/*******************************************************************************
 * Filename:  target_core_iblock.c
 *
 * This file contains the Storage Engine  <-> Linux BlockIO transport
 * specific functions.
 *
 * Copyright (c) 2003, 2004, 2005 PyX Technologies, Inc.
 * Copyright (c) 2005, 2006, 2007 SBE, Inc.
 * Copyright (c) 2007-2010 Rising Tide Systems
 * Copyright (c) 2008-2010 Linux-iSCSI.org
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 * 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/string.h>
#include <linux/parser.h>
#include <linux/timer.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/bio.h>
#include <linux/genhd.h>
#include <linux/file.h>
#include <linux/module.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>

#include <target/target_core_base.h>
#include <target/target_core_backend.h>

#include "target_core_iblock.h"

static struct se_subsystem_api iblock_template;

static void iblock_bio_done(struct bio *, int);

/*      iblock_attach_hba(): (Part of se_subsystem_api_t template)
 *
 *
 */
static int iblock_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct iblock_hba *ib_host;

        ib_host = kzalloc(sizeof(struct iblock_hba), GFP_KERNEL);
        if (!ib_host) {
                pr_err("Unable to allocate memory for"
                                " struct iblock_hba\n");
                return -ENOMEM;
        }

        ib_host->iblock_host_id = host_id;

        hba->hba_ptr = ib_host;

        pr_debug("CORE_HBA[%d] - TCM iBlock HBA Driver %s on"
                " Generic Target Core Stack %s\n", hba->hba_id,
                IBLOCK_VERSION, TARGET_CORE_MOD_VERSION);

        pr_debug("CORE_HBA[%d] - Attached iBlock HBA: %u to Generic\n",
                hba->hba_id, ib_host->iblock_host_id);

        return 0;
}

static void iblock_detach_hba(struct se_hba *hba)
{
        struct iblock_hba *ib_host = hba->hba_ptr;

        pr_debug("CORE_HBA[%d] - Detached iBlock HBA: %u from Generic"
                " Target Core\n", hba->hba_id, ib_host->iblock_host_id);

        kfree(ib_host);
        hba->hba_ptr = NULL;
}

static void *iblock_allocate_virtdevice(struct se_hba *hba, const char *name)
{
        struct iblock_dev *ib_dev = NULL;
        struct iblock_hba *ib_host = hba->hba_ptr;

        ib_dev = kzalloc(sizeof(struct iblock_dev), GFP_KERNEL);
        if (!ib_dev) {
                pr_err("Unable to allocate struct iblock_dev\n");
                return NULL;
        }
        ib_dev->ibd_host = ib_host;

        pr_debug( "IBLOCK: Allocated ib_dev for %s\n", name);

        return ib_dev;
}

static struct se_device *iblock_create_virtdevice(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        void *p)
{
        struct iblock_dev *ib_dev = p;
        struct se_device *dev;
        struct se_dev_limits dev_limits;
        struct block_device *bd = NULL;
        struct request_queue *q;
        struct queue_limits *limits;
        u32 dev_flags = 0;
        int ret = -EINVAL;

        if (!ib_dev) {
                pr_err("Unable to locate struct iblock_dev parameter\n");
                return ERR_PTR(ret);
        }
        memset(&dev_limits, 0, sizeof(struct se_dev_limits));
        /*
         * These settings need to be made tunable..
         */
        ib_dev->ibd_bio_set = bioset_create(32, 0);
        if (!ib_dev->ibd_bio_set) {
                pr_err("IBLOCK: Unable to create bioset()\n");
                return ERR_PTR(-ENOMEM);
        }
        pr_debug("IBLOCK: Created bio_set()\n");
        /*
         * iblock_check_configfs_dev_params() ensures that ib_dev->ibd_udev_path
         * must already have been set in order for echo 1 > $HBA/$DEV/enable to run.
         */
        pr_debug( "IBLOCK: Claiming struct block_device: %s\n",
                        ib_dev->ibd_udev_path);

        bd = blkdev_get_by_path(ib_dev->ibd_udev_path,
                                FMODE_WRITE|FMODE_READ|FMODE_EXCL, ib_dev);
        if (IS_ERR(bd)) {
                ret = PTR_ERR(bd);
                goto failed;
        }
        /*
         * Setup the local scope queue_limits from struct request_queue->limits
         * to pass into transport_add_device_to_core_hba() as struct se_dev_limits.
         */
        q = bdev_get_queue(bd);
        limits = &dev_limits.limits;
        limits->logical_block_size = bdev_logical_block_size(bd);
        limits->max_hw_sectors = queue_max_hw_sectors(q);
        limits->max_sectors = queue_max_sectors(q);
        dev_limits.hw_queue_depth = q->nr_requests;
        dev_limits.queue_depth = q->nr_requests;

        ib_dev->ibd_bd = bd;

        dev = transport_add_device_to_core_hba(hba,
                        &iblock_template, se_dev, dev_flags, ib_dev,
                        &dev_limits, "IBLOCK", IBLOCK_VERSION);
        if (!dev)
                goto failed;

        /*
         * Check if the underlying struct block_device request_queue supports
         * the QUEUE_FLAG_DISCARD bit for UNMAP/WRITE_SAME in SCSI + TRIM
         * in ATA and we need to set TPE=1
         */
        if (blk_queue_discard(q)) {
                dev->se_sub_dev->se_dev_attrib.max_unmap_lba_count =
                                q->limits.max_discard_sectors;
                /*
                 * Currently hardcoded to 1 in Linux/SCSI code..
                 */
                dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count = 1;
                dev->se_sub_dev->se_dev_attrib.unmap_granularity =
                                q->limits.discard_granularity >> 9;
                dev->se_sub_dev->se_dev_attrib.unmap_granularity_alignment =
                                q->limits.discard_alignment;

                pr_debug("IBLOCK: BLOCK Discard support available,"
                                " disabled by default\n");
        }

        if (blk_queue_nonrot(q))
                dev->se_sub_dev->se_dev_attrib.is_nonrot = 1;

        return dev;

failed:
        if (ib_dev->ibd_bio_set) {
                bioset_free(ib_dev->ibd_bio_set);
                ib_dev->ibd_bio_set = NULL;
        }
        ib_dev->ibd_bd = NULL;
        return ERR_PTR(ret);
}

static void iblock_free_device(void *p)
{
        struct iblock_dev *ib_dev = p;

        if (ib_dev->ibd_bd != NULL)
                blkdev_put(ib_dev->ibd_bd, FMODE_WRITE|FMODE_READ|FMODE_EXCL);
        if (ib_dev->ibd_bio_set != NULL)
                bioset_free(ib_dev->ibd_bio_set);
        kfree(ib_dev);
}

static inline struct iblock_req *IBLOCK_REQ(struct se_task *task)
{
        return container_of(task, struct iblock_req, ib_task);
}

static struct se_task *
iblock_alloc_task(unsigned char *cdb)
{
        struct iblock_req *ib_req;

        ib_req = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
        if (!ib_req) {
                pr_err("Unable to allocate memory for struct iblock_req\n");
                return NULL;
        }

        atomic_set(&ib_req->ib_bio_cnt, 0);
        return &ib_req->ib_task;
}

static unsigned long long iblock_emulate_read_cap_with_block_size(
        struct se_device *dev,
        struct block_device *bd,
        struct request_queue *q)
{
        unsigned long long blocks_long = (div_u64(i_size_read(bd->bd_inode),
                                        bdev_logical_block_size(bd)) - 1);
        u32 block_size = bdev_logical_block_size(bd);

        if (block_size == dev->se_sub_dev->se_dev_attrib.block_size)
                return blocks_long;

        switch (block_size) {
        case 4096:
                switch (dev->se_sub_dev->se_dev_attrib.block_size) {
                case 2048:
                        blocks_long <<= 1;
                        break;
                case 1024:
                        blocks_long <<= 2;
                        break;
                case 512:
                        blocks_long <<= 3;
                default:
                        break;
                }
                break;
        case 2048:
                switch (dev->se_sub_dev->se_dev_attrib.block_size) {
                case 4096:
                        blocks_long >>= 1;
                        break;
                case 1024:
                        blocks_long <<= 1;
                        break;
                case 512:
                        blocks_long <<= 2;
                        break;
                default:
                        break;
                }
                break;
        case 1024:
                switch (dev->se_sub_dev->se_dev_attrib.block_size) {
                case 4096:
                        blocks_long >>= 2;
                        break;
                case 2048:
                        blocks_long >>= 1;
                        break;
                case 512:
                        blocks_long <<= 1;
                        break;
                default:
                        break;
                }
                break;
        case 512:
                switch (dev->se_sub_dev->se_dev_attrib.block_size) {
                case 4096:
                        blocks_long >>= 3;
                        break;
                case 2048:
                        blocks_long >>= 2;
                        break;
                case 1024:
                        blocks_long >>= 1;
                        break;
                default:
                        break;
                }
                break;
        default:
                break;
        }

        return blocks_long;
}

static void iblock_end_io_flush(struct bio *bio, int err)
{
        struct se_cmd *cmd = bio->bi_private;

        if (err)
                pr_err("IBLOCK: cache flush failed: %d\n", err);

        if (cmd)
                transport_complete_sync_cache(cmd, err == 0);
        bio_put(bio);
}

/*
 * Implement SYCHRONIZE CACHE.  Note that we can't handle lba ranges and must
 * always flush the whole cache.
 */
static void iblock_emulate_sync_cache(struct se_task *task)
{
        struct se_cmd *cmd = task->task_se_cmd;
        struct iblock_dev *ib_dev = cmd->se_dev->dev_ptr;
        int immed = (cmd->t_task_cdb[1] & 0x2);
        struct bio *bio;

        /*
         * If the Immediate bit is set, queue up the GOOD response
         * for this SYNCHRONIZE_CACHE op.
         */
        if (immed)
                transport_complete_sync_cache(cmd, 1);

        bio = bio_alloc(GFP_KERNEL, 0);
        bio->bi_end_io = iblock_end_io_flush;
        bio->bi_bdev = ib_dev->ibd_bd;
        if (!immed)
                bio->bi_private = cmd;
        submit_bio(WRITE_FLUSH, bio);
}

static int iblock_do_discard(struct se_device *dev, sector_t lba, u32 range)
{
        struct iblock_dev *ibd = dev->dev_ptr;
        struct block_device *bd = ibd->ibd_bd;
        int barrier = 0;

        return blkdev_issue_discard(bd, lba, range, GFP_KERNEL, barrier);
}

static void iblock_free_task(struct se_task *task)
{
        kfree(IBLOCK_REQ(task));
}

enum {
        Opt_udev_path, Opt_force, Opt_err
};

static match_table_t tokens = {
        {Opt_udev_path, "udev_path=%s"},
        {Opt_force, "force=%d"},
        {Opt_err, NULL}
};

static ssize_t iblock_set_configfs_dev_params(struct se_hba *hba,
                                               struct se_subsystem_dev *se_dev,
                                               const char *page, ssize_t count)
{
        struct iblock_dev *ib_dev = se_dev->se_dev_su_ptr;
        char *orig, *ptr, *arg_p, *opts;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, token;

        opts = kstrdup(page, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;

        orig = opts;

        while ((ptr = strsep(&opts, ",\n")) != NULL) {
                if (!*ptr)
                        continue;

                token = match_token(ptr, tokens, args);
                switch (token) {
                case Opt_udev_path:
                        if (ib_dev->ibd_bd) {
                                pr_err("Unable to set udev_path= while"
                                        " ib_dev->ibd_bd exists\n");
                                ret = -EEXIST;
                                goto out;
                        }
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        snprintf(ib_dev->ibd_udev_path, SE_UDEV_PATH_LEN,
                                        "%s", arg_p);
                        kfree(arg_p);
                        pr_debug("IBLOCK: Referencing UDEV path: %s\n",
                                        ib_dev->ibd_udev_path);
                        ib_dev->ibd_flags |= IBDF_HAS_UDEV_PATH;
                        break;
                case Opt_force:
                        break;
                default:
                        break;
                }
        }

out:
        kfree(orig);
        return (!ret) ? count : ret;
}

static ssize_t iblock_check_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev)
{
        struct iblock_dev *ibd = se_dev->se_dev_su_ptr;

        if (!(ibd->ibd_flags & IBDF_HAS_UDEV_PATH)) {
                pr_err("Missing udev_path= parameters for IBLOCK\n");
                return -EINVAL;
        }

        return 0;
}

static ssize_t iblock_show_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        char *b)
{
        struct iblock_dev *ibd = se_dev->se_dev_su_ptr;
        struct block_device *bd = ibd->ibd_bd;
        char buf[BDEVNAME_SIZE];
        ssize_t bl = 0;

        if (bd)
                bl += sprintf(b + bl, "iBlock device: %s",
                                bdevname(bd, buf));
        if (ibd->ibd_flags & IBDF_HAS_UDEV_PATH) {
                bl += sprintf(b + bl, "  UDEV PATH: %s\n",
                                ibd->ibd_udev_path);
        } else
                bl += sprintf(b + bl, "\n");

        bl += sprintf(b + bl, "        ");
        if (bd) {
                bl += sprintf(b + bl, "Major: %d Minor: %d  %s\n",
                        MAJOR(bd->bd_dev), MINOR(bd->bd_dev), (!bd->bd_contains) ?
                        "" : (bd->bd_holder == ibd) ?
                        "CLAIMED: IBLOCK" : "CLAIMED: OS");
        } else {
                bl += sprintf(b + bl, "Major: 0 Minor: 0\n");
        }

        return bl;
}

static void iblock_bio_destructor(struct bio *bio)
{
        struct se_task *task = bio->bi_private;
        struct iblock_dev *ib_dev = task->task_se_cmd->se_dev->dev_ptr;

        bio_free(bio, ib_dev->ibd_bio_set);
}

static struct bio *
iblock_get_bio(struct se_task *task, sector_t lba, u32 sg_num)
{
        struct iblock_dev *ib_dev = task->task_se_cmd->se_dev->dev_ptr;
        struct iblock_req *ib_req = IBLOCK_REQ(task);
        struct bio *bio;

        /*
         * Only allocate as many vector entries as the bio code allows us to,
         * we'll loop later on until we have handled the whole request.
         */
        if (sg_num > BIO_MAX_PAGES)
                sg_num = BIO_MAX_PAGES;

        bio = bio_alloc_bioset(GFP_NOIO, sg_num, ib_dev->ibd_bio_set);
        if (!bio) {
                pr_err("Unable to allocate memory for bio\n");
                return NULL;
        }

        pr_debug("Allocated bio: %p task_sg_nents: %u using ibd_bio_set:"
                " %p\n", bio, task->task_sg_nents, ib_dev->ibd_bio_set);
        pr_debug("Allocated bio: %p task_size: %u\n", bio, task->task_size);

        bio->bi_bdev = ib_dev->ibd_bd;
        bio->bi_private = task;
        bio->bi_destructor = iblock_bio_destructor;
        bio->bi_end_io = &iblock_bio_done;
        bio->bi_sector = lba;
        atomic_inc(&ib_req->ib_bio_cnt);

        pr_debug("Set bio->bi_sector: %llu\n", (unsigned long long)bio->bi_sector);
        pr_debug("Set ib_req->ib_bio_cnt: %d\n",
                        atomic_read(&ib_req->ib_bio_cnt));
        return bio;
}

static int iblock_do_task(struct se_task *task)
{
        struct se_cmd *cmd = task->task_se_cmd;
        struct se_device *dev = cmd->se_dev;
        struct bio *bio;
        struct bio_list list;
        struct scatterlist *sg;
        u32 i, sg_num = task->task_sg_nents;
        sector_t block_lba;
        struct blk_plug plug;
        int rw;

        if (task->task_data_direction == DMA_TO_DEVICE) {
                /*
                 * Force data to disk if we pretend to not have a volatile
                 * write cache, or the initiator set the Force Unit Access bit.
                 */
                if (dev->se_sub_dev->se_dev_attrib.emulate_write_cache == 0 ||
                    (dev->se_sub_dev->se_dev_attrib.emulate_fua_write > 0 &&
                     (cmd->se_cmd_flags & SCF_FUA)))
                        rw = WRITE_FUA;
                else
                        rw = WRITE;
        } else {
                rw = READ;
        }

        /*
         * Do starting conversion up from non 512-byte blocksize with
         * struct se_task SCSI blocksize into Linux/Block 512 units for BIO.
         */
        if (dev->se_sub_dev->se_dev_attrib.block_size == 4096)
                block_lba = (task->task_lba << 3);
        else if (dev->se_sub_dev->se_dev_attrib.block_size == 2048)
                block_lba = (task->task_lba << 2);
        else if (dev->se_sub_dev->se_dev_attrib.block_size == 1024)
                block_lba = (task->task_lba << 1);
        else if (dev->se_sub_dev->se_dev_attrib.block_size == 512)
                block_lba = task->task_lba;
        else {
                pr_err("Unsupported SCSI -> BLOCK LBA conversion:"
                                " %u\n", dev->se_sub_dev->se_dev_attrib.block_size);
                cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                return -ENOSYS;
        }

        bio = iblock_get_bio(task, block_lba, sg_num);
        if (!bio) {
                cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                return -ENOMEM;
        }

        bio_list_init(&list);
        bio_list_add(&list, bio);

        for_each_sg(task->task_sg, sg, task->task_sg_nents, i) {
                /*
                 * XXX: if the length the device accepts is shorter than the
                 *      length of the S/G list entry this will cause and
                 *      endless loop.  Better hope no driver uses huge pages.
                 */
                while (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)
                                != sg->length) {
                        bio = iblock_get_bio(task, block_lba, sg_num);
                        if (!bio)
                                goto fail;
                        bio_list_add(&list, bio);
                }

                /* Always in 512 byte units for Linux/Block */
                block_lba += sg->length >> IBLOCK_LBA_SHIFT;
                sg_num--;
        }

        blk_start_plug(&plug);
        while ((bio = bio_list_pop(&list)))
                submit_bio(rw, bio);
        blk_finish_plug(&plug);

        return 0;

fail:
        while ((bio = bio_list_pop(&list)))
                bio_put(bio);
        cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        return -ENOMEM;
}

static u32 iblock_get_device_rev(struct se_device *dev)
{
        return SCSI_SPC_2; /* Returns SPC-3 in Initiator Data */
}

static u32 iblock_get_device_type(struct se_device *dev)
{
        return TYPE_DISK;
}

static sector_t iblock_get_blocks(struct se_device *dev)
{
        struct iblock_dev *ibd = dev->dev_ptr;
        struct block_device *bd = ibd->ibd_bd;
        struct request_queue *q = bdev_get_queue(bd);

        return iblock_emulate_read_cap_with_block_size(dev, bd, q);
}

static void iblock_bio_done(struct bio *bio, int err)
{
        struct se_task *task = bio->bi_private;
        struct iblock_req *ibr = IBLOCK_REQ(task);

        /*
         * Set -EIO if !BIO_UPTODATE and the passed is still err=0
         */
        if (!test_bit(BIO_UPTODATE, &bio->bi_flags) && !err)
                err = -EIO;

        if (err != 0) {
                pr_err("test_bit(BIO_UPTODATE) failed for bio: %p,"
                        " err: %d\n", bio, err);
                /*
                 * Bump the ib_bio_err_cnt and release bio.
                 */
                atomic_inc(&ibr->ib_bio_err_cnt);
                smp_mb__after_atomic_inc();
        }

        bio_put(bio);

        if (!atomic_dec_and_test(&ibr->ib_bio_cnt))
                return;

        pr_debug("done[%p] bio: %p task_lba: %llu bio_lba: %llu err=%d\n",
                 task, bio, task->task_lba,
                 (unsigned long long)bio->bi_sector, err);

        transport_complete_task(task, !atomic_read(&ibr->ib_bio_err_cnt));
}

static struct se_subsystem_api iblock_template = {
        .name                   = "iblock",
        .owner                  = THIS_MODULE,
        .transport_type         = TRANSPORT_PLUGIN_VHBA_PDEV,
        .write_cache_emulated   = 1,
        .fua_write_emulated     = 1,
        .attach_hba             = iblock_attach_hba,
        .detach_hba             = iblock_detach_hba,
        .allocate_virtdevice    = iblock_allocate_virtdevice,
        .create_virtdevice      = iblock_create_virtdevice,
        .free_device            = iblock_free_device,
        .alloc_task             = iblock_alloc_task,
        .do_task                = iblock_do_task,
        .do_discard             = iblock_do_discard,
        .do_sync_cache          = iblock_emulate_sync_cache,
        .free_task              = iblock_free_task,
        .check_configfs_dev_params = iblock_check_configfs_dev_params,
        .set_configfs_dev_params = iblock_set_configfs_dev_params,
        .show_configfs_dev_params = iblock_show_configfs_dev_params,
        .get_device_rev         = iblock_get_device_rev,
        .get_device_type        = iblock_get_device_type,
        .get_blocks             = iblock_get_blocks,
};

static int __init iblock_module_init(void)
{
        return transport_subsystem_register(&iblock_template);
}

static void iblock_module_exit(void)
{
        transport_subsystem_release(&iblock_template);
}

MODULE_DESCRIPTION("TCM IBLOCK subsystem plugin");
MODULE_AUTHOR("nab@Linux-iSCSI.org");
MODULE_LICENSE("GPL");

module_init(iblock_module_init);
module_exit(iblock_module_exit);