scsi_dh_alua.c

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/*
 * 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 <linux/slab.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <scsi/scsi.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_dh.h>

#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_INQUIRY_SIZE       36
#define ALUA_FAILOVER_TIMEOUT       60
#define ALUA_FAILOVER_RETRIES       5

/* flags passed from user level */
#define ALUA_OPTIMIZE_STPG      1

struct alua_dh_data {
    int         group_id;
    int         rel_port;
    int         tpgs;
    int         state;
    int         pref;
    unsigned        flags; /* used for optimizing STPG */
    unsigned char       inq[ALUA_INQUIRY_SIZE];
    unsigned char       *buff;
    int         bufflen;
    unsigned char       transition_tmo;
    unsigned char       sense[SCSI_SENSE_BUFFERSIZE];
    int         senselen;
    struct scsi_device  *sdev;
    activate_complete   callback_fn;
    void            *callback_data;
};

#define ALUA_POLICY_SWITCH_CURRENT  0
#define ALUA_POLICY_SWITCH_ALL      1

static char print_alua_state(int);
static int alua_check_sense(struct scsi_device *, struct scsi_sense_hdr *);

static inline struct alua_dh_data *get_alua_data(struct scsi_device *sdev)
{
    struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
    BUG_ON(scsi_dh_data == NULL);
    return ((struct alua_dh_data *) scsi_dh_data->buf);
}

static int realloc_buffer(struct alua_dh_data *h, unsigned len)
{
    if (h->buff && h->buff != h->inq)
        kfree(h->buff);

    h->buff = kmalloc(len, GFP_NOIO);
    if (!h->buff) {
        h->buff = h->inq;
        h->bufflen = ALUA_INQUIRY_SIZE;
        return 1;
    }
    h->bufflen = len;
    return 0;
}

static struct request *get_alua_req(struct scsi_device *sdev,
                    void *buffer, unsigned buflen, int rw)
{
    struct request *rq;
    struct request_queue *q = sdev->request_queue;

    rq = blk_get_request(q, rw, GFP_NOIO);

    if (!rq) {
        sdev_printk(KERN_INFO, sdev,
                "%s: blk_get_request failed\n", __func__);
        return NULL;
    }

    if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_NOIO)) {
        blk_put_request(rq);
        sdev_printk(KERN_INFO, sdev,
                "%s: blk_rq_map_kern failed\n", __func__);
        return NULL;
    }

    rq->cmd_type = REQ_TYPE_BLOCK_PC;
    rq->cmd_flags |= REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
             REQ_FAILFAST_DRIVER;
    rq->retries = ALUA_FAILOVER_RETRIES;
    rq->timeout = ALUA_FAILOVER_TIMEOUT * HZ;

    return rq;
}

/*
 * submit_vpd_inquiry - Issue an INQUIRY VPD page 0x83 command
 * @sdev: sdev the command should be sent to
 */
static int submit_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
{
    struct request *rq;
    int err = SCSI_DH_RES_TEMP_UNAVAIL;

    rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
    if (!rq)
        goto done;

    /* Prepare the command. */
    rq->cmd[0] = INQUIRY;
    rq->cmd[1] = 1;
    rq->cmd[2] = 0x83;
    rq->cmd[4] = h->bufflen;
    rq->cmd_len = COMMAND_SIZE(INQUIRY);

    rq->sense = h->sense;
    memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
    rq->sense_len = h->senselen = 0;

    err = blk_execute_rq(rq->q, NULL, rq, 1);
    if (err == -EIO) {
        sdev_printk(KERN_INFO, sdev,
                "%s: evpd inquiry failed with %x\n",
                ALUA_DH_NAME, rq->errors);
        h->senselen = rq->sense_len;
        err = SCSI_DH_IO;
    }
    blk_put_request(rq);
done:
    return err;
}

/*
 * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 * @sdev: sdev the command should be sent to
 */
static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h,
                bool rtpg_ext_hdr_req)
{
    struct request *rq;
    int err = SCSI_DH_RES_TEMP_UNAVAIL;

    rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
    if (!rq)
        goto done;

    /* Prepare the command. */
    rq->cmd[0] = MAINTENANCE_IN;
    if (rtpg_ext_hdr_req)
        rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
    else
        rq->cmd[1] = MI_REPORT_TARGET_PGS;
    rq->cmd[6] = (h->bufflen >> 24) & 0xff;
    rq->cmd[7] = (h->bufflen >> 16) & 0xff;
    rq->cmd[8] = (h->bufflen >>  8) & 0xff;
    rq->cmd[9] = h->bufflen & 0xff;
    rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);

    rq->sense = h->sense;
    memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
    rq->sense_len = h->senselen = 0;

    err = blk_execute_rq(rq->q, NULL, rq, 1);
    if (err == -EIO) {
        sdev_printk(KERN_INFO, sdev,
                "%s: rtpg failed with %x\n",
                ALUA_DH_NAME, rq->errors);
        h->senselen = rq->sense_len;
        err = SCSI_DH_IO;
    }
    blk_put_request(rq);
done:
    return err;
}

/*
 * alua_stpg - Evaluate SET TARGET GROUP STATES
 * @sdev: the device to be evaluated
 * @state: the new target group state
 *
 * Send a SET TARGET GROUP STATES command to the device.
 * We only have to test here if we should resubmit the command;
 * any other error is assumed as a failure.
 */
static void stpg_endio(struct request *req, int error)
{
    struct alua_dh_data *h = req->end_io_data;
    struct scsi_sense_hdr sense_hdr;
    unsigned err = SCSI_DH_OK;

    if (error || host_byte(req->errors) != DID_OK ||
            msg_byte(req->errors) != COMMAND_COMPLETE) {
        err = SCSI_DH_IO;
        goto done;
    }

    if (h->senselen > 0) {
        err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
                       &sense_hdr);
        if (!err) {
            err = SCSI_DH_IO;
            goto done;
        }
        err = alua_check_sense(h->sdev, &sense_hdr);
        if (err == ADD_TO_MLQUEUE) {
            err = SCSI_DH_RETRY;
            goto done;
        }
        sdev_printk(KERN_INFO, h->sdev,
                "%s: stpg sense code: %02x/%02x/%02x\n",
                ALUA_DH_NAME, sense_hdr.sense_key,
                sense_hdr.asc, sense_hdr.ascq);
        err = SCSI_DH_IO;
    }
    if (err == SCSI_DH_OK) {
        h->state = TPGS_STATE_OPTIMIZED;
        sdev_printk(KERN_INFO, h->sdev,
                "%s: port group %02x switched to state %c\n",
                ALUA_DH_NAME, h->group_id,
                print_alua_state(h->state));
    }
done:
    req->end_io_data = NULL;
    __blk_put_request(req->q, req);
    if (h->callback_fn) {
        h->callback_fn(h->callback_data, err);
        h->callback_fn = h->callback_data = NULL;
    }
    return;
}

/*
 * submit_stpg - Issue a SET TARGET GROUP STATES 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 unsigned submit_stpg(struct alua_dh_data *h)
{
    struct request *rq;
    int stpg_len = 8;
    struct scsi_device *sdev = h->sdev;

    /* Prepare the data buffer */
    memset(h->buff, 0, stpg_len);
    h->buff[4] = TPGS_STATE_OPTIMIZED & 0x0f;
    h->buff[6] = (h->group_id >> 8) & 0xff;
    h->buff[7] = h->group_id & 0xff;

    rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
    if (!rq)
        return SCSI_DH_RES_TEMP_UNAVAIL;

    /* Prepare the command. */
    rq->cmd[0] = MAINTENANCE_OUT;
    rq->cmd[1] = MO_SET_TARGET_PGS;
    rq->cmd[6] = (stpg_len >> 24) & 0xff;
    rq->cmd[7] = (stpg_len >> 16) & 0xff;
    rq->cmd[8] = (stpg_len >>  8) & 0xff;
    rq->cmd[9] = stpg_len & 0xff;
    rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);

    rq->sense = h->sense;
    memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
    rq->sense_len = h->senselen = 0;
    rq->end_io_data = h;

    blk_execute_rq_nowait(rq->q, NULL, rq, 1, stpg_endio);
    return SCSI_DH_OK;
}

/*
 * 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, struct alua_dh_data *h)
{
    int err = SCSI_DH_OK;

    h->tpgs = scsi_device_tpgs(sdev);
    switch (h->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;
    default:
        h->tpgs = TPGS_MODE_NONE;
        sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
                ALUA_DH_NAME);
        err = SCSI_DH_DEV_UNSUPP;
        break;
    }

    return err;
}

/*
 * alua_vpd_inquiry - 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_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
{
    int len;
    unsigned err;
    unsigned char *d;

 retry:
    err = submit_vpd_inquiry(sdev, h);

    if (err != SCSI_DH_OK)
        return err;

    /* Check if vpd page exceeds initial buffer */
    len = (h->buff[2] << 8) + h->buff[3] + 4;
    if (len > h->bufflen) {
        /* Resubmit with the correct length */
        if (realloc_buffer(h, len)) {
            sdev_printk(KERN_WARNING, sdev,
                    "%s: kmalloc buffer failed\n",
                    ALUA_DH_NAME);
            /* Temporary failure, bypass */
            return SCSI_DH_DEV_TEMP_BUSY;
        }
        goto retry;
    }

    /*
     * Now look for the correct descriptor.
     */
    d = h->buff + 4;
    while (d < h->buff + len) {
        switch (d[1] & 0xf) {
        case 0x4:
            /* Relative target port */
            h->rel_port = (d[6] << 8) + d[7];
            break;
        case 0x5:
            /* Target port group */
            h->group_id = (d[6] << 8) + d[7];
            break;
        default:
            break;
        }
        d += d[3] + 4;
    }

    if (h->group_id == -1) {
        /*
         * 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);
        h->state = TPGS_STATE_OPTIMIZED;
        h->tpgs = TPGS_MODE_NONE;
        err = SCSI_DH_DEV_UNSUPP;
    } else {
        sdev_printk(KERN_INFO, sdev,
                "%s: port group %02x rel port %02x\n",
                ALUA_DH_NAME, h->group_id, h->rel_port);
    }

    return err;
}

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;
        if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0b)
            /*
             * LUN Not Accessible -- Target port in standby state
             */
            return SUCCESS;
        if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0c)
            /*
             * LUN Not Accessible -- Target port in unavailable state
             */
            return SUCCESS;
        if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x12)
            /*
             * LUN Not Ready -- Offline
             */
            return SUCCESS;
        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 == 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_dh_data *h)
{
    struct scsi_sense_hdr sense_hdr;
    int len, k, off, valid_states = 0;
    unsigned char *ucp;
    unsigned err;
    bool rtpg_ext_hdr_req = 1;
    unsigned long expiry, interval = 0;
    unsigned int tpg_desc_tbl_off;
    unsigned char orig_transition_tmo;

    if (!h->transition_tmo)
        expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
    else
        expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);

 retry:
    err = submit_rtpg(sdev, h, rtpg_ext_hdr_req);

    if (err == SCSI_DH_IO && h->senselen > 0) {
        err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
                       &sense_hdr);
        if (!err)
            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 (rtpg_ext_hdr_req == 1 &&
            sense_hdr.sense_key == ILLEGAL_REQUEST &&
            sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
            rtpg_ext_hdr_req = 0;
            goto retry;
        }

        err = alua_check_sense(sdev, &sense_hdr);
        if (err == ADD_TO_MLQUEUE && time_before(jiffies, expiry))
            goto retry;
        sdev_printk(KERN_INFO, sdev,
                "%s: rtpg sense code %02x/%02x/%02x\n",
                ALUA_DH_NAME, sense_hdr.sense_key,
                sense_hdr.asc, sense_hdr.ascq);
        err = SCSI_DH_IO;
    }
    if (err != SCSI_DH_OK)
        return err;

    len = (h->buff[0] << 24) + (h->buff[1] << 16) +
        (h->buff[2] << 8) + h->buff[3] + 4;

    if (len > h->bufflen) {
        /* Resubmit with the correct length */
        if (realloc_buffer(h, len)) {
            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 = h->transition_tmo;
    if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && h->buff[5] != 0)
        h->transition_tmo = h->buff[5];
    else
        h->transition_tmo = ALUA_FAILOVER_TIMEOUT;

    if (orig_transition_tmo != h->transition_tmo) {
        sdev_printk(KERN_INFO, sdev,
                "%s: transition timeout set to %d seconds\n",
                ALUA_DH_NAME, h->transition_tmo);
        expiry = jiffies + h->transition_tmo * HZ;
    }

    if ((h->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 = h->buff + tpg_desc_tbl_off;
         k < len;
         k += off, ucp += off) {

        if (h->group_id == (ucp[2] << 8) + ucp[3]) {
            h->state = ucp[0] & 0x0f;
            h->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, h->group_id, print_alua_state(h->state),
            h->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 (h->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;
        h->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;
    }
    return err;
}

/*
 * 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;

    err = alua_check_tpgs(sdev, h);
    if (err != SCSI_DH_OK)
        goto out;

    err = alua_vpd_inquiry(sdev, h);
    if (err != SCSI_DH_OK)
        goto out;

    err = alua_rtpg(sdev, h);
    if (err != SCSI_DH_OK)
        goto out;

out:
    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 = get_alua_data(sdev);
    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;

    if (optimize)
        h->flags |= ALUA_OPTIMIZE_STPG;
    else
        h->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 = get_alua_data(sdev);
    int err = SCSI_DH_OK;
    int stpg = 0;

    err = alua_rtpg(sdev, h);
    if (err != SCSI_DH_OK)
        goto out;

    if (h->tpgs & TPGS_MODE_EXPLICIT) {
        switch (h->state) {
        case TPGS_STATE_NONOPTIMIZED:
            stpg = 1;
            if ((h->flags & ALUA_OPTIMIZE_STPG) &&
                (!h->pref) &&
                (h->tpgs & TPGS_MODE_IMPLICIT))
                stpg = 0;
            break;
        case TPGS_STATE_STANDBY:
        case TPGS_STATE_UNAVAILABLE:
            stpg = 1;
            break;
        case TPGS_STATE_OFFLINE:
            err = SCSI_DH_IO;
            break;
        case TPGS_STATE_TRANSITIONING:
            err = SCSI_DH_RETRY;
            break;
        default:
            break;
        }
    }

    if (stpg) {
        h->callback_fn = fn;
        h->callback_data = data;
        err = submit_stpg(h);
        if (err == SCSI_DH_OK)
            return 0;
        h->callback_fn = h->callback_data = NULL;
    }

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 = get_alua_data(sdev);
    int ret = BLKPREP_OK;

    if (h->state == TPGS_STATE_TRANSITIONING)
        ret = BLKPREP_DEFER;
    else if (h->state != TPGS_STATE_OPTIMIZED &&
         h->state != TPGS_STATE_NONOPTIMIZED &&
         h->state != TPGS_STATE_LBA_DEPENDENT) {
        ret = BLKPREP_KILL;
        req->cmd_flags |= REQ_QUIET;
    }
    return ret;

}

static bool alua_match(struct scsi_device *sdev)
{
    return (scsi_device_tpgs(sdev) != 0);
}

static int alua_bus_attach(struct scsi_device *sdev);
static void alua_bus_detach(struct scsi_device *sdev);

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,
    .match = alua_match,
};

/*
 * alua_bus_attach - Attach device handler
 * @sdev: device to be attached to
 */
static int alua_bus_attach(struct scsi_device *sdev)
{
    struct scsi_dh_data *scsi_dh_data;
    struct alua_dh_data *h;
    unsigned long flags;
    int err = SCSI_DH_OK;

    scsi_dh_data = kzalloc(sizeof(*scsi_dh_data)
                   + sizeof(*h) , GFP_KERNEL);
    if (!scsi_dh_data) {
        sdev_printk(KERN_ERR, sdev, "%s: Attach failed\n",
                ALUA_DH_NAME);
        return -ENOMEM;
    }

    scsi_dh_data->scsi_dh = &alua_dh;
    h = (struct alua_dh_data *) scsi_dh_data->buf;
    h->tpgs = TPGS_MODE_UNINITIALIZED;
    h->state = TPGS_STATE_OPTIMIZED;
    h->group_id = -1;
    h->rel_port = -1;
    h->buff = h->inq;
    h->bufflen = ALUA_INQUIRY_SIZE;
    h->sdev = sdev;

    err = alua_initialize(sdev, h);
    if ((err != SCSI_DH_OK) && (err != SCSI_DH_DEV_OFFLINED))
        goto failed;

    if (!try_module_get(THIS_MODULE))
        goto failed;

    spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
    sdev->scsi_dh_data = scsi_dh_data;
    spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
    sdev_printk(KERN_NOTICE, sdev, "%s: Attached\n", ALUA_DH_NAME);

    return 0;

failed:
    kfree(scsi_dh_data);
    sdev_printk(KERN_ERR, sdev, "%s: not attached\n", ALUA_DH_NAME);
    return -EINVAL;
}

/*
 * alua_bus_detach - Detach device handler
 * @sdev: device to be detached from
 */
static void alua_bus_detach(struct scsi_device *sdev)
{
    struct scsi_dh_data *scsi_dh_data;
    struct alua_dh_data *h;
    unsigned long flags;

    spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
    scsi_dh_data = sdev->scsi_dh_data;
    sdev->scsi_dh_data = NULL;
    spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);

    h = (struct alua_dh_data *) scsi_dh_data->buf;
    if (h->buff && h->inq != h->buff)
        kfree(h->buff);
    kfree(scsi_dh_data);
    module_put(THIS_MODULE);
    sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", ALUA_DH_NAME);
}

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 <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_VERSION(ALUA_DH_VER);