tty: Simplify tty_set_ldisc() exit handling

[linux/fpc-iii.git] / drivers / target / target_core_user.c

/*
 * Copyright (C) 2013 Shaohua Li <shli@kernel.org>
 * Copyright (C) 2014 Red Hat, Inc.
 * Copyright (C) 2015 Arrikto, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/parser.h>
#include <linux/vmalloc.h>
#include <linux/uio_driver.h>
#include <linux/stringify.h>
#include <net/genetlink.h>
#include <scsi/scsi_common.h>
#include <scsi/scsi_proto.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric.h>
#include <target/target_core_backend.h>

#include <linux/target_core_user.h>

/*
 * Define a shared-memory interface for LIO to pass SCSI commands and
 * data to userspace for processing. This is to allow backends that
 * are too complex for in-kernel support to be possible.
 *
 * It uses the UIO framework to do a lot of the device-creation and
 * introspection work for us.
 *
 * See the .h file for how the ring is laid out. Note that while the
 * command ring is defined, the particulars of the data area are
 * not. Offset values in the command entry point to other locations
 * internal to the mmap()ed area. There is separate space outside the
 * command ring for data buffers. This leaves maximum flexibility for
 * moving buffer allocations, or even page flipping or other
 * allocation techniques, without altering the command ring layout.
 *
 * SECURITY:
 * The user process must be assumed to be malicious. There's no way to
 * prevent it breaking the command ring protocol if it wants, but in
 * order to prevent other issues we must only ever read *data* from
 * the shared memory area, not offsets or sizes. This applies to
 * command ring entries as well as the mailbox. Extra code needed for
 * this may have a 'UAM' comment.
 */


#define TCMU_TIME_OUT (30 * MSEC_PER_SEC)

#define CMDR_SIZE (16 * 4096)
#define DATA_SIZE (257 * 4096)

#define TCMU_RING_SIZE (CMDR_SIZE + DATA_SIZE)

static struct device *tcmu_root_device;

struct tcmu_hba {
        u32 host_id;
};

#define TCMU_CONFIG_LEN 256

struct tcmu_dev {
        struct se_device se_dev;

        char *name;
        struct se_hba *hba;

#define TCMU_DEV_BIT_OPEN 0
#define TCMU_DEV_BIT_BROKEN 1
        unsigned long flags;

        struct uio_info uio_info;

        struct tcmu_mailbox *mb_addr;
        size_t dev_size;
        u32 cmdr_size;
        u32 cmdr_last_cleaned;
        /* Offset of data ring from start of mb */
        size_t data_off;
        size_t data_size;
        /* Ring head + tail values. */
        /* Must add data_off and mb_addr to get the address */
        size_t data_head;
        size_t data_tail;

        wait_queue_head_t wait_cmdr;
        /* TODO should this be a mutex? */
        spinlock_t cmdr_lock;

        struct idr commands;
        spinlock_t commands_lock;

        struct timer_list timeout;

        char dev_config[TCMU_CONFIG_LEN];
};

#define TCMU_DEV(_se_dev) container_of(_se_dev, struct tcmu_dev, se_dev)

#define CMDR_OFF sizeof(struct tcmu_mailbox)

struct tcmu_cmd {
        struct se_cmd *se_cmd;
        struct tcmu_dev *tcmu_dev;

        uint16_t cmd_id;

        /* Can't use se_cmd->data_length when cleaning up expired cmds, because if
           cmd has been completed then accessing se_cmd is off limits */
        size_t data_length;

        unsigned long deadline;

#define TCMU_CMD_BIT_EXPIRED 0
        unsigned long flags;
};

static struct kmem_cache *tcmu_cmd_cache;

/* multicast group */
enum tcmu_multicast_groups {
        TCMU_MCGRP_CONFIG,
};

static const struct genl_multicast_group tcmu_mcgrps[] = {
        [TCMU_MCGRP_CONFIG] = { .name = "config", },
};

/* Our generic netlink family */
static struct genl_family tcmu_genl_family = {
        .id = GENL_ID_GENERATE,
        .hdrsize = 0,
        .name = "TCM-USER",
        .version = 1,
        .maxattr = TCMU_ATTR_MAX,
        .mcgrps = tcmu_mcgrps,
        .n_mcgrps = ARRAY_SIZE(tcmu_mcgrps),
};

static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
{
        struct se_device *se_dev = se_cmd->se_dev;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        struct tcmu_cmd *tcmu_cmd;
        int cmd_id;

        tcmu_cmd = kmem_cache_zalloc(tcmu_cmd_cache, GFP_KERNEL);
        if (!tcmu_cmd)
                return NULL;

        tcmu_cmd->se_cmd = se_cmd;
        tcmu_cmd->tcmu_dev = udev;
        tcmu_cmd->data_length = se_cmd->data_length;

        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
                tcmu_cmd->data_length += se_cmd->t_bidi_data_sg->length;
        }

        tcmu_cmd->deadline = jiffies + msecs_to_jiffies(TCMU_TIME_OUT);

        idr_preload(GFP_KERNEL);
        spin_lock_irq(&udev->commands_lock);
        cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 0,
                USHRT_MAX, GFP_NOWAIT);
        spin_unlock_irq(&udev->commands_lock);
        idr_preload_end();

        if (cmd_id < 0) {
                kmem_cache_free(tcmu_cmd_cache, tcmu_cmd);
                return NULL;
        }
        tcmu_cmd->cmd_id = cmd_id;

        return tcmu_cmd;
}

static inline void tcmu_flush_dcache_range(void *vaddr, size_t size)
{
        unsigned long offset = (unsigned long) vaddr & ~PAGE_MASK;

        size = round_up(size+offset, PAGE_SIZE);
        vaddr -= offset;

        while (size) {
                flush_dcache_page(virt_to_page(vaddr));
                size -= PAGE_SIZE;
        }
}

/*
 * Some ring helper functions. We don't assume size is a power of 2 so
 * we can't use circ_buf.h.
 */
static inline size_t spc_used(size_t head, size_t tail, size_t size)
{
        int diff = head - tail;

        if (diff >= 0)
                return diff;
        else
                return size + diff;
}

static inline size_t spc_free(size_t head, size_t tail, size_t size)
{
        /* Keep 1 byte unused or we can't tell full from empty */
        return (size - spc_used(head, tail, size) - 1);
}

static inline size_t head_to_end(size_t head, size_t size)
{
        return size - head;
}

#define UPDATE_HEAD(head, used, size) smp_store_release(&head, ((head % size) + used) % size)

static void alloc_and_scatter_data_area(struct tcmu_dev *udev,
        struct scatterlist *data_sg, unsigned int data_nents,
        struct iovec **iov, int *iov_cnt, bool copy_data)
{
        int i;
        void *from, *to;
        size_t copy_bytes;
        struct scatterlist *sg;

        for_each_sg(data_sg, sg, data_nents, i) {
                copy_bytes = min_t(size_t, sg->length,
                                 head_to_end(udev->data_head, udev->data_size));
                from = kmap_atomic(sg_page(sg)) + sg->offset;
                to = (void *) udev->mb_addr + udev->data_off + udev->data_head;

                if (copy_data) {
                        memcpy(to, from, copy_bytes);
                        tcmu_flush_dcache_range(to, copy_bytes);
                }

                /* Even iov_base is relative to mb_addr */
                (*iov)->iov_len = copy_bytes;
                (*iov)->iov_base = (void __user *) udev->data_off +
                                                udev->data_head;
                (*iov_cnt)++;
                (*iov)++;

                UPDATE_HEAD(udev->data_head, copy_bytes, udev->data_size);

                /* Uh oh, we wrapped the buffer. Must split sg across 2 iovs. */
                if (sg->length != copy_bytes) {
                        void *from_skip = from + copy_bytes;

                        copy_bytes = sg->length - copy_bytes;

                        (*iov)->iov_len = copy_bytes;
                        (*iov)->iov_base = (void __user *) udev->data_off +
                                                        udev->data_head;

                        if (copy_data) {
                                to = (void *) udev->mb_addr +
                                        udev->data_off + udev->data_head;
                                memcpy(to, from_skip, copy_bytes);
                                tcmu_flush_dcache_range(to, copy_bytes);
                        }

                        (*iov_cnt)++;
                        (*iov)++;

                        UPDATE_HEAD(udev->data_head,
                                copy_bytes, udev->data_size);
                }

                kunmap_atomic(from - sg->offset);
        }
}

static void gather_and_free_data_area(struct tcmu_dev *udev,
        struct scatterlist *data_sg, unsigned int data_nents)
{
        int i;
        void *from, *to;
        size_t copy_bytes;
        struct scatterlist *sg;

        /* It'd be easier to look at entry's iovec again, but UAM */
        for_each_sg(data_sg, sg, data_nents, i) {
                copy_bytes = min_t(size_t, sg->length,
                                 head_to_end(udev->data_tail, udev->data_size));

                to = kmap_atomic(sg_page(sg)) + sg->offset;
                WARN_ON(sg->length + sg->offset > PAGE_SIZE);
                from = (void *) udev->mb_addr +
                        udev->data_off + udev->data_tail;
                tcmu_flush_dcache_range(from, copy_bytes);
                memcpy(to, from, copy_bytes);

                UPDATE_HEAD(udev->data_tail, copy_bytes, udev->data_size);

                /* Uh oh, wrapped the data buffer for this sg's data */
                if (sg->length != copy_bytes) {
                        void *to_skip = to + copy_bytes;

                        from = (void *) udev->mb_addr +
                                udev->data_off + udev->data_tail;
                        WARN_ON(udev->data_tail);
                        copy_bytes = sg->length - copy_bytes;
                        tcmu_flush_dcache_range(from, copy_bytes);
                        memcpy(to_skip, from, copy_bytes);

                        UPDATE_HEAD(udev->data_tail,
                                copy_bytes, udev->data_size);
                }
                kunmap_atomic(to - sg->offset);
        }
}

/*
 * We can't queue a command until we have space available on the cmd ring *and*
 * space available on the data ring.
 *
 * Called with ring lock held.
 */
static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t data_needed)
{
        struct tcmu_mailbox *mb = udev->mb_addr;
        size_t space;
        u32 cmd_head;
        size_t cmd_needed;

        tcmu_flush_dcache_range(mb, sizeof(*mb));

        cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */

        /*
         * If cmd end-of-ring space is too small then we need space for a NOP plus
         * original cmd - cmds are internally contiguous.
         */
        if (head_to_end(cmd_head, udev->cmdr_size) >= cmd_size)
                cmd_needed = cmd_size;
        else
                cmd_needed = cmd_size + head_to_end(cmd_head, udev->cmdr_size);

        space = spc_free(cmd_head, udev->cmdr_last_cleaned, udev->cmdr_size);
        if (space < cmd_needed) {
                pr_debug("no cmd space: %u %u %u\n", cmd_head,
                       udev->cmdr_last_cleaned, udev->cmdr_size);
                return false;
        }

        space = spc_free(udev->data_head, udev->data_tail, udev->data_size);
        if (space < data_needed) {
                pr_debug("no data space: %zu %zu %zu\n", udev->data_head,
                       udev->data_tail, udev->data_size);
                return false;
        }

        return true;
}

static int tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
{
        struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
        size_t base_command_size, command_size;
        struct tcmu_mailbox *mb;
        struct tcmu_cmd_entry *entry;
        struct iovec *iov;
        int iov_cnt;
        uint32_t cmd_head;
        uint64_t cdb_off;
        bool copy_to_data_area;

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags))
                return -EINVAL;

        /*
         * Must be a certain minimum size for response sense info, but
         * also may be larger if the iov array is large.
         *
         * iovs = sgl_nents+1, for end-of-ring case, plus another 1
         * b/c size == offsetof one-past-element.
        */
        base_command_size = max(offsetof(struct tcmu_cmd_entry,
                                         req.iov[se_cmd->t_bidi_data_nents +
                                                 se_cmd->t_data_nents + 2]),
                                sizeof(struct tcmu_cmd_entry));
        command_size = base_command_size
                + round_up(scsi_command_size(se_cmd->t_task_cdb), TCMU_OP_ALIGN_SIZE);

        WARN_ON(command_size & (TCMU_OP_ALIGN_SIZE-1));

        spin_lock_irq(&udev->cmdr_lock);

        mb = udev->mb_addr;
        cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
        if ((command_size > (udev->cmdr_size / 2))
            || tcmu_cmd->data_length > (udev->data_size - 1))
                pr_warn("TCMU: Request of size %zu/%zu may be too big for %u/%zu "
                        "cmd/data ring buffers\n", command_size, tcmu_cmd->data_length,
                        udev->cmdr_size, udev->data_size);

        while (!is_ring_space_avail(udev, command_size, tcmu_cmd->data_length)) {
                int ret;
                DEFINE_WAIT(__wait);

                prepare_to_wait(&udev->wait_cmdr, &__wait, TASK_INTERRUPTIBLE);

                pr_debug("sleeping for ring space\n");
                spin_unlock_irq(&udev->cmdr_lock);
                ret = schedule_timeout(msecs_to_jiffies(TCMU_TIME_OUT));
                finish_wait(&udev->wait_cmdr, &__wait);
                if (!ret) {
                        pr_warn("tcmu: command timed out\n");
                        return -ETIMEDOUT;
                }

                spin_lock_irq(&udev->cmdr_lock);

                /* We dropped cmdr_lock, cmd_head is stale */
                cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
        }

        /* Insert a PAD if end-of-ring space is too small */
        if (head_to_end(cmd_head, udev->cmdr_size) < command_size) {
                size_t pad_size = head_to_end(cmd_head, udev->cmdr_size);

                entry = (void *) mb + CMDR_OFF + cmd_head;
                tcmu_flush_dcache_range(entry, sizeof(*entry));
                tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_PAD);
                tcmu_hdr_set_len(&entry->hdr.len_op, pad_size);
                entry->hdr.cmd_id = 0; /* not used for PAD */
                entry->hdr.kflags = 0;
                entry->hdr.uflags = 0;

                UPDATE_HEAD(mb->cmd_head, pad_size, udev->cmdr_size);

                cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
                WARN_ON(cmd_head != 0);
        }

        entry = (void *) mb + CMDR_OFF + cmd_head;
        tcmu_flush_dcache_range(entry, sizeof(*entry));
        tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_CMD);
        tcmu_hdr_set_len(&entry->hdr.len_op, command_size);
        entry->hdr.cmd_id = tcmu_cmd->cmd_id;
        entry->hdr.kflags = 0;
        entry->hdr.uflags = 0;

        /*
         * Fix up iovecs, and handle if allocation in data ring wrapped.
         */
        iov = &entry->req.iov[0];
        iov_cnt = 0;
        copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE
                || se_cmd->se_cmd_flags & SCF_BIDI);
        alloc_and_scatter_data_area(udev, se_cmd->t_data_sg,
                se_cmd->t_data_nents, &iov, &iov_cnt, copy_to_data_area);
        entry->req.iov_cnt = iov_cnt;
        entry->req.iov_dif_cnt = 0;

        /* Handle BIDI commands */
        iov_cnt = 0;
        alloc_and_scatter_data_area(udev, se_cmd->t_bidi_data_sg,
                se_cmd->t_bidi_data_nents, &iov, &iov_cnt, false);
        entry->req.iov_bidi_cnt = iov_cnt;

        /* All offsets relative to mb_addr, not start of entry! */
        cdb_off = CMDR_OFF + cmd_head + base_command_size;
        memcpy((void *) mb + cdb_off, se_cmd->t_task_cdb, scsi_command_size(se_cmd->t_task_cdb));
        entry->req.cdb_off = cdb_off;
        tcmu_flush_dcache_range(entry, sizeof(*entry));

        UPDATE_HEAD(mb->cmd_head, command_size, udev->cmdr_size);
        tcmu_flush_dcache_range(mb, sizeof(*mb));

        spin_unlock_irq(&udev->cmdr_lock);

        /* TODO: only if FLUSH and FUA? */
        uio_event_notify(&udev->uio_info);

        mod_timer(&udev->timeout,
                round_jiffies_up(jiffies + msecs_to_jiffies(TCMU_TIME_OUT)));

        return 0;
}

static int tcmu_queue_cmd(struct se_cmd *se_cmd)
{
        struct se_device *se_dev = se_cmd->se_dev;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        struct tcmu_cmd *tcmu_cmd;
        int ret;

        tcmu_cmd = tcmu_alloc_cmd(se_cmd);
        if (!tcmu_cmd)
                return -ENOMEM;

        ret = tcmu_queue_cmd_ring(tcmu_cmd);
        if (ret < 0) {
                pr_err("TCMU: Could not queue command\n");
                spin_lock_irq(&udev->commands_lock);
                idr_remove(&udev->commands, tcmu_cmd->cmd_id);
                spin_unlock_irq(&udev->commands_lock);

                kmem_cache_free(tcmu_cmd_cache, tcmu_cmd);
        }

        return ret;
}

static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *entry)
{
        struct se_cmd *se_cmd = cmd->se_cmd;
        struct tcmu_dev *udev = cmd->tcmu_dev;

        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
                /* cmd has been completed already from timeout, just reclaim data
                   ring space */
                UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
                return;
        }

        if (entry->hdr.uflags & TCMU_UFLAG_UNKNOWN_OP) {
                UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
                pr_warn("TCMU: Userspace set UNKNOWN_OP flag on se_cmd %p\n",
                        cmd->se_cmd);
                entry->rsp.scsi_status = SAM_STAT_CHECK_CONDITION;
        } else if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) {
                memcpy(se_cmd->sense_buffer, entry->rsp.sense_buffer,
                               se_cmd->scsi_sense_length);

                UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
        } else if (se_cmd->se_cmd_flags & SCF_BIDI) {
                /* Discard data_out buffer */
                UPDATE_HEAD(udev->data_tail,
                        (size_t)se_cmd->t_data_sg->length, udev->data_size);

                /* Get Data-In buffer */
                gather_and_free_data_area(udev,
                        se_cmd->t_bidi_data_sg, se_cmd->t_bidi_data_nents);
        } else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
                gather_and_free_data_area(udev,
                        se_cmd->t_data_sg, se_cmd->t_data_nents);
        } else if (se_cmd->data_direction == DMA_TO_DEVICE) {
                UPDATE_HEAD(udev->data_tail, cmd->data_length, udev->data_size);
        } else if (se_cmd->data_direction != DMA_NONE) {
                pr_warn("TCMU: data direction was %d!\n",
                        se_cmd->data_direction);
        }

        target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status);
        cmd->se_cmd = NULL;

        kmem_cache_free(tcmu_cmd_cache, cmd);
}

static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
{
        struct tcmu_mailbox *mb;
        unsigned long flags;
        int handled = 0;

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
                pr_err("ring broken, not handling completions\n");
                return 0;
        }

        spin_lock_irqsave(&udev->cmdr_lock, flags);

        mb = udev->mb_addr;
        tcmu_flush_dcache_range(mb, sizeof(*mb));

        while (udev->cmdr_last_cleaned != ACCESS_ONCE(mb->cmd_tail)) {

                struct tcmu_cmd_entry *entry = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned;
                struct tcmu_cmd *cmd;

                tcmu_flush_dcache_range(entry, sizeof(*entry));

                if (tcmu_hdr_get_op(entry->hdr.len_op) == TCMU_OP_PAD) {
                        UPDATE_HEAD(udev->cmdr_last_cleaned,
                                    tcmu_hdr_get_len(entry->hdr.len_op),
                                    udev->cmdr_size);
                        continue;
                }
                WARN_ON(tcmu_hdr_get_op(entry->hdr.len_op) != TCMU_OP_CMD);

                spin_lock(&udev->commands_lock);
                cmd = idr_find(&udev->commands, entry->hdr.cmd_id);
                if (cmd)
                        idr_remove(&udev->commands, cmd->cmd_id);
                spin_unlock(&udev->commands_lock);

                if (!cmd) {
                        pr_err("cmd_id not found, ring is broken\n");
                        set_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
                        break;
                }

                tcmu_handle_completion(cmd, entry);

                UPDATE_HEAD(udev->cmdr_last_cleaned,
                            tcmu_hdr_get_len(entry->hdr.len_op),
                            udev->cmdr_size);

                handled++;
        }

        if (mb->cmd_tail == mb->cmd_head)
                del_timer(&udev->timeout); /* no more pending cmds */

        spin_unlock_irqrestore(&udev->cmdr_lock, flags);

        wake_up(&udev->wait_cmdr);

        return handled;
}

static int tcmu_check_expired_cmd(int id, void *p, void *data)
{
        struct tcmu_cmd *cmd = p;

        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
                return 0;

        if (!time_after(jiffies, cmd->deadline))
                return 0;

        set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
        target_complete_cmd(cmd->se_cmd, SAM_STAT_CHECK_CONDITION);
        cmd->se_cmd = NULL;

        kmem_cache_free(tcmu_cmd_cache, cmd);

        return 0;
}

static void tcmu_device_timedout(unsigned long data)
{
        struct tcmu_dev *udev = (struct tcmu_dev *)data;
        unsigned long flags;
        int handled;

        handled = tcmu_handle_completions(udev);

        pr_warn("%d completions handled from timeout\n", handled);

        spin_lock_irqsave(&udev->commands_lock, flags);
        idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
        spin_unlock_irqrestore(&udev->commands_lock, flags);

        /*
         * We don't need to wakeup threads on wait_cmdr since they have their
         * own timeout.
         */
}

static int tcmu_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct tcmu_hba *tcmu_hba;

        tcmu_hba = kzalloc(sizeof(struct tcmu_hba), GFP_KERNEL);
        if (!tcmu_hba)
                return -ENOMEM;

        tcmu_hba->host_id = host_id;
        hba->hba_ptr = tcmu_hba;

        return 0;
}

static void tcmu_detach_hba(struct se_hba *hba)
{
        kfree(hba->hba_ptr);
        hba->hba_ptr = NULL;
}

static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
{
        struct tcmu_dev *udev;

        udev = kzalloc(sizeof(struct tcmu_dev), GFP_KERNEL);
        if (!udev)
                return NULL;

        udev->name = kstrdup(name, GFP_KERNEL);
        if (!udev->name) {
                kfree(udev);
                return NULL;
        }

        udev->hba = hba;

        init_waitqueue_head(&udev->wait_cmdr);
        spin_lock_init(&udev->cmdr_lock);

        idr_init(&udev->commands);
        spin_lock_init(&udev->commands_lock);

        setup_timer(&udev->timeout, tcmu_device_timedout,
                (unsigned long)udev);

        return &udev->se_dev;
}

static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
{
        struct tcmu_dev *tcmu_dev = container_of(info, struct tcmu_dev, uio_info);

        tcmu_handle_completions(tcmu_dev);

        return 0;
}

/*
 * mmap code from uio.c. Copied here because we want to hook mmap()
 * and this stuff must come along.
 */
static int tcmu_find_mem_index(struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = vma->vm_private_data;
        struct uio_info *info = &udev->uio_info;

        if (vma->vm_pgoff < MAX_UIO_MAPS) {
                if (info->mem[vma->vm_pgoff].size == 0)
                        return -1;
                return (int)vma->vm_pgoff;
        }
        return -1;
}

static int tcmu_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct tcmu_dev *udev = vma->vm_private_data;
        struct uio_info *info = &udev->uio_info;
        struct page *page;
        unsigned long offset;
        void *addr;

        int mi = tcmu_find_mem_index(vma);
        if (mi < 0)
                return VM_FAULT_SIGBUS;

        /*
         * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
         * to use mem[N].
         */
        offset = (vmf->pgoff - mi) << PAGE_SHIFT;

        addr = (void *)(unsigned long)info->mem[mi].addr + offset;
        if (info->mem[mi].memtype == UIO_MEM_LOGICAL)
                page = virt_to_page(addr);
        else
                page = vmalloc_to_page(addr);
        get_page(page);
        vmf->page = page;
        return 0;
}

static const struct vm_operations_struct tcmu_vm_ops = {
        .fault = tcmu_vma_fault,
};

static int tcmu_mmap(struct uio_info *info, struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_ops = &tcmu_vm_ops;

        vma->vm_private_data = udev;

        /* Ensure the mmap is exactly the right size */
        if (vma_pages(vma) != (TCMU_RING_SIZE >> PAGE_SHIFT))
                return -EINVAL;

        return 0;
}

static int tcmu_open(struct uio_info *info, struct inode *inode)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        /* O_EXCL not supported for char devs, so fake it? */
        if (test_and_set_bit(TCMU_DEV_BIT_OPEN, &udev->flags))
                return -EBUSY;

        pr_debug("open\n");

        return 0;
}

static int tcmu_release(struct uio_info *info, struct inode *inode)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        clear_bit(TCMU_DEV_BIT_OPEN, &udev->flags);

        pr_debug("close\n");

        return 0;
}

static int tcmu_netlink_event(enum tcmu_genl_cmd cmd, const char *name, int minor)
{
        struct sk_buff *skb;
        void *msg_header;
        int ret = -ENOMEM;

        skb = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!skb)
                return ret;

        msg_header = genlmsg_put(skb, 0, 0, &tcmu_genl_family, 0, cmd);
        if (!msg_header)
                goto free_skb;

        ret = nla_put_string(skb, TCMU_ATTR_DEVICE, name);
        if (ret < 0)
                goto free_skb;

        ret = nla_put_u32(skb, TCMU_ATTR_MINOR, minor);
        if (ret < 0)
                goto free_skb;

        genlmsg_end(skb, msg_header);

        ret = genlmsg_multicast(&tcmu_genl_family, skb, 0,
                                TCMU_MCGRP_CONFIG, GFP_KERNEL);

        /* We don't care if no one is listening */
        if (ret == -ESRCH)
                ret = 0;

        return ret;
free_skb:
        nlmsg_free(skb);
        return ret;
}

static int tcmu_configure_device(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        struct tcmu_hba *hba = udev->hba->hba_ptr;
        struct uio_info *info;
        struct tcmu_mailbox *mb;
        size_t size;
        size_t used;
        int ret = 0;
        char *str;

        info = &udev->uio_info;

        size = snprintf(NULL, 0, "tcm-user/%u/%s/%s", hba->host_id, udev->name,
                        udev->dev_config);
        size += 1; /* for \0 */
        str = kmalloc(size, GFP_KERNEL);
        if (!str)
                return -ENOMEM;

        used = snprintf(str, size, "tcm-user/%u/%s", hba->host_id, udev->name);

        if (udev->dev_config[0])
                snprintf(str + used, size - used, "/%s", udev->dev_config);

        info->name = str;

        udev->mb_addr = vzalloc(TCMU_RING_SIZE);
        if (!udev->mb_addr) {
                ret = -ENOMEM;
                goto err_vzalloc;
        }

        /* mailbox fits in first part of CMDR space */
        udev->cmdr_size = CMDR_SIZE - CMDR_OFF;
        udev->data_off = CMDR_SIZE;
        udev->data_size = TCMU_RING_SIZE - CMDR_SIZE;

        mb = udev->mb_addr;
        mb->version = TCMU_MAILBOX_VERSION;
        mb->cmdr_off = CMDR_OFF;
        mb->cmdr_size = udev->cmdr_size;

        WARN_ON(!PAGE_ALIGNED(udev->data_off));
        WARN_ON(udev->data_size % PAGE_SIZE);

        info->version = __stringify(TCMU_MAILBOX_VERSION);

        info->mem[0].name = "tcm-user command & data buffer";
        info->mem[0].addr = (phys_addr_t) udev->mb_addr;
        info->mem[0].size = TCMU_RING_SIZE;
        info->mem[0].memtype = UIO_MEM_VIRTUAL;

        info->irqcontrol = tcmu_irqcontrol;
        info->irq = UIO_IRQ_CUSTOM;

        info->mmap = tcmu_mmap;
        info->open = tcmu_open;
        info->release = tcmu_release;

        ret = uio_register_device(tcmu_root_device, info);
        if (ret)
                goto err_register;

        /* Other attributes can be configured in userspace */
        dev->dev_attrib.hw_block_size = 512;
        dev->dev_attrib.hw_max_sectors = 128;
        dev->dev_attrib.hw_queue_depth = 128;

        ret = tcmu_netlink_event(TCMU_CMD_ADDED_DEVICE, udev->uio_info.name,
                                 udev->uio_info.uio_dev->minor);
        if (ret)
                goto err_netlink;

        return 0;

err_netlink:
        uio_unregister_device(&udev->uio_info);
err_register:
        vfree(udev->mb_addr);
err_vzalloc:
        kfree(info->name);

        return ret;
}

static int tcmu_check_pending_cmd(int id, void *p, void *data)
{
        struct tcmu_cmd *cmd = p;

        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
                return 0;
        return -EINVAL;
}

static void tcmu_dev_call_rcu(struct rcu_head *p)
{
        struct se_device *dev = container_of(p, struct se_device, rcu_head);
        struct tcmu_dev *udev = TCMU_DEV(dev);

        kfree(udev);
}

static void tcmu_free_device(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        int i;

        del_timer_sync(&udev->timeout);

        vfree(udev->mb_addr);

        /* Upper layer should drain all requests before calling this */
        spin_lock_irq(&udev->commands_lock);
        i = idr_for_each(&udev->commands, tcmu_check_pending_cmd, NULL);
        idr_destroy(&udev->commands);
        spin_unlock_irq(&udev->commands_lock);
        WARN_ON(i);

        /* Device was configured */
        if (udev->uio_info.uio_dev) {
                tcmu_netlink_event(TCMU_CMD_REMOVED_DEVICE, udev->uio_info.name,
                                   udev->uio_info.uio_dev->minor);

                uio_unregister_device(&udev->uio_info);
                kfree(udev->uio_info.name);
                kfree(udev->name);
        }
        call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
}

enum {
        Opt_dev_config, Opt_dev_size, Opt_hw_block_size, Opt_err,
};

static match_table_t tokens = {
        {Opt_dev_config, "dev_config=%s"},
        {Opt_dev_size, "dev_size=%u"},
        {Opt_hw_block_size, "hw_block_size=%u"},
        {Opt_err, NULL}
};

static ssize_t tcmu_set_configfs_dev_params(struct se_device *dev,
                const char *page, ssize_t count)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        char *orig, *ptr, *opts, *arg_p;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, token;
        unsigned long tmp_ul;

        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_dev_config:
                        if (match_strlcpy(udev->dev_config, &args[0],
                                          TCMU_CONFIG_LEN) == 0) {
                                ret = -EINVAL;
                                break;
                        }
                        pr_debug("TCMU: Referencing Path: %s\n", udev->dev_config);
                        break;
                case Opt_dev_size:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = kstrtoul(arg_p, 0, (unsigned long *) &udev->dev_size);
                        kfree(arg_p);
                        if (ret < 0)
                                pr_err("kstrtoul() failed for dev_size=\n");
                        break;
                case Opt_hw_block_size:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = kstrtoul(arg_p, 0, &tmp_ul);
                        kfree(arg_p);
                        if (ret < 0) {
                                pr_err("kstrtoul() failed for hw_block_size=\n");
                                break;
                        }
                        if (!tmp_ul) {
                                pr_err("hw_block_size must be nonzero\n");
                                break;
                        }
                        dev->dev_attrib.hw_block_size = tmp_ul;
                        break;
                default:
                        break;
                }
        }

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

static ssize_t tcmu_show_configfs_dev_params(struct se_device *dev, char *b)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        ssize_t bl = 0;

        bl = sprintf(b + bl, "Config: %s ",
                     udev->dev_config[0] ? udev->dev_config : "NULL");
        bl += sprintf(b + bl, "Size: %zu\n", udev->dev_size);

        return bl;
}

static sector_t tcmu_get_blocks(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);

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

static sense_reason_t
tcmu_pass_op(struct se_cmd *se_cmd)
{
        int ret = tcmu_queue_cmd(se_cmd);

        if (ret != 0)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        else
                return TCM_NO_SENSE;
}

static sense_reason_t
tcmu_parse_cdb(struct se_cmd *cmd)
{
        return passthrough_parse_cdb(cmd, tcmu_pass_op);
}

static const struct target_backend_ops tcmu_ops = {
        .name                   = "user",
        .owner                  = THIS_MODULE,
        .transport_flags        = TRANSPORT_FLAG_PASSTHROUGH,
        .attach_hba             = tcmu_attach_hba,
        .detach_hba             = tcmu_detach_hba,
        .alloc_device           = tcmu_alloc_device,
        .configure_device       = tcmu_configure_device,
        .free_device            = tcmu_free_device,
        .parse_cdb              = tcmu_parse_cdb,
        .set_configfs_dev_params = tcmu_set_configfs_dev_params,
        .show_configfs_dev_params = tcmu_show_configfs_dev_params,
        .get_device_type        = sbc_get_device_type,
        .get_blocks             = tcmu_get_blocks,
        .tb_dev_attrib_attrs    = passthrough_attrib_attrs,
};

static int __init tcmu_module_init(void)
{
        int ret;

        BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0);

        tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache",
                                sizeof(struct tcmu_cmd),
                                __alignof__(struct tcmu_cmd),
                                0, NULL);
        if (!tcmu_cmd_cache)
                return -ENOMEM;

        tcmu_root_device = root_device_register("tcm_user");
        if (IS_ERR(tcmu_root_device)) {
                ret = PTR_ERR(tcmu_root_device);
                goto out_free_cache;
        }

        ret = genl_register_family(&tcmu_genl_family);
        if (ret < 0) {
                goto out_unreg_device;
        }

        ret = transport_backend_register(&tcmu_ops);
        if (ret)
                goto out_unreg_genl;

        return 0;

out_unreg_genl:
        genl_unregister_family(&tcmu_genl_family);
out_unreg_device:
        root_device_unregister(tcmu_root_device);
out_free_cache:
        kmem_cache_destroy(tcmu_cmd_cache);

        return ret;
}

static void __exit tcmu_module_exit(void)
{
        target_backend_unregister(&tcmu_ops);
        genl_unregister_family(&tcmu_genl_family);
        root_device_unregister(tcmu_root_device);
        kmem_cache_destroy(tcmu_cmd_cache);
}

MODULE_DESCRIPTION("TCM USER subsystem plugin");
MODULE_AUTHOR("Shaohua Li <shli@kernel.org>");
MODULE_AUTHOR("Andy Grover <agrover@redhat.com>");
MODULE_LICENSE("GPL");

module_init(tcmu_module_init);
module_exit(tcmu_module_exit);