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1/*******************************************************************************
2 * Filename: target_core_ua.c
3 *
4 * This file contains logic for SPC-3 Unit Attention emulation
5 *
6 * Copyright (c) 2009,2010 Rising Tide Systems
7 * Copyright (c) 2009,2010 Linux-iSCSI.org
8 *
9 * Nicholas A. Bellinger <nab@kernel.org>
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation; either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 *
25 ******************************************************************************/
26
27#include <linux/version.h>
28#include <linux/slab.h>
29#include <linux/spinlock.h>
30#include <scsi/scsi.h>
31#include <scsi/scsi_cmnd.h>
32
33#include <target/target_core_base.h>
34#include <target/target_core_device.h>
35#include <target/target_core_transport.h>
36#include <target/target_core_fabric_ops.h>
37#include <target/target_core_configfs.h>
38
39#include "target_core_alua.h"
40#include "target_core_hba.h"
41#include "target_core_pr.h"
42#include "target_core_ua.h"
43
44int core_scsi3_ua_check(
45 struct se_cmd *cmd,
46 unsigned char *cdb)
47{
48 struct se_dev_entry *deve;
49 struct se_session *sess = cmd->se_sess;
50 struct se_node_acl *nacl;
51
52 if (!sess)
53 return 0;
54
55 nacl = sess->se_node_acl;
56 if (!nacl)
57 return 0;
58
59 deve = &nacl->device_list[cmd->orig_fe_lun];
60 if (!atomic_read(&deve->ua_count))
61 return 0;
62 /*
63 * From sam4r14, section 5.14 Unit attention condition:
64 *
65 * a) if an INQUIRY command enters the enabled command state, the
66 * device server shall process the INQUIRY command and shall neither
67 * report nor clear any unit attention condition;
68 * b) if a REPORT LUNS command enters the enabled command state, the
69 * device server shall process the REPORT LUNS command and shall not
70 * report any unit attention condition;
71 * e) if a REQUEST SENSE command enters the enabled command state while
72 * a unit attention condition exists for the SCSI initiator port
73 * associated with the I_T nexus on which the REQUEST SENSE command
74 * was received, then the device server shall process the command
75 * and either:
76 */
77 switch (cdb[0]) {
78 case INQUIRY:
79 case REPORT_LUNS:
80 case REQUEST_SENSE:
81 return 0;
82 default:
83 return -EINVAL;
84 }
85
86 return -EINVAL;
87}
88
89int core_scsi3_ua_allocate(
90 struct se_node_acl *nacl,
91 u32 unpacked_lun,
92 u8 asc,
93 u8 ascq)
94{
95 struct se_dev_entry *deve;
96 struct se_ua *ua, *ua_p, *ua_tmp;
97 /*
98 * PASSTHROUGH OPS
99 */
100 if (!nacl)
101 return -EINVAL;
102
103 ua = kmem_cache_zalloc(se_ua_cache, GFP_ATOMIC);
104 if (!ua) {
105 pr_err("Unable to allocate struct se_ua\n");
106 return -ENOMEM;
107 }
108 INIT_LIST_HEAD(&ua->ua_dev_list);
109 INIT_LIST_HEAD(&ua->ua_nacl_list);
110
111 ua->ua_nacl = nacl;
112 ua->ua_asc = asc;
113 ua->ua_ascq = ascq;
114
115 spin_lock_irq(&nacl->device_list_lock);
116 deve = &nacl->device_list[unpacked_lun];
117
118 spin_lock(&deve->ua_lock);
119 list_for_each_entry_safe(ua_p, ua_tmp, &deve->ua_list, ua_nacl_list) {
120 /*
121 * Do not report the same UNIT ATTENTION twice..
122 */
123 if ((ua_p->ua_asc == asc) && (ua_p->ua_ascq == ascq)) {
124 spin_unlock(&deve->ua_lock);
125 spin_unlock_irq(&nacl->device_list_lock);
126 kmem_cache_free(se_ua_cache, ua);
127 return 0;
128 }
129 /*
130 * Attach the highest priority Unit Attention to
131 * the head of the list following sam4r14,
132 * Section 5.14 Unit Attention Condition:
133 *
134 * POWER ON, RESET, OR BUS DEVICE RESET OCCURRED highest
135 * POWER ON OCCURRED or
136 * DEVICE INTERNAL RESET
137 * SCSI BUS RESET OCCURRED or
138 * MICROCODE HAS BEEN CHANGED or
139 * protocol specific
140 * BUS DEVICE RESET FUNCTION OCCURRED
141 * I_T NEXUS LOSS OCCURRED
142 * COMMANDS CLEARED BY POWER LOSS NOTIFICATION
143 * all others Lowest
144 *
145 * Each of the ASCQ codes listed above are defined in
146 * the 29h ASC family, see spc4r17 Table D.1
147 */
148 if (ua_p->ua_asc == 0x29) {
149 if ((asc == 0x29) && (ascq > ua_p->ua_ascq))
150 list_add(&ua->ua_nacl_list,
151 &deve->ua_list);
152 else
153 list_add_tail(&ua->ua_nacl_list,
154 &deve->ua_list);
155 } else if (ua_p->ua_asc == 0x2a) {
156 /*
157 * Incoming Family 29h ASCQ codes will override
158 * Family 2AHh ASCQ codes for Unit Attention condition.
159 */
160 if ((asc == 0x29) || (ascq > ua_p->ua_asc))
161 list_add(&ua->ua_nacl_list,
162 &deve->ua_list);
163 else
164 list_add_tail(&ua->ua_nacl_list,
165 &deve->ua_list);
166 } else
167 list_add_tail(&ua->ua_nacl_list,
168 &deve->ua_list);
169 spin_unlock(&deve->ua_lock);
170 spin_unlock_irq(&nacl->device_list_lock);
171
172 atomic_inc(&deve->ua_count);
173 smp_mb__after_atomic_inc();
174 return 0;
175 }
176 list_add_tail(&ua->ua_nacl_list, &deve->ua_list);
177 spin_unlock(&deve->ua_lock);
178 spin_unlock_irq(&nacl->device_list_lock);
179
180 pr_debug("[%s]: Allocated UNIT ATTENTION, mapped LUN: %u, ASC:"
181 " 0x%02x, ASCQ: 0x%02x\n",
182 nacl->se_tpg->se_tpg_tfo->get_fabric_name(), unpacked_lun,
183 asc, ascq);
184
185 atomic_inc(&deve->ua_count);
186 smp_mb__after_atomic_inc();
187 return 0;
188}
189
190void core_scsi3_ua_release_all(
191 struct se_dev_entry *deve)
192{
193 struct se_ua *ua, *ua_p;
194
195 spin_lock(&deve->ua_lock);
196 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
197 list_del(&ua->ua_nacl_list);
198 kmem_cache_free(se_ua_cache, ua);
199
200 atomic_dec(&deve->ua_count);
201 smp_mb__after_atomic_dec();
202 }
203 spin_unlock(&deve->ua_lock);
204}
205
206void core_scsi3_ua_for_check_condition(
207 struct se_cmd *cmd,
208 u8 *asc,
209 u8 *ascq)
210{
211 struct se_device *dev = cmd->se_dev;
212 struct se_dev_entry *deve;
213 struct se_session *sess = cmd->se_sess;
214 struct se_node_acl *nacl;
215 struct se_ua *ua = NULL, *ua_p;
216 int head = 1;
217
218 if (!sess)
219 return;
220
221 nacl = sess->se_node_acl;
222 if (!nacl)
223 return;
224
225 spin_lock_irq(&nacl->device_list_lock);
226 deve = &nacl->device_list[cmd->orig_fe_lun];
227 if (!atomic_read(&deve->ua_count)) {
228 spin_unlock_irq(&nacl->device_list_lock);
229 return;
230 }
231 /*
232 * The highest priority Unit Attentions are placed at the head of the
233 * struct se_dev_entry->ua_list, and will be returned in CHECK_CONDITION +
234 * sense data for the received CDB.
235 */
236 spin_lock(&deve->ua_lock);
237 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
238 /*
239 * For ua_intlck_ctrl code not equal to 00b, only report the
240 * highest priority UNIT_ATTENTION and ASC/ASCQ without
241 * clearing it.
242 */
243 if (dev->se_sub_dev->se_dev_attrib.emulate_ua_intlck_ctrl != 0) {
244 *asc = ua->ua_asc;
245 *ascq = ua->ua_ascq;
246 break;
247 }
248 /*
249 * Otherwise for the default 00b, release the UNIT ATTENTION
250 * condition. Return the ASC/ASCQ of the highest priority UA
251 * (head of the list) in the outgoing CHECK_CONDITION + sense.
252 */
253 if (head) {
254 *asc = ua->ua_asc;
255 *ascq = ua->ua_ascq;
256 head = 0;
257 }
258 list_del(&ua->ua_nacl_list);
259 kmem_cache_free(se_ua_cache, ua);
260
261 atomic_dec(&deve->ua_count);
262 smp_mb__after_atomic_dec();
263 }
264 spin_unlock(&deve->ua_lock);
265 spin_unlock_irq(&nacl->device_list_lock);
266
267 pr_debug("[%s]: %s UNIT ATTENTION condition with"
268 " INTLCK_CTRL: %d, mapped LUN: %u, got CDB: 0x%02x"
269 " reported ASC: 0x%02x, ASCQ: 0x%02x\n",
270 nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
271 (dev->se_sub_dev->se_dev_attrib.emulate_ua_intlck_ctrl != 0) ? "Reporting" :
272 "Releasing", dev->se_sub_dev->se_dev_attrib.emulate_ua_intlck_ctrl,
273 cmd->orig_fe_lun, cmd->t_task_cdb[0], *asc, *ascq);
274}
275
276int core_scsi3_ua_clear_for_request_sense(
277 struct se_cmd *cmd,
278 u8 *asc,
279 u8 *ascq)
280{
281 struct se_dev_entry *deve;
282 struct se_session *sess = cmd->se_sess;
283 struct se_node_acl *nacl;
284 struct se_ua *ua = NULL, *ua_p;
285 int head = 1;
286
287 if (!sess)
288 return -EINVAL;
289
290 nacl = sess->se_node_acl;
291 if (!nacl)
292 return -EINVAL;
293
294 spin_lock_irq(&nacl->device_list_lock);
295 deve = &nacl->device_list[cmd->orig_fe_lun];
296 if (!atomic_read(&deve->ua_count)) {
297 spin_unlock_irq(&nacl->device_list_lock);
298 return -EPERM;
299 }
300 /*
301 * The highest priority Unit Attentions are placed at the head of the
302 * struct se_dev_entry->ua_list. The First (and hence highest priority)
303 * ASC/ASCQ will be returned in REQUEST_SENSE payload data for the
304 * matching struct se_lun.
305 *
306 * Once the returning ASC/ASCQ values are set, we go ahead and
307 * release all of the Unit Attention conditions for the associated
308 * struct se_lun.
309 */
310 spin_lock(&deve->ua_lock);
311 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
312 if (head) {
313 *asc = ua->ua_asc;
314 *ascq = ua->ua_ascq;
315 head = 0;
316 }
317 list_del(&ua->ua_nacl_list);
318 kmem_cache_free(se_ua_cache, ua);
319
320 atomic_dec(&deve->ua_count);
321 smp_mb__after_atomic_dec();
322 }
323 spin_unlock(&deve->ua_lock);
324 spin_unlock_irq(&nacl->device_list_lock);
325
326 pr_debug("[%s]: Released UNIT ATTENTION condition, mapped"
327 " LUN: %u, got REQUEST_SENSE reported ASC: 0x%02x,"
328 " ASCQ: 0x%02x\n", nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
329 cmd->orig_fe_lun, *asc, *ascq);
330
331 return (head) ? -EPERM : 0;
332}
1/*******************************************************************************
2 * Filename: target_core_ua.c
3 *
4 * This file contains logic for SPC-3 Unit Attention emulation
5 *
6 * (c) Copyright 2009-2013 Datera, Inc.
7 *
8 * Nicholas A. Bellinger <nab@kernel.org>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
23 *
24 ******************************************************************************/
25
26#include <linux/slab.h>
27#include <linux/spinlock.h>
28#include <scsi/scsi_proto.h>
29
30#include <target/target_core_base.h>
31#include <target/target_core_fabric.h>
32
33#include "target_core_internal.h"
34#include "target_core_alua.h"
35#include "target_core_pr.h"
36#include "target_core_ua.h"
37
38sense_reason_t
39target_scsi3_ua_check(struct se_cmd *cmd)
40{
41 struct se_dev_entry *deve;
42 struct se_session *sess = cmd->se_sess;
43 struct se_node_acl *nacl;
44
45 if (!sess)
46 return 0;
47
48 nacl = sess->se_node_acl;
49 if (!nacl)
50 return 0;
51
52 rcu_read_lock();
53 deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
54 if (!deve) {
55 rcu_read_unlock();
56 return 0;
57 }
58 if (!atomic_read(&deve->ua_count)) {
59 rcu_read_unlock();
60 return 0;
61 }
62 rcu_read_unlock();
63 /*
64 * From sam4r14, section 5.14 Unit attention condition:
65 *
66 * a) if an INQUIRY command enters the enabled command state, the
67 * device server shall process the INQUIRY command and shall neither
68 * report nor clear any unit attention condition;
69 * b) if a REPORT LUNS command enters the enabled command state, the
70 * device server shall process the REPORT LUNS command and shall not
71 * report any unit attention condition;
72 * e) if a REQUEST SENSE command enters the enabled command state while
73 * a unit attention condition exists for the SCSI initiator port
74 * associated with the I_T nexus on which the REQUEST SENSE command
75 * was received, then the device server shall process the command
76 * and either:
77 */
78 switch (cmd->t_task_cdb[0]) {
79 case INQUIRY:
80 case REPORT_LUNS:
81 case REQUEST_SENSE:
82 return 0;
83 default:
84 return TCM_CHECK_CONDITION_UNIT_ATTENTION;
85 }
86}
87
88int core_scsi3_ua_allocate(
89 struct se_dev_entry *deve,
90 u8 asc,
91 u8 ascq)
92{
93 struct se_ua *ua, *ua_p, *ua_tmp;
94
95 ua = kmem_cache_zalloc(se_ua_cache, GFP_ATOMIC);
96 if (!ua) {
97 pr_err("Unable to allocate struct se_ua\n");
98 return -ENOMEM;
99 }
100 INIT_LIST_HEAD(&ua->ua_nacl_list);
101
102 ua->ua_asc = asc;
103 ua->ua_ascq = ascq;
104
105 spin_lock(&deve->ua_lock);
106 list_for_each_entry_safe(ua_p, ua_tmp, &deve->ua_list, ua_nacl_list) {
107 /*
108 * Do not report the same UNIT ATTENTION twice..
109 */
110 if ((ua_p->ua_asc == asc) && (ua_p->ua_ascq == ascq)) {
111 spin_unlock(&deve->ua_lock);
112 kmem_cache_free(se_ua_cache, ua);
113 return 0;
114 }
115 /*
116 * Attach the highest priority Unit Attention to
117 * the head of the list following sam4r14,
118 * Section 5.14 Unit Attention Condition:
119 *
120 * POWER ON, RESET, OR BUS DEVICE RESET OCCURRED highest
121 * POWER ON OCCURRED or
122 * DEVICE INTERNAL RESET
123 * SCSI BUS RESET OCCURRED or
124 * MICROCODE HAS BEEN CHANGED or
125 * protocol specific
126 * BUS DEVICE RESET FUNCTION OCCURRED
127 * I_T NEXUS LOSS OCCURRED
128 * COMMANDS CLEARED BY POWER LOSS NOTIFICATION
129 * all others Lowest
130 *
131 * Each of the ASCQ codes listed above are defined in
132 * the 29h ASC family, see spc4r17 Table D.1
133 */
134 if (ua_p->ua_asc == 0x29) {
135 if ((asc == 0x29) && (ascq > ua_p->ua_ascq))
136 list_add(&ua->ua_nacl_list,
137 &deve->ua_list);
138 else
139 list_add_tail(&ua->ua_nacl_list,
140 &deve->ua_list);
141 } else if (ua_p->ua_asc == 0x2a) {
142 /*
143 * Incoming Family 29h ASCQ codes will override
144 * Family 2AHh ASCQ codes for Unit Attention condition.
145 */
146 if ((asc == 0x29) || (ascq > ua_p->ua_asc))
147 list_add(&ua->ua_nacl_list,
148 &deve->ua_list);
149 else
150 list_add_tail(&ua->ua_nacl_list,
151 &deve->ua_list);
152 } else
153 list_add_tail(&ua->ua_nacl_list,
154 &deve->ua_list);
155 spin_unlock(&deve->ua_lock);
156
157 atomic_inc_mb(&deve->ua_count);
158 return 0;
159 }
160 list_add_tail(&ua->ua_nacl_list, &deve->ua_list);
161 spin_unlock(&deve->ua_lock);
162
163 pr_debug("Allocated UNIT ATTENTION, mapped LUN: %llu, ASC:"
164 " 0x%02x, ASCQ: 0x%02x\n", deve->mapped_lun,
165 asc, ascq);
166
167 atomic_inc_mb(&deve->ua_count);
168 return 0;
169}
170
171void target_ua_allocate_lun(struct se_node_acl *nacl,
172 u32 unpacked_lun, u8 asc, u8 ascq)
173{
174 struct se_dev_entry *deve;
175
176 if (!nacl)
177 return;
178
179 rcu_read_lock();
180 deve = target_nacl_find_deve(nacl, unpacked_lun);
181 if (!deve) {
182 rcu_read_unlock();
183 return;
184 }
185
186 core_scsi3_ua_allocate(deve, asc, ascq);
187 rcu_read_unlock();
188}
189
190void core_scsi3_ua_release_all(
191 struct se_dev_entry *deve)
192{
193 struct se_ua *ua, *ua_p;
194
195 spin_lock(&deve->ua_lock);
196 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
197 list_del(&ua->ua_nacl_list);
198 kmem_cache_free(se_ua_cache, ua);
199
200 atomic_dec_mb(&deve->ua_count);
201 }
202 spin_unlock(&deve->ua_lock);
203}
204
205void core_scsi3_ua_for_check_condition(
206 struct se_cmd *cmd,
207 u8 *asc,
208 u8 *ascq)
209{
210 struct se_device *dev = cmd->se_dev;
211 struct se_dev_entry *deve;
212 struct se_session *sess = cmd->se_sess;
213 struct se_node_acl *nacl;
214 struct se_ua *ua = NULL, *ua_p;
215 int head = 1;
216
217 if (!sess)
218 return;
219
220 nacl = sess->se_node_acl;
221 if (!nacl)
222 return;
223
224 rcu_read_lock();
225 deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
226 if (!deve) {
227 rcu_read_unlock();
228 return;
229 }
230 if (!atomic_read(&deve->ua_count)) {
231 rcu_read_unlock();
232 return;
233 }
234 /*
235 * The highest priority Unit Attentions are placed at the head of the
236 * struct se_dev_entry->ua_list, and will be returned in CHECK_CONDITION +
237 * sense data for the received CDB.
238 */
239 spin_lock(&deve->ua_lock);
240 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
241 /*
242 * For ua_intlck_ctrl code not equal to 00b, only report the
243 * highest priority UNIT_ATTENTION and ASC/ASCQ without
244 * clearing it.
245 */
246 if (dev->dev_attrib.emulate_ua_intlck_ctrl != 0) {
247 *asc = ua->ua_asc;
248 *ascq = ua->ua_ascq;
249 break;
250 }
251 /*
252 * Otherwise for the default 00b, release the UNIT ATTENTION
253 * condition. Return the ASC/ASCQ of the highest priority UA
254 * (head of the list) in the outgoing CHECK_CONDITION + sense.
255 */
256 if (head) {
257 *asc = ua->ua_asc;
258 *ascq = ua->ua_ascq;
259 head = 0;
260 }
261 list_del(&ua->ua_nacl_list);
262 kmem_cache_free(se_ua_cache, ua);
263
264 atomic_dec_mb(&deve->ua_count);
265 }
266 spin_unlock(&deve->ua_lock);
267 rcu_read_unlock();
268
269 pr_debug("[%s]: %s UNIT ATTENTION condition with"
270 " INTLCK_CTRL: %d, mapped LUN: %llu, got CDB: 0x%02x"
271 " reported ASC: 0x%02x, ASCQ: 0x%02x\n",
272 nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
273 (dev->dev_attrib.emulate_ua_intlck_ctrl != 0) ? "Reporting" :
274 "Releasing", dev->dev_attrib.emulate_ua_intlck_ctrl,
275 cmd->orig_fe_lun, cmd->t_task_cdb[0], *asc, *ascq);
276}
277
278int core_scsi3_ua_clear_for_request_sense(
279 struct se_cmd *cmd,
280 u8 *asc,
281 u8 *ascq)
282{
283 struct se_dev_entry *deve;
284 struct se_session *sess = cmd->se_sess;
285 struct se_node_acl *nacl;
286 struct se_ua *ua = NULL, *ua_p;
287 int head = 1;
288
289 if (!sess)
290 return -EINVAL;
291
292 nacl = sess->se_node_acl;
293 if (!nacl)
294 return -EINVAL;
295
296 rcu_read_lock();
297 deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
298 if (!deve) {
299 rcu_read_unlock();
300 return -EINVAL;
301 }
302 if (!atomic_read(&deve->ua_count)) {
303 rcu_read_unlock();
304 return -EPERM;
305 }
306 /*
307 * The highest priority Unit Attentions are placed at the head of the
308 * struct se_dev_entry->ua_list. The First (and hence highest priority)
309 * ASC/ASCQ will be returned in REQUEST_SENSE payload data for the
310 * matching struct se_lun.
311 *
312 * Once the returning ASC/ASCQ values are set, we go ahead and
313 * release all of the Unit Attention conditions for the associated
314 * struct se_lun.
315 */
316 spin_lock(&deve->ua_lock);
317 list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
318 if (head) {
319 *asc = ua->ua_asc;
320 *ascq = ua->ua_ascq;
321 head = 0;
322 }
323 list_del(&ua->ua_nacl_list);
324 kmem_cache_free(se_ua_cache, ua);
325
326 atomic_dec_mb(&deve->ua_count);
327 }
328 spin_unlock(&deve->ua_lock);
329 rcu_read_unlock();
330
331 pr_debug("[%s]: Released UNIT ATTENTION condition, mapped"
332 " LUN: %llu, got REQUEST_SENSE reported ASC: 0x%02x,"
333 " ASCQ: 0x%02x\n", nacl->se_tpg->se_tpg_tfo->get_fabric_name(),
334 cmd->orig_fe_lun, *asc, *ascq);
335
336 return (head) ? -EPERM : 0;
337}