LU-6020 gss: properly map buffers to sg

LU-6020 gss: properly map buffers to sg

A lot of buffer pointers passed to buf_to_sg() as input are coming
from vmalloc(), e.g. OBD_ALLOC_LARGE() in ptlrpc_add_rqs_to_pool().
sg_set_buf() uses virt_to_page() to map virtual addresses to
struct page, which does not work for vmalloc addresses.

The original code for buf_to_sg() caused the following crash:

BUG: unable to handle kernel paging request at ffffeb040057c040
IP: [<ffffffff81300367>] scatterwalk_pagedone+0x27/0x70
PGD 0
Oops: 0000 [#1] SMP
CPU 1
Pid: 2374, comm: ptlrpcd_3 Tainted: G           O 3.6.10-030610-generic
RIP: 0010:[<ffffffff81300367>]  [<ffffffff81300367>] scatterwalk_pagedone+0x27/0x70
RSP: 0018:ffff8801a3c178a8  EFLAGS: 00010282
RAX: ffffeb040057c040 RBX: ffff8801a3c17938 RCX: ffffeb040057c040
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801a3c17970
RBP: ffff8801a3c178a8 R08: 00000000000005a8 R09: ffff8801a3c17a40
R10: ffff8801a30370d0 R11: 0000000000000a68 R12: 0000000000000010
R13: ffff8801a3c17a08 R14: ffff8801a3c17970 R15: ffff88017d1c2c80
FS:  0000000000000000(0000) GS:ffff8801afa40000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffffeb040057c040 CR3: 0000000001c0c000 CR4: 00000000001407e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process ptlrpcd_3 (pid: 2374, threadinfo ffff8801a3c16000, task ffff8801a44e0000)
Stack:
 ffff8801a3c178b8 ffffffff813004bd ffff8801a3c17908 ffffffff8130303f
 ffff880100000000 ffffffff00000000 ffff8801a3c17908 ffff8801a3c17b18
 ffffc90015f015a8 0000000000000000 0000000000000010 0000000000000010
Call Trace:
 [<ffffffff813004bd>] scatterwalk_done+0x3d/0x50
 [<ffffffff8130303f>] blkcipher_walk_done+0x8f/0x230
 [<ffffffff8130a39f>] crypto_cbc_encrypt+0xff/0x190
 [<ffffffffa0688660>] ? aes_decrypt+0x80/0x80 [aesni_intel]
 [<ffffffffa0a1a1e4>] krb5_encrypt_bulk+0x164/0x5b0 [ptlrpc_gss]
 [<ffffffffa0a1a812>] gss_wrap_bulk_kerberos+0x1e2/0x490 [ptlrpc_gss]
 [<ffffffffa0a1600e>] lgss_wrap_bulk+0x2e/0x100 [ptlrpc_gss]
 [<ffffffffa0a0d98e>] gss_cli_ctx_wrap_bulk+0x44e/0x650 [ptlrpc_gss]
 [<ffffffffa0ab867c>] sptlrpc_cli_wrap_bulk+0x3c/0x70 [ptlrpc]
 [<ffffffffa0aba2d0>] sptlrpc_cli_wrap_request+0x60/0x360 [ptlrpc]
 [<ffffffffa0a8cde4>] ptl_send_rpc+0x164/0xc30 [ptlrpc]
 [<ffffffffa07be957>] ? libcfs_debug_msg+0x47/0x50 [libcfs]
 [<ffffffffa0a80ee0>] ptlrpc_send_new_req+0x3b0/0x940 [ptlrpc]
 [<ffffffffa0a86530>] ptlrpc_check_set+0x8e0/0x1d50 [ptlrpc]
 [<ffffffff816ac9f6>] ? schedule_timeout+0x146/0x260
 [<ffffffffa0ab0c9b>] ptlrpcd_check+0x4eb/0x5d0 [ptlrpc]
 [<ffffffffa0ab105f>] ptlrpcd+0x2df/0x420 [ptlrpc]
 [<ffffffff8108efa0>] ? try_to_wake_up+0x200/0x200
 [<ffffffffa0ab0d80>] ? ptlrpcd_check+0x5d0/0x5d0 [ptlrpc]
 [<ffffffff8107c5f3>] kthread+0x93/0xa0
 [<ffffffff816b8d04>] kernel_thread_helper+0x4/0x10
 [<ffffffff8107c560>] ? flush_kthread_worker+0xb0/0xb0
 [<ffffffff816b8d00>] ? gs_change+0x13/0x13

Change-Id: I346d50568b65ed10da2762ca34562fc2858a05d8
Signed-off-by: Andrew Perepechko <andrew.perepechko@seagate.com>
Xyratex-bug-id: SNT-15
Reviewed-on: http://review.whamcloud.com/17319
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>