// SPDX-License-Identifier: GPL-2.0-or-later
/*******************************************************************************
 * Filename:  target_core_iblock.c
 *
 * This file contains the Storage Engine  <-> Linux BlockIO transport
 * specific functions.
 *
 * (c) Copyright 2003-2013 Datera, Inc.
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 ******************************************************************************/

#include <linux/string.h>
#include <linux/parser.h>
#include <linux/timer.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/blk-integrity.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/bio.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/pr.h>
#include <scsi/scsi_proto.h>
#include <scsi/scsi_common.h>
#include <linux/unaligned.h>

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

#include "target_core_iblock.h"
#include "target_core_pr.h"

#define IBLOCK_MAX_BIO_PER_TASK  32     /* max # of bios to submit at a time */
#define IBLOCK_BIO_POOL_SIZE    128

static inline struct iblock_dev *IBLOCK_DEV(struct se_device *dev)
{
        return container_of(dev, struct iblock_dev, dev);
}


static int iblock_attach_hba(struct se_hba *hba, u32 host_id)
{
        pr_debug("CORE_HBA[%d] - TCM iBlock HBA Driver %s on"
                " Generic Target Core Stack %s\n", hba->hba_id,
                IBLOCK_VERSION, TARGET_CORE_VERSION);
        return 0;
}

static void iblock_detach_hba(struct se_hba *hba)
{
}

static struct se_device *iblock_alloc_device(struct se_hba *hba, const char *name)
{
        struct iblock_dev *ib_dev = NULL;

        ib_dev = kzalloc_obj(struct iblock_dev);
        if (!ib_dev) {
                pr_err("Unable to allocate struct iblock_dev\n");
                return NULL;
        }
        ib_dev->ibd_exclusive = true;

        ib_dev->ibd_plug = kzalloc_objs(*ib_dev->ibd_plug, nr_cpu_ids);
        if (!ib_dev->ibd_plug)
                goto free_dev;

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

        return &ib_dev->dev;

free_dev:
        kfree(ib_dev);
        return NULL;
}

static bool iblock_configure_unmap(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

        return target_configure_unmap_from_bdev(&dev->dev_attrib,
                                                ib_dev->ibd_bd);
}

static int iblock_configure_device(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct request_queue *q;
        struct file *bdev_file;
        struct block_device *bd;
        struct blk_integrity *bi;
        blk_mode_t mode = BLK_OPEN_READ;
        void *holder = ib_dev;
        unsigned int max_write_zeroes_sectors;
        int ret;

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

        ret = bioset_init(&ib_dev->ibd_bio_set, IBLOCK_BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
        if (ret) {
                pr_err("IBLOCK: Unable to create bioset\n");
                goto out;
        }

        pr_debug("IBLOCK: Claiming struct block_device: %s: %d\n",
                 ib_dev->ibd_udev_path, ib_dev->ibd_exclusive);

        if (!ib_dev->ibd_readonly)
                mode |= BLK_OPEN_WRITE;
        else
                dev->dev_flags |= DF_READ_ONLY;

        if (!ib_dev->ibd_exclusive)
                holder = NULL;

        bdev_file = bdev_file_open_by_path(ib_dev->ibd_udev_path, mode, holder,
                                        NULL);
        if (IS_ERR(bdev_file)) {
                ret = PTR_ERR(bdev_file);
                goto out_free_bioset;
        }
        ib_dev->ibd_bdev_file = bdev_file;
        ib_dev->ibd_bd = bd = file_bdev(bdev_file);

        q = bdev_get_queue(bd);

        dev->dev_attrib.hw_block_size = bdev_logical_block_size(bd);
        dev->dev_attrib.hw_max_sectors = mult_frac(queue_max_hw_sectors(q),
                        SECTOR_SIZE,
                        dev->dev_attrib.hw_block_size);
        dev->dev_attrib.hw_queue_depth = q->nr_requests;

        /*
         * Enable write same emulation for IBLOCK and use 0xFFFF as
         * the smaller WRITE_SAME(10) only has a two-byte block count.
         */
        max_write_zeroes_sectors = bdev_write_zeroes_sectors(bd);
        if (max_write_zeroes_sectors)
                dev->dev_attrib.max_write_same_len = max_write_zeroes_sectors;
        else
                dev->dev_attrib.max_write_same_len = 0xFFFF;

        if (bdev_nonrot(bd))
                dev->dev_attrib.is_nonrot = 1;

        target_configure_write_atomic_from_bdev(&dev->dev_attrib, bd);

        bi = bdev_get_integrity(bd);
        if (!bi)
                return 0;

        switch (bi->csum_type) {
        case BLK_INTEGRITY_CSUM_IP:
                pr_err("IBLOCK export of blk_integrity: %s not supported\n",
                        blk_integrity_profile_name(bi));
                ret = -ENOSYS;
                goto out_blkdev_put;
        case BLK_INTEGRITY_CSUM_CRC:
                if (bi->flags & BLK_INTEGRITY_REF_TAG)
                        dev->dev_attrib.pi_prot_type = TARGET_DIF_TYPE1_PROT;
                else
                        dev->dev_attrib.pi_prot_type = TARGET_DIF_TYPE3_PROT;
                break;
        default:
                break;
        }

        dev->dev_attrib.hw_pi_prot_type = dev->dev_attrib.pi_prot_type;
        return 0;

out_blkdev_put:
        fput(ib_dev->ibd_bdev_file);
out_free_bioset:
        bioset_exit(&ib_dev->ibd_bio_set);
out:
        return ret;
}

static void iblock_dev_call_rcu(struct rcu_head *p)
{
        struct se_device *dev = container_of(p, struct se_device, rcu_head);
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

        kfree(ib_dev->ibd_plug);
        kfree(ib_dev);
}

static void iblock_free_device(struct se_device *dev)
{
        call_rcu(&dev->rcu_head, iblock_dev_call_rcu);
}

static void iblock_destroy_device(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

        if (ib_dev->ibd_bdev_file)
                fput(ib_dev->ibd_bdev_file);
        bioset_exit(&ib_dev->ibd_bio_set);
}

static struct se_dev_plug *iblock_plug_device(struct se_device *se_dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(se_dev);
        struct iblock_dev_plug *ib_dev_plug;

        /*
         * Each se_device has a per cpu work this can be run from. We
         * shouldn't have multiple threads on the same cpu calling this
         * at the same time.
         */
        ib_dev_plug = &ib_dev->ibd_plug[raw_smp_processor_id()];
        if (test_and_set_bit(IBD_PLUGF_PLUGGED, &ib_dev_plug->flags))
                return NULL;

        blk_start_plug(&ib_dev_plug->blk_plug);
        return &ib_dev_plug->se_plug;
}

static void iblock_unplug_device(struct se_dev_plug *se_plug)
{
        struct iblock_dev_plug *ib_dev_plug = container_of(se_plug,
                                        struct iblock_dev_plug, se_plug);

        blk_finish_plug(&ib_dev_plug->blk_plug);
        clear_bit(IBD_PLUGF_PLUGGED, &ib_dev_plug->flags);
}

static sector_t iblock_get_blocks(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        u32 block_size = bdev_logical_block_size(ib_dev->ibd_bd);
        unsigned long long blocks_long =
                div_u64(bdev_nr_bytes(ib_dev->ibd_bd), block_size) - 1;

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

        switch (block_size) {
        case 4096:
                switch (dev->dev_attrib.block_size) {
                case 2048:
                        blocks_long <<= 1;
                        break;
                case 1024:
                        blocks_long <<= 2;
                        break;
                case 512:
                        blocks_long <<= 3;
                        break;
                default:
                        break;
                }
                break;
        case 2048:
                switch (dev->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->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->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_complete_cmd(struct se_cmd *cmd, blk_status_t blk_status)
{
        struct iblock_req *ibr = cmd->priv;
        u8 status;

        if (!refcount_dec_and_test(&ibr->pending))
                return;

        if (blk_status == BLK_STS_RESV_CONFLICT)
                status = SAM_STAT_RESERVATION_CONFLICT;
        else if (atomic_read(&ibr->ib_bio_err_cnt))
                status = SAM_STAT_CHECK_CONDITION;
        else
                status = SAM_STAT_GOOD;

        target_complete_cmd(cmd, status);
        kfree(ibr);
}

static void iblock_bio_done(struct bio *bio)
{
        struct se_cmd *cmd = bio->bi_private;
        struct iblock_req *ibr = cmd->priv;
        blk_status_t blk_status = bio->bi_status;

        if (bio->bi_status) {
                pr_err("bio error: %p,  err: %d\n", bio, bio->bi_status);
                /*
                 * Bump the ib_bio_err_cnt and release bio.
                 */
                atomic_inc(&ibr->ib_bio_err_cnt);
                smp_mb__after_atomic();
        }

        bio_put(bio);

        iblock_complete_cmd(cmd, blk_status);
}

static struct bio *iblock_get_bio(struct se_cmd *cmd, sector_t lba, u32 sg_num,
                                  blk_opf_t opf)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(cmd->se_dev);
        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.
         */
        bio = bio_alloc_bioset(ib_dev->ibd_bd, bio_max_segs(sg_num), opf,
                               GFP_NOIO, &ib_dev->ibd_bio_set);
        if (!bio) {
                pr_err("Unable to allocate memory for bio\n");
                return NULL;
        }

        bio->bi_private = cmd;
        bio->bi_end_io = &iblock_bio_done;
        bio->bi_iter.bi_sector = lba;

        return bio;
}

static void iblock_submit_bios(struct bio_list *list)
{
        struct blk_plug plug;
        struct bio *bio;
        /*
         * The block layer handles nested plugs, so just plug/unplug to handle
         * fabric drivers that didn't support batching and multi bio cmds.
         */
        blk_start_plug(&plug);
        while ((bio = bio_list_pop(list)))
                submit_bio(bio);
        blk_finish_plug(&plug);
}

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

        if (bio->bi_status)
                pr_err("IBLOCK: cache flush failed: %d\n", bio->bi_status);

        if (cmd) {
                if (bio->bi_status)
                        target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
                else
                        target_complete_cmd(cmd, SAM_STAT_GOOD);
        }

        bio_put(bio);
}

/*
 * Implement SYCHRONIZE CACHE.  Note that we can't handle lba ranges and must
 * always flush the whole cache.
 */
static sense_reason_t
iblock_execute_sync_cache(struct se_cmd *cmd)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(cmd->se_dev);
        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)
                target_complete_cmd(cmd, SAM_STAT_GOOD);

        bio = bio_alloc(ib_dev->ibd_bd, 0, REQ_OP_WRITE | REQ_PREFLUSH,
                        GFP_KERNEL);
        bio->bi_end_io = iblock_end_io_flush;
        if (!immed)
                bio->bi_private = cmd;
        submit_bio(bio);
        return 0;
}

static sense_reason_t
iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
{
        struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
        struct se_device *dev = cmd->se_dev;
        int ret;

        ret = blkdev_issue_discard(bdev,
                                   target_to_linux_sector(dev, lba),
                                   target_to_linux_sector(dev,  nolb),
                                   GFP_KERNEL);
        if (ret < 0) {
                pr_err("blkdev_issue_discard() failed: %d\n", ret);
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        return 0;
}

static sense_reason_t
iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct scatterlist *sg = &cmd->t_data_sg[0];
        unsigned char *buf, *not_zero;
        int ret;

        buf = kmap(sg_page(sg)) + sg->offset;
        if (!buf)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        /*
         * Fall back to block_execute_write_same() slow-path if
         * incoming WRITE_SAME payload does not contain zeros.
         */
        not_zero = memchr_inv(buf, 0x00, cmd->data_length);
        kunmap(sg_page(sg));

        if (not_zero)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        ret = blkdev_issue_zeroout(bdev,
                                target_to_linux_sector(dev, cmd->t_task_lba),
                                target_to_linux_sector(dev,
                                        sbc_get_write_same_sectors(cmd)),
                                GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
        if (ret)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

static sense_reason_t
iblock_execute_write_same(struct se_cmd *cmd)
{
        struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
        struct iblock_req *ibr;
        struct scatterlist *sg;
        struct bio *bio;
        struct bio_list list;
        struct se_device *dev = cmd->se_dev;
        sector_t block_lba = target_to_linux_sector(dev, cmd->t_task_lba);
        sector_t sectors = target_to_linux_sector(dev,
                                        sbc_get_write_same_sectors(cmd));

        if (cmd->prot_op) {
                pr_err("WRITE_SAME: Protection information with IBLOCK"
                       " backends not supported\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        if (!cmd->t_data_nents)
                return TCM_INVALID_CDB_FIELD;

        sg = &cmd->t_data_sg[0];

        if (cmd->t_data_nents > 1 ||
            sg->length != cmd->se_dev->dev_attrib.block_size) {
                pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"
                        " block_size: %u\n", cmd->t_data_nents, sg->length,
                        cmd->se_dev->dev_attrib.block_size);
                return TCM_INVALID_CDB_FIELD;
        }

        if (bdev_write_zeroes_sectors(bdev)) {
                if (!iblock_execute_zero_out(bdev, cmd))
                        return 0;
        }

        ibr = kzalloc_obj(struct iblock_req);
        if (!ibr)
                goto fail;
        cmd->priv = ibr;

        bio = iblock_get_bio(cmd, block_lba, 1, REQ_OP_WRITE);
        if (!bio)
                goto fail_free_ibr;

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

        refcount_set(&ibr->pending, 1);

        while (sectors) {
                while (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)
                                != sg->length) {

                        bio = iblock_get_bio(cmd, block_lba, 1, REQ_OP_WRITE);
                        if (!bio)
                                goto fail_put_bios;

                        refcount_inc(&ibr->pending);
                        bio_list_add(&list, bio);
                }

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

        iblock_submit_bios(&list);
        return 0;

fail_put_bios:
        while ((bio = bio_list_pop(&list)))
                bio_put(bio);
fail_free_ibr:
        kfree(ibr);
fail:
        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
}

enum {
        Opt_udev_path, Opt_readonly, Opt_force, Opt_exclusive, Opt_err,
};

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

static ssize_t iblock_set_configfs_dev_params(struct se_device *dev,
                const char *page, ssize_t count)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        char *orig, *ptr, *arg_p, *opts;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, token, tmp_exclusive;
        unsigned long tmp_readonly;

        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;
                        }
                        if (match_strlcpy(ib_dev->ibd_udev_path, &args[0],
                                SE_UDEV_PATH_LEN) == 0) {
                                ret = -EINVAL;
                                break;
                        }
                        pr_debug("IBLOCK: Referencing UDEV path: %s\n",
                                        ib_dev->ibd_udev_path);
                        ib_dev->ibd_flags |= IBDF_HAS_UDEV_PATH;
                        break;
                case Opt_readonly:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = kstrtoul(arg_p, 0, &tmp_readonly);
                        kfree(arg_p);
                        if (ret < 0) {
                                pr_err("kstrtoul() failed for"
                                                " readonly=\n");
                                goto out;
                        }
                        ib_dev->ibd_readonly = tmp_readonly;
                        pr_debug("IBLOCK: readonly: %d\n", ib_dev->ibd_readonly);
                        break;
                case Opt_exclusive:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = kstrtoint(arg_p, 0, &tmp_exclusive);
                        kfree(arg_p);
                        if (ret < 0) {
                                pr_err("kstrtoul() failed for exclusive=\n");
                                goto out;
                        }
                        ib_dev->ibd_exclusive = tmp_exclusive;
                        pr_debug("IBLOCK: exclusive: %d\n",
                                 ib_dev->ibd_exclusive);
                        break;
                case Opt_force:
                        break;
                default:
                        break;
                }
        }

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

static ssize_t iblock_show_configfs_dev_params(struct se_device *dev, char *b)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bd = ib_dev->ibd_bd;
        ssize_t bl = 0;

        if (bd)
                bl += sprintf(b + bl, "iBlock device: %pg", bd);
        if (ib_dev->ibd_flags & IBDF_HAS_UDEV_PATH)
                bl += sprintf(b + bl, "  UDEV PATH: %s",
                                ib_dev->ibd_udev_path);
        bl += sprintf(b + bl, "  readonly: %d\n", ib_dev->ibd_readonly);
        bl += sprintf(b + bl, "  exclusive: %d\n", ib_dev->ibd_exclusive);

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

        return bl;
}

static int
iblock_alloc_bip(struct se_cmd *cmd, struct bio *bio,
                 struct sg_mapping_iter *miter)
{
        struct se_device *dev = cmd->se_dev;
        struct blk_integrity *bi;
        struct bio_integrity_payload *bip;
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        int rc;
        size_t resid, len;

        bi = bdev_get_integrity(ib_dev->ibd_bd);
        if (!bi) {
                pr_err("Unable to locate bio_integrity\n");
                return -ENODEV;
        }

        bip = bio_integrity_alloc(bio, GFP_NOIO, bio_max_segs(cmd->t_prot_nents));
        if (IS_ERR(bip)) {
                pr_err("Unable to allocate bio_integrity_payload\n");
                return PTR_ERR(bip);
        }

        /* virtual start sector must be in integrity interval units */
        bip_set_seed(bip, bio->bi_iter.bi_sector >>
                                  (bi->interval_exp - SECTOR_SHIFT));

        pr_debug("IBLOCK BIP Size: %u Sector: %llu\n", bip->bip_iter.bi_size,
                 (unsigned long long)bip->bip_iter.bi_sector);

        resid = bio_integrity_bytes(bi, bio_sectors(bio));
        while (resid > 0 && sg_miter_next(miter)) {

                len = min_t(size_t, miter->length, resid);
                rc = bio_integrity_add_page(bio, miter->page, len,
                                            offset_in_page(miter->addr));
                if (rc != len) {
                        pr_err("bio_integrity_add_page() failed; %d\n", rc);
                        sg_miter_stop(miter);
                        return -ENOMEM;
                }

                pr_debug("Added bio integrity page: %p length: %zu offset: %lu\n",
                          miter->page, len, offset_in_page(miter->addr));

                resid -= len;
                if (len < miter->length)
                        miter->consumed -= miter->length - len;
        }
        sg_miter_stop(miter);

        return 0;
}

static sense_reason_t
iblock_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
                  enum dma_data_direction data_direction)
{
        struct se_device *dev = cmd->se_dev;
        sector_t block_lba = target_to_linux_sector(dev, cmd->t_task_lba);
        struct iblock_req *ibr;
        struct bio *bio;
        struct bio_list list;
        struct scatterlist *sg;
        u32 sg_num = sgl_nents;
        blk_opf_t opf;
        unsigned bio_cnt;
        int i, rc;
        struct sg_mapping_iter prot_miter;
        unsigned int miter_dir;

        if (data_direction == DMA_TO_DEVICE) {
                struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

                /*
                 * Set bits to indicate WRITE_ODIRECT so we are not throttled
                 * by WBT.
                 */
                opf = REQ_OP_WRITE | REQ_SYNC | REQ_IDLE;
                /*
                 * Force writethrough using REQ_FUA if a volatile write cache
                 * is not enabled, or if initiator set the Force Unit Access bit.
                 */
                miter_dir = SG_MITER_TO_SG;
                if (bdev_fua(ib_dev->ibd_bd)) {
                        if (cmd->se_cmd_flags & SCF_FUA)
                                opf |= REQ_FUA;
                        else if (!bdev_write_cache(ib_dev->ibd_bd))
                                opf |= REQ_FUA;
                }

                if (cmd->se_cmd_flags & SCF_ATOMIC)
                        opf |= REQ_ATOMIC;
        } else {
                opf = REQ_OP_READ;
                miter_dir = SG_MITER_FROM_SG;
        }

        ibr = kzalloc_obj(struct iblock_req);
        if (!ibr)
                goto fail;
        cmd->priv = ibr;

        if (!sgl_nents) {
                refcount_set(&ibr->pending, 1);
                iblock_complete_cmd(cmd, BLK_STS_OK);
                return 0;
        }

        bio = iblock_get_bio(cmd, block_lba, sgl_nents, opf);
        if (!bio)
                goto fail_free_ibr;

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

        refcount_set(&ibr->pending, 2);
        bio_cnt = 1;

        if (cmd->prot_type && dev->dev_attrib.pi_prot_type)
                sg_miter_start(&prot_miter, cmd->t_prot_sg, cmd->t_prot_nents,
                               miter_dir);

        for_each_sg(sgl, sg, sgl_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) {
                        if (cmd->prot_type && dev->dev_attrib.pi_prot_type) {
                                rc = iblock_alloc_bip(cmd, bio, &prot_miter);
                                if (rc)
                                        goto fail_put_bios;
                        }

                        if (bio_cnt >= IBLOCK_MAX_BIO_PER_TASK) {
                                iblock_submit_bios(&list);
                                bio_cnt = 0;
                        }

                        bio = iblock_get_bio(cmd, block_lba, sg_num, opf);
                        if (!bio)
                                goto fail_put_bios;

                        refcount_inc(&ibr->pending);
                        bio_list_add(&list, bio);
                        bio_cnt++;
                }

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

        if (cmd->prot_type && dev->dev_attrib.pi_prot_type) {
                rc = iblock_alloc_bip(cmd, bio, &prot_miter);
                if (rc)
                        goto fail_put_bios;
        }

        iblock_submit_bios(&list);
        iblock_complete_cmd(cmd, BLK_STS_OK);
        return 0;

fail_put_bios:
        while ((bio = bio_list_pop(&list)))
                bio_put(bio);
fail_free_ibr:
        kfree(ibr);
fail:
        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
}

static sense_reason_t iblock_execute_pr_out(struct se_cmd *cmd, u8 sa, u64 key,
                                            u64 sa_key, u8 type, bool aptpl)
{
        struct se_device *dev = cmd->se_dev;
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bdev = ib_dev->ibd_bd;
        const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
        int ret;

        if (!ops) {
                pr_err("Block device does not support pr_ops but iblock device has been configured for PR passthrough.\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        switch (sa) {
        case PRO_REGISTER:
        case PRO_REGISTER_AND_IGNORE_EXISTING_KEY:
                if (!ops->pr_register) {
                        pr_err("block device does not support pr_register.\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }

                /* The block layer pr ops always enables aptpl */
                if (!aptpl)
                        pr_info("APTPL not set by initiator, but will be used.\n");

                ret = ops->pr_register(bdev, key, sa_key,
                                sa == PRO_REGISTER ? 0 : PR_FL_IGNORE_KEY);
                break;
        case PRO_RESERVE:
                if (!ops->pr_reserve) {
                        pr_err("block_device does not support pr_reserve.\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }

                ret = ops->pr_reserve(bdev, key, scsi_pr_type_to_block(type), 0);
                break;
        case PRO_CLEAR:
                if (!ops->pr_clear) {
                        pr_err("block_device does not support pr_clear.\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }

                ret = ops->pr_clear(bdev, key);
                break;
        case PRO_PREEMPT:
        case PRO_PREEMPT_AND_ABORT:
                if (!ops->pr_clear) {
                        pr_err("block_device does not support pr_preempt.\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }

                ret = ops->pr_preempt(bdev, key, sa_key,
                                      scsi_pr_type_to_block(type),
                                      sa == PRO_PREEMPT_AND_ABORT);
                break;
        case PRO_RELEASE:
                if (!ops->pr_clear) {
                        pr_err("block_device does not support pr_pclear.\n");
                        return TCM_UNSUPPORTED_SCSI_OPCODE;
                }

                ret = ops->pr_release(bdev, key, scsi_pr_type_to_block(type));
                break;
        default:
                pr_err("Unknown PERSISTENT_RESERVE_OUT SA: 0x%02x\n", sa);
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        if (!ret)
                return TCM_NO_SENSE;
        else if (ret == PR_STS_RESERVATION_CONFLICT)
                return TCM_RESERVATION_CONFLICT;
        else
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
}

static void iblock_pr_report_caps(unsigned char *param_data)
{
        u16 len = 8;

        put_unaligned_be16(len, &param_data[0]);
        /*
         * When using the pr_ops passthrough method we only support exporting
         * the device through one target port because from the backend module
         * level we can't see the target port config. As a result we only
         * support registration directly from the I_T nexus the cmd is sent
         * through and do not set ATP_C here.
         *
         * The block layer pr_ops do not support passing in initiators so
         * we don't set SIP_C here.
         */
        /* PTPL_C: Persistence across Target Power Loss bit */
        param_data[2] |= 0x01;
        /*
         * We are filling in the PERSISTENT RESERVATION TYPE MASK below, so
         * set the TMV: Task Mask Valid bit.
         */
        param_data[3] |= 0x80;
        /*
         * Change ALLOW COMMANDs to 0x20 or 0x40 later from Table 166
         */
        param_data[3] |= 0x10; /* ALLOW COMMANDs field 001b */
        /*
         * PTPL_A: Persistence across Target Power Loss Active bit. The block
         * layer pr ops always enables this so report it active.
         */
        param_data[3] |= 0x01;
        /*
         * Setup the PERSISTENT RESERVATION TYPE MASK from Table 212 spc4r37.
         */
        param_data[4] |= 0x80; /* PR_TYPE_EXCLUSIVE_ACCESS_ALLREG */
        param_data[4] |= 0x40; /* PR_TYPE_EXCLUSIVE_ACCESS_REGONLY */
        param_data[4] |= 0x20; /* PR_TYPE_WRITE_EXCLUSIVE_REGONLY */
        param_data[4] |= 0x08; /* PR_TYPE_EXCLUSIVE_ACCESS */
        param_data[4] |= 0x02; /* PR_TYPE_WRITE_EXCLUSIVE */
        param_data[5] |= 0x01; /* PR_TYPE_EXCLUSIVE_ACCESS_ALLREG */
}

static sense_reason_t iblock_pr_read_keys(struct se_cmd *cmd,
                                          unsigned char *param_data)
{
        struct se_device *dev = cmd->se_dev;
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bdev = ib_dev->ibd_bd;
        const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
        int i, len, paths, data_offset;
        struct pr_keys *keys;
        sense_reason_t ret;

        if (!ops) {
                pr_err("Block device does not support pr_ops but iblock device has been configured for PR passthrough.\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        if (!ops->pr_read_keys) {
                pr_err("Block device does not support read_keys.\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        /*
         * We don't know what's under us, but dm-multipath will register every
         * path with the same key, so start off with enough space for 16 paths.
         * which is not a lot of memory and should normally be enough.
         */
        paths = 16;
retry:
        len = 8 * paths;
        keys = kzalloc(sizeof(*keys) + len, GFP_KERNEL);
        if (!keys)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        keys->num_keys = paths;
        if (!ops->pr_read_keys(bdev, keys)) {
                if (keys->num_keys > paths) {
                        kfree(keys);
                        paths *= 2;
                        goto retry;
                }
        } else {
                ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                goto free_keys;
        }

        ret = TCM_NO_SENSE;

        put_unaligned_be32(keys->generation, &param_data[0]);
        if (!keys->num_keys) {
                put_unaligned_be32(0, &param_data[4]);
                goto free_keys;
        }

        put_unaligned_be32(8 * keys->num_keys, &param_data[4]);

        data_offset = 8;
        for (i = 0; i < keys->num_keys; i++) {
                if (data_offset + 8 > cmd->data_length)
                        break;

                put_unaligned_be64(keys->keys[i], &param_data[data_offset]);
                data_offset += 8;
        }

free_keys:
        kfree(keys);
        return ret;
}

static sense_reason_t iblock_pr_read_reservation(struct se_cmd *cmd,
                                                 unsigned char *param_data)
{
        struct se_device *dev = cmd->se_dev;
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bdev = ib_dev->ibd_bd;
        const struct pr_ops *ops = bdev->bd_disk->fops->pr_ops;
        struct pr_held_reservation rsv = { };

        if (!ops) {
                pr_err("Block device does not support pr_ops but iblock device has been configured for PR passthrough.\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        if (!ops->pr_read_reservation) {
                pr_err("Block device does not support read_keys.\n");
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        if (ops->pr_read_reservation(bdev, &rsv))
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        put_unaligned_be32(rsv.generation, &param_data[0]);
        if (!block_pr_type_to_scsi(rsv.type)) {
                put_unaligned_be32(0, &param_data[4]);
                return TCM_NO_SENSE;
        }

        put_unaligned_be32(16, &param_data[4]);

        if (cmd->data_length < 16)
                return TCM_NO_SENSE;
        put_unaligned_be64(rsv.key, &param_data[8]);

        if (cmd->data_length < 22)
                return TCM_NO_SENSE;
        param_data[21] = block_pr_type_to_scsi(rsv.type);

        return TCM_NO_SENSE;
}

static sense_reason_t iblock_execute_pr_in(struct se_cmd *cmd, u8 sa,
                                           unsigned char *param_data)
{
        sense_reason_t ret = TCM_NO_SENSE;

        switch (sa) {
        case PRI_REPORT_CAPABILITIES:
                iblock_pr_report_caps(param_data);
                break;
        case PRI_READ_KEYS:
                ret = iblock_pr_read_keys(cmd, param_data);
                break;
        case PRI_READ_RESERVATION:
                ret = iblock_pr_read_reservation(cmd, param_data);
                break;
        default:
                pr_err("Unknown PERSISTENT_RESERVE_IN SA: 0x%02x\n", sa);
                return TCM_UNSUPPORTED_SCSI_OPCODE;
        }

        return ret;
}

static sector_t iblock_get_alignment_offset_lbas(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bd = ib_dev->ibd_bd;
        int ret;

        ret = bdev_alignment_offset(bd);
        if (ret == -1)
                return 0;

        /* convert offset-bytes to offset-lbas */
        return ret / bdev_logical_block_size(bd);
}

static unsigned int iblock_get_lbppbe(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bd = ib_dev->ibd_bd;
        unsigned int logs_per_phys =
                bdev_physical_block_size(bd) / bdev_logical_block_size(bd);

        return ilog2(logs_per_phys);
}

static unsigned int iblock_get_io_min(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bd = ib_dev->ibd_bd;

        return bdev_io_min(bd);
}

static unsigned int iblock_get_io_opt(struct se_device *dev)
{
        struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
        struct block_device *bd = ib_dev->ibd_bd;

        return bdev_io_opt(bd);
}

static struct exec_cmd_ops iblock_exec_cmd_ops = {
        .execute_rw             = iblock_execute_rw,
        .execute_sync_cache     = iblock_execute_sync_cache,
        .execute_write_same     = iblock_execute_write_same,
        .execute_unmap          = iblock_execute_unmap,
        .execute_pr_out         = iblock_execute_pr_out,
        .execute_pr_in          = iblock_execute_pr_in,
};

static sense_reason_t
iblock_parse_cdb(struct se_cmd *cmd)
{
        return sbc_parse_cdb(cmd, &iblock_exec_cmd_ops);
}

static bool iblock_get_write_cache(struct se_device *dev)
{
        return bdev_write_cache(IBLOCK_DEV(dev)->ibd_bd);
}

static const struct target_backend_ops iblock_ops = {
        .name                   = "iblock",
        .inquiry_prod           = "IBLOCK",
        .transport_flags_changeable = TRANSPORT_FLAG_PASSTHROUGH_PGR,
        .inquiry_rev            = IBLOCK_VERSION,
        .owner                  = THIS_MODULE,
        .attach_hba             = iblock_attach_hba,
        .detach_hba             = iblock_detach_hba,
        .alloc_device           = iblock_alloc_device,
        .configure_device       = iblock_configure_device,
        .destroy_device         = iblock_destroy_device,
        .free_device            = iblock_free_device,
        .configure_unmap        = iblock_configure_unmap,
        .plug_device            = iblock_plug_device,
        .unplug_device          = iblock_unplug_device,
        .parse_cdb              = iblock_parse_cdb,
        .set_configfs_dev_params = iblock_set_configfs_dev_params,
        .show_configfs_dev_params = iblock_show_configfs_dev_params,
        .get_device_type        = sbc_get_device_type,
        .get_blocks             = iblock_get_blocks,
        .get_alignment_offset_lbas = iblock_get_alignment_offset_lbas,
        .get_lbppbe             = iblock_get_lbppbe,
        .get_io_min             = iblock_get_io_min,
        .get_io_opt             = iblock_get_io_opt,
        .get_write_cache        = iblock_get_write_cache,
        .tb_dev_attrib_attrs    = sbc_attrib_attrs,
};

static int __init iblock_module_init(void)
{
        return transport_backend_register(&iblock_ops);
}

static void __exit iblock_module_exit(void)
{
        target_backend_unregister(&iblock_ops);
}

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);