous in the context of the function
that creates an RDMA channel, rename srp_sq_size into sq_size.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Avoid that warnings about missing parameter descriptions are reported
when building with W=1.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Fixes: commit a42d985b ("ib_srpt: Initial SRP Target merge for v3.3-rc1")
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Make sure that the initiator port GUID is stored in ch->ini_guid.
Note: when initiating a connection sgid and dgid members in struct
sa_path_rec represent the source and destination GIDs. When accepting
a connection however sgid represents the destination GID and dgid the
source GID.

Fixes: commit 2bce1a6d ("IB/srpt: Accept GUIDs as port names")
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>

With the SRP protocol all RDMA operations are initiated by the target.
Since no RDMA operations are initiated by the initiator, do not grant
the initiator permission to submit RDMA reads or writes to the target.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>

The use_srq configfs attribute is created after it is read. Hence
modify srpt_tpg_attrib_use_srq_store() such that this function
switches dynamically between non-SRQ and SRQ mode.
Reported-by: NMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Introduce the helper function srpt_set_enabled(). Protect
sport->enabled changes with sdev->mutex. Makes configfs writes
into 'enabled' wait until all channel resources have been freed.
Wait until channel release has finished during kernel module
unload.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Except for changing a BUG_ON() call into a WARN_ON_ONCE() call, this
patch does not change any functionality.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

The only functional change in this patch is in the srpt_add_one()
error path: if allocating the ring buffer for the SRQ fails, fall
back to non-SRQ mode instead of disabling SRP target functionality.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

IB and iWARP specs both spell out that posting a receive work request
to a queue pair in the RESET state is an invalid operation and required
to fail.  Postpone posting receive work requests until after the
transition to the INIT state.

Fixes: commit dea26209 ("IB/srpt: Change default behavior from using SRQ to using RC")
Signed-off-by: NMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Several function prototypes for the set/get functions defined by
module_param_call() have a slightly wrong argument types. This fixes
those in an effort to clean up the calls when running under type-enforced
compiler instrumentation for CFI. This is the result of running the
following semantic patch:

@match_module_param_call_function@
declarer name module_param_call;
identifier _name, _set_func, _get_func;
expression _arg, _mode;
@@

 module_param_call(_name, _set_func, _get_func, _arg, _mode);

@fix_set_prototype
 depends on match_module_param_call_function@
identifier match_module_param_call_function._set_func;
identifier _val, _param;
type _val_type, _param_type;
@@

 int _set_func(
-_val_type _val
+const char * _val
 ,
-_param_type _param
+const struct kernel_param * _param
 ) { ... }

@fix_get_prototype
 depends on match_module_param_call_function@
identifier match_module_param_call_function._get_func;
identifier _val, _param;
type _val_type, _param_type;
@@

 int _get_func(
-_val_type _val
+char * _val
 ,
-_param_type _param
+const struct kernel_param * _param
 ) { ... }

Two additional by-hand changes are included for places where the above
Coccinelle script didn't notice them:

	drivers/platform/x86/thinkpad_acpi.c
	fs/lockd/svc.c
Signed-off-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NJessica Yu <jeyu@kernel.org>

Although in the RC mode more resources are needed that mode has three
advantages over SRQ:
- It works with all RDMA adapters, even those that do not support
  SRQ.
- Posting WRs and polling WCs does not trigger lock contention
  because only one thread at a time accesses a WR or WC queue in
  non-SRQ mode.
- The end-to-end flow control mechanism is used.

>From the IB spec:

    C9-150.2.1: For QPs that are not associated with an SRQ, each HCA
    receive queue shall generate end-to-end flow control credits. If
    a QP is associated with an SRQ, the HCA receive queue shall not
    generate end-to-end flow control credits.

Add new configfs attributes that allow to configure which mode to use
(/sys/kernel/config/target/srpt/$GUID/$GUID/attrib/use_srq). Note:
only the attribute for port 1 is relevant on multi-port adapters.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

This patch is a micro-optimization for the hot path.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Additionally, correct the comment about ch->rq_size.
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Make srpt_parse_i_port_id() return a negative value if hex2bin()
fails.

Fixes: commit a42d985b ("ib_srpt: Initial SRP Target merge for v3.3-rc1")
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

The functions ib_register_event_handler() and
ib_unregister_event_handler() always returned success and they can't fail.

Let's convert those functions to be void, remove redundant checks and
cleanup tons of goto statements.
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Reviewed-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Do not only report the state of the I/O context before srpt_abort_cmd()
was called but also the new state assigned by srpt_abort_cmd()
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: David Disseldorp <ddiss@suse.de>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Avoid that the following warning is triggered:

WARNING: CPU: 10 PID: 166 at ../drivers/infiniband/ulp/srpt/ib_srpt.c:2674 srpt_release_cmd+0x139/0x140 [ib_srpt]
CPU: 10 PID: 166 Comm: kworker/u24:8 Not tainted 4.9.4-1-default #1
Workqueue: tmr-fileio target_tmr_work [target_core_mod]
Call Trace:
 [<ffffffffaa3c4f70>] dump_stack+0x63/0x83
 [<ffffffffaa0844eb>] __warn+0xcb/0xf0
 [<ffffffffaa0845dd>] warn_slowpath_null+0x1d/0x20
 [<ffffffffc06ba429>] srpt_release_cmd+0x139/0x140 [ib_srpt]
 [<ffffffffc06e4377>] target_release_cmd_kref+0xb7/0x120 [target_core_mod]
 [<ffffffffc06e4d7f>] target_put_sess_cmd+0x2f/0x60 [target_core_mod]
 [<ffffffffc06e15e0>] core_tmr_lun_reset+0x340/0x790 [target_core_mod]
 [<ffffffffc06e4816>] target_tmr_work+0xe6/0x140 [target_core_mod]
 [<ffffffffaa09e4d3>] process_one_work+0x1f3/0x4d0
 [<ffffffffaa09e7f8>] worker_thread+0x48/0x4e0
 [<ffffffffaa09e7b0>] ? process_one_work+0x4d0/0x4d0
 [<ffffffffaa0a46da>] kthread+0xca/0xe0
 [<ffffffffaa0a4610>] ? kthread_park+0x60/0x60
 [<ffffffffaa71b775>] ret_from_fork+0x25/0x30
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Disseldorp <ddiss@suse.de>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Let the target core check the CMD_T_ABORTED flag instead of the SRP
target driver. Hence remove the transport_check_aborted_status()
call. Since state == SRPT_STATE_CMD_RSP_SENT is something that really
should not happen, do not try to recover if srpt_queue_response() is
called for an I/O context that is in that state. This patch is a bug
fix because the srpt_abort_cmd() call is misplaced - if that function
is called from srpt_queue_response() it should either be called
before the command state is changed or after the response has been
sent.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: David Disseldorp <ddiss@suse.de>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Rename ib_destroy_ah to rdma_destroy_ah so its in sync with the
rename of the ib address handle attribute
Reviewed-by: NIra Weiny <ira.weiny@intel.com>
Reviewed-by: NDon Hiatt <don.hiatt@intel.com>
Reviewed-by: NSean Hefty <sean.hefty@intel.com>
Reviewed-by: NNiranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
Signed-off-by: NDasaratharaman Chandramouli <dasaratharaman.chandramouli@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Port and ACL information must be configured before an initiator
logs in.  Make it possible to configure this information before
a subnet prefix has been assigned to a port by not only accepting
GIDs as target port and initiator port names but by also accepting
port GUIDs.

Add a 'priv' member to struct se_wwn to allow target drivers to
associate their own data with struct se_wwn.
Reported-by: NDoug Ledford <dledford@redhat.com>
References: http://www.spinics.net/lists/linux-rdma/msg39505.htmlSigned-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Since a later patch will remove ib_device.dma_device and since knowing
the value of that pointer is not too important, remove dma_device from
the debug output.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Some but not all architectures provide set_dma_ops(). Move dma_ops
from struct dev_archdata into struct device such that it becomes
possible on all architectures to configure dma_ops per device.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Acked-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Russell King <linux@armlinux.org.uk>
Cc: x86@kernel.org
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Report the following message only once if no ACL has been configured
yet for an initiator port:

"Rejected login because no ACL has been configured yet for initiator %s.\n"
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@grimberg.me>
Reviewed-by: NMax Gurtovoy <maxg@mellanox.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Instead of exposing ib_get_dma_mr to ULPs and letting them use it more or
less unchecked, this moves the capability of creating a global rkey into
the RDMA core, where it can be easily audited.  It also prints a warning
everytime this feature is used as well.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

If port_guid is set with the default subnet_prefix, then we get a change
event and run a port refresh, we don't update the port_guid.  As a
result, attempts to create a target device that uses the new
subnet_prefix in the wwn will fail to find a match and be rejected by
the ib_srpt driver.  This makes it impossible to configure a port if it
was initialized with a default subnet_prefix and later changed to any
non-default subnet-prefix.  Updating the port refresh task to always
update the wwn based upon the current subnext_prefix solves this
problem.

Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: nab@linux-iscsi.org
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Initialize first_wr to &send_wr. This allows to remove a ternary
operator and an else branch. This patch does not change the behavior
of srpt_queue_response().
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Tested-by: NSteve Wise <swise@opengridcomputing.com>
Tested-by: NLaurence Oberman <loberman@redhat.com>
Cc: Parav Pandit <pandit.parav@gmail.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Limit the number of SG elements per work request to what the HCA
and the queue pair support.

Fixes: 34693573fde0 ("IB/srpt: Reduce QP buffer size")
Reported-by: NParav Pandit <pandit.parav@gmail.com>
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Steve Wise <swise@opengridcomputing.com>
Cc: Parav Pandit <pandit.parav@gmail.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: <stable@vger.kernel.org> #v4.7+
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

The memory needed for the send and receive queues associated with
a QP is proportional to the max_sge parameter. The current value
of that parameter is such that with an mlx4 HCA the QP buffer size
is 8 MB. Since DMA is used for communication between HCA and CPU
that buffer either has to be allocated coherently or map_single()
must succeed for that buffer. Since large contiguous allocations
are fragile and since the maximum segment size for e.g. swiotlb
is 256 KB, reduce the max_sge parameter. This patch avoids that
the following text appears on the console after SRP logout and
relogin on a system equipped with multiple IB HCAs:

mlx4_core 0000:05:00.0: swiotlb buffer is full (sz: 8388608 bytes)
swiotlb: coherent allocation failed for device 0000:05:00.0 size=8388608
CPU: 11 PID: 148 Comm: kworker/11:1 Not tainted 4.7.0-rc4-dbg+ #1
Call Trace:
 [<ffffffff812c6d35>] dump_stack+0x67/0x92
 [<ffffffff812efe71>] swiotlb_alloc_coherent+0x141/0x150
 [<ffffffff810458be>] x86_swiotlb_alloc_coherent+0x3e/0x50
 [<ffffffffa03861fa>] mlx4_buf_direct_alloc.isra.5+0x9a/0x120 [mlx4_core]
 [<ffffffffa0386545>] mlx4_buf_alloc+0x165/0x1a0 [mlx4_core]
 [<ffffffffa035053d>] create_qp_common.isra.29+0x57d/0xff0 [mlx4_ib]
 [<ffffffffa03510da>] mlx4_ib_create_qp+0x12a/0x3f0 [mlx4_ib]
 [<ffffffffa031154a>] ib_create_qp+0x3a/0x250 [ib_core]
 [<ffffffffa055dd4b>] srpt_cm_handler+0x4bb/0xcad [ib_srpt]
 [<ffffffffa02c1ab0>] cm_process_work+0x20/0xf0 [ib_cm]
 [<ffffffffa02c3640>] cm_work_handler+0x1ac0/0x2059 [ib_cm]
 [<ffffffff810737ed>] process_one_work+0x19d/0x490
 [<ffffffff81073b29>] worker_thread+0x49/0x490
 [<ffffffff8107a0ea>] kthread+0xea/0x100
 [<ffffffff815b25af>] ret_from_fork+0x1f/0x40

Fixes: b99f8e4d ("IB/srpt: convert to the generic RDMA READ/WRITE API")
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Change struct ib_class_port_info to conform to IB Spec 1.3
That in order to get specific capability mask from ClassPortInfo mad.

>From the IB Spec, ClassPortInfo section:
        "CapabilityMask2 Bits 0-26: Additional class-specific capabilities...
         RespTimeValue the rest 5 bits"

The new struct now has one field for capabilitymask2 (previously was the
reserved field) and the resp_time field.

And it fixes up qib and srpt, use of the field repurposed to be used as
capabilitymask2:
IB/qib: Change pma_get_classportinfo
IB/srpt: Adjust the use of ib_class_port_info
Signed-off-by: NErez Shitrit <erezsh@mellanox.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Reviewed-by: NHal Rosenstock <hal@mellanox.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Replace the homegrown RDMA READ/WRITE code in srpt with the generic API.
The only real twist here is that we need to allocate one Linux scatterlist
per direct buffer in the SRP command, and chain them before handing them
off to the target core.

As a side-effect of the conversion the driver will also chain the SEND
of the SRP response to the RDMA WRITE WRs for a DATA OUT command, and
properly account for RDMA WRITE WRs instead of just for RDMA READ WRs
like the driver previously did.

We now allocate half of the SQ size to RDMA READ/WRITE contexts, assuming
by default one RDMA READ or WRITE operation per command.  If a command
has multiple operations it will eat into the budget but will still succeed,
possible after waiting for WQEs to be available.

Also ensure the QPs request the maximum allowed SGEs so that RDMA R/W API
works correctly.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

Turns out the template and thus many drivers got the return value wrong:
0 means the fabrics driver needs to put a session reference, which no
driver except for the iSCSI target drivers did.  Fortunately none of these
drivers supports explicit Node ACLs, so the bug was harmless.

Even without that only qla2xxx and iscsi every did real work in
shutdown_session, so get rid of the boilerplate code in all other
drivers.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

This reverts commit 0fd10721.

That patch causes the ib_srpt driver to crash as soon as the first SCSI
command is received:

  kernel BUG at drivers/infiniband/ulp/srpt/ib_srpt.c:1439!
  invalid opcode: 0000 [#1] SMP
  Workqueue: target_completion target_complete_ok_work [target_core_mod]
  RIP: srpt_queue_response+0x437/0x4a0 [ib_srpt]
  Call Trace:
    srpt_queue_data_in+0x9/0x10 [ib_srpt]
    target_complete_ok_work+0x152/0x2b0 [target_core_mod]
    process_one_work+0x197/0x480
    worker_thread+0x49/0x490
    kthread+0xea/0x100
    ret_from_fork+0x22/0x40

Aside from the crash, the shortcomings of that patch are as follows:

 - It makes the ib_srpt driver use I/O contexts allocated by
   transport_alloc_session_tags() but it does not initialize these I/O
   contexts properly.  All the initializations performed by
   srpt_alloc_ioctx() are skipped.

 - It swaps the order of the send ioctx allocation and the transition to
   RTR mode which is wrong.

 - The amount of memory that is needed for I/O contexts is doubled.

 - srpt_rdma_ch.free_list is no longer used but is not removed.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The first argument of WARN_ON() is a condition, so it means the warning
message here will just be the name without the ->qp_num information.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

This patch converts ib_srpt to use existing percpu_ida tag
pre-allocation for struct srpt_send_ioctx.

This allows ib_srpt to drop it's internal pre-allocation
mechanisms with the extra spin_lock_irqsave, and use
percpu_ida common code for doing this.

Cc: Vu Pham <vu@mellanox.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>