/*******************************************************************************
 * Filename:  target_core_file.c
 *
 * This file contains the Storage Engine <-> FILEIO transport specific functions
 *
 * Copyright (c) 2005 PyX Technologies, Inc.
 * Copyright (c) 2005-2006 SBE, Inc.  All Rights Reserved.
 * 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/blkdev.h>
#include <linux/slab.h>
#include <linux/spinlock.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_file.h"

static struct se_subsystem_api fileio_template;

/*      fd_attach_hba(): (Part of se_subsystem_api_t template)
 *
 *
 */
static int fd_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct fd_host *fd_host;

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

        fd_host->fd_host_id = host_id;

        hba->hba_ptr = fd_host;

        pr_debug("CORE_HBA[%d] - TCM FILEIO HBA Driver %s on Generic"
                " Target Core Stack %s\n", hba->hba_id, FD_VERSION,
                TARGET_CORE_MOD_VERSION);
        pr_debug("CORE_HBA[%d] - Attached FILEIO HBA: %u to Generic"
                " MaxSectors: %u\n",
                hba->hba_id, fd_host->fd_host_id, FD_MAX_SECTORS);

        return 0;
}

static void fd_detach_hba(struct se_hba *hba)
{
        struct fd_host *fd_host = hba->hba_ptr;

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

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

static void *fd_allocate_virtdevice(struct se_hba *hba, const char *name)
{
        struct fd_dev *fd_dev;
        struct fd_host *fd_host = hba->hba_ptr;

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

        fd_dev->fd_host = fd_host;

        pr_debug("FILEIO: Allocated fd_dev for %p\n", name);

        return fd_dev;
}

/*      fd_create_virtdevice(): (Part of se_subsystem_api_t template)
 *
 *
 */
static struct se_device *fd_create_virtdevice(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        void *p)
{
        struct se_device *dev;
        struct se_dev_limits dev_limits;
        struct queue_limits *limits;
        struct fd_dev *fd_dev = p;
        struct fd_host *fd_host = hba->hba_ptr;
        struct file *file;
        struct inode *inode = NULL;
        int dev_flags = 0, flags, ret = -EINVAL;

        memset(&dev_limits, 0, sizeof(struct se_dev_limits));

        /*
         * Use O_DSYNC by default instead of O_SYNC to forgo syncing
         * of pure timestamp updates.
         */
        flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
        /*
         * Optionally allow fd_buffered_io=1 to be enabled for people
         * who want use the fs buffer cache as an WriteCache mechanism.
         *
         * This means that in event of a hard failure, there is a risk
         * of silent data-loss if the SCSI client has *not* performed a
         * forced unit access (FUA) write, or issued SYNCHRONIZE_CACHE
         * to write-out the entire device cache.
         */
        if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) {
                pr_debug("FILEIO: Disabling O_DSYNC, using buffered FILEIO\n");
                flags &= ~O_DSYNC;
        }

        file = filp_open(fd_dev->fd_dev_name, flags, 0600);
        if (IS_ERR(file)) {
                pr_err("filp_open(%s) failed\n", fd_dev->fd_dev_name);
                ret = PTR_ERR(file);
                goto fail;
        }
        fd_dev->fd_file = file;
        /*
         * If using a block backend with this struct file, we extract
         * fd_dev->fd_[block,dev]_size from struct block_device.
         *
         * Otherwise, we use the passed fd_size= from configfs
         */
        inode = file->f_mapping->host;
        if (S_ISBLK(inode->i_mode)) {
                struct request_queue *q;
                unsigned long long dev_size;
                /*
                 * 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(inode->i_bdev);
                limits = &dev_limits.limits;
                limits->logical_block_size = bdev_logical_block_size(inode->i_bdev);
                limits->max_hw_sectors = queue_max_hw_sectors(q);
                limits->max_sectors = queue_max_sectors(q);
                /*
                 * Determine the number of bytes from i_size_read() minus
                 * one (1) logical sector from underlying struct block_device
                 */
                fd_dev->fd_block_size = bdev_logical_block_size(inode->i_bdev);
                dev_size = (i_size_read(file->f_mapping->host) -
                                       fd_dev->fd_block_size);

                pr_debug("FILEIO: Using size: %llu bytes from struct"
                        " block_device blocks: %llu logical_block_size: %d\n",
                        dev_size, div_u64(dev_size, fd_dev->fd_block_size),
                        fd_dev->fd_block_size);
        } else {
                if (!(fd_dev->fbd_flags & FBDF_HAS_SIZE)) {
                        pr_err("FILEIO: Missing fd_dev_size="
                                " parameter, and no backing struct"
                                " block_device\n");
                        goto fail;
                }

                limits = &dev_limits.limits;
                limits->logical_block_size = FD_BLOCKSIZE;
                limits->max_hw_sectors = FD_MAX_SECTORS;
                limits->max_sectors = FD_MAX_SECTORS;
                fd_dev->fd_block_size = FD_BLOCKSIZE;
        }

        dev_limits.hw_queue_depth = FD_MAX_DEVICE_QUEUE_DEPTH;
        dev_limits.queue_depth = FD_DEVICE_QUEUE_DEPTH;

        dev = transport_add_device_to_core_hba(hba, &fileio_template,
                                se_dev, dev_flags, fd_dev,
                                &dev_limits, "FILEIO", FD_VERSION);
        if (!dev)
                goto fail;

        if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) {
                pr_debug("FILEIO: Forcing setting of emulate_write_cache=1"
                        " with FDBD_HAS_BUFFERED_IO_WCE\n");
                dev->se_sub_dev->se_dev_attrib.emulate_write_cache = 1;
        }

        fd_dev->fd_dev_id = fd_host->fd_host_dev_id_count++;
        fd_dev->fd_queue_depth = dev->queue_depth;

        pr_debug("CORE_FILE[%u] - Added TCM FILEIO Device ID: %u at %s,"
                " %llu total bytes\n", fd_host->fd_host_id, fd_dev->fd_dev_id,
                        fd_dev->fd_dev_name, fd_dev->fd_dev_size);

        return dev;
fail:
        if (fd_dev->fd_file) {
                filp_close(fd_dev->fd_file, NULL);
                fd_dev->fd_file = NULL;
        }
        return ERR_PTR(ret);
}

/*      fd_free_device(): (Part of se_subsystem_api_t template)
 *
 *
 */
static void fd_free_device(void *p)
{
        struct fd_dev *fd_dev = p;

        if (fd_dev->fd_file) {
                filp_close(fd_dev->fd_file, NULL);
                fd_dev->fd_file = NULL;
        }

        kfree(fd_dev);
}

static int fd_do_readv(struct se_cmd *cmd, struct scatterlist *sgl,
                u32 sgl_nents)
{
        struct se_device *se_dev = cmd->se_dev;
        struct fd_dev *dev = se_dev->dev_ptr;
        struct file *fd = dev->fd_file;
        struct scatterlist *sg;
        struct iovec *iov;
        mm_segment_t old_fs;
        loff_t pos = (cmd->t_task_lba *
                      se_dev->se_sub_dev->se_dev_attrib.block_size);
        int ret = 0, i;

        iov = kzalloc(sizeof(struct iovec) * sgl_nents, GFP_KERNEL);
        if (!iov) {
                pr_err("Unable to allocate fd_do_readv iov[]\n");
                return -ENOMEM;
        }

        for_each_sg(sgl, sg, sgl_nents, i) {
                iov[i].iov_len = sg->length;
                iov[i].iov_base = kmap(sg_page(sg)) + sg->offset;
        }

        old_fs = get_fs();
        set_fs(get_ds());
        ret = vfs_readv(fd, &iov[0], sgl_nents, &pos);
        set_fs(old_fs);

        for_each_sg(sgl, sg, sgl_nents, i)
                kunmap(sg_page(sg));
        kfree(iov);
        /*
         * Return zeros and GOOD status even if the READ did not return
         * the expected virt_size for struct file w/o a backing struct
         * block_device.
         */
        if (S_ISBLK(fd->f_dentry->d_inode->i_mode)) {
                if (ret < 0 || ret != cmd->data_length) {
                        pr_err("vfs_readv() returned %d,"
                                " expecting %d for S_ISBLK\n", ret,
                                (int)cmd->data_length);
                        return (ret < 0 ? ret : -EINVAL);
                }
        } else {
                if (ret < 0) {
                        pr_err("vfs_readv() returned %d for non"
                                " S_ISBLK\n", ret);
                        return ret;
                }
        }

        return 1;
}

static int fd_do_writev(struct se_cmd *cmd, struct scatterlist *sgl,
                u32 sgl_nents)
{
        struct se_device *se_dev = cmd->se_dev;
        struct fd_dev *dev = se_dev->dev_ptr;
        struct file *fd = dev->fd_file;
        struct scatterlist *sg;
        struct iovec *iov;
        mm_segment_t old_fs;
        loff_t pos = (cmd->t_task_lba *
                      se_dev->se_sub_dev->se_dev_attrib.block_size);
        int ret, i = 0;

        iov = kzalloc(sizeof(struct iovec) * sgl_nents, GFP_KERNEL);
        if (!iov) {
                pr_err("Unable to allocate fd_do_writev iov[]\n");
                return -ENOMEM;
        }

        for_each_sg(sgl, sg, sgl_nents, i) {
                iov[i].iov_len = sg->length;
                iov[i].iov_base = kmap(sg_page(sg)) + sg->offset;
        }

        old_fs = get_fs();
        set_fs(get_ds());
        ret = vfs_writev(fd, &iov[0], sgl_nents, &pos);
        set_fs(old_fs);

        for_each_sg(sgl, sg, sgl_nents, i)
                kunmap(sg_page(sg));

        kfree(iov);

        if (ret < 0 || ret != cmd->data_length) {
                pr_err("vfs_writev() returned %d\n", ret);
                return (ret < 0 ? ret : -EINVAL);
        }

        return 1;
}

static int fd_execute_sync_cache(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct fd_dev *fd_dev = dev->dev_ptr;
        int immed = (cmd->t_task_cdb[1] & 0x2);
        loff_t start, end;
        int ret;

        /*
         * 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);

        /*
         * Determine if we will be flushing the entire device.
         */
        if (cmd->t_task_lba == 0 && cmd->data_length == 0) {
                start = 0;
                end = LLONG_MAX;
        } else {
                start = cmd->t_task_lba * dev->se_sub_dev->se_dev_attrib.block_size;
                if (cmd->data_length)
                        end = start + cmd->data_length;
                else
                        end = LLONG_MAX;
        }

        ret = vfs_fsync_range(fd_dev->fd_file, start, end, 1);
        if (ret != 0)
                pr_err("FILEIO: vfs_fsync_range() failed: %d\n", ret);

        if (immed)
                return 0;

        if (ret) {
                cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
        } else {
                target_complete_cmd(cmd, SAM_STAT_GOOD);
        }

        return 0;
}

static int fd_execute_rw(struct se_cmd *cmd)
{
        struct scatterlist *sgl = cmd->t_data_sg;
        u32 sgl_nents = cmd->t_data_nents;
        enum dma_data_direction data_direction = cmd->data_direction;
        struct se_device *dev = cmd->se_dev;
        int ret = 0;

        /*
         * Call vectorized fileio functions to map struct scatterlist
         * physical memory addresses to struct iovec virtual memory.
         */
        if (data_direction == DMA_FROM_DEVICE) {
                ret = fd_do_readv(cmd, sgl, sgl_nents);
        } else {
                ret = fd_do_writev(cmd, sgl, sgl_nents);
                /*
                 * Perform implict vfs_fsync_range() for fd_do_writev() ops
                 * for SCSI WRITEs with Forced Unit Access (FUA) set.
                 * Allow this to happen independent of WCE=0 setting.
                 */
                if (ret > 0 &&
                    dev->se_sub_dev->se_dev_attrib.emulate_fua_write > 0 &&
                    (cmd->se_cmd_flags & SCF_FUA)) {
                        struct fd_dev *fd_dev = dev->dev_ptr;
                        loff_t start = cmd->t_task_lba *
                                dev->se_sub_dev->se_dev_attrib.block_size;
                        loff_t end = start + cmd->data_length;

                        vfs_fsync_range(fd_dev->fd_file, start, end, 1);
                }
        }

        if (ret < 0) {
                cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                return ret;
        }
        if (ret)
                target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

enum {
        Opt_fd_dev_name, Opt_fd_dev_size, Opt_fd_buffered_io, Opt_err
};

static match_table_t tokens = {
        {Opt_fd_dev_name, "fd_dev_name=%s"},
        {Opt_fd_dev_size, "fd_dev_size=%s"},
        {Opt_fd_buffered_io, "fd_buffered_io=%d"},
        {Opt_err, NULL}
};

static ssize_t fd_set_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        const char *page, ssize_t count)
{
        struct fd_dev *fd_dev = se_dev->se_dev_su_ptr;
        char *orig, *ptr, *arg_p, *opts;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, 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_fd_dev_name:
                        if (match_strlcpy(fd_dev->fd_dev_name, &args[0],
                                FD_MAX_DEV_NAME) == 0) {
                                ret = -EINVAL;
                                break;
                        }
                        pr_debug("FILEIO: Referencing Path: %s\n",
                                        fd_dev->fd_dev_name);
                        fd_dev->fbd_flags |= FBDF_HAS_PATH;
                        break;
                case Opt_fd_dev_size:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = strict_strtoull(arg_p, 0, &fd_dev->fd_dev_size);
                        kfree(arg_p);
                        if (ret < 0) {
                                pr_err("strict_strtoull() failed for"
                                                " fd_dev_size=\n");
                                goto out;
                        }
                        pr_debug("FILEIO: Referencing Size: %llu"
                                        " bytes\n", fd_dev->fd_dev_size);
                        fd_dev->fbd_flags |= FBDF_HAS_SIZE;
                        break;
                case Opt_fd_buffered_io:
                        match_int(args, &arg);
                        if (arg != 1) {
                                pr_err("bogus fd_buffered_io=%d value\n", arg);
                                ret = -EINVAL;
                                goto out;
                        }

                        pr_debug("FILEIO: Using buffered I/O"
                                " operations for struct fd_dev\n");

                        fd_dev->fbd_flags |= FDBD_HAS_BUFFERED_IO_WCE;
                        break;
                default:
                        break;
                }
        }

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

static ssize_t fd_check_configfs_dev_params(struct se_hba *hba, struct se_subsystem_dev *se_dev)
{
        struct fd_dev *fd_dev = se_dev->se_dev_su_ptr;

        if (!(fd_dev->fbd_flags & FBDF_HAS_PATH)) {
                pr_err("Missing fd_dev_name=\n");
                return -EINVAL;
        }

        return 0;
}

static ssize_t fd_show_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        char *b)
{
        struct fd_dev *fd_dev = se_dev->se_dev_su_ptr;
        ssize_t bl = 0;

        bl = sprintf(b + bl, "TCM FILEIO ID: %u", fd_dev->fd_dev_id);
        bl += sprintf(b + bl, "        File: %s  Size: %llu  Mode: %s\n",
                fd_dev->fd_dev_name, fd_dev->fd_dev_size,
                (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) ?
                "Buffered-WCE" : "O_DSYNC");
        return bl;
}

/*      fd_get_device_rev(): (Part of se_subsystem_api_t template)
 *
 *
 */
static u32 fd_get_device_rev(struct se_device *dev)
{
        return SCSI_SPC_2; /* Returns SPC-3 in Initiator Data */
}

/*      fd_get_device_type(): (Part of se_subsystem_api_t template)
 *
 *
 */
static u32 fd_get_device_type(struct se_device *dev)
{
        return TYPE_DISK;
}

static sector_t fd_get_blocks(struct se_device *dev)
{
        struct fd_dev *fd_dev = dev->dev_ptr;
        struct file *f = fd_dev->fd_file;
        struct inode *i = f->f_mapping->host;
        unsigned long long dev_size;
        /*
         * When using a file that references an underlying struct block_device,
         * ensure dev_size is always based on the current inode size in order
         * to handle underlying block_device resize operations.
         */
        if (S_ISBLK(i->i_mode))
                dev_size = (i_size_read(i) - fd_dev->fd_block_size);
        else
                dev_size = fd_dev->fd_dev_size;

        return div_u64(dev_size, dev->se_sub_dev->se_dev_attrib.block_size);
}

static struct spc_ops fd_spc_ops = {
        .execute_rw             = fd_execute_rw,
        .execute_sync_cache     = fd_execute_sync_cache,
};

static int fd_parse_cdb(struct se_cmd *cmd)
{
        return sbc_parse_cdb(cmd, &fd_spc_ops);
}

static struct se_subsystem_api fileio_template = {
        .name                   = "fileio",
        .owner                  = THIS_MODULE,
        .transport_type         = TRANSPORT_PLUGIN_VHBA_PDEV,
        .attach_hba             = fd_attach_hba,
        .detach_hba             = fd_detach_hba,
        .allocate_virtdevice    = fd_allocate_virtdevice,
        .create_virtdevice      = fd_create_virtdevice,
        .free_device            = fd_free_device,
        .parse_cdb              = fd_parse_cdb,
        .check_configfs_dev_params = fd_check_configfs_dev_params,
        .set_configfs_dev_params = fd_set_configfs_dev_params,
        .show_configfs_dev_params = fd_show_configfs_dev_params,
        .get_device_rev         = fd_get_device_rev,
        .get_device_type        = fd_get_device_type,
        .get_blocks             = fd_get_blocks,
};

static int __init fileio_module_init(void)
{
        return transport_subsystem_register(&fileio_template);
}

static void fileio_module_exit(void)
{
        transport_subsystem_release(&fileio_template);
}

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

module_init(fileio_module_init);
module_exit(fileio_module_exit);