IB/isert: Fix for lib/dma_debug check_sync warning

IB/isert: Fix for lib/dma_debug check_sync warning

The following error message occurs on a target host in a debug build
during session login:

[ 3524.411874] WARNING: CPU: 5 PID: 12063 at lib/dma-debug.c:1207 check_sync+0x4ec/0x5b0
[ 3524.421057] infiniband hfi1_0: DMA-API: device driver tries to sync DMA memory it has not allocated [device address=0x0000000000000000] [size=76 bytes]
......snip .....

[ 3524.535846] CPU: 5 PID: 12063 Comm: iscsi_np Kdump: loaded Not tainted 3.10.0-862.el7.x86_64.debug #1
[ 3524.546764] Hardware name: Dell Inc. PowerEdge R430/03XKDV, BIOS 1.2.6 06/08/2015
[ 3524.555740] Call Trace:
[ 3524.559102]  [<ffffffffa5fe915b>] dump_stack+0x19/0x1b
[ 3524.565477]  [<ffffffffa58a2f58>] __warn+0xd8/0x100
[ 3524.571557]  [<ffffffffa58a2fdf>] warn_slowpath_fmt+0x5f/0x80
[ 3524.578610]  [<ffffffffa5bf5b8c>] check_sync+0x4ec/0x5b0
[ 3524.585177]  [<ffffffffa58efc3f>] ? set_cpus_allowed_ptr+0x5f/0x1c0
[ 3524.592812]  [<ffffffffa5bf5cd0>] debug_dma_sync_single_for_cpu+0x80/0x90
[ 3524.601029]  [<ffffffffa586add3>] ? x2apic_send_IPI_mask+0x13/0x20
[ 3524.608574]  [<ffffffffa585ee1b>] ? native_smp_send_reschedule+0x5b/0x80
[ 3524.616699]  [<ffffffffa58e9b76>] ? resched_curr+0xf6/0x140
[ 3524.623567]  [<ffffffffc0879af0>] isert_create_send_desc.isra.26+0xe0/0x110 [ib_isert]
[ 3524.633060]  [<ffffffffc087af95>] isert_put_login_tx+0x55/0x8b0 [ib_isert]
[ 3524.641383]  [<ffffffffa58ef114>] ? try_to_wake_up+0x1a4/0x430
[ 3524.648561]  [<ffffffffc098cfed>] iscsi_target_do_tx_login_io+0xdd/0x230 [iscsi_target_mod]
[ 3524.658557]  [<ffffffffc098d827>] iscsi_target_do_login+0x1a7/0x600 [iscsi_target_mod]
[ 3524.668084]  [<ffffffffa59f9bc9>] ? kstrdup+0x49/0x60
[ 3524.674420]  [<ffffffffc098e976>] iscsi_target_start_negotiation+0x56/0xc0 [iscsi_target_mod]
[ 3524.684656]  [<ffffffffc098c2ee>] __iscsi_target_login_thread+0x90e/0x1070 [iscsi_target_mod]
[ 3524.694901]  [<ffffffffc098ca50>] ? __iscsi_target_login_thread+0x1070/0x1070 [iscsi_target_mod]
[ 3524.705446]  [<ffffffffc098ca50>] ? __iscsi_target_login_thread+0x1070/0x1070 [iscsi_target_mod]
[ 3524.715976]  [<ffffffffc098ca78>] iscsi_target_login_thread+0x28/0x60 [iscsi_target_mod]
[ 3524.725739]  [<ffffffffa58d60ff>] kthread+0xef/0x100
[ 3524.732007]  [<ffffffffa58d6010>] ? insert_kthread_work+0x80/0x80
[ 3524.739540]  [<ffffffffa5fff1b7>] ret_from_fork_nospec_begin+0x21/0x21
[ 3524.747558]  [<ffffffffa58d6010>] ? insert_kthread_work+0x80/0x80
[ 3524.755088] ---[ end trace 23f8bf9238bd1ed8 ]---
[ 3595.510822] iSCSI/iqn.1994-05.com.redhat:537fa56299: Unsupported SCSI Opcode 0xa3, sending CHECK_CONDITION.

The code calls dma_sync on login_tx_desc->dma_addr prior to initializing it
with dma-mapped address.
login_tx_desc is a part of iser_conn structure and is used only once
during login negotiation, so the issue is fixed by eliminating
dma_sync call for this buffer using a special case routine.

Cc: <stable@vger.kernel.org>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Don Dutile <ddutile@redhat.com>
Signed-off-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>