// SPDX-License-Identifier: GPL-2.0-or-later
/*******************************************************************************
 * Filename:  target_core_rd.c
 *
 * This file contains the Storage Engine <-> Ramdisk 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/highmem.h>
#include <linux/timer.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <scsi/scsi_proto.h>

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

#include "target_core_rd.h"

static inline struct rd_dev *RD_DEV(struct se_device *dev)
{
        return container_of(dev, struct rd_dev, dev);
}

static int rd_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct rd_host *rd_host;

        rd_host = kzalloc_obj(*rd_host);
        if (!rd_host)
                return -ENOMEM;

        rd_host->rd_host_id = host_id;

        hba->hba_ptr = rd_host;

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

        return 0;
}

static void rd_detach_hba(struct se_hba *hba)
{
        struct rd_host *rd_host = hba->hba_ptr;

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

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

static u32 rd_release_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *sg_table,
                                 u32 sg_table_count)
{
        struct page *pg;
        struct scatterlist *sg;
        u32 i, j, page_count = 0, sg_per_table;

        for (i = 0; i < sg_table_count; i++) {
                sg = sg_table[i].sg_table;
                sg_per_table = sg_table[i].rd_sg_count;

                for (j = 0; j < sg_per_table; j++) {
                        pg = sg_page(&sg[j]);
                        if (pg) {
                                __free_page(pg);
                                page_count++;
                        }
                }
                kfree(sg);
        }

        kfree(sg_table);
        return page_count;
}

static void rd_release_device_space(struct rd_dev *rd_dev)
{
        u32 page_count;

        if (!rd_dev->sg_table_array || !rd_dev->sg_table_count)
                return;

        page_count = rd_release_sgl_table(rd_dev, rd_dev->sg_table_array,
                                          rd_dev->sg_table_count);

        pr_debug("CORE_RD[%u] - Released device space for Ramdisk"
                " Device ID: %u, pages %u in %u tables total bytes %lu\n",
                rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count,
                rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE);

        rd_dev->sg_table_array = NULL;
        rd_dev->sg_table_count = 0;
}


/*      rd_build_device_space():
 *
 *
 */
static int rd_allocate_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *sg_table,
                                 u32 total_sg_needed, unsigned char init_payload)
{
        u32 i = 0, j, page_offset = 0, sg_per_table;
        u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));
        struct page *pg;
        struct scatterlist *sg;
        unsigned char *p;

        while (total_sg_needed) {
                unsigned int chain_entry = 0;

                sg_per_table = (total_sg_needed > max_sg_per_table) ?
                        max_sg_per_table : total_sg_needed;

                /*
                 * Reserve extra element for chain entry
                 */
                if (sg_per_table < total_sg_needed)
                        chain_entry = 1;

                sg = kmalloc_objs(*sg, sg_per_table + chain_entry);
                if (!sg)
                        return -ENOMEM;

                sg_init_table(sg, sg_per_table + chain_entry);

                if (i > 0) {
                        sg_chain(sg_table[i - 1].sg_table,
                                 max_sg_per_table + 1, sg);
                }

                sg_table[i].sg_table = sg;
                sg_table[i].rd_sg_count = sg_per_table;
                sg_table[i].page_start_offset = page_offset;
                sg_table[i++].page_end_offset = (page_offset + sg_per_table)
                                                - 1;

                for (j = 0; j < sg_per_table; j++) {
                        pg = alloc_pages(GFP_KERNEL, 0);
                        if (!pg) {
                                pr_err("Unable to allocate scatterlist"
                                        " pages for struct rd_dev_sg_table\n");
                                return -ENOMEM;
                        }
                        sg_assign_page(&sg[j], pg);
                        sg[j].length = PAGE_SIZE;

                        p = kmap(pg);
                        memset(p, init_payload, PAGE_SIZE);
                        kunmap(pg);
                }

                page_offset += sg_per_table;
                total_sg_needed -= sg_per_table;
        }

        return 0;
}

static int rd_build_device_space(struct rd_dev *rd_dev)
{
        struct rd_dev_sg_table *sg_table;
        u32 sg_tables, total_sg_needed;
        u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));
        int rc;

        if (rd_dev->rd_page_count <= 0) {
                pr_err("Illegal page count: %u for Ramdisk device\n",
                       rd_dev->rd_page_count);
                return -EINVAL;
        }

        /* Don't need backing pages for NULLIO */
        if (rd_dev->rd_flags & RDF_NULLIO)
                return 0;

        total_sg_needed = rd_dev->rd_page_count;

        sg_tables = (total_sg_needed / max_sg_per_table) + 1;
        sg_table = kzalloc_objs(*sg_table, sg_tables);
        if (!sg_table)
                return -ENOMEM;

        rd_dev->sg_table_array = sg_table;
        rd_dev->sg_table_count = sg_tables;

        rc = rd_allocate_sgl_table(rd_dev, sg_table, total_sg_needed, 0x00);
        if (rc)
                return rc;

        pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u space of"
                 " %u pages in %u tables\n", rd_dev->rd_host->rd_host_id,
                 rd_dev->rd_dev_id, rd_dev->rd_page_count,
                 rd_dev->sg_table_count);

        return 0;
}

static void rd_release_prot_space(struct rd_dev *rd_dev)
{
        u32 page_count;

        if (!rd_dev->sg_prot_array || !rd_dev->sg_prot_count)
                return;

        page_count = rd_release_sgl_table(rd_dev, rd_dev->sg_prot_array,
                                          rd_dev->sg_prot_count);

        pr_debug("CORE_RD[%u] - Released protection space for Ramdisk"
                 " Device ID: %u, pages %u in %u tables total bytes %lu\n",
                 rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count,
                 rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE);

        rd_dev->sg_prot_array = NULL;
        rd_dev->sg_prot_count = 0;
}

static int rd_build_prot_space(struct rd_dev *rd_dev, int prot_length, int block_size)
{
        struct rd_dev_sg_table *sg_table;
        u32 total_sg_needed, sg_tables;
        u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));
        int rc;

        if (rd_dev->rd_flags & RDF_NULLIO)
                return 0;
        /*
         * prot_length=8byte dif data
         * tot sg needed = rd_page_count * (PGSZ/block_size) *
         *                 (prot_length/block_size) + pad
         * PGSZ canceled each other.
         */
        total_sg_needed = (rd_dev->rd_page_count * prot_length / block_size) + 1;

        sg_tables = (total_sg_needed / max_sg_per_table) + 1;
        sg_table = kzalloc_objs(*sg_table, sg_tables);
        if (!sg_table)
                return -ENOMEM;

        rd_dev->sg_prot_array = sg_table;
        rd_dev->sg_prot_count = sg_tables;

        rc = rd_allocate_sgl_table(rd_dev, sg_table, total_sg_needed, 0xff);
        if (rc)
                return rc;

        pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u prot space of"
                 " %u pages in %u tables\n", rd_dev->rd_host->rd_host_id,
                 rd_dev->rd_dev_id, total_sg_needed, rd_dev->sg_prot_count);

        return 0;
}

static struct se_device *rd_alloc_device(struct se_hba *hba, const char *name)
{
        struct rd_dev *rd_dev;
        struct rd_host *rd_host = hba->hba_ptr;

        rd_dev = kzalloc_obj(*rd_dev);
        if (!rd_dev)
                return NULL;

        rd_dev->rd_host = rd_host;

        return &rd_dev->dev;
}

static int rd_configure_device(struct se_device *dev)
{
        struct rd_dev *rd_dev = RD_DEV(dev);
        struct rd_host *rd_host = dev->se_hba->hba_ptr;
        int ret;

        if (!(rd_dev->rd_flags & RDF_HAS_PAGE_COUNT)) {
                pr_debug("Missing rd_pages= parameter\n");
                return -EINVAL;
        }

        ret = rd_build_device_space(rd_dev);
        if (ret < 0)
                goto fail;

        dev->dev_attrib.hw_block_size = RD_BLOCKSIZE;
        dev->dev_attrib.hw_max_sectors = UINT_MAX;
        dev->dev_attrib.hw_queue_depth = RD_MAX_DEVICE_QUEUE_DEPTH;
        dev->dev_attrib.is_nonrot = 1;

        rd_dev->rd_dev_id = rd_host->rd_host_dev_id_count++;

        pr_debug("CORE_RD[%u] - Added TCM MEMCPY Ramdisk Device ID: %u of"
                " %u pages in %u tables, %lu total bytes\n",
                rd_host->rd_host_id, rd_dev->rd_dev_id, rd_dev->rd_page_count,
                rd_dev->sg_table_count,
                (unsigned long)(rd_dev->rd_page_count * PAGE_SIZE));

        return 0;

fail:
        rd_release_device_space(rd_dev);
        return ret;
}

static void rd_dev_call_rcu(struct rcu_head *p)
{
        struct se_device *dev = container_of(p, struct se_device, rcu_head);
        struct rd_dev *rd_dev = RD_DEV(dev);

        kfree(rd_dev);
}

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

static void rd_destroy_device(struct se_device *dev)
{
        struct rd_dev *rd_dev = RD_DEV(dev);

        rd_release_device_space(rd_dev);
}

static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
{
        struct rd_dev_sg_table *sg_table;
        u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));

        i = page / sg_per_table;
        if (i < rd_dev->sg_table_count) {
                sg_table = &rd_dev->sg_table_array[i];
                if ((sg_table->page_start_offset <= page) &&
                    (sg_table->page_end_offset >= page))
                        return sg_table;
        }

        pr_err("Unable to locate struct rd_dev_sg_table for page: %u\n",
                        page);

        return NULL;
}

static struct rd_dev_sg_table *rd_get_prot_table(struct rd_dev *rd_dev, u32 page)
{
        struct rd_dev_sg_table *sg_table;
        u32 i, sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));

        i = page / sg_per_table;
        if (i < rd_dev->sg_prot_count) {
                sg_table = &rd_dev->sg_prot_array[i];
                if ((sg_table->page_start_offset <= page) &&
                     (sg_table->page_end_offset >= page))
                        return sg_table;
        }

        pr_err("Unable to locate struct prot rd_dev_sg_table for page: %u\n",
                        page);

        return NULL;
}

static sense_reason_t rd_do_prot_rw(struct se_cmd *cmd, bool is_read)
{
        struct se_device *se_dev = cmd->se_dev;
        struct rd_dev *dev = RD_DEV(se_dev);
        struct rd_dev_sg_table *prot_table;
        struct scatterlist *prot_sg;
        u32 sectors = cmd->data_length / se_dev->dev_attrib.block_size;
        u32 prot_offset, prot_page;
        u32 prot_npages __maybe_unused;
        u64 tmp;
        sense_reason_t rc = 0;

        tmp = cmd->t_task_lba * se_dev->prot_length;
        prot_offset = do_div(tmp, PAGE_SIZE);
        prot_page = tmp;

        prot_table = rd_get_prot_table(dev, prot_page);
        if (!prot_table)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        prot_sg = &prot_table->sg_table[prot_page -
                                        prot_table->page_start_offset];

        if (se_dev->dev_attrib.pi_prot_verify) {
                if (is_read)
                        rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors, 0,
                                            prot_sg, prot_offset);
                else
                        rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors, 0,
                                            cmd->t_prot_sg, 0);
        }
        if (!rc)
                sbc_dif_copy_prot(cmd, sectors, is_read, prot_sg, prot_offset);

        return rc;
}

static sense_reason_t
rd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
              enum dma_data_direction data_direction)
{
        struct se_device *se_dev = cmd->se_dev;
        struct rd_dev *dev = RD_DEV(se_dev);
        struct rd_dev_sg_table *table;
        struct scatterlist *rd_sg;
        struct sg_mapping_iter m;
        u32 rd_offset;
        u32 rd_size;
        u32 rd_page;
        u32 src_len;
        u64 tmp;
        sense_reason_t rc;

        if (dev->rd_flags & RDF_NULLIO) {
                target_complete_cmd(cmd, SAM_STAT_GOOD);
                return 0;
        }

        tmp = cmd->t_task_lba * se_dev->dev_attrib.block_size;
        rd_offset = do_div(tmp, PAGE_SIZE);
        rd_page = tmp;
        rd_size = cmd->data_length;

        table = rd_get_sg_table(dev, rd_page);
        if (!table)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        rd_sg = &table->sg_table[rd_page - table->page_start_offset];

        pr_debug("RD[%u]: %s LBA: %llu, Size: %u Page: %u, Offset: %u\n",
                        dev->rd_dev_id,
                        data_direction == DMA_FROM_DEVICE ? "Read" : "Write",
                        cmd->t_task_lba, rd_size, rd_page, rd_offset);

        if (cmd->prot_type && se_dev->dev_attrib.pi_prot_type &&
            data_direction == DMA_TO_DEVICE) {
                rc = rd_do_prot_rw(cmd, false);
                if (rc)
                        return rc;
        }

        src_len = PAGE_SIZE - rd_offset;
        sg_miter_start(&m, sgl, sgl_nents,
                        data_direction == DMA_FROM_DEVICE ?
                                SG_MITER_TO_SG : SG_MITER_FROM_SG);
        while (rd_size) {
                u32 len;
                void *rd_addr;

                sg_miter_next(&m);
                if (!(u32)m.length) {
                        pr_debug("RD[%u]: invalid sgl %p len %zu\n",
                                 dev->rd_dev_id, m.addr, m.length);
                        sg_miter_stop(&m);
                        return TCM_INCORRECT_AMOUNT_OF_DATA;
                }
                len = min((u32)m.length, src_len);
                if (len > rd_size) {
                        pr_debug("RD[%u]: size underrun page %d offset %d "
                                 "size %d\n", dev->rd_dev_id,
                                 rd_page, rd_offset, rd_size);
                        len = rd_size;
                }
                m.consumed = len;

                rd_addr = sg_virt(rd_sg) + rd_offset;

                if (data_direction == DMA_FROM_DEVICE)
                        memcpy(m.addr, rd_addr, len);
                else
                        memcpy(rd_addr, m.addr, len);

                rd_size -= len;
                if (!rd_size)
                        continue;

                src_len -= len;
                if (src_len) {
                        rd_offset += len;
                        continue;
                }

                /* rd page completed, next one please */
                rd_page++;
                rd_offset = 0;
                src_len = PAGE_SIZE;
                if (rd_page <= table->page_end_offset) {
                        rd_sg++;
                        continue;
                }

                table = rd_get_sg_table(dev, rd_page);
                if (!table) {
                        sg_miter_stop(&m);
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }

                /* since we increment, the first sg entry is correct */
                rd_sg = table->sg_table;
        }
        sg_miter_stop(&m);

        if (cmd->prot_type && se_dev->dev_attrib.pi_prot_type &&
            data_direction == DMA_FROM_DEVICE) {
                rc = rd_do_prot_rw(cmd, true);
                if (rc)
                        return rc;
        }

        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

enum {
        Opt_rd_pages, Opt_rd_nullio, Opt_rd_dummy, Opt_err
};

static match_table_t tokens = {
        {Opt_rd_pages, "rd_pages=%d"},
        {Opt_rd_nullio, "rd_nullio=%d"},
        {Opt_rd_dummy, "rd_dummy=%d"},
        {Opt_err, NULL}
};

static ssize_t rd_set_configfs_dev_params(struct se_device *dev,
                const char *page, ssize_t count)
{
        struct rd_dev *rd_dev = RD_DEV(dev);
        char *orig, *ptr, *opts;
        substring_t args[MAX_OPT_ARGS];
        int arg, 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_rd_pages:
                        match_int(args, &arg);
                        rd_dev->rd_page_count = arg;
                        pr_debug("RAMDISK: Referencing Page"
                                " Count: %u\n", rd_dev->rd_page_count);
                        rd_dev->rd_flags |= RDF_HAS_PAGE_COUNT;
                        break;
                case Opt_rd_nullio:
                        match_int(args, &arg);
                        if (arg != 1)
                                break;

                        pr_debug("RAMDISK: Setting NULLIO flag: %d\n", arg);
                        rd_dev->rd_flags |= RDF_NULLIO;
                        break;
                case Opt_rd_dummy:
                        match_int(args, &arg);
                        if (arg != 1)
                                break;

                        pr_debug("RAMDISK: Setting DUMMY flag: %d\n", arg);
                        rd_dev->rd_flags |= RDF_DUMMY;
                        break;
                default:
                        break;
                }
        }

        kfree(orig);
        return count;
}

static ssize_t rd_show_configfs_dev_params(struct se_device *dev, char *b)
{
        struct rd_dev *rd_dev = RD_DEV(dev);

        ssize_t bl = sprintf(b, "TCM RamDisk ID: %u  RamDisk Makeup: rd_mcp\n",
                        rd_dev->rd_dev_id);
        bl += sprintf(b + bl, "        PAGES/PAGE_SIZE: %u*%lu"
                        "  SG_table_count: %u  nullio: %d dummy: %d\n",
                        rd_dev->rd_page_count,
                        PAGE_SIZE, rd_dev->sg_table_count,
                        !!(rd_dev->rd_flags & RDF_NULLIO),
                        !!(rd_dev->rd_flags & RDF_DUMMY));
        return bl;
}

static u32 rd_get_device_type(struct se_device *dev)
{
        if (RD_DEV(dev)->rd_flags & RDF_DUMMY)
                return 0x3f; /* Unknown device type, not connected */
        else
                return sbc_get_device_type(dev);
}

static sector_t rd_get_blocks(struct se_device *dev)
{
        struct rd_dev *rd_dev = RD_DEV(dev);

        unsigned long long blocks_long = ((rd_dev->rd_page_count * PAGE_SIZE) /
                        dev->dev_attrib.block_size) - 1;

        return blocks_long;
}

static int rd_init_prot(struct se_device *dev)
{
        struct rd_dev *rd_dev = RD_DEV(dev);

        if (!dev->dev_attrib.pi_prot_type)
                return 0;

        return rd_build_prot_space(rd_dev, dev->prot_length,
                                   dev->dev_attrib.block_size);
}

static void rd_free_prot(struct se_device *dev)
{
        struct rd_dev *rd_dev = RD_DEV(dev);

        rd_release_prot_space(rd_dev);
}

static struct exec_cmd_ops rd_exec_cmd_ops = {
        .execute_rw             = rd_execute_rw,
};

static sense_reason_t
rd_parse_cdb(struct se_cmd *cmd)
{
        return sbc_parse_cdb(cmd, &rd_exec_cmd_ops);
}

static const struct target_backend_ops rd_mcp_ops = {
        .name                   = "rd_mcp",
        .inquiry_prod           = "RAMDISK-MCP",
        .inquiry_rev            = RD_MCP_VERSION,
        .attach_hba             = rd_attach_hba,
        .detach_hba             = rd_detach_hba,
        .alloc_device           = rd_alloc_device,
        .configure_device       = rd_configure_device,
        .destroy_device         = rd_destroy_device,
        .free_device            = rd_free_device,
        .parse_cdb              = rd_parse_cdb,
        .set_configfs_dev_params = rd_set_configfs_dev_params,
        .show_configfs_dev_params = rd_show_configfs_dev_params,
        .get_device_type        = rd_get_device_type,
        .get_blocks             = rd_get_blocks,
        .init_prot              = rd_init_prot,
        .free_prot              = rd_free_prot,
        .tb_dev_attrib_attrs    = sbc_attrib_attrs,
};

int __init rd_module_init(void)
{
        return transport_backend_register(&rd_mcp_ops);
}

void rd_module_exit(void)
{
        target_backend_unregister(&rd_mcp_ops);
}