/*******************************************************************************
 * Filename:  target_core_file.c
 *
 * This file contains the Storage Engine <-> FILEIO transport specific functions
 *
 * (c) Copyright 2005-2013 Datera, Inc.
 *
 * 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 <linux/vmalloc.h>
#include <linux/falloc.h>
#include <linux/uio.h>
#include <scsi/scsi_proto.h>
#include <asm/unaligned.h>

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

#include "target_core_file.h"

static inline struct fd_dev *FD_DEV(struct se_device *dev)
{
        return container_of(dev, struct fd_dev, dev);
}

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_VERSION);
        pr_debug("CORE_HBA[%d] - Attached FILEIO HBA: %u to Generic\n",
                hba->hba_id, fd_host->fd_host_id);

        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 struct se_device *fd_alloc_device(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->dev;
}

static int fd_configure_device(struct se_device *dev)
{
        struct fd_dev *fd_dev = FD_DEV(dev);
        struct fd_host *fd_host = dev->se_hba->hba_ptr;
        struct file *file;
        struct inode *inode = NULL;
        int flags, ret = -EINVAL;

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

        /*
         * 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 = bdev_get_queue(inode->i_bdev);
                unsigned long long dev_size;

                fd_dev->fd_block_size = bdev_logical_block_size(inode->i_bdev);
                /*
                 * Determine the number of bytes from i_size_read() minus
                 * one (1) logical sector from underlying struct block_device
                 */
                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);

                if (target_configure_unmap_from_queue(&dev->dev_attrib, q))
                        pr_debug("IFILE: BLOCK Discard support available,"
                                 " disabled by default\n");
                /*
                 * Enable write same emulation for IBLOCK and use 0xFFFF as
                 * the smaller WRITE_SAME(10) only has a two-byte block count.
                 */
                dev->dev_attrib.max_write_same_len = 0xFFFF;

                if (blk_queue_nonrot(q))
                        dev->dev_attrib.is_nonrot = 1;
        } 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;
                }

                fd_dev->fd_block_size = FD_BLOCKSIZE;
                /*
                 * Limit UNMAP emulation to 8k Number of LBAs (NoLB)
                 */
                dev->dev_attrib.max_unmap_lba_count = 0x2000;
                /*
                 * Currently hardcoded to 1 in Linux/SCSI code..
                 */
                dev->dev_attrib.max_unmap_block_desc_count = 1;
                dev->dev_attrib.unmap_granularity = 1;
                dev->dev_attrib.unmap_granularity_alignment = 0;

                /*
                 * Limit WRITE_SAME w/ UNMAP=0 emulation to 8k Number of LBAs (NoLB)
                 * based upon struct iovec limit for vfs_writev()
                 */
                dev->dev_attrib.max_write_same_len = 0x1000;
        }

        dev->dev_attrib.hw_block_size = fd_dev->fd_block_size;
        dev->dev_attrib.max_bytes_per_io = FD_MAX_BYTES;
        dev->dev_attrib.hw_max_sectors = FD_MAX_BYTES / fd_dev->fd_block_size;
        dev->dev_attrib.hw_queue_depth = FD_MAX_DEVICE_QUEUE_DEPTH;

        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->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 0;
fail:
        if (fd_dev->fd_file) {
                filp_close(fd_dev->fd_file, NULL);
                fd_dev->fd_file = NULL;
        }
        return ret;
}

static void fd_dev_call_rcu(struct rcu_head *p)
{
        struct se_device *dev = container_of(p, struct se_device, rcu_head);
        struct fd_dev *fd_dev = FD_DEV(dev);

        kfree(fd_dev);
}

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

static void fd_destroy_device(struct se_device *dev)
{
        struct fd_dev *fd_dev = FD_DEV(dev);

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

struct target_core_file_cmd {
        unsigned long   len;
        struct se_cmd   *cmd;
        struct kiocb    iocb;
};

static void cmd_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
{
        struct target_core_file_cmd *cmd;

        cmd = container_of(iocb, struct target_core_file_cmd, iocb);

        if (ret != cmd->len)
                target_complete_cmd(cmd->cmd, SAM_STAT_CHECK_CONDITION);
        else
                target_complete_cmd(cmd->cmd, SAM_STAT_GOOD);

        kfree(cmd);
}

static sense_reason_t
fd_execute_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
              enum dma_data_direction data_direction)
{
        int is_write = !(data_direction == DMA_FROM_DEVICE);
        struct se_device *dev = cmd->se_dev;
        struct fd_dev *fd_dev = FD_DEV(dev);
        struct file *file = fd_dev->fd_file;
        struct target_core_file_cmd *aio_cmd;
        struct iov_iter iter = {};
        struct scatterlist *sg;
        struct bio_vec *bvec;
        ssize_t len = 0;
        int ret = 0, i;

        aio_cmd = kmalloc(sizeof(struct target_core_file_cmd), GFP_KERNEL);
        if (!aio_cmd)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        bvec = kcalloc(sgl_nents, sizeof(struct bio_vec), GFP_KERNEL);
        if (!bvec) {
                kfree(aio_cmd);
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        for_each_sg(sgl, sg, sgl_nents, i) {
                bvec[i].bv_page = sg_page(sg);
                bvec[i].bv_len = sg->length;
                bvec[i].bv_offset = sg->offset;

                len += sg->length;
        }

        iov_iter_bvec(&iter, is_write, bvec, sgl_nents, len);

        aio_cmd->cmd = cmd;
        aio_cmd->len = len;
        aio_cmd->iocb.ki_pos = cmd->t_task_lba * dev->dev_attrib.block_size;
        aio_cmd->iocb.ki_filp = file;
        aio_cmd->iocb.ki_complete = cmd_rw_aio_complete;
        aio_cmd->iocb.ki_flags = IOCB_DIRECT;

        if (is_write && (cmd->se_cmd_flags & SCF_FUA))
                aio_cmd->iocb.ki_flags |= IOCB_DSYNC;

        if (is_write)
                ret = call_write_iter(file, &aio_cmd->iocb, &iter);
        else
                ret = call_read_iter(file, &aio_cmd->iocb, &iter);

        kfree(bvec);

        if (ret != -EIOCBQUEUED)
                cmd_rw_aio_complete(&aio_cmd->iocb, ret, 0);

        return 0;
}

static int fd_do_rw(struct se_cmd *cmd, struct file *fd,
                    u32 block_size, struct scatterlist *sgl,
                    u32 sgl_nents, u32 data_length, int is_write)
{
        struct scatterlist *sg;
        struct iov_iter iter;
        struct bio_vec *bvec;
        ssize_t len = 0;
        loff_t pos = (cmd->t_task_lba * block_size);
        int ret = 0, i;

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

        for_each_sg(sgl, sg, sgl_nents, i) {
                bvec[i].bv_page = sg_page(sg);
                bvec[i].bv_len = sg->length;
                bvec[i].bv_offset = sg->offset;

                len += sg->length;
        }

        iov_iter_bvec(&iter, READ, bvec, sgl_nents, len);
        if (is_write)
                ret = vfs_iter_write(fd, &iter, &pos, 0);
        else
                ret = vfs_iter_read(fd, &iter, &pos, 0);

        if (is_write) {
                if (ret < 0 || ret != data_length) {
                        pr_err("%s() write returned %d\n", __func__, ret);
                        if (ret >= 0)
                                ret = -EINVAL;
                }
        } else {
                /*
                 * 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(file_inode(fd)->i_mode)) {
                        if (ret < 0 || ret != data_length) {
                                pr_err("%s() returned %d, expecting %u for "
                                                "S_ISBLK\n", __func__, ret,
                                                data_length);
                                if (ret >= 0)
                                        ret = -EINVAL;
                        }
                } else {
                        if (ret < 0) {
                                pr_err("%s() returned %d for non S_ISBLK\n",
                                                __func__, ret);
                        } else if (ret != data_length) {
                                /*
                                 * Short read case:
                                 * Probably some one truncate file under us.
                                 * We must explicitly zero sg-pages to prevent
                                 * expose uninizialized pages to userspace.
                                 */
                                if (ret < data_length)
                                        ret += iov_iter_zero(data_length - ret, &iter);
                                else
                                        ret = -EINVAL;
                        }
                }
        }
        kfree(bvec);
        return ret;
}

static sense_reason_t
fd_execute_sync_cache(struct se_cmd *cmd)
{
        struct se_device *dev = cmd->se_dev;
        struct fd_dev *fd_dev = FD_DEV(dev);
        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->dev_attrib.block_size;
                if (cmd->data_length)
                        end = start + cmd->data_length - 1;
                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)
                target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
        else
                target_complete_cmd(cmd, SAM_STAT_GOOD);

        return 0;
}

static sense_reason_t
fd_execute_write_same(struct se_cmd *cmd)
{
        struct se_device *se_dev = cmd->se_dev;
        struct fd_dev *fd_dev = FD_DEV(se_dev);
        loff_t pos = cmd->t_task_lba * se_dev->dev_attrib.block_size;
        sector_t nolb = sbc_get_write_same_sectors(cmd);
        struct iov_iter iter;
        struct bio_vec *bvec;
        unsigned int len = 0, i;
        ssize_t ret;

        if (!nolb) {
                target_complete_cmd(cmd, SAM_STAT_GOOD);
                return 0;
        }
        if (cmd->prot_op) {
                pr_err("WRITE_SAME: Protection information with FILEIO"
                       " backends not supported\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        if (cmd->t_data_nents > 1 ||
            cmd->t_data_sg[0].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,
                        cmd->t_data_sg[0].length,
                        cmd->se_dev->dev_attrib.block_size);
                return TCM_INVALID_CDB_FIELD;
        }

        bvec = kcalloc(nolb, sizeof(struct bio_vec), GFP_KERNEL);
        if (!bvec)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        for (i = 0; i < nolb; i++) {
                bvec[i].bv_page = sg_page(&cmd->t_data_sg[0]);
                bvec[i].bv_len = cmd->t_data_sg[0].length;
                bvec[i].bv_offset = cmd->t_data_sg[0].offset;

                len += se_dev->dev_attrib.block_size;
        }

        iov_iter_bvec(&iter, READ, bvec, nolb, len);
        ret = vfs_iter_write(fd_dev->fd_file, &iter, &pos, 0);

        kfree(bvec);
        if (ret < 0 || ret != len) {
                pr_err("vfs_iter_write() returned %zd for write same\n", ret);
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

static int
fd_do_prot_fill(struct se_device *se_dev, sector_t lba, sector_t nolb,
                void *buf, size_t bufsize)
{
        struct fd_dev *fd_dev = FD_DEV(se_dev);
        struct file *prot_fd = fd_dev->fd_prot_file;
        sector_t prot_length, prot;
        loff_t pos = lba * se_dev->prot_length;

        if (!prot_fd) {
                pr_err("Unable to locate fd_dev->fd_prot_file\n");
                return -ENODEV;
        }

        prot_length = nolb * se_dev->prot_length;

        for (prot = 0; prot < prot_length;) {
                sector_t len = min_t(sector_t, bufsize, prot_length - prot);
                ssize_t ret = kernel_write(prot_fd, buf, len, &pos);

                if (ret != len) {
                        pr_err("vfs_write to prot file failed: %zd\n", ret);
                        return ret < 0 ? ret : -ENODEV;
                }
                prot += ret;
        }

        return 0;
}

static int
fd_do_prot_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
{
        void *buf;
        int rc;

        buf = (void *)__get_free_page(GFP_KERNEL);
        if (!buf) {
                pr_err("Unable to allocate FILEIO prot buf\n");
                return -ENOMEM;
        }
        memset(buf, 0xff, PAGE_SIZE);

        rc = fd_do_prot_fill(cmd->se_dev, lba, nolb, buf, PAGE_SIZE);

        free_page((unsigned long)buf);

        return rc;
}

static sense_reason_t
fd_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
{
        struct file *file = FD_DEV(cmd->se_dev)->fd_file;
        struct inode *inode = file->f_mapping->host;
        int ret;

        if (!nolb) {
                return 0;
        }

        if (cmd->se_dev->dev_attrib.pi_prot_type) {
                ret = fd_do_prot_unmap(cmd, lba, nolb);
                if (ret)
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        if (S_ISBLK(inode->i_mode)) {
                /* The backend is block device, use discard */
                struct block_device *bdev = inode->i_bdev;
                struct se_device *dev = cmd->se_dev;

                ret = blkdev_issue_discard(bdev,
                                           target_to_linux_sector(dev, lba),
                                           target_to_linux_sector(dev,  nolb),
                                           GFP_KERNEL, 0);
                if (ret < 0) {
                        pr_warn("FILEIO: blkdev_issue_discard() failed: %d\n",
                                ret);
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }
        } else {
                /* The backend is normal file, use fallocate */
                struct se_device *se_dev = cmd->se_dev;
                loff_t pos = lba * se_dev->dev_attrib.block_size;
                unsigned int len = nolb * se_dev->dev_attrib.block_size;
                int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;

                if (!file->f_op->fallocate)
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

                ret = file->f_op->fallocate(file, mode, pos, len);
                if (ret < 0) {
                        pr_warn("FILEIO: fallocate() failed: %d\n", ret);
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }
        }

        return 0;
}

static sense_reason_t
fd_execute_rw_buffered(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
              enum dma_data_direction data_direction)
{
        struct se_device *dev = cmd->se_dev;
        struct fd_dev *fd_dev = FD_DEV(dev);
        struct file *file = fd_dev->fd_file;
        struct file *pfile = fd_dev->fd_prot_file;
        sense_reason_t rc;
        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) {
                if (cmd->prot_type && dev->dev_attrib.pi_prot_type) {
                        ret = fd_do_rw(cmd, pfile, dev->prot_length,
                                       cmd->t_prot_sg, cmd->t_prot_nents,
                                       cmd->prot_length, 0);
                        if (ret < 0)
                                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }

                ret = fd_do_rw(cmd, file, dev->dev_attrib.block_size,
                               sgl, sgl_nents, cmd->data_length, 0);

                if (ret > 0 && cmd->prot_type && dev->dev_attrib.pi_prot_type &&
                    dev->dev_attrib.pi_prot_verify) {
                        u32 sectors = cmd->data_length >>
                                        ilog2(dev->dev_attrib.block_size);

                        rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors,
                                            0, cmd->t_prot_sg, 0);
                        if (rc)
                                return rc;
                }
        } else {
                if (cmd->prot_type && dev->dev_attrib.pi_prot_type &&
                    dev->dev_attrib.pi_prot_verify) {
                        u32 sectors = cmd->data_length >>
                                        ilog2(dev->dev_attrib.block_size);

                        rc = sbc_dif_verify(cmd, cmd->t_task_lba, sectors,
                                            0, cmd->t_prot_sg, 0);
                        if (rc)
                                return rc;
                }

                ret = fd_do_rw(cmd, file, dev->dev_attrib.block_size,
                               sgl, sgl_nents, cmd->data_length, 1);
                /*
                 * Perform implicit 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 && (cmd->se_cmd_flags & SCF_FUA)) {
                        loff_t start = cmd->t_task_lba *
                                dev->dev_attrib.block_size;
                        loff_t end;

                        if (cmd->data_length)
                                end = start + cmd->data_length - 1;
                        else
                                end = LLONG_MAX;

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

                if (ret > 0 && cmd->prot_type && dev->dev_attrib.pi_prot_type) {
                        ret = fd_do_rw(cmd, pfile, dev->prot_length,
                                       cmd->t_prot_sg, cmd->t_prot_nents,
                                       cmd->prot_length, 1);
                        if (ret < 0)
                                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }
        }

        if (ret < 0)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
}

static sense_reason_t
fd_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;
        struct fd_dev *fd_dev = FD_DEV(dev);

        /*
         * We are currently limited by the number of iovecs (2048) per
         * single vfs_[writev,readv] call.
         */
        if (cmd->data_length > FD_MAX_BYTES) {
                pr_err("FILEIO: Not able to process I/O of %u bytes due to"
                       "FD_MAX_BYTES: %u iovec count limitation\n",
                        cmd->data_length, FD_MAX_BYTES);
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }

        if (fd_dev->fbd_flags & FDBD_HAS_ASYNC_IO)
                return fd_execute_rw_aio(cmd, sgl, sgl_nents, data_direction);
        return fd_execute_rw_buffered(cmd, sgl, sgl_nents, data_direction);
}

enum {
        Opt_fd_dev_name, Opt_fd_dev_size, Opt_fd_buffered_io,
        Opt_fd_async_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_fd_async_io, "fd_async_io=%d"},
        {Opt_err, NULL}
};

static ssize_t fd_set_configfs_dev_params(struct se_device *dev,
                const char *page, ssize_t count)
{
        struct fd_dev *fd_dev = FD_DEV(dev);
        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 = kstrtoull(arg_p, 0, &fd_dev->fd_dev_size);
                        kfree(arg_p);
                        if (ret < 0) {
                                pr_err("kstrtoull() 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:
                        ret = match_int(args, &arg);
                        if (ret)
                                goto out;
                        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;
                case Opt_fd_async_io:
                        ret = match_int(args, &arg);
                        if (ret)
                                goto out;
                        if (arg != 1) {
                                pr_err("bogus fd_async_io=%d value\n", arg);
                                ret = -EINVAL;
                                goto out;
                        }

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

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

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

static ssize_t fd_show_configfs_dev_params(struct se_device *dev, char *b)
{
        struct fd_dev *fd_dev = FD_DEV(dev);
        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 Async: %d\n",
                fd_dev->fd_dev_name, fd_dev->fd_dev_size,
                (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) ?
                "Buffered-WCE" : "O_DSYNC",
                !!(fd_dev->fbd_flags & FDBD_HAS_ASYNC_IO));
        return bl;
}

static sector_t fd_get_blocks(struct se_device *dev)
{
        struct fd_dev *fd_dev = FD_DEV(dev);
        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);
        else
                dev_size = fd_dev->fd_dev_size;

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

static int fd_init_prot(struct se_device *dev)
{
        struct fd_dev *fd_dev = FD_DEV(dev);
        struct file *prot_file, *file = fd_dev->fd_file;
        struct inode *inode;
        int ret, flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
        char buf[FD_MAX_DEV_PROT_NAME];

        if (!file) {
                pr_err("Unable to locate fd_dev->fd_file\n");
                return -ENODEV;
        }

        inode = file->f_mapping->host;
        if (S_ISBLK(inode->i_mode)) {
                pr_err("FILEIO Protection emulation only supported on"
                       " !S_ISBLK\n");
                return -ENOSYS;
        }

        if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE)
                flags &= ~O_DSYNC;

        snprintf(buf, FD_MAX_DEV_PROT_NAME, "%s.protection",
                 fd_dev->fd_dev_name);

        prot_file = filp_open(buf, flags, 0600);
        if (IS_ERR(prot_file)) {
                pr_err("filp_open(%s) failed\n", buf);
                ret = PTR_ERR(prot_file);
                return ret;
        }
        fd_dev->fd_prot_file = prot_file;

        return 0;
}

static int fd_format_prot(struct se_device *dev)
{
        unsigned char *buf;
        int unit_size = FDBD_FORMAT_UNIT_SIZE * dev->dev_attrib.block_size;
        int ret;

        if (!dev->dev_attrib.pi_prot_type) {
                pr_err("Unable to format_prot while pi_prot_type == 0\n");
                return -ENODEV;
        }

        buf = vzalloc(unit_size);
        if (!buf) {
                pr_err("Unable to allocate FILEIO prot buf\n");
                return -ENOMEM;
        }

        pr_debug("Using FILEIO prot_length: %llu\n",
                 (unsigned long long)(dev->transport->get_blocks(dev) + 1) *
                                        dev->prot_length);

        memset(buf, 0xff, unit_size);
        ret = fd_do_prot_fill(dev, 0, dev->transport->get_blocks(dev) + 1,
                              buf, unit_size);
        vfree(buf);
        return ret;
}

static void fd_free_prot(struct se_device *dev)
{
        struct fd_dev *fd_dev = FD_DEV(dev);

        if (!fd_dev->fd_prot_file)
                return;

        filp_close(fd_dev->fd_prot_file, NULL);
        fd_dev->fd_prot_file = NULL;
}

static struct sbc_ops fd_sbc_ops = {
        .execute_rw             = fd_execute_rw,
        .execute_sync_cache     = fd_execute_sync_cache,
        .execute_write_same     = fd_execute_write_same,
        .execute_unmap          = fd_execute_unmap,
};

static sense_reason_t
fd_parse_cdb(struct se_cmd *cmd)
{
        return sbc_parse_cdb(cmd, &fd_sbc_ops);
}

static const struct target_backend_ops fileio_ops = {
        .name                   = "fileio",
        .inquiry_prod           = "FILEIO",
        .inquiry_rev            = FD_VERSION,
        .owner                  = THIS_MODULE,
        .attach_hba             = fd_attach_hba,
        .detach_hba             = fd_detach_hba,
        .alloc_device           = fd_alloc_device,
        .configure_device       = fd_configure_device,
        .destroy_device         = fd_destroy_device,
        .free_device            = fd_free_device,
        .parse_cdb              = fd_parse_cdb,
        .set_configfs_dev_params = fd_set_configfs_dev_params,
        .show_configfs_dev_params = fd_show_configfs_dev_params,
        .get_device_type        = sbc_get_device_type,
        .get_blocks             = fd_get_blocks,
        .init_prot              = fd_init_prot,
        .format_prot            = fd_format_prot,
        .free_prot              = fd_free_prot,
        .tb_dev_attrib_attrs    = sbc_attrib_attrs,
};

static int __init fileio_module_init(void)
{
        return transport_backend_register(&fileio_ops);
}

static void __exit fileio_module_exit(void)
{
        target_backend_unregister(&fileio_ops);
}

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);