staging/lustre/ofd: refill env in ofd_get_info

Because ofd_get_info(KEY_FIEMAP) might be called from
ptlrpc_server_handle_req_in(see the stack below),
where env might not be initialized correctly(see LBUG below),
so it refill refill in ofd_get_info.

LutreError: 19182:0:(ofd_internal.h:518:ofd_info_init()) LBUG
Pid: 19182, comm: ll_ost_io00_001
Call Trace:
[<ffffffffa044e895>] libcfs_debug_dumpstack+0x55/0x80 [libcfs]
[<ffffffffa044ee97>] lbug_with_loc+0x47/0xb0 [libcfs]
[<ffffffffa0e03e62>] ofd_info_init+0x92/0x130 [ofd]
[<ffffffffa0e05835>] ofd_get_info+0x2e5/0xa90 [ofd]
[<ffffffff812805cd>] ? pointer+0x8d/0x830
[<ffffffffa029f7e5>] ? lprocfs_counter_add+0x125/0x182 [lvfs]
[<ffffffffa078528a>] nrs_orr_range_fill_physical+0x18a/0x540
[ptlrpc]
[<ffffffffa0762dd6>] ? __req_capsule_get+0x166/0x700 [ptlrpc]
[<ffffffffa073e630>] ? lustre_swab_ost_body+0x0/0x10 [ptlrpc]
[<ffffffffa07871d7>] nrs_orr_res_get+0x817/0xb80 [ptlrpc]
[<ffffffffa077d306>] nrs_resource_get+0x56/0x110 [ptlrpc]
[<ffffffffa077dccb>] nrs_resource_get_safe+0x8b/0x100 [ptlrpc]
[<ffffffffa0780248>] ptlrpc_nrs_req_initialize+0x38/0x90 [ptlrpc]
[<ffffffffa074cff0>] ptlrpc_main+0x1170/0x16f0 [ptlrpc]
[<ffffffffa074be80>] ? ptlrpc_main+0x0/0x16f0 [ptlrpc]
[<ffffffff8100c0ca>] child_rip+0xa/0x20
[<ffffffffa074be80>] ? ptlrpc_main+0x0/0x16f0 [ptlrpc]
[<ffffffffa074be80>] ? ptlrpc_main+0x0/0x16f0 [ptlrpc]
[<ffffffff8100c0c0>] ? child_rip+0x0/0x20

[picked ptlrpc part for upstream kernel submission]
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3239
Lustre-change: http://review.whamcloud.com/6204Signed-off-by: wang di <di.wang@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Nikitas Angelinas <nikitas_angelinas@xyratex.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ptlrpc/service.c

@@ -2396,6 +2396,7 @@ static int ptlrpc_main(void *arg)
 		/* Process all incoming reqs before handling any */
 		if (ptlrpc_server_request_incoming(svcpt)) {
 			lu_context_enter(&env->le_ctx);
+			env->le_ses = NULL;
 			ptlrpc_server_handle_req_in(svcpt, thread);
 			lu_context_exit(&env->le_ctx);