/* * Generic SCSI-3 ALUA SCSI Device Handler * * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH. * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * */ #include #include #include #include #include #include #include #include #define ALUA_DH_NAME "alua" #define ALUA_DH_VER "1.3" #define TPGS_STATE_OPTIMIZED 0x0 #define TPGS_STATE_NONOPTIMIZED 0x1 #define TPGS_STATE_STANDBY 0x2 #define TPGS_STATE_UNAVAILABLE 0x3 #define TPGS_STATE_LBA_DEPENDENT 0x4 #define TPGS_STATE_OFFLINE 0xe #define TPGS_STATE_TRANSITIONING 0xf #define TPGS_SUPPORT_NONE 0x00 #define TPGS_SUPPORT_OPTIMIZED 0x01 #define TPGS_SUPPORT_NONOPTIMIZED 0x02 #define TPGS_SUPPORT_STANDBY 0x04 #define TPGS_SUPPORT_UNAVAILABLE 0x08 #define TPGS_SUPPORT_LBA_DEPENDENT 0x10 #define TPGS_SUPPORT_OFFLINE 0x40 #define TPGS_SUPPORT_TRANSITION 0x80 #define RTPG_FMT_MASK 0x70 #define RTPG_FMT_EXT_HDR 0x10 #define TPGS_MODE_UNINITIALIZED -1 #define TPGS_MODE_NONE 0x0 #define TPGS_MODE_IMPLICIT 0x1 #define TPGS_MODE_EXPLICIT 0x2 #define ALUA_RTPG_SIZE 128 #define ALUA_FAILOVER_TIMEOUT 60 #define ALUA_FAILOVER_RETRIES 5 /* device handler flags */ #define ALUA_OPTIMIZE_STPG 1 #define ALUA_RTPG_EXT_HDR_UNSUPP 2 static uint optimize_stpg; module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR); MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0."); static LIST_HEAD(port_group_list); static DEFINE_SPINLOCK(port_group_lock); struct alua_port_group { struct kref kref; struct list_head node; unsigned char device_id_str[256]; int device_id_len; int group_id; int tpgs; int state; int pref; unsigned flags; /* used for optimizing STPG */ unsigned char transition_tmo; }; struct alua_dh_data { struct alua_port_group *pg; int group_id; struct scsi_device *sdev; activate_complete callback_fn; void *callback_data; }; #define ALUA_POLICY_SWITCH_CURRENT 0 #define ALUA_POLICY_SWITCH_ALL 1 static int alua_rtpg(struct scsi_device *, struct alua_port_group *); static char print_alua_state(int); static void release_port_group(struct kref *kref) { struct alua_port_group *pg; pg = container_of(kref, struct alua_port_group, kref); spin_lock(&port_group_lock); list_del(&pg->node); spin_unlock(&port_group_lock); kfree(pg); } /* * submit_rtpg - Issue a REPORT TARGET GROUP STATES command * @sdev: sdev the command should be sent to */ static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff, int bufflen, struct scsi_sense_hdr *sshdr, int flags) { u8 cdb[COMMAND_SIZE(MAINTENANCE_IN)]; int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER; /* Prepare the command. */ memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_IN)); cdb[0] = MAINTENANCE_IN; if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP)) cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT; else cdb[1] = MI_REPORT_TARGET_PGS; put_unaligned_be32(bufflen, &cdb[6]); return scsi_execute_req_flags(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, sshdr, ALUA_FAILOVER_TIMEOUT * HZ, ALUA_FAILOVER_RETRIES, NULL, req_flags); } /* * submit_stpg - Issue a SET TARGET PORT GROUP command * * Currently we're only setting the current target port group state * to 'active/optimized' and let the array firmware figure out * the states of the remaining groups. */ static int submit_stpg(struct scsi_device *sdev, int group_id, struct scsi_sense_hdr *sshdr) { u8 cdb[COMMAND_SIZE(MAINTENANCE_OUT)]; unsigned char stpg_data[8]; int stpg_len = 8; int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER; /* Prepare the data buffer */ memset(stpg_data, 0, stpg_len); stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f; put_unaligned_be16(group_id, &stpg_data[6]); /* Prepare the command. */ memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_OUT)); cdb[0] = MAINTENANCE_OUT; cdb[1] = MO_SET_TARGET_PGS; put_unaligned_be32(stpg_len, &cdb[6]); return scsi_execute_req_flags(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, sshdr, ALUA_FAILOVER_TIMEOUT * HZ, ALUA_FAILOVER_RETRIES, NULL, req_flags); } struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size, int group_id) { struct alua_port_group *pg; list_for_each_entry(pg, &port_group_list, node) { if (pg->group_id != group_id) continue; if (pg->device_id_len != id_size) continue; if (strncmp(pg->device_id_str, id_str, id_size)) continue; if (!kref_get_unless_zero(&pg->kref)) continue; return pg; } return NULL; } /* * alua_alloc_pg - Allocate a new port_group structure * @sdev: scsi device * @h: alua device_handler data * @group_id: port group id * * Allocate a new port_group structure for a given * device. */ struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev, int group_id, int tpgs) { struct alua_port_group *pg, *tmp_pg; pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL); if (!pg) return ERR_PTR(-ENOMEM); pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str, sizeof(pg->device_id_str)); if (pg->device_id_len <= 0) { /* * Internal error: TPGS supported but no device * identifcation found. Disable ALUA support. */ kfree(pg); sdev_printk(KERN_INFO, sdev, "%s: No device descriptors found\n", ALUA_DH_NAME); return ERR_PTR(-ENXIO); } pg->group_id = group_id; pg->tpgs = tpgs; pg->state = TPGS_STATE_OPTIMIZED; if (optimize_stpg) pg->flags |= ALUA_OPTIMIZE_STPG; kref_init(&pg->kref); spin_lock(&port_group_lock); tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len, group_id); if (tmp_pg) { spin_unlock(&port_group_lock); kfree(pg); return tmp_pg; } list_add(&pg->node, &port_group_list); spin_unlock(&port_group_lock); return pg; } /* * alua_check_tpgs - Evaluate TPGS setting * @sdev: device to be checked * * Examine the TPGS setting of the sdev to find out if ALUA * is supported. */ static int alua_check_tpgs(struct scsi_device *sdev) { int tpgs = TPGS_MODE_NONE; /* * ALUA support for non-disk devices is fraught with * difficulties, so disable it for now. */ if (sdev->type != TYPE_DISK) { sdev_printk(KERN_INFO, sdev, "%s: disable for non-disk devices\n", ALUA_DH_NAME); return tpgs; } tpgs = scsi_device_tpgs(sdev); switch (tpgs) { case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT: sdev_printk(KERN_INFO, sdev, "%s: supports implicit and explicit TPGS\n", ALUA_DH_NAME); break; case TPGS_MODE_EXPLICIT: sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n", ALUA_DH_NAME); break; case TPGS_MODE_IMPLICIT: sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n", ALUA_DH_NAME); break; case TPGS_MODE_NONE: sdev_printk(KERN_INFO, sdev, "%s: not supported\n", ALUA_DH_NAME); break; default: sdev_printk(KERN_INFO, sdev, "%s: unsupported TPGS setting %d\n", ALUA_DH_NAME, tpgs); tpgs = TPGS_MODE_NONE; break; } return tpgs; } /* * alua_check_vpd - Evaluate INQUIRY vpd page 0x83 * @sdev: device to be checked * * Extract the relative target port and the target port group * descriptor from the list of identificators. */ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h, int tpgs) { int rel_port = -1, group_id; group_id = scsi_vpd_tpg_id(sdev, &rel_port); if (group_id < 0) { /* * Internal error; TPGS supported but required * VPD identification descriptors not present. * Disable ALUA support */ sdev_printk(KERN_INFO, sdev, "%s: No target port descriptors found\n", ALUA_DH_NAME); return SCSI_DH_DEV_UNSUPP; } h->pg = alua_alloc_pg(sdev, group_id, tpgs); if (IS_ERR(h->pg)) { if (PTR_ERR(h->pg) == -ENOMEM) return SCSI_DH_NOMEM; return SCSI_DH_DEV_UNSUPP; } sdev_printk(KERN_INFO, sdev, "%s: device %s port group %x rel port %x\n", ALUA_DH_NAME, h->pg->device_id_str, h->group_id, rel_port); return alua_rtpg(sdev, h->pg); } static char print_alua_state(int state) { switch (state) { case TPGS_STATE_OPTIMIZED: return 'A'; case TPGS_STATE_NONOPTIMIZED: return 'N'; case TPGS_STATE_STANDBY: return 'S'; case TPGS_STATE_UNAVAILABLE: return 'U'; case TPGS_STATE_LBA_DEPENDENT: return 'L'; case TPGS_STATE_OFFLINE: return 'O'; case TPGS_STATE_TRANSITIONING: return 'T'; default: return 'X'; } } static int alua_check_sense(struct scsi_device *sdev, struct scsi_sense_hdr *sense_hdr) { switch (sense_hdr->sense_key) { case NOT_READY: if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) /* * LUN Not Accessible - ALUA state transition */ return ADD_TO_MLQUEUE; break; case UNIT_ATTENTION: if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) /* * Power On, Reset, or Bus Device Reset, just retry. */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04) /* * Device internal reset */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01) /* * Mode Parameters Changed */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) /* * ALUA state changed */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) /* * Implicit ALUA state transition failed */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03) /* * Inquiry data has changed */ return ADD_TO_MLQUEUE; if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e) /* * REPORTED_LUNS_DATA_HAS_CHANGED is reported * when switching controllers on targets like * Intel Multi-Flex. We can just retry. */ return ADD_TO_MLQUEUE; break; } return SCSI_RETURN_NOT_HANDLED; } /* * alua_rtpg - Evaluate REPORT TARGET GROUP STATES * @sdev: the device to be evaluated. * * Evaluate the Target Port Group State. * Returns SCSI_DH_DEV_OFFLINED if the path is * found to be unusable. */ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg) { struct scsi_sense_hdr sense_hdr; int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE; unsigned char *ucp, *buff; unsigned err, retval; unsigned long expiry, interval = 0; unsigned int tpg_desc_tbl_off; unsigned char orig_transition_tmo; if (!pg->transition_tmo) expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ); else expiry = round_jiffies_up(jiffies + pg->transition_tmo * HZ); buff = kzalloc(bufflen, GFP_KERNEL); if (!buff) return SCSI_DH_DEV_TEMP_BUSY; retry: retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags); if (retval) { if (!scsi_sense_valid(&sense_hdr)) { sdev_printk(KERN_INFO, sdev, "%s: rtpg failed, result %d\n", ALUA_DH_NAME, retval); kfree(buff); if (driver_byte(retval) == DRIVER_ERROR) return SCSI_DH_DEV_TEMP_BUSY; return SCSI_DH_IO; } /* * submit_rtpg() has failed on existing arrays * when requesting extended header info, and * the array doesn't support extended headers, * even though it shouldn't according to T10. * The retry without rtpg_ext_hdr_req set * handles this. */ if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) && sense_hdr.sense_key == ILLEGAL_REQUEST && sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) { pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP; goto retry; } /* * Retry on ALUA state transition or if any * UNIT ATTENTION occurred. */ if (sense_hdr.sense_key == NOT_READY && sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) err = SCSI_DH_RETRY; else if (sense_hdr.sense_key == UNIT_ATTENTION) err = SCSI_DH_RETRY; if (err == SCSI_DH_RETRY && time_before(jiffies, expiry)) { sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n", ALUA_DH_NAME); scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr); goto retry; } sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n", ALUA_DH_NAME); scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr); kfree(buff); return SCSI_DH_IO; } len = get_unaligned_be32(&buff[0]) + 4; if (len > bufflen) { /* Resubmit with the correct length */ kfree(buff); bufflen = len; buff = kmalloc(bufflen, GFP_KERNEL); if (!buff) { sdev_printk(KERN_WARNING, sdev, "%s: kmalloc buffer failed\n",__func__); /* Temporary failure, bypass */ return SCSI_DH_DEV_TEMP_BUSY; } goto retry; } orig_transition_tmo = pg->transition_tmo; if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0) pg->transition_tmo = buff[5]; else pg->transition_tmo = ALUA_FAILOVER_TIMEOUT; if (orig_transition_tmo != pg->transition_tmo) { sdev_printk(KERN_INFO, sdev, "%s: transition timeout set to %d seconds\n", ALUA_DH_NAME, pg->transition_tmo); expiry = jiffies + pg->transition_tmo * HZ; } if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR) tpg_desc_tbl_off = 8; else tpg_desc_tbl_off = 4; for (k = tpg_desc_tbl_off, ucp = buff + tpg_desc_tbl_off; k < len; k += off, ucp += off) { if (pg->group_id == get_unaligned_be16(&ucp[2])) { pg->state = ucp[0] & 0x0f; pg->pref = ucp[0] >> 7; valid_states = ucp[1]; } off = 8 + (ucp[7] * 4); } sdev_printk(KERN_INFO, sdev, "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n", ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state), pg->pref ? "preferred" : "non-preferred", valid_states&TPGS_SUPPORT_TRANSITION?'T':'t', valid_states&TPGS_SUPPORT_OFFLINE?'O':'o', valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l', valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u', valid_states&TPGS_SUPPORT_STANDBY?'S':'s', valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n', valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a'); switch (pg->state) { case TPGS_STATE_TRANSITIONING: if (time_before(jiffies, expiry)) { /* State transition, retry */ interval += 2000; msleep(interval); goto retry; } /* Transitioning time exceeded, set port to standby */ err = SCSI_DH_RETRY; pg->state = TPGS_STATE_STANDBY; break; case TPGS_STATE_OFFLINE: /* Path unusable */ err = SCSI_DH_DEV_OFFLINED; break; default: /* Useable path if active */ err = SCSI_DH_OK; break; } kfree(buff); return err; } /* * alua_stpg - Issue a SET TARGET PORT GROUP command * * Issue a SET TARGET PORT GROUP command and evaluate the * response. Returns SCSI_DH_RETRY per default to trigger * a re-evaluation of the target group state or SCSI_DH_OK * if no further action needs to be taken. */ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg) { int retval; struct scsi_sense_hdr sense_hdr; if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) { /* Only implicit ALUA supported, retry */ return SCSI_DH_RETRY; } switch (pg->state) { case TPGS_STATE_OPTIMIZED: return SCSI_DH_OK; case TPGS_STATE_NONOPTIMIZED: if ((pg->flags & ALUA_OPTIMIZE_STPG) && !pg->pref && (pg->tpgs & TPGS_MODE_IMPLICIT)) return SCSI_DH_OK; break; case TPGS_STATE_STANDBY: case TPGS_STATE_UNAVAILABLE: break; case TPGS_STATE_OFFLINE: return SCSI_DH_IO; case TPGS_STATE_TRANSITIONING: break; default: sdev_printk(KERN_INFO, sdev, "%s: stpg failed, unhandled TPGS state %d", ALUA_DH_NAME, pg->state); return SCSI_DH_NOSYS; } retval = submit_stpg(sdev, pg->group_id, &sense_hdr); if (retval) { if (!scsi_sense_valid(&sense_hdr)) { sdev_printk(KERN_INFO, sdev, "%s: stpg failed, result %d", ALUA_DH_NAME, retval); if (driver_byte(retval) == DRIVER_ERROR) return SCSI_DH_DEV_TEMP_BUSY; } else { sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n", ALUA_DH_NAME); scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr); } } /* Retry RTPG */ return SCSI_DH_RETRY; } /* * alua_initialize - Initialize ALUA state * @sdev: the device to be initialized * * For the prep_fn to work correctly we have * to initialize the ALUA state for the device. */ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h) { int err = SCSI_DH_DEV_UNSUPP, tpgs; tpgs = alua_check_tpgs(sdev); if (tpgs != TPGS_MODE_NONE) err = alua_check_vpd(sdev, h, tpgs); return err; } /* * alua_set_params - set/unset the optimize flag * @sdev: device on the path to be activated * params - parameters in the following format * "no_of_params\0param1\0param2\0param3\0...\0" * For example, to set the flag pass the following parameters * from multipath.conf * hardware_handler "2 alua 1" */ static int alua_set_params(struct scsi_device *sdev, const char *params) { struct alua_dh_data *h = sdev->handler_data; struct alua_port_group *pg = NULL; unsigned int optimize = 0, argc; const char *p = params; int result = SCSI_DH_OK; if ((sscanf(params, "%u", &argc) != 1) || (argc != 1)) return -EINVAL; while (*p++) ; if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1)) return -EINVAL; pg = h->pg; if (!pg) return -ENXIO; if (optimize) pg->flags |= ALUA_OPTIMIZE_STPG; else pg->flags &= ~ALUA_OPTIMIZE_STPG; return result; } /* * alua_activate - activate a path * @sdev: device on the path to be activated * * We're currently switching the port group to be activated only and * let the array figure out the rest. * There may be other arrays which require us to switch all port groups * based on a certain policy. But until we actually encounter them it * should be okay. */ static int alua_activate(struct scsi_device *sdev, activate_complete fn, void *data) { struct alua_dh_data *h = sdev->handler_data; int err = SCSI_DH_OK; if (!h->pg) goto out; kref_get(&h->pg->kref); err = alua_rtpg(sdev, h->pg); if (err != SCSI_DH_OK) { kref_put(&h->pg->kref, release_port_group); goto out; } err = alua_stpg(sdev, h->pg); if (err == SCSI_DH_RETRY) err = alua_rtpg(sdev, h->pg); kref_put(&h->pg->kref, release_port_group); out: if (fn) fn(data, err); return 0; } /* * alua_prep_fn - request callback * * Fail I/O to all paths not in state * active/optimized or active/non-optimized. */ static int alua_prep_fn(struct scsi_device *sdev, struct request *req) { struct alua_dh_data *h = sdev->handler_data; int state; int ret = BLKPREP_OK; if (!h->pg) return ret; kref_get(&h->pg->kref); state = h->pg->state; kref_put(&h->pg->kref, release_port_group); if (state == TPGS_STATE_TRANSITIONING) ret = BLKPREP_DEFER; else if (state != TPGS_STATE_OPTIMIZED && state != TPGS_STATE_NONOPTIMIZED && state != TPGS_STATE_LBA_DEPENDENT) { ret = BLKPREP_KILL; req->cmd_flags |= REQ_QUIET; } return ret; } /* * alua_bus_attach - Attach device handler * @sdev: device to be attached to */ static int alua_bus_attach(struct scsi_device *sdev) { struct alua_dh_data *h; int err, ret = -EINVAL; h = kzalloc(sizeof(*h) , GFP_KERNEL); if (!h) return -ENOMEM; h->pg = NULL; h->sdev = sdev; err = alua_initialize(sdev, h); if (err == SCSI_DH_NOMEM) ret = -ENOMEM; if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED) goto failed; sdev->handler_data = h; return 0; failed: kfree(h); return ret; } /* * alua_bus_detach - Detach device handler * @sdev: device to be detached from */ static void alua_bus_detach(struct scsi_device *sdev) { struct alua_dh_data *h = sdev->handler_data; if (h->pg) { kref_put(&h->pg->kref, release_port_group); h->pg = NULL; } sdev->handler_data = NULL; kfree(h); } static struct scsi_device_handler alua_dh = { .name = ALUA_DH_NAME, .module = THIS_MODULE, .attach = alua_bus_attach, .detach = alua_bus_detach, .prep_fn = alua_prep_fn, .check_sense = alua_check_sense, .activate = alua_activate, .set_params = alua_set_params, }; static int __init alua_init(void) { int r; r = scsi_register_device_handler(&alua_dh); if (r != 0) printk(KERN_ERR "%s: Failed to register scsi device handler", ALUA_DH_NAME); return r; } static void __exit alua_exit(void) { scsi_unregister_device_handler(&alua_dh); } module_init(alua_init); module_exit(alua_exit); MODULE_DESCRIPTION("DM Multipath ALUA support"); MODULE_AUTHOR("Hannes Reinecke "); MODULE_LICENSE("GPL"); MODULE_VERSION(ALUA_DH_VER);