Re: [PATCH 3/7] scsi_dh: add generic SPC-3 alua handler

Chandra Seetharaman
2008-05-15T02:48:01Z

I do not know the functionality of this module. So, my comments are only
related to code.

blk_request_rq() frees up the request before it returns (in
blk_end_sync_rq()). So, there is no need for blk_put_request().

On Wed, 2008-05-14 at 16:43 +0200, Hannes Reinecke wrote:
> This patch adds a generic SPC-3 ALUA handler.
>
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
> drivers/scsi/device_handler/Kconfig | 8 +
> drivers/scsi/device_handler/Makefile | 1 +
> drivers/scsi/device_handler/scsi_dh_alua.c | 806 ++++++++++++++++++++++++++++
> include/scsi/scsi.h | 3 +
> include/scsi/scsi_dh.h | 2 +
> 5 files changed, 820 insertions(+), 0 deletions(-)
> create mode 100644 drivers/scsi/device_handler/scsi_dh_alua.c
>
> diff --git a/drivers/scsi/device_handler/Kconfig b/drivers/scsi/device_handler/Kconfig
> index 2adc0f6..6707025 100644
> --- a/drivers/scsi/device_handler/Kconfig
> +++ b/drivers/scsi/device_handler/Kconfig
> @@ -30,3 +30,11 @@ config SCSI_DH_EMC
> depends on SCSI_DH
> help
> If you have a EMC CLARiiON select y. Otherwise, say N.
> +
> +config SCSI_DH_ALUA
> + tristate "SPC-3 ALUA Device Handler (EXPERIMENTAL)"
> + depends on SCSI_DH && EXPERIMENTAL
> + help
> + SCSI Device handler for generic SPC-3 Asymmetric Logical Unit
> + Access (ALUA).
> +
> diff --git a/drivers/scsi/device_handler/Makefile b/drivers/scsi/device_handler/Makefile
> index 35272e9..e1d2ea0 100644
> --- a/drivers/scsi/device_handler/Makefile
> +++ b/drivers/scsi/device_handler/Makefile
> @@ -5,3 +5,4 @@ obj-$(CONFIG_SCSI_DH) += scsi_dh.o
> obj-$(CONFIG_SCSI_DH_RDAC) += scsi_dh_rdac.o
> obj-$(CONFIG_SCSI_DH_HP_SW) += scsi_dh_hp_sw.o
> obj-$(CONFIG_SCSI_DH_EMC) += scsi_dh_emc.o
> +obj-$(CONFIG_SCSI_DH_ALUA) += scsi_dh_alua.o
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
> new file mode 100644
> index 0000000..854e043
> --- /dev/null
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -0,0 +1,806 @@
> +/*
> + * Generic SCSI-3 ALUA SCSI Device Handler
> + *
> + * Copyright (C) 2007, 2008 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 <scsi/scsi.h>
> +#include <scsi/scsi_eh.h>
> +#include <scsi/scsi_dh.h>
> +
> +#define ALUA_DH_NAME "alua"
> +#define ALUA_DH_VER "1.1"
> +
> +#define TPGS_STATE_OPTIMIZED 0x0
> +#define TPGS_STATE_NONOPTIMIZED 0x1
> +#define TPGS_STATE_STANDBY 0x2
> +#define TPGS_STATE_UNAVAILABLE 0x3
> +#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_OFFLINE 0x40
> +#define TPGS_SUPPORT_TRANSITION 0x80
> +
> +#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 * HZ)
> +#define ALUA_FAILOVER_RETRIES 5
> +
> +struct alua_dh_data {
> + int group_id;
> + int rel_port;
> + int tpgs;
> + int state;
> + unsigned char inq[ALUA_INQUIRY_SIZE];
> + unsigned char *buff;
> + int bufflen;
> + unsigned char sense[SCSI_SENSE_BUFFERSIZE];
> +};
> +
> +#define ALUA_POLICY_SWITCH_CURRENT 0
> +#define ALUA_POLICY_SWITCH_ALL 1
> +
> +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_ATOMIC);
> + 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;
> + struct alua_dh_data *h = get_alua_data(sdev);
> +
> + rq = blk_get_request(q, rw, GFP_KERNEL);
> +
> + if (!rq) {
> + sdev_printk(KERN_INFO, sdev,
> + "%s: blk_get_request failed\n", __FUNCTION__);
> + return NULL;
> + }
> +
> + if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_KERNEL)) {
> + blk_put_request(rq);
> + sdev_printk(KERN_INFO, sdev,
> + "%s: blk_rq_map_kern failed\n", __FUNCTION__);
> + return NULL;
> + }
> +
> + rq->sense = h->sense;
> + memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
> + rq->sense_len = 0;
> +
> + rq->cmd_type = REQ_TYPE_BLOCK_PC;
> + rq->cmd_flags |= REQ_FAILFAST | REQ_NOMERGE;
> + rq->retries = ALUA_FAILOVER_RETRIES;
> + rq->timeout = ALUA_FAILOVER_TIMEOUT;
> +
> + return rq;
> +}
> +
> +/*
> + * submit_std_inquiry - Issue a standard INQUIRY command
> + * @sdev: sdev the command should be send to
> + */
> +static int submit_std_inquiry(struct scsi_device *sdev)
> +{
> + struct request *rq;
> + struct alua_dh_data *h = get_alua_data(sdev);
> + int err = SCSI_DH_RES_TEMP_UNAVAIL;
> +
> + rq = get_alua_req(sdev, h->inq, ALUA_INQUIRY_SIZE, READ);
> + if (!rq)
> + goto done;
> +
> + /* Prepare the command. */
> + rq->cmd[0] = INQUIRY;
> + rq->cmd[1] = 0;
> + rq->cmd[2] = 0;
> + rq->cmd[4] = ALUA_INQUIRY_SIZE;
> + rq->cmd_len = COMMAND_SIZE(INQUIRY);
> +
> + err = blk_execute_rq(rq->q, NULL, rq, 1);
> + if (err == -EIO) {
> + sdev_printk(KERN_INFO, sdev,
> + "%s: failed to send std inquiry: %x\n",
> + ALUA_DH_NAME, rq->errors);
> + err = SCSI_DH_IO;
> + }
> + blk_put_request(rq);
> +done:
> + return err;
> +}
> +
> +/*
> + * 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 request *rq;
> + struct alua_dh_data *h = get_alua_data(sdev);
> + 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);
> +
> + err = blk_execute_rq(rq->q, NULL, rq, 1);
> + if (err == -EIO) {
> + sdev_printk(KERN_INFO, sdev,
> + "%s: failed to send vpd inquiry: %x\n",
> + ALUA_DH_NAME, rq->errors);
> + 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 request *rq;
> + struct alua_dh_data *h = get_alua_data(sdev);
> + 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;
> + 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);
> +
> + err = blk_execute_rq(rq->q, NULL, rq, 1);
> + if (err == -EIO) {
> + sdev_printk(KERN_INFO, sdev,
> + "%s: failed to send rtpg: %x\n",
> + ALUA_DH_NAME, rq->errors);
> + if (status_byte(rq->errors) == CHECK_CONDITION)
> + err = SCSI_DH_SENSE_AVAIL;
> + else
> + err = SCSI_DH_IO;
> + }
> + blk_put_request(rq);
> +done:
> + return err;
> +}
> +
> +/*
> + * submit_stpg - Issue a SET TARGET GROUP STATES command
> + * @sdev: sdev the command should be sent to
> + *
> + * 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 scsi_device *sdev)
> +{
> + struct request *rq;
> + struct alua_dh_data *h = get_alua_data(sdev);
> + int err = SCSI_DH_RES_TEMP_UNAVAIL;
> + int stpg_len = 8;
> +
> + /* Prepare the data buffer */
> + memset(h->buff, 0, stpg_len);
> + h->buff[4] = TPGS_STATE_OPTIMIZED & 0x0f;
> + h->buff[6] = (h->group_id >> 8) & 0x0f;
> + h->buff[7] = h->group_id & 0x0f;
> +
> + rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
> + if (!rq)
> + goto done;
> +
> + /* 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);
> +
> + err = blk_execute_rq(rq->q, NULL, rq, 1);
> + if (err == -EIO) {
> + sdev_printk(KERN_INFO, sdev,
> + "%s: failed to send stpg: %x\n",
> + ALUA_DH_NAME, rq->errors);
> + if (status_byte(rq->errors) == CHECK_CONDITION)
> + err = SCSI_DH_SENSE_AVAIL;
> + else
> + err = SCSI_DH_IO;
> + }
> + blk_put_request(rq);
> +done:
> + return err;
> +}
> +
> +/*
> + * alua_std_inquiry - Evaluate standard INQUIRY command
> + * @sdev: device to be checked
> + *
> + * Just extract the TPGS setting to find out if ALUA
> + * is supported.
> + */
> +static int alua_std_inquiry(struct scsi_device *sdev)
> +{
> + int err;
> + struct alua_dh_data *h = get_alua_data(sdev);
> +
> + err = submit_std_inquiry(sdev);
> +
> + if (err != SCSI_DH_OK)
> + return err;
> +
> + /* Check TPGS setting */
> + h->tpgs = (h->inq[5] >> 4) & 0x3;
> + 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 = get_alua_data(sdev);
> + int len;
> + unsigned err;
> + unsigned char *d;
> +
> + retry:
> + err = submit_vpd_inquiry(sdev);
> +
> + 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_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 NEEDS_RETRY;
> + 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 NEEDS_RETRY;
> + if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
> + /*
> + * ALUA state changed
> + */
> + return NEEDS_RETRY;
> + }
> + if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
> + /*
> + * Implicit ALUA state transition failed
> + */
> + return NEEDS_RETRY;
> + }
> + break;
> + }
> +
> + return SCSI_RETURN_NOT_HANDLED;
> +}
> +
> +/*
> + * 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 int alua_stpg(struct scsi_device *sdev, int state)
> +{
> + struct alua_dh_data *h = get_alua_data(sdev);
> + struct scsi_sense_hdr sense_hdr;
> + unsigned err;
> + int retry = ALUA_FAILOVER_RETRIES;
> +
> + retry:
> + err = submit_stpg(sdev);
> + if (err == SCSI_DH_SENSE_AVAIL) {
> + err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
> + &sense_hdr);
> + if (!err)
> + return SCSI_DH_IO;
> + err = alua_check_sense(sdev, &sense_hdr);
> + if (retry > 0 && err == NEEDS_RETRY) {
> + retry--;
> + goto retry;
> + }
> + sdev_printk(KERN_INFO, 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 = state;
> + sdev_printk(KERN_INFO, sdev,
> + "%s: port group %02x switched to state %c\n",
> + ALUA_DH_NAME, h->group_id,
> + print_alua_state(h->state) );
> + }
> + return err;
> +}
> +
> +/*
> + * 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 unuseable.
> + */
> +static int alua_rtpg(struct scsi_device *sdev)
> +{
> + struct alua_dh_data *h = get_alua_data(sdev);
> + struct scsi_sense_hdr sense_hdr;
> + int len, k, off, valid_states = 0;
> + char *ucp;
> + unsigned err;
> +
> + retry:
> + err = submit_rtpg(sdev);
> +
> + if (err == SCSI_DH_SENSE_AVAIL) {
> + err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
> + &sense_hdr);
> + if (!err)
> + return SCSI_DH_IO;
> +
> + err = alua_check_sense(sdev, &sense_hdr);
> + if (err == NEEDS_RETRY)
> + goto retry;

Retry without any escape route ? Or am I missing something.

> + 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",__FUNCTION__);
> + /* Temporary failure, bypass */
> + return SCSI_DH_DEV_TEMP_BUSY;
> + }
> + goto retry;
> + }
> +
> + for (k = 4, ucp = h->buff + 4; k < len; k += off, ucp += off) {
> + if (h->group_id == (ucp[2] << 8) + ucp[3]) {
> + h->state = ucp[0] & 0x0f;
> + valid_states = ucp[1];
> + }
> + off = 8 + (ucp[7] * 4);
> + }
> +
> + sdev_printk(KERN_INFO, sdev,
> + "%s: port group %02x state %c supports %c%c%c%c%c%c\n",
> + ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
> + valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
> + valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
> + 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');
> +
> + if (h->tpgs & TPGS_MODE_EXPLICIT) {
> + switch (h->state) {
> + case TPGS_STATE_TRANSITIONING:
> + /* State transition, retry */
> + goto retry;
> + break;
> + case TPGS_STATE_OFFLINE:
> + /* Path is offline, fail */
> + err = SCSI_DH_DEV_OFFLINED;
> + break;
> + default:
> + break;
> + }
> + } else {
> + /* Only Implicit ALUA support */
> + if (h->state == TPGS_STATE_OPTIMIZED ||
> + h->state == TPGS_STATE_NONOPTIMIZED ||
> + h->state == TPGS_STATE_STANDBY)
> + /* Useable path if active */
> + err = SCSI_DH_OK;
> + else
> + /* Path unuseable for unavailable/offline */
> + err = SCSI_DH_DEV_OFFLINED;
> + }
> + 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)
> +{
> + int err;
> +
> + err = alua_std_inquiry(sdev);
> + if (err != SCSI_DH_OK)
> + goto out;
> +
> + err = alua_vpd_inquiry(sdev);
> + if (err != SCSI_DH_OK)
> + goto out;
> +
> + err = alua_rtpg(sdev);
> + if (err != SCSI_DH_OK)
> + goto out;
> +
> +out:
> + return err;
> +}
> +
> +/*
> + * 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)
> +{
> + struct alua_dh_data *h = get_alua_data(sdev);
> + int err = SCSI_DH_OK;
> +
> + if (h->group_id != -1) {
> + err = alua_rtpg(sdev);
> + if (err != SCSI_DH_OK)
> + goto out;
> + }
> +
> + if (h->tpgs == TPGS_MODE_EXPLICIT && h->state != TPGS_STATE_OPTIMIZED)
> + err = alua_stpg(sdev, TPGS_STATE_OPTIMIZED);
> +

Looks like this code can return without doing anything even if things
have changed since last inquiry. What am I missing ?

> +out:
> + return err;
> +}
> +
> +/*
> + * 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_OPTIMIZED &&
> + h->state != TPGS_STATE_NONOPTIMIZED) {
> + ret = BLKPREP_KILL;
> + req->cmd_flags |= REQ_QUIET;
> + }
> + return ret;
> +
> +}
> +
> +const struct scsi_dh_devlist alua_dev_list[] = {
> + {"HP", "MSA VOLUME" },
> + {"HP", "HSV101" },
> + {"HP", "HSV111" },
> + {"HP", "HSV200" },
> + {"HP", "HSV210" },
> + {"HP", "HSV300" },
> + {"IBM", "2107900" },
> + {"IBM", "2145" },
> + {"Pillar", "Axiom" },
> + {NULL, NULL}
> +};
> +
> +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,
> + .devlist = alua_dev_list,
> + .attach = alua_bus_attach,
> + .detach = alua_bus_detach,
> + .prep_fn = alua_prep_fn,
> + .check_sense = alua_check_sense,
> + .activate = alua_activate,
> +};
> +
> +/*
> + * 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(struct scsi_device_handler *)
> + + 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;
> +
> + 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);

We can move this below (after initialize). It is not good to publish (it
in sdev) and withdraw immediately.

> +
> + err = alua_initialize(sdev);
> + if (err != SCSI_DH_OK)
> + goto failed;
> +
> + try_module_get(THIS_MODULE);
> + sdev_printk(KERN_NOTICE, sdev, "%s: Attached\n", ALUA_DH_NAME);
> +
> + return 0;
> +
> +failed:
> + spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
> + sdev->scsi_dh_data = NULL;
> + spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
> + 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;
> +
> + if (sdev->scsi_dh_data == NULL ||
> + sdev->scsi_dh_data->scsi_dh != &alua_dh)
> + return;
> +
> + 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 <hare@suse.de>");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION(ALUA_DH_VER);
> diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
> index 2b5b935..45e5eb9 100644
> --- a/include/scsi/scsi.h
> +++ b/include/scsi/scsi.h
> @@ -105,6 +105,7 @@
> #define VARIABLE_LENGTH_CMD 0x7f
> #define REPORT_LUNS 0xa0
> #define MAINTENANCE_IN 0xa3
> +#define MAINTENANCE_OUT 0xa4
> #define MOVE_MEDIUM 0xa5
> #define EXCHANGE_MEDIUM 0xa6
> #define READ_12 0xa8
> @@ -124,6 +125,8 @@
> #define SAI_READ_CAPACITY_16 0x10
> /* values for maintenance in */
> #define MI_REPORT_TARGET_PGS 0x0a
> +/* values for maintenance out */
> +#define MO_SET_TARGET_PGS 0x0a
>
> /* Values for T10/04-262r7 */
> #define ATA_16 0x85 /* 16-byte pass-thru */
> diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
> index 04d0d84..5d05ac0 100644
> --- a/include/scsi/scsi_dh.h
> +++ b/include/scsi/scsi_dh.h
> @@ -32,6 +32,7 @@ enum {
> */
> SCSI_DH_DEV_FAILED, /* generic device error */
> SCSI_DH_DEV_TEMP_BUSY,
> + SCSI_DH_DEV_UNSUPP, /* device handler not supported */
> SCSI_DH_DEVICE_MAX, /* max device blkerr definition */
>
> /*
> @@ -52,6 +53,7 @@ enum {
> SCSI_DH_RES_TEMP_UNAVAIL,
> SCSI_DH_DEV_OFFLINED,
> SCSI_DH_NOSYS,
> + SCSI_DH_SENSE_AVAIL, /* Sense code available */
> SCSI_DH_DRIVER_MAX,
> };
>