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0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Generic SCSI-3 ALUA SCSI Device Handler
0004  *
0005  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
0006  * All rights reserved.
0007  */
0008 #include <linux/slab.h>
0009 #include <linux/delay.h>
0010 #include <linux/module.h>
0011 #include <asm/unaligned.h>
0012 #include <scsi/scsi.h>
0013 #include <scsi/scsi_proto.h>
0014 #include <scsi/scsi_dbg.h>
0015 #include <scsi/scsi_eh.h>
0016 #include <scsi/scsi_dh.h>
0017 
0018 #define ALUA_DH_NAME "alua"
0019 #define ALUA_DH_VER "2.0"
0020 
0021 #define TPGS_SUPPORT_NONE       0x00
0022 #define TPGS_SUPPORT_OPTIMIZED      0x01
0023 #define TPGS_SUPPORT_NONOPTIMIZED   0x02
0024 #define TPGS_SUPPORT_STANDBY        0x04
0025 #define TPGS_SUPPORT_UNAVAILABLE    0x08
0026 #define TPGS_SUPPORT_LBA_DEPENDENT  0x10
0027 #define TPGS_SUPPORT_OFFLINE        0x40
0028 #define TPGS_SUPPORT_TRANSITION     0x80
0029 #define TPGS_SUPPORT_ALL        0xdf
0030 
0031 #define RTPG_FMT_MASK           0x70
0032 #define RTPG_FMT_EXT_HDR        0x10
0033 
0034 #define TPGS_MODE_UNINITIALIZED      -1
0035 #define TPGS_MODE_NONE          0x0
0036 #define TPGS_MODE_IMPLICIT      0x1
0037 #define TPGS_MODE_EXPLICIT      0x2
0038 
0039 #define ALUA_RTPG_SIZE          128
0040 #define ALUA_FAILOVER_TIMEOUT       60
0041 #define ALUA_FAILOVER_RETRIES       5
0042 #define ALUA_RTPG_DELAY_MSECS       5
0043 #define ALUA_RTPG_RETRY_DELAY       2
0044 
0045 /* device handler flags */
0046 #define ALUA_OPTIMIZE_STPG      0x01
0047 #define ALUA_RTPG_EXT_HDR_UNSUPP    0x02
0048 /* State machine flags */
0049 #define ALUA_PG_RUN_RTPG        0x10
0050 #define ALUA_PG_RUN_STPG        0x20
0051 #define ALUA_PG_RUNNING         0x40
0052 
0053 static uint optimize_stpg;
0054 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
0055 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.");
0056 
0057 static LIST_HEAD(port_group_list);
0058 static DEFINE_SPINLOCK(port_group_lock);
0059 static struct workqueue_struct *kaluad_wq;
0060 
0061 struct alua_port_group {
0062     struct kref     kref;
0063     struct rcu_head     rcu;
0064     struct list_head    node;
0065     struct list_head    dh_list;
0066     unsigned char       device_id_str[256];
0067     int         device_id_len;
0068     int         group_id;
0069     int         tpgs;
0070     int         state;
0071     int         pref;
0072     int         valid_states;
0073     unsigned        flags; /* used for optimizing STPG */
0074     unsigned char       transition_tmo;
0075     unsigned long       expiry;
0076     unsigned long       interval;
0077     struct delayed_work rtpg_work;
0078     spinlock_t      lock;
0079     struct list_head    rtpg_list;
0080     struct scsi_device  *rtpg_sdev;
0081 };
0082 
0083 struct alua_dh_data {
0084     struct list_head    node;
0085     struct alua_port_group __rcu *pg;
0086     int         group_id;
0087     spinlock_t      pg_lock;
0088     struct scsi_device  *sdev;
0089     int         init_error;
0090     struct mutex        init_mutex;
0091     bool            disabled;
0092 };
0093 
0094 struct alua_queue_data {
0095     struct list_head    entry;
0096     activate_complete   callback_fn;
0097     void            *callback_data;
0098 };
0099 
0100 #define ALUA_POLICY_SWITCH_CURRENT  0
0101 #define ALUA_POLICY_SWITCH_ALL      1
0102 
0103 static void alua_rtpg_work(struct work_struct *work);
0104 static bool alua_rtpg_queue(struct alua_port_group *pg,
0105                 struct scsi_device *sdev,
0106                 struct alua_queue_data *qdata, bool force);
0107 static void alua_check(struct scsi_device *sdev, bool force);
0108 
0109 static void release_port_group(struct kref *kref)
0110 {
0111     struct alua_port_group *pg;
0112 
0113     pg = container_of(kref, struct alua_port_group, kref);
0114     if (pg->rtpg_sdev)
0115         flush_delayed_work(&pg->rtpg_work);
0116     spin_lock(&port_group_lock);
0117     list_del(&pg->node);
0118     spin_unlock(&port_group_lock);
0119     kfree_rcu(pg, rcu);
0120 }
0121 
0122 /*
0123  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
0124  * @sdev: sdev the command should be sent to
0125  */
0126 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
0127                int bufflen, struct scsi_sense_hdr *sshdr, int flags)
0128 {
0129     u8 cdb[MAX_COMMAND_SIZE];
0130     blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
0131         REQ_FAILFAST_DRIVER;
0132 
0133     /* Prepare the command. */
0134     memset(cdb, 0x0, MAX_COMMAND_SIZE);
0135     cdb[0] = MAINTENANCE_IN;
0136     if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
0137         cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
0138     else
0139         cdb[1] = MI_REPORT_TARGET_PGS;
0140     put_unaligned_be32(bufflen, &cdb[6]);
0141 
0142     return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
0143             sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
0144             ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
0145 }
0146 
0147 /*
0148  * submit_stpg - Issue a SET TARGET PORT GROUP command
0149  *
0150  * Currently we're only setting the current target port group state
0151  * to 'active/optimized' and let the array firmware figure out
0152  * the states of the remaining groups.
0153  */
0154 static int submit_stpg(struct scsi_device *sdev, int group_id,
0155                struct scsi_sense_hdr *sshdr)
0156 {
0157     u8 cdb[MAX_COMMAND_SIZE];
0158     unsigned char stpg_data[8];
0159     int stpg_len = 8;
0160     blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
0161         REQ_FAILFAST_DRIVER;
0162 
0163     /* Prepare the data buffer */
0164     memset(stpg_data, 0, stpg_len);
0165     stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
0166     put_unaligned_be16(group_id, &stpg_data[6]);
0167 
0168     /* Prepare the command. */
0169     memset(cdb, 0x0, MAX_COMMAND_SIZE);
0170     cdb[0] = MAINTENANCE_OUT;
0171     cdb[1] = MO_SET_TARGET_PGS;
0172     put_unaligned_be32(stpg_len, &cdb[6]);
0173 
0174     return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
0175             sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
0176             ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
0177 }
0178 
0179 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
0180                         int group_id)
0181 {
0182     struct alua_port_group *pg;
0183 
0184     if (!id_str || !id_size || !strlen(id_str))
0185         return NULL;
0186 
0187     list_for_each_entry(pg, &port_group_list, node) {
0188         if (pg->group_id != group_id)
0189             continue;
0190         if (!pg->device_id_len || pg->device_id_len != id_size)
0191             continue;
0192         if (strncmp(pg->device_id_str, id_str, id_size))
0193             continue;
0194         if (!kref_get_unless_zero(&pg->kref))
0195             continue;
0196         return pg;
0197     }
0198 
0199     return NULL;
0200 }
0201 
0202 /*
0203  * alua_alloc_pg - Allocate a new port_group structure
0204  * @sdev: scsi device
0205  * @group_id: port group id
0206  * @tpgs: target port group settings
0207  *
0208  * Allocate a new port_group structure for a given
0209  * device.
0210  */
0211 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
0212                          int group_id, int tpgs)
0213 {
0214     struct alua_port_group *pg, *tmp_pg;
0215 
0216     pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
0217     if (!pg)
0218         return ERR_PTR(-ENOMEM);
0219 
0220     pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
0221                         sizeof(pg->device_id_str));
0222     if (pg->device_id_len <= 0) {
0223         /*
0224          * TPGS supported but no device identification found.
0225          * Generate private device identification.
0226          */
0227         sdev_printk(KERN_INFO, sdev,
0228                 "%s: No device descriptors found\n",
0229                 ALUA_DH_NAME);
0230         pg->device_id_str[0] = '\0';
0231         pg->device_id_len = 0;
0232     }
0233     pg->group_id = group_id;
0234     pg->tpgs = tpgs;
0235     pg->state = SCSI_ACCESS_STATE_OPTIMAL;
0236     pg->valid_states = TPGS_SUPPORT_ALL;
0237     if (optimize_stpg)
0238         pg->flags |= ALUA_OPTIMIZE_STPG;
0239     kref_init(&pg->kref);
0240     INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
0241     INIT_LIST_HEAD(&pg->rtpg_list);
0242     INIT_LIST_HEAD(&pg->node);
0243     INIT_LIST_HEAD(&pg->dh_list);
0244     spin_lock_init(&pg->lock);
0245 
0246     spin_lock(&port_group_lock);
0247     tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
0248                   group_id);
0249     if (tmp_pg) {
0250         spin_unlock(&port_group_lock);
0251         kfree(pg);
0252         return tmp_pg;
0253     }
0254 
0255     list_add(&pg->node, &port_group_list);
0256     spin_unlock(&port_group_lock);
0257 
0258     return pg;
0259 }
0260 
0261 /*
0262  * alua_check_tpgs - Evaluate TPGS setting
0263  * @sdev: device to be checked
0264  *
0265  * Examine the TPGS setting of the sdev to find out if ALUA
0266  * is supported.
0267  */
0268 static int alua_check_tpgs(struct scsi_device *sdev)
0269 {
0270     int tpgs = TPGS_MODE_NONE;
0271 
0272     /*
0273      * ALUA support for non-disk devices is fraught with
0274      * difficulties, so disable it for now.
0275      */
0276     if (sdev->type != TYPE_DISK) {
0277         sdev_printk(KERN_INFO, sdev,
0278                 "%s: disable for non-disk devices\n",
0279                 ALUA_DH_NAME);
0280         return tpgs;
0281     }
0282 
0283     tpgs = scsi_device_tpgs(sdev);
0284     switch (tpgs) {
0285     case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
0286         sdev_printk(KERN_INFO, sdev,
0287                 "%s: supports implicit and explicit TPGS\n",
0288                 ALUA_DH_NAME);
0289         break;
0290     case TPGS_MODE_EXPLICIT:
0291         sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
0292                 ALUA_DH_NAME);
0293         break;
0294     case TPGS_MODE_IMPLICIT:
0295         sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
0296                 ALUA_DH_NAME);
0297         break;
0298     case TPGS_MODE_NONE:
0299         sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
0300                 ALUA_DH_NAME);
0301         break;
0302     default:
0303         sdev_printk(KERN_INFO, sdev,
0304                 "%s: unsupported TPGS setting %d\n",
0305                 ALUA_DH_NAME, tpgs);
0306         tpgs = TPGS_MODE_NONE;
0307         break;
0308     }
0309 
0310     return tpgs;
0311 }
0312 
0313 /*
0314  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
0315  * @sdev: device to be checked
0316  *
0317  * Extract the relative target port and the target port group
0318  * descriptor from the list of identificators.
0319  */
0320 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
0321               int tpgs)
0322 {
0323     int rel_port = -1, group_id;
0324     struct alua_port_group *pg, *old_pg = NULL;
0325     bool pg_updated = false;
0326     unsigned long flags;
0327 
0328     group_id = scsi_vpd_tpg_id(sdev, &rel_port);
0329     if (group_id < 0) {
0330         /*
0331          * Internal error; TPGS supported but required
0332          * VPD identification descriptors not present.
0333          * Disable ALUA support
0334          */
0335         sdev_printk(KERN_INFO, sdev,
0336                 "%s: No target port descriptors found\n",
0337                 ALUA_DH_NAME);
0338         return SCSI_DH_DEV_UNSUPP;
0339     }
0340 
0341     pg = alua_alloc_pg(sdev, group_id, tpgs);
0342     if (IS_ERR(pg)) {
0343         if (PTR_ERR(pg) == -ENOMEM)
0344             return SCSI_DH_NOMEM;
0345         return SCSI_DH_DEV_UNSUPP;
0346     }
0347     if (pg->device_id_len)
0348         sdev_printk(KERN_INFO, sdev,
0349                 "%s: device %s port group %x rel port %x\n",
0350                 ALUA_DH_NAME, pg->device_id_str,
0351                 group_id, rel_port);
0352     else
0353         sdev_printk(KERN_INFO, sdev,
0354                 "%s: port group %x rel port %x\n",
0355                 ALUA_DH_NAME, group_id, rel_port);
0356 
0357     /* Check for existing port group references */
0358     spin_lock(&h->pg_lock);
0359     old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
0360     if (old_pg != pg) {
0361         /* port group has changed. Update to new port group */
0362         if (h->pg) {
0363             spin_lock_irqsave(&old_pg->lock, flags);
0364             list_del_rcu(&h->node);
0365             spin_unlock_irqrestore(&old_pg->lock, flags);
0366         }
0367         rcu_assign_pointer(h->pg, pg);
0368         pg_updated = true;
0369     }
0370 
0371     spin_lock_irqsave(&pg->lock, flags);
0372     if (pg_updated)
0373         list_add_rcu(&h->node, &pg->dh_list);
0374     spin_unlock_irqrestore(&pg->lock, flags);
0375 
0376     alua_rtpg_queue(rcu_dereference_protected(h->pg,
0377                           lockdep_is_held(&h->pg_lock)),
0378             sdev, NULL, true);
0379     spin_unlock(&h->pg_lock);
0380 
0381     if (old_pg)
0382         kref_put(&old_pg->kref, release_port_group);
0383 
0384     return SCSI_DH_OK;
0385 }
0386 
0387 static char print_alua_state(unsigned char state)
0388 {
0389     switch (state) {
0390     case SCSI_ACCESS_STATE_OPTIMAL:
0391         return 'A';
0392     case SCSI_ACCESS_STATE_ACTIVE:
0393         return 'N';
0394     case SCSI_ACCESS_STATE_STANDBY:
0395         return 'S';
0396     case SCSI_ACCESS_STATE_UNAVAILABLE:
0397         return 'U';
0398     case SCSI_ACCESS_STATE_LBA:
0399         return 'L';
0400     case SCSI_ACCESS_STATE_OFFLINE:
0401         return 'O';
0402     case SCSI_ACCESS_STATE_TRANSITIONING:
0403         return 'T';
0404     default:
0405         return 'X';
0406     }
0407 }
0408 
0409 static enum scsi_disposition alua_check_sense(struct scsi_device *sdev,
0410                           struct scsi_sense_hdr *sense_hdr)
0411 {
0412     struct alua_dh_data *h = sdev->handler_data;
0413     struct alua_port_group *pg;
0414 
0415     switch (sense_hdr->sense_key) {
0416     case NOT_READY:
0417         if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
0418             /*
0419              * LUN Not Accessible - ALUA state transition
0420              */
0421             rcu_read_lock();
0422             pg = rcu_dereference(h->pg);
0423             if (pg)
0424                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
0425             rcu_read_unlock();
0426             alua_check(sdev, false);
0427             return NEEDS_RETRY;
0428         }
0429         break;
0430     case UNIT_ATTENTION:
0431         if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
0432             /*
0433              * Power On, Reset, or Bus Device Reset.
0434              * Might have obscured a state transition,
0435              * so schedule a recheck.
0436              */
0437             alua_check(sdev, true);
0438             return ADD_TO_MLQUEUE;
0439         }
0440         if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
0441             /*
0442              * Device internal reset
0443              */
0444             return ADD_TO_MLQUEUE;
0445         if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
0446             /*
0447              * Mode Parameters Changed
0448              */
0449             return ADD_TO_MLQUEUE;
0450         if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
0451             /*
0452              * ALUA state changed
0453              */
0454             alua_check(sdev, true);
0455             return ADD_TO_MLQUEUE;
0456         }
0457         if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
0458             /*
0459              * Implicit ALUA state transition failed
0460              */
0461             alua_check(sdev, true);
0462             return ADD_TO_MLQUEUE;
0463         }
0464         if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
0465             /*
0466              * Inquiry data has changed
0467              */
0468             return ADD_TO_MLQUEUE;
0469         if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
0470             /*
0471              * REPORTED_LUNS_DATA_HAS_CHANGED is reported
0472              * when switching controllers on targets like
0473              * Intel Multi-Flex. We can just retry.
0474              */
0475             return ADD_TO_MLQUEUE;
0476         break;
0477     }
0478 
0479     return SCSI_RETURN_NOT_HANDLED;
0480 }
0481 
0482 /*
0483  * alua_tur - Send a TEST UNIT READY
0484  * @sdev: device to which the TEST UNIT READY command should be send
0485  *
0486  * Send a TEST UNIT READY to @sdev to figure out the device state
0487  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
0488  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
0489  */
0490 static int alua_tur(struct scsi_device *sdev)
0491 {
0492     struct scsi_sense_hdr sense_hdr;
0493     int retval;
0494 
0495     retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
0496                       ALUA_FAILOVER_RETRIES, &sense_hdr);
0497     if (sense_hdr.sense_key == NOT_READY &&
0498         sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
0499         return SCSI_DH_RETRY;
0500     else if (retval)
0501         return SCSI_DH_IO;
0502     else
0503         return SCSI_DH_OK;
0504 }
0505 
0506 /*
0507  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
0508  * @sdev: the device to be evaluated.
0509  *
0510  * Evaluate the Target Port Group State.
0511  * Returns SCSI_DH_DEV_OFFLINED if the path is
0512  * found to be unusable.
0513  */
0514 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
0515 {
0516     struct scsi_sense_hdr sense_hdr;
0517     struct alua_port_group *tmp_pg;
0518     int len, k, off, bufflen = ALUA_RTPG_SIZE;
0519     int group_id_old, state_old, pref_old, valid_states_old;
0520     unsigned char *desc, *buff;
0521     unsigned err;
0522     int retval;
0523     unsigned int tpg_desc_tbl_off;
0524     unsigned char orig_transition_tmo;
0525     unsigned long flags;
0526     bool transitioning_sense = false;
0527 
0528     group_id_old = pg->group_id;
0529     state_old = pg->state;
0530     pref_old = pg->pref;
0531     valid_states_old = pg->valid_states;
0532 
0533     if (!pg->expiry) {
0534         unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
0535 
0536         if (pg->transition_tmo)
0537             transition_tmo = pg->transition_tmo * HZ;
0538 
0539         pg->expiry = round_jiffies_up(jiffies + transition_tmo);
0540     }
0541 
0542     buff = kzalloc(bufflen, GFP_KERNEL);
0543     if (!buff)
0544         return SCSI_DH_DEV_TEMP_BUSY;
0545 
0546  retry:
0547     err = 0;
0548     retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
0549 
0550     if (retval) {
0551         /*
0552          * Some (broken) implementations have a habit of returning
0553          * an error during things like firmware update etc.
0554          * But if the target only supports active/optimized there's
0555          * not much we can do; it's not that we can switch paths
0556          * or anything.
0557          * So ignore any errors to avoid spurious failures during
0558          * path failover.
0559          */
0560         if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
0561             sdev_printk(KERN_INFO, sdev,
0562                     "%s: ignoring rtpg result %d\n",
0563                     ALUA_DH_NAME, retval);
0564             kfree(buff);
0565             return SCSI_DH_OK;
0566         }
0567         if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
0568             sdev_printk(KERN_INFO, sdev,
0569                     "%s: rtpg failed, result %d\n",
0570                     ALUA_DH_NAME, retval);
0571             kfree(buff);
0572             if (retval < 0)
0573                 return SCSI_DH_DEV_TEMP_BUSY;
0574             if (host_byte(retval) == DID_NO_CONNECT)
0575                 return SCSI_DH_RES_TEMP_UNAVAIL;
0576             return SCSI_DH_IO;
0577         }
0578 
0579         /*
0580          * submit_rtpg() has failed on existing arrays
0581          * when requesting extended header info, and
0582          * the array doesn't support extended headers,
0583          * even though it shouldn't according to T10.
0584          * The retry without rtpg_ext_hdr_req set
0585          * handles this.
0586          * Note:  some arrays return a sense key of ILLEGAL_REQUEST
0587          * with ASC 00h if they don't support the extended header.
0588          */
0589         if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
0590             sense_hdr.sense_key == ILLEGAL_REQUEST) {
0591             pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
0592             goto retry;
0593         }
0594         /*
0595          * If the array returns with 'ALUA state transition'
0596          * sense code here it cannot return RTPG data during
0597          * transition. So set the state to 'transitioning' directly.
0598          */
0599         if (sense_hdr.sense_key == NOT_READY &&
0600             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
0601             transitioning_sense = true;
0602             goto skip_rtpg;
0603         }
0604         /*
0605          * Retry on any other UNIT ATTENTION occurred.
0606          */
0607         if (sense_hdr.sense_key == UNIT_ATTENTION)
0608             err = SCSI_DH_RETRY;
0609         if (err == SCSI_DH_RETRY &&
0610             pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
0611             sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
0612                     ALUA_DH_NAME);
0613             scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
0614             kfree(buff);
0615             return err;
0616         }
0617         sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
0618                 ALUA_DH_NAME);
0619         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
0620         kfree(buff);
0621         pg->expiry = 0;
0622         return SCSI_DH_IO;
0623     }
0624 
0625     len = get_unaligned_be32(&buff[0]) + 4;
0626 
0627     if (len > bufflen) {
0628         /* Resubmit with the correct length */
0629         kfree(buff);
0630         bufflen = len;
0631         buff = kmalloc(bufflen, GFP_KERNEL);
0632         if (!buff) {
0633             sdev_printk(KERN_WARNING, sdev,
0634                     "%s: kmalloc buffer failed\n",__func__);
0635             /* Temporary failure, bypass */
0636             pg->expiry = 0;
0637             return SCSI_DH_DEV_TEMP_BUSY;
0638         }
0639         goto retry;
0640     }
0641 
0642     orig_transition_tmo = pg->transition_tmo;
0643     if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
0644         pg->transition_tmo = buff[5];
0645     else
0646         pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
0647 
0648     if (orig_transition_tmo != pg->transition_tmo) {
0649         sdev_printk(KERN_INFO, sdev,
0650                 "%s: transition timeout set to %d seconds\n",
0651                 ALUA_DH_NAME, pg->transition_tmo);
0652         pg->expiry = jiffies + pg->transition_tmo * HZ;
0653     }
0654 
0655     if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
0656         tpg_desc_tbl_off = 8;
0657     else
0658         tpg_desc_tbl_off = 4;
0659 
0660     for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
0661          k < len;
0662          k += off, desc += off) {
0663         u16 group_id = get_unaligned_be16(&desc[2]);
0664 
0665         spin_lock_irqsave(&port_group_lock, flags);
0666         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
0667                       group_id);
0668         spin_unlock_irqrestore(&port_group_lock, flags);
0669         if (tmp_pg) {
0670             if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
0671                 if ((tmp_pg == pg) ||
0672                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
0673                     struct alua_dh_data *h;
0674 
0675                     tmp_pg->state = desc[0] & 0x0f;
0676                     tmp_pg->pref = desc[0] >> 7;
0677                     rcu_read_lock();
0678                     list_for_each_entry_rcu(h,
0679                         &tmp_pg->dh_list, node) {
0680                         if (!h->sdev)
0681                             continue;
0682                         h->sdev->access_state = desc[0];
0683                     }
0684                     rcu_read_unlock();
0685                 }
0686                 if (tmp_pg == pg)
0687                     tmp_pg->valid_states = desc[1];
0688                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
0689             }
0690             kref_put(&tmp_pg->kref, release_port_group);
0691         }
0692         off = 8 + (desc[7] * 4);
0693     }
0694 
0695  skip_rtpg:
0696     spin_lock_irqsave(&pg->lock, flags);
0697     if (transitioning_sense)
0698         pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
0699 
0700     if (group_id_old != pg->group_id || state_old != pg->state ||
0701         pref_old != pg->pref || valid_states_old != pg->valid_states)
0702         sdev_printk(KERN_INFO, sdev,
0703             "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
0704             ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
0705             pg->pref ? "preferred" : "non-preferred",
0706             pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
0707             pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
0708             pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
0709             pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
0710             pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
0711             pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
0712             pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
0713 
0714     switch (pg->state) {
0715     case SCSI_ACCESS_STATE_TRANSITIONING:
0716         if (time_before(jiffies, pg->expiry)) {
0717             /* State transition, retry */
0718             pg->interval = ALUA_RTPG_RETRY_DELAY;
0719             err = SCSI_DH_RETRY;
0720         } else {
0721             struct alua_dh_data *h;
0722 
0723             /* Transitioning time exceeded, set port to standby */
0724             err = SCSI_DH_IO;
0725             pg->state = SCSI_ACCESS_STATE_STANDBY;
0726             pg->expiry = 0;
0727             rcu_read_lock();
0728             list_for_each_entry_rcu(h, &pg->dh_list, node) {
0729                 if (!h->sdev)
0730                     continue;
0731                 h->sdev->access_state =
0732                     (pg->state & SCSI_ACCESS_STATE_MASK);
0733                 if (pg->pref)
0734                     h->sdev->access_state |=
0735                         SCSI_ACCESS_STATE_PREFERRED;
0736             }
0737             rcu_read_unlock();
0738         }
0739         break;
0740     case SCSI_ACCESS_STATE_OFFLINE:
0741         /* Path unusable */
0742         err = SCSI_DH_DEV_OFFLINED;
0743         pg->expiry = 0;
0744         break;
0745     default:
0746         /* Useable path if active */
0747         err = SCSI_DH_OK;
0748         pg->expiry = 0;
0749         break;
0750     }
0751     spin_unlock_irqrestore(&pg->lock, flags);
0752     kfree(buff);
0753     return err;
0754 }
0755 
0756 /*
0757  * alua_stpg - Issue a SET TARGET PORT GROUP command
0758  *
0759  * Issue a SET TARGET PORT GROUP command and evaluate the
0760  * response. Returns SCSI_DH_RETRY per default to trigger
0761  * a re-evaluation of the target group state or SCSI_DH_OK
0762  * if no further action needs to be taken.
0763  */
0764 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
0765 {
0766     int retval;
0767     struct scsi_sense_hdr sense_hdr;
0768 
0769     if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
0770         /* Only implicit ALUA supported, retry */
0771         return SCSI_DH_RETRY;
0772     }
0773     switch (pg->state) {
0774     case SCSI_ACCESS_STATE_OPTIMAL:
0775         return SCSI_DH_OK;
0776     case SCSI_ACCESS_STATE_ACTIVE:
0777         if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
0778             !pg->pref &&
0779             (pg->tpgs & TPGS_MODE_IMPLICIT))
0780             return SCSI_DH_OK;
0781         break;
0782     case SCSI_ACCESS_STATE_STANDBY:
0783     case SCSI_ACCESS_STATE_UNAVAILABLE:
0784         break;
0785     case SCSI_ACCESS_STATE_OFFLINE:
0786         return SCSI_DH_IO;
0787     case SCSI_ACCESS_STATE_TRANSITIONING:
0788         break;
0789     default:
0790         sdev_printk(KERN_INFO, sdev,
0791                 "%s: stpg failed, unhandled TPGS state %d",
0792                 ALUA_DH_NAME, pg->state);
0793         return SCSI_DH_NOSYS;
0794     }
0795     retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
0796 
0797     if (retval) {
0798         if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
0799             sdev_printk(KERN_INFO, sdev,
0800                     "%s: stpg failed, result %d",
0801                     ALUA_DH_NAME, retval);
0802             if (retval < 0)
0803                 return SCSI_DH_DEV_TEMP_BUSY;
0804         } else {
0805             sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
0806                     ALUA_DH_NAME);
0807             scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
0808         }
0809     }
0810     /* Retry RTPG */
0811     return SCSI_DH_RETRY;
0812 }
0813 
0814 static bool alua_rtpg_select_sdev(struct alua_port_group *pg)
0815 {
0816     struct alua_dh_data *h;
0817     struct scsi_device *sdev = NULL;
0818 
0819     lockdep_assert_held(&pg->lock);
0820     if (WARN_ON(!pg->rtpg_sdev))
0821         return false;
0822 
0823     /*
0824      * RCU protection isn't necessary for dh_list here
0825      * as we hold pg->lock, but for access to h->pg.
0826      */
0827     rcu_read_lock();
0828     list_for_each_entry_rcu(h, &pg->dh_list, node) {
0829         if (!h->sdev)
0830             continue;
0831         if (h->sdev == pg->rtpg_sdev) {
0832             h->disabled = true;
0833             continue;
0834         }
0835         if (rcu_dereference(h->pg) == pg &&
0836             !h->disabled &&
0837             !scsi_device_get(h->sdev)) {
0838             sdev = h->sdev;
0839             break;
0840         }
0841     }
0842     rcu_read_unlock();
0843 
0844     if (!sdev) {
0845         pr_warn("%s: no device found for rtpg\n",
0846             (pg->device_id_len ?
0847              (char *)pg->device_id_str : "(nameless PG)"));
0848         return false;
0849     }
0850 
0851     sdev_printk(KERN_INFO, sdev, "rtpg retry on different device\n");
0852 
0853     scsi_device_put(pg->rtpg_sdev);
0854     pg->rtpg_sdev = sdev;
0855 
0856     return true;
0857 }
0858 
0859 static void alua_rtpg_work(struct work_struct *work)
0860 {
0861     struct alua_port_group *pg =
0862         container_of(work, struct alua_port_group, rtpg_work.work);
0863     struct scsi_device *sdev;
0864     LIST_HEAD(qdata_list);
0865     int err = SCSI_DH_OK;
0866     struct alua_queue_data *qdata, *tmp;
0867     struct alua_dh_data *h;
0868     unsigned long flags;
0869 
0870     spin_lock_irqsave(&pg->lock, flags);
0871     sdev = pg->rtpg_sdev;
0872     if (!sdev) {
0873         WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
0874         WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
0875         spin_unlock_irqrestore(&pg->lock, flags);
0876         kref_put(&pg->kref, release_port_group);
0877         return;
0878     }
0879     pg->flags |= ALUA_PG_RUNNING;
0880     if (pg->flags & ALUA_PG_RUN_RTPG) {
0881         int state = pg->state;
0882 
0883         pg->flags &= ~ALUA_PG_RUN_RTPG;
0884         spin_unlock_irqrestore(&pg->lock, flags);
0885         if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
0886             if (alua_tur(sdev) == SCSI_DH_RETRY) {
0887                 spin_lock_irqsave(&pg->lock, flags);
0888                 pg->flags &= ~ALUA_PG_RUNNING;
0889                 pg->flags |= ALUA_PG_RUN_RTPG;
0890                 if (!pg->interval)
0891                     pg->interval = ALUA_RTPG_RETRY_DELAY;
0892                 spin_unlock_irqrestore(&pg->lock, flags);
0893                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
0894                            pg->interval * HZ);
0895                 return;
0896             }
0897             /* Send RTPG on failure or if TUR indicates SUCCESS */
0898         }
0899         err = alua_rtpg(sdev, pg);
0900         spin_lock_irqsave(&pg->lock, flags);
0901 
0902         /* If RTPG failed on the current device, try using another */
0903         if (err == SCSI_DH_RES_TEMP_UNAVAIL &&
0904             alua_rtpg_select_sdev(pg))
0905             err = SCSI_DH_IMM_RETRY;
0906 
0907         if (err == SCSI_DH_RETRY || err == SCSI_DH_IMM_RETRY ||
0908             pg->flags & ALUA_PG_RUN_RTPG) {
0909             pg->flags &= ~ALUA_PG_RUNNING;
0910             if (err == SCSI_DH_IMM_RETRY)
0911                 pg->interval = 0;
0912             else if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
0913                 pg->interval = ALUA_RTPG_RETRY_DELAY;
0914             pg->flags |= ALUA_PG_RUN_RTPG;
0915             spin_unlock_irqrestore(&pg->lock, flags);
0916             queue_delayed_work(kaluad_wq, &pg->rtpg_work,
0917                        pg->interval * HZ);
0918             return;
0919         }
0920         if (err != SCSI_DH_OK)
0921             pg->flags &= ~ALUA_PG_RUN_STPG;
0922     }
0923     if (pg->flags & ALUA_PG_RUN_STPG) {
0924         pg->flags &= ~ALUA_PG_RUN_STPG;
0925         spin_unlock_irqrestore(&pg->lock, flags);
0926         err = alua_stpg(sdev, pg);
0927         spin_lock_irqsave(&pg->lock, flags);
0928         if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
0929             pg->flags |= ALUA_PG_RUN_RTPG;
0930             pg->interval = 0;
0931             pg->flags &= ~ALUA_PG_RUNNING;
0932             spin_unlock_irqrestore(&pg->lock, flags);
0933             queue_delayed_work(kaluad_wq, &pg->rtpg_work,
0934                        pg->interval * HZ);
0935             return;
0936         }
0937     }
0938 
0939     list_splice_init(&pg->rtpg_list, &qdata_list);
0940     /*
0941      * We went through an RTPG, for good or bad.
0942      * Re-enable all devices for the next attempt.
0943      */
0944     list_for_each_entry(h, &pg->dh_list, node)
0945         h->disabled = false;
0946     pg->rtpg_sdev = NULL;
0947     spin_unlock_irqrestore(&pg->lock, flags);
0948 
0949     list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
0950         list_del(&qdata->entry);
0951         if (qdata->callback_fn)
0952             qdata->callback_fn(qdata->callback_data, err);
0953         kfree(qdata);
0954     }
0955     spin_lock_irqsave(&pg->lock, flags);
0956     pg->flags &= ~ALUA_PG_RUNNING;
0957     spin_unlock_irqrestore(&pg->lock, flags);
0958     scsi_device_put(sdev);
0959     kref_put(&pg->kref, release_port_group);
0960 }
0961 
0962 /**
0963  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
0964  * @pg: ALUA port group associated with @sdev.
0965  * @sdev: SCSI device for which to submit an RTPG.
0966  * @qdata: Information about the callback to invoke after the RTPG.
0967  * @force: Whether or not to submit an RTPG if a work item that will submit an
0968  *         RTPG already has been scheduled.
0969  *
0970  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
0971  * That function is responsible for calling @qdata->fn().
0972  */
0973 static bool alua_rtpg_queue(struct alua_port_group *pg,
0974                 struct scsi_device *sdev,
0975                 struct alua_queue_data *qdata, bool force)
0976 {
0977     int start_queue = 0;
0978     unsigned long flags;
0979     if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
0980         return false;
0981 
0982     spin_lock_irqsave(&pg->lock, flags);
0983     if (qdata) {
0984         list_add_tail(&qdata->entry, &pg->rtpg_list);
0985         pg->flags |= ALUA_PG_RUN_STPG;
0986         force = true;
0987     }
0988     if (pg->rtpg_sdev == NULL) {
0989         pg->interval = 0;
0990         pg->flags |= ALUA_PG_RUN_RTPG;
0991         kref_get(&pg->kref);
0992         pg->rtpg_sdev = sdev;
0993         start_queue = 1;
0994     } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
0995         pg->flags |= ALUA_PG_RUN_RTPG;
0996         /* Do not queue if the worker is already running */
0997         if (!(pg->flags & ALUA_PG_RUNNING)) {
0998             kref_get(&pg->kref);
0999             start_queue = 1;
1000         }
1001     }
1002 
1003     spin_unlock_irqrestore(&pg->lock, flags);
1004 
1005     if (start_queue) {
1006         if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
1007                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
1008             sdev = NULL;
1009         else
1010             kref_put(&pg->kref, release_port_group);
1011     }
1012     if (sdev)
1013         scsi_device_put(sdev);
1014 
1015     return true;
1016 }
1017 
1018 /*
1019  * alua_initialize - Initialize ALUA state
1020  * @sdev: the device to be initialized
1021  *
1022  * For the prep_fn to work correctly we have
1023  * to initialize the ALUA state for the device.
1024  */
1025 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
1026 {
1027     int err = SCSI_DH_DEV_UNSUPP, tpgs;
1028 
1029     mutex_lock(&h->init_mutex);
1030     h->disabled = false;
1031     tpgs = alua_check_tpgs(sdev);
1032     if (tpgs != TPGS_MODE_NONE)
1033         err = alua_check_vpd(sdev, h, tpgs);
1034     h->init_error = err;
1035     mutex_unlock(&h->init_mutex);
1036     return err;
1037 }
1038 /*
1039  * alua_set_params - set/unset the optimize flag
1040  * @sdev: device on the path to be activated
1041  * params - parameters in the following format
1042  *      "no_of_params\0param1\0param2\0param3\0...\0"
1043  * For example, to set the flag pass the following parameters
1044  * from multipath.conf
1045  *     hardware_handler        "2 alua 1"
1046  */
1047 static int alua_set_params(struct scsi_device *sdev, const char *params)
1048 {
1049     struct alua_dh_data *h = sdev->handler_data;
1050     struct alua_port_group *pg = NULL;
1051     unsigned int optimize = 0, argc;
1052     const char *p = params;
1053     int result = SCSI_DH_OK;
1054     unsigned long flags;
1055 
1056     if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
1057         return -EINVAL;
1058 
1059     while (*p++)
1060         ;
1061     if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
1062         return -EINVAL;
1063 
1064     rcu_read_lock();
1065     pg = rcu_dereference(h->pg);
1066     if (!pg) {
1067         rcu_read_unlock();
1068         return -ENXIO;
1069     }
1070     spin_lock_irqsave(&pg->lock, flags);
1071     if (optimize)
1072         pg->flags |= ALUA_OPTIMIZE_STPG;
1073     else
1074         pg->flags &= ~ALUA_OPTIMIZE_STPG;
1075     spin_unlock_irqrestore(&pg->lock, flags);
1076     rcu_read_unlock();
1077 
1078     return result;
1079 }
1080 
1081 /*
1082  * alua_activate - activate a path
1083  * @sdev: device on the path to be activated
1084  *
1085  * We're currently switching the port group to be activated only and
1086  * let the array figure out the rest.
1087  * There may be other arrays which require us to switch all port groups
1088  * based on a certain policy. But until we actually encounter them it
1089  * should be okay.
1090  */
1091 static int alua_activate(struct scsi_device *sdev,
1092             activate_complete fn, void *data)
1093 {
1094     struct alua_dh_data *h = sdev->handler_data;
1095     int err = SCSI_DH_OK;
1096     struct alua_queue_data *qdata;
1097     struct alua_port_group *pg;
1098 
1099     qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1100     if (!qdata) {
1101         err = SCSI_DH_RES_TEMP_UNAVAIL;
1102         goto out;
1103     }
1104     qdata->callback_fn = fn;
1105     qdata->callback_data = data;
1106 
1107     mutex_lock(&h->init_mutex);
1108     rcu_read_lock();
1109     pg = rcu_dereference(h->pg);
1110     if (!pg || !kref_get_unless_zero(&pg->kref)) {
1111         rcu_read_unlock();
1112         kfree(qdata);
1113         err = h->init_error;
1114         mutex_unlock(&h->init_mutex);
1115         goto out;
1116     }
1117     rcu_read_unlock();
1118     mutex_unlock(&h->init_mutex);
1119 
1120     if (alua_rtpg_queue(pg, sdev, qdata, true))
1121         fn = NULL;
1122     else
1123         err = SCSI_DH_DEV_OFFLINED;
1124     kref_put(&pg->kref, release_port_group);
1125 out:
1126     if (fn)
1127         fn(data, err);
1128     return 0;
1129 }
1130 
1131 /*
1132  * alua_check - check path status
1133  * @sdev: device on the path to be checked
1134  *
1135  * Check the device status
1136  */
1137 static void alua_check(struct scsi_device *sdev, bool force)
1138 {
1139     struct alua_dh_data *h = sdev->handler_data;
1140     struct alua_port_group *pg;
1141 
1142     rcu_read_lock();
1143     pg = rcu_dereference(h->pg);
1144     if (!pg || !kref_get_unless_zero(&pg->kref)) {
1145         rcu_read_unlock();
1146         return;
1147     }
1148     rcu_read_unlock();
1149     alua_rtpg_queue(pg, sdev, NULL, force);
1150     kref_put(&pg->kref, release_port_group);
1151 }
1152 
1153 /*
1154  * alua_prep_fn - request callback
1155  *
1156  * Fail I/O to all paths not in state
1157  * active/optimized or active/non-optimized.
1158  */
1159 static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
1160 {
1161     struct alua_dh_data *h = sdev->handler_data;
1162     struct alua_port_group *pg;
1163     unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1164 
1165     rcu_read_lock();
1166     pg = rcu_dereference(h->pg);
1167     if (pg)
1168         state = pg->state;
1169     rcu_read_unlock();
1170 
1171     switch (state) {
1172     case SCSI_ACCESS_STATE_OPTIMAL:
1173     case SCSI_ACCESS_STATE_ACTIVE:
1174     case SCSI_ACCESS_STATE_LBA:
1175     case SCSI_ACCESS_STATE_TRANSITIONING:
1176         return BLK_STS_OK;
1177     default:
1178         req->rq_flags |= RQF_QUIET;
1179         return BLK_STS_IOERR;
1180     }
1181 }
1182 
1183 static void alua_rescan(struct scsi_device *sdev)
1184 {
1185     struct alua_dh_data *h = sdev->handler_data;
1186 
1187     alua_initialize(sdev, h);
1188 }
1189 
1190 /*
1191  * alua_bus_attach - Attach device handler
1192  * @sdev: device to be attached to
1193  */
1194 static int alua_bus_attach(struct scsi_device *sdev)
1195 {
1196     struct alua_dh_data *h;
1197     int err;
1198 
1199     h = kzalloc(sizeof(*h) , GFP_KERNEL);
1200     if (!h)
1201         return SCSI_DH_NOMEM;
1202     spin_lock_init(&h->pg_lock);
1203     rcu_assign_pointer(h->pg, NULL);
1204     h->init_error = SCSI_DH_OK;
1205     h->sdev = sdev;
1206     INIT_LIST_HEAD(&h->node);
1207 
1208     mutex_init(&h->init_mutex);
1209     err = alua_initialize(sdev, h);
1210     if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1211         goto failed;
1212 
1213     sdev->handler_data = h;
1214     return SCSI_DH_OK;
1215 failed:
1216     kfree(h);
1217     return err;
1218 }
1219 
1220 /*
1221  * alua_bus_detach - Detach device handler
1222  * @sdev: device to be detached from
1223  */
1224 static void alua_bus_detach(struct scsi_device *sdev)
1225 {
1226     struct alua_dh_data *h = sdev->handler_data;
1227     struct alua_port_group *pg;
1228 
1229     spin_lock(&h->pg_lock);
1230     pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1231     rcu_assign_pointer(h->pg, NULL);
1232     spin_unlock(&h->pg_lock);
1233     if (pg) {
1234         spin_lock_irq(&pg->lock);
1235         list_del_rcu(&h->node);
1236         spin_unlock_irq(&pg->lock);
1237         kref_put(&pg->kref, release_port_group);
1238     }
1239     sdev->handler_data = NULL;
1240     synchronize_rcu();
1241     kfree(h);
1242 }
1243 
1244 static struct scsi_device_handler alua_dh = {
1245     .name = ALUA_DH_NAME,
1246     .module = THIS_MODULE,
1247     .attach = alua_bus_attach,
1248     .detach = alua_bus_detach,
1249     .prep_fn = alua_prep_fn,
1250     .check_sense = alua_check_sense,
1251     .activate = alua_activate,
1252     .rescan = alua_rescan,
1253     .set_params = alua_set_params,
1254 };
1255 
1256 static int __init alua_init(void)
1257 {
1258     int r;
1259 
1260     kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1261     if (!kaluad_wq)
1262         return -ENOMEM;
1263 
1264     r = scsi_register_device_handler(&alua_dh);
1265     if (r != 0) {
1266         printk(KERN_ERR "%s: Failed to register scsi device handler",
1267             ALUA_DH_NAME);
1268         destroy_workqueue(kaluad_wq);
1269     }
1270     return r;
1271 }
1272 
1273 static void __exit alua_exit(void)
1274 {
1275     scsi_unregister_device_handler(&alua_dh);
1276     destroy_workqueue(kaluad_wq);
1277 }
1278 
1279 module_init(alua_init);
1280 module_exit(alua_exit);
1281 
1282 MODULE_DESCRIPTION("DM Multipath ALUA support");
1283 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1284 MODULE_LICENSE("GPL");
1285 MODULE_VERSION(ALUA_DH_VER);
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