// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2018 Cambridge Greys Ltd
 * Copyright (C) 2015-2016 Anton Ivanov (aivanov@brocade.com)
 * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
 */

/* 2001-09-28...2002-04-17
 * Partition stuff by James_McMechan@hotmail.com
 * old style ubd by setting UBD_SHIFT to 0
 * 2002-09-27...2002-10-18 massive tinkering for 2.5
 * partitions have changed in 2.5
 * 2003-01-29 more tinkering for 2.5.59-1
 * This should now address the sysfs problems and has
 * the symlink for devfs to allow for booting with
 * the common /dev/ubd/discX/... names rather than
 * only /dev/ubdN/discN this version also has lots of
 * clean ups preparing for ubd-many.
 * James McMechan
 */

#define UBD_SHIFT 4

#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.h>
#include <linux/ata.h>
#include <linux/hdreg.h>
#include <linux/cdrom.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/platform_device.h>
#include <linux/scatterlist.h>
#include <asm/tlbflush.h>
#include <kern_util.h>
#include "mconsole_kern.h"
#include <init.h>
#include <irq_kern.h>
#include "ubd.h"
#include <os.h>
#include "cow.h"

/* Max request size is determined by sector mask - 32K */
#define UBD_MAX_REQUEST (8 * sizeof(long))

struct io_desc {
        char *buffer;
        unsigned long length;
        unsigned long sector_mask;
        unsigned long long cow_offset;
        unsigned long bitmap_words[2];
};

struct io_thread_req {
        struct request *req;
        int fds[2];
        unsigned long offsets[2];
        unsigned long long offset;
        int sectorsize;
        int error;

        int desc_cnt;
        /* io_desc has to be the last element of the struct */
        struct io_desc io_desc[];
};


static struct io_thread_req * (*irq_req_buffer)[];
static struct io_thread_req *irq_remainder;
static int irq_remainder_size;

static struct io_thread_req * (*io_req_buffer)[];
static struct io_thread_req *io_remainder;
static int io_remainder_size;



static inline int ubd_test_bit(__u64 bit, unsigned char *data)
{
        __u64 n;
        int bits, off;

        bits = sizeof(data[0]) * 8;
        n = bit / bits;
        off = bit % bits;
        return (data[n] & (1 << off)) != 0;
}

static inline void ubd_set_bit(__u64 bit, unsigned char *data)
{
        __u64 n;
        int bits, off;

        bits = sizeof(data[0]) * 8;
        n = bit / bits;
        off = bit % bits;
        data[n] |= (1 << off);
}
/*End stuff from ubd_user.h*/

#define DRIVER_NAME "uml-blkdev"

static DEFINE_MUTEX(ubd_lock);
static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */

static int ubd_open(struct block_device *bdev, fmode_t mode);
static void ubd_release(struct gendisk *disk, fmode_t mode);
static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
                     unsigned int cmd, unsigned long arg);
static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);

#define MAX_DEV (16)

static const struct block_device_operations ubd_blops = {
        .owner          = THIS_MODULE,
        .open           = ubd_open,
        .release        = ubd_release,
        .ioctl          = ubd_ioctl,
        .compat_ioctl   = blkdev_compat_ptr_ioctl,
        .getgeo         = ubd_getgeo,
};

/* Protected by ubd_lock */
static struct gendisk *ubd_gendisk[MAX_DEV];

#ifdef CONFIG_BLK_DEV_UBD_SYNC
#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
                                         .cl = 1 })
#else
#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
                                         .cl = 1 })
#endif
static struct openflags global_openflags = OPEN_FLAGS;

struct cow {
        /* backing file name */
        char *file;
        /* backing file fd */
        int fd;
        unsigned long *bitmap;
        unsigned long bitmap_len;
        int bitmap_offset;
        int data_offset;
};

#define MAX_SG 64

struct ubd {
        /* name (and fd, below) of the file opened for writing, either the
         * backing or the cow file. */
        char *file;
        char *serial;
        int count;
        int fd;
        __u64 size;
        struct openflags boot_openflags;
        struct openflags openflags;
        unsigned shared:1;
        unsigned no_cow:1;
        unsigned no_trim:1;
        struct cow cow;
        struct platform_device pdev;
        struct request_queue *queue;
        struct blk_mq_tag_set tag_set;
        spinlock_t lock;
};

#define DEFAULT_COW { \
        .file =                 NULL, \
        .fd =                   -1,     \
        .bitmap =               NULL, \
        .bitmap_offset =        0, \
        .data_offset =          0, \
}

#define DEFAULT_UBD { \
        .file =                 NULL, \
        .serial =               NULL, \
        .count =                0, \
        .fd =                   -1, \
        .size =                 -1, \
        .boot_openflags =       OPEN_FLAGS, \
        .openflags =            OPEN_FLAGS, \
        .no_cow =               0, \
        .no_trim =              0, \
        .shared =               0, \
        .cow =                  DEFAULT_COW, \
        .lock =                 __SPIN_LOCK_UNLOCKED(ubd_devs.lock), \
}

/* Protected by ubd_lock */
static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };

static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
                                 const struct blk_mq_queue_data *bd);

static int fake_ide_setup(char *str)
{
        pr_warn("The fake_ide option has been removed\n");
        return 1;
}
__setup("fake_ide", fake_ide_setup);

__uml_help(fake_ide_setup,
"fake_ide\n"
"    Obsolete stub.\n\n"
);

static int parse_unit(char **ptr)
{
        char *str = *ptr, *end;
        int n = -1;

        if(isdigit(*str)) {
                n = simple_strtoul(str, &end, 0);
                if(end == str)
                        return -1;
                *ptr = end;
        }
        else if (('a' <= *str) && (*str <= 'z')) {
                n = *str - 'a';
                str++;
                *ptr = str;
        }
        return n;
}

/* If *index_out == -1 at exit, the passed option was a general one;
 * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
 * should not be freed on exit.
 */
static int ubd_setup_common(char *str, int *index_out, char **error_out)
{
        struct ubd *ubd_dev;
        struct openflags flags = global_openflags;
        char *file, *backing_file, *serial;
        int n, err = 0, i;

        if(index_out) *index_out = -1;
        n = *str;
        if(n == '='){
                str++;
                if(!strcmp(str, "sync")){
                        global_openflags = of_sync(global_openflags);
                        return err;
                }

                pr_warn("fake major not supported any more\n");
                return 0;
        }

        n = parse_unit(&str);
        if(n < 0){
                *error_out = "Couldn't parse device number";
                return -EINVAL;
        }
        if(n >= MAX_DEV){
                *error_out = "Device number out of range";
                return 1;
        }

        err = -EBUSY;
        mutex_lock(&ubd_lock);

        ubd_dev = &ubd_devs[n];
        if(ubd_dev->file != NULL){
                *error_out = "Device is already configured";
                goto out;
        }

        if (index_out)
                *index_out = n;

        err = -EINVAL;
        for (i = 0; i < sizeof("rscdt="); i++) {
                switch (*str) {
                case 'r':
                        flags.w = 0;
                        break;
                case 's':
                        flags.s = 1;
                        break;
                case 'd':
                        ubd_dev->no_cow = 1;
                        break;
                case 'c':
                        ubd_dev->shared = 1;
                        break;
                case 't':
                        ubd_dev->no_trim = 1;
                        break;
                case '=':
                        str++;
                        goto break_loop;
                default:
                        *error_out = "Expected '=' or flag letter "
                                "(r, s, c, t or d)";
                        goto out;
                }
                str++;
        }

        if (*str == '=')
                *error_out = "Too many flags specified";
        else
                *error_out = "Missing '='";
        goto out;

break_loop:
        file = strsep(&str, ",:");
        if (*file == '\0')
                file = NULL;

        backing_file = strsep(&str, ",:");
        if (backing_file && *backing_file == '\0')
                backing_file = NULL;

        serial = strsep(&str, ",:");
        if (serial && *serial == '\0')
                serial = NULL;

        if (backing_file && ubd_dev->no_cow) {
                *error_out = "Can't specify both 'd' and a cow file";
                goto out;
        }

        err = 0;
        ubd_dev->file = file;
        ubd_dev->cow.file = backing_file;
        ubd_dev->serial = serial;
        ubd_dev->boot_openflags = flags;
out:
        mutex_unlock(&ubd_lock);
        return err;
}

static int ubd_setup(char *str)
{
        char *error;
        int err;

        err = ubd_setup_common(str, NULL, &error);
        if(err)
                printk(KERN_ERR "Failed to initialize device with \"%s\" : "
                       "%s\n", str, error);
        return 1;
}

__setup("ubd", ubd_setup);
__uml_help(ubd_setup,
"ubd<n><flags>=<filename>[(:|,)<filename2>][(:|,)<serial>]\n"
"    This is used to associate a device with a file in the underlying\n"
"    filesystem. When specifying two filenames, the first one is the\n"
"    COW name and the second is the backing file name. As separator you can\n"
"    use either a ':' or a ',': the first one allows writing things like;\n"
"       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
"    while with a ',' the shell would not expand the 2nd '~'.\n"
"    When using only one filename, UML will detect whether to treat it like\n"
"    a COW file or a backing file. To override this detection, add the 'd'\n"
"    flag:\n"
"       ubd0d=BackingFile\n"
"    Usually, there is a filesystem in the file, but \n"
"    that's not required. Swap devices containing swap files can be\n"
"    specified like this. Also, a file which doesn't contain a\n"
"    filesystem can have its contents read in the virtual \n"
"    machine by running 'dd' on the device. <n> must be in the range\n"
"    0 to 7. Appending an 'r' to the number will cause that device\n"
"    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
"    an 's' will cause data to be written to disk on the host immediately.\n"
"    'c' will cause the device to be treated as being shared between multiple\n"
"    UMLs and file locking will be turned off - this is appropriate for a\n"
"    cluster filesystem and inappropriate at almost all other times.\n\n"
"    't' will disable trim/discard support on the device (enabled by default).\n\n"
"    An optional device serial number can be exposed using the serial parameter\n"
"    on the cmdline which is exposed as a sysfs entry. This is particularly\n"
"    useful when a unique number should be given to the device. Note when\n"
"    specifying a label, the filename2 must be also presented. It can be\n"
"    an empty string, in which case the backing file is not used:\n"
"       ubd0=File,,Serial\n"
);

static int udb_setup(char *str)
{
        printk("udb%s specified on command line is almost certainly a ubd -> "
               "udb TYPO\n", str);
        return 1;
}

__setup("udb", udb_setup);
__uml_help(udb_setup,
"udb\n"
"    This option is here solely to catch ubd -> udb typos, which can be\n"
"    to impossible to catch visually unless you specifically look for\n"
"    them.  The only result of any option starting with 'udb' is an error\n"
"    in the boot output.\n\n"
);

/* Only changed by ubd_init, which is an initcall. */
static int thread_fd = -1;

/* Function to read several request pointers at a time
* handling fractional reads if (and as) needed
*/

static int bulk_req_safe_read(
        int fd,
        struct io_thread_req * (*request_buffer)[],
        struct io_thread_req **remainder,
        int *remainder_size,
        int max_recs
        )
{
        int n = 0;
        int res = 0;

        if (*remainder_size > 0) {
                memmove(
                        (char *) request_buffer,
                        (char *) remainder, *remainder_size
                );
                n = *remainder_size;
        }

        res = os_read_file(
                        fd,
                        ((char *) request_buffer) + *remainder_size,
                        sizeof(struct io_thread_req *)*max_recs
                                - *remainder_size
                );
        if (res > 0) {
                n += res;
                if ((n % sizeof(struct io_thread_req *)) > 0) {
                        /*
                        * Read somehow returned not a multiple of dword
                        * theoretically possible, but never observed in the
                        * wild, so read routine must be able to handle it
                        */
                        *remainder_size = n % sizeof(struct io_thread_req *);
                        WARN(*remainder_size > 0, "UBD IPC read returned a partial result");
                        memmove(
                                remainder,
                                ((char *) request_buffer) +
                                        (n/sizeof(struct io_thread_req *))*sizeof(struct io_thread_req *),
                                *remainder_size
                        );
                        n = n - *remainder_size;
                }
        } else {
                n = res;
        }
        return n;
}

/* Called without dev->lock held, and only in interrupt context. */
static void ubd_handler(void)
{
        int n;
        int count;

        while(1){
                n = bulk_req_safe_read(
                        thread_fd,
                        irq_req_buffer,
                        &irq_remainder,
                        &irq_remainder_size,
                        UBD_REQ_BUFFER_SIZE
                );
                if (n < 0) {
                        if(n == -EAGAIN)
                                break;
                        printk(KERN_ERR "spurious interrupt in ubd_handler, "
                               "err = %d\n", -n);
                        return;
                }
                for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
                        struct io_thread_req *io_req = (*irq_req_buffer)[count];

                        if ((io_req->error == BLK_STS_NOTSUPP) && (req_op(io_req->req) == REQ_OP_DISCARD)) {
                                blk_queue_max_discard_sectors(io_req->req->q, 0);
                                blk_queue_max_write_zeroes_sectors(io_req->req->q, 0);
                                blk_queue_flag_clear(QUEUE_FLAG_DISCARD, io_req->req->q);
                        }
                        blk_mq_end_request(io_req->req, io_req->error);
                        kfree(io_req);
                }
        }
}

static irqreturn_t ubd_intr(int irq, void *dev)
{
        ubd_handler();
        return IRQ_HANDLED;
}

/* Only changed by ubd_init, which is an initcall. */
static int io_pid = -1;

static void kill_io_thread(void)
{
        if(io_pid != -1)
                os_kill_process(io_pid, 1);
}

__uml_exitcall(kill_io_thread);

static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
{
        char *file;
        int fd;
        int err;

        __u32 version;
        __u32 align;
        char *backing_file;
        time64_t mtime;
        unsigned long long size;
        int sector_size;
        int bitmap_offset;

        if (ubd_dev->file && ubd_dev->cow.file) {
                file = ubd_dev->cow.file;

                goto out;
        }

        fd = os_open_file(ubd_dev->file, of_read(OPENFLAGS()), 0);
        if (fd < 0)
                return fd;

        err = read_cow_header(file_reader, &fd, &version, &backing_file, \
                &mtime, &size, &sector_size, &align, &bitmap_offset);
        os_close_file(fd);

        if(err == -EINVAL)
                file = ubd_dev->file;
        else
                file = backing_file;

out:
        return os_file_size(file, size_out);
}

static int read_cow_bitmap(int fd, void *buf, int offset, int len)
{
        int err;

        err = os_pread_file(fd, buf, len, offset);
        if (err < 0)
                return err;

        return 0;
}

static int backing_file_mismatch(char *file, __u64 size, time64_t mtime)
{
        time64_t modtime;
        unsigned long long actual;
        int err;

        err = os_file_modtime(file, &modtime);
        if (err < 0) {
                printk(KERN_ERR "Failed to get modification time of backing "
                       "file \"%s\", err = %d\n", file, -err);
                return err;
        }

        err = os_file_size(file, &actual);
        if (err < 0) {
                printk(KERN_ERR "Failed to get size of backing file \"%s\", "
                       "err = %d\n", file, -err);
                return err;
        }

        if (actual != size) {
                /*__u64 can be a long on AMD64 and with %lu GCC complains; so
                 * the typecast.*/
                printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
                       "vs backing file\n", (unsigned long long) size, actual);
                return -EINVAL;
        }
        if (modtime != mtime) {
                printk(KERN_ERR "mtime mismatch (%lld vs %lld) of COW header vs "
                       "backing file\n", mtime, modtime);
                return -EINVAL;
        }
        return 0;
}

static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
{
        struct uml_stat buf1, buf2;
        int err;

        if (from_cmdline == NULL)
                return 0;
        if (!strcmp(from_cmdline, from_cow))
                return 0;

        err = os_stat_file(from_cmdline, &buf1);
        if (err < 0) {
                printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
                       -err);
                return 0;
        }
        err = os_stat_file(from_cow, &buf2);
        if (err < 0) {
                printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
                       -err);
                return 1;
        }
        if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
                return 0;

        printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
               "\"%s\" specified in COW header of \"%s\"\n",
               from_cmdline, from_cow, cow);
        return 1;
}

static int open_ubd_file(char *file, struct openflags *openflags, int shared,
                  char **backing_file_out, int *bitmap_offset_out,
                  unsigned long *bitmap_len_out, int *data_offset_out,
                  int *create_cow_out)
{
        time64_t mtime;
        unsigned long long size;
        __u32 version, align;
        char *backing_file;
        int fd, err, sectorsize, asked_switch, mode = 0644;

        fd = os_open_file(file, *openflags, mode);
        if (fd < 0) {
                if ((fd == -ENOENT) && (create_cow_out != NULL))
                        *create_cow_out = 1;
                if (!openflags->w ||
                    ((fd != -EROFS) && (fd != -EACCES)))
                        return fd;
                openflags->w = 0;
                fd = os_open_file(file, *openflags, mode);
                if (fd < 0)
                        return fd;
        }

        if (shared)
                printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
        else {
                err = os_lock_file(fd, openflags->w);
                if (err < 0) {
                        printk(KERN_ERR "Failed to lock '%s', err = %d\n",
                               file, -err);
                        goto out_close;
                }
        }

        /* Successful return case! */
        if (backing_file_out == NULL)
                return fd;

        err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
                              &size, &sectorsize, &align, bitmap_offset_out);
        if (err && (*backing_file_out != NULL)) {
                printk(KERN_ERR "Failed to read COW header from COW file "
                       "\"%s\", errno = %d\n", file, -err);
                goto out_close;
        }
        if (err)
                return fd;

        asked_switch = path_requires_switch(*backing_file_out, backing_file,
                                            file);

        /* Allow switching only if no mismatch. */
        if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
                                                   mtime)) {
                printk(KERN_ERR "Switching backing file to '%s'\n",
                       *backing_file_out);
                err = write_cow_header(file, fd, *backing_file_out,
                                       sectorsize, align, &size);
                if (err) {
                        printk(KERN_ERR "Switch failed, errno = %d\n", -err);
                        goto out_close;
                }
        } else {
                *backing_file_out = backing_file;
                err = backing_file_mismatch(*backing_file_out, size, mtime);
                if (err)
                        goto out_close;
        }

        cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
                  bitmap_len_out, data_offset_out);

        return fd;
 out_close:
        os_close_file(fd);
        return err;
}

static int create_cow_file(char *cow_file, char *backing_file,
                    struct openflags flags,
                    int sectorsize, int alignment, int *bitmap_offset_out,
                    unsigned long *bitmap_len_out, int *data_offset_out)
{
        int err, fd;

        flags.c = 1;
        fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
        if (fd < 0) {
                err = fd;
                printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
                       cow_file, -err);
                goto out;
        }

        err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
                            bitmap_offset_out, bitmap_len_out,
                            data_offset_out);
        if (!err)
                return fd;
        os_close_file(fd);
 out:
        return err;
}

static void ubd_close_dev(struct ubd *ubd_dev)
{
        os_close_file(ubd_dev->fd);
        if(ubd_dev->cow.file == NULL)
                return;

        os_close_file(ubd_dev->cow.fd);
        vfree(ubd_dev->cow.bitmap);
        ubd_dev->cow.bitmap = NULL;
}

static int ubd_open_dev(struct ubd *ubd_dev)
{
        struct openflags flags;
        char **back_ptr;
        int err, create_cow, *create_ptr;
        int fd;

        ubd_dev->openflags = ubd_dev->boot_openflags;
        create_cow = 0;
        create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
        back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;

        fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
                                back_ptr, &ubd_dev->cow.bitmap_offset,
                                &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
                                create_ptr);

        if((fd == -ENOENT) && create_cow){
                fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
                                          ubd_dev->openflags, SECTOR_SIZE, PAGE_SIZE,
                                          &ubd_dev->cow.bitmap_offset,
                                          &ubd_dev->cow.bitmap_len,
                                          &ubd_dev->cow.data_offset);
                if(fd >= 0){
                        printk(KERN_INFO "Creating \"%s\" as COW file for "
                               "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
                }
        }

        if(fd < 0){
                printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
                       -fd);
                return fd;
        }
        ubd_dev->fd = fd;

        if(ubd_dev->cow.file != NULL){
                blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));

                err = -ENOMEM;
                ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
                if(ubd_dev->cow.bitmap == NULL){
                        printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
                        goto error;
                }
                flush_tlb_kernel_vm();

                err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
                                      ubd_dev->cow.bitmap_offset,
                                      ubd_dev->cow.bitmap_len);
                if(err < 0)
                        goto error;

                flags = ubd_dev->openflags;
                flags.w = 0;
                err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
                                    NULL, NULL, NULL, NULL);
                if(err < 0) goto error;
                ubd_dev->cow.fd = err;
        }
        if (ubd_dev->no_trim == 0) {
                ubd_dev->queue->limits.discard_granularity = SECTOR_SIZE;
                ubd_dev->queue->limits.discard_alignment = SECTOR_SIZE;
                blk_queue_max_discard_sectors(ubd_dev->queue, UBD_MAX_REQUEST);
                blk_queue_max_write_zeroes_sectors(ubd_dev->queue, UBD_MAX_REQUEST);
                blk_queue_flag_set(QUEUE_FLAG_DISCARD, ubd_dev->queue);
        }
        blk_queue_flag_set(QUEUE_FLAG_NONROT, ubd_dev->queue);
        return 0;
 error:
        os_close_file(ubd_dev->fd);
        return err;
}

static void ubd_device_release(struct device *dev)
{
        struct ubd *ubd_dev = dev_get_drvdata(dev);

        blk_mq_free_tag_set(&ubd_dev->tag_set);
        *ubd_dev = ((struct ubd) DEFAULT_UBD);
}

static ssize_t serial_show(struct device *dev,
                           struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);
        struct ubd *ubd_dev = disk->private_data;

        if (!ubd_dev)
                return 0;

        return sprintf(buf, "%s", ubd_dev->serial);
}

static DEVICE_ATTR_RO(serial);

static struct attribute *ubd_attrs[] = {
        &dev_attr_serial.attr,
        NULL,
};

static umode_t ubd_attrs_are_visible(struct kobject *kobj,
                                     struct attribute *a, int n)
{
        return a->mode;
}

static const struct attribute_group ubd_attr_group = {
        .attrs = ubd_attrs,
        .is_visible = ubd_attrs_are_visible,
};

static const struct attribute_group *ubd_attr_groups[] = {
        &ubd_attr_group,
        NULL,
};

static void ubd_disk_register(int major, u64 size, int unit,
                              struct gendisk *disk)
{
        disk->major = major;
        disk->first_minor = unit << UBD_SHIFT;
        disk->minors = 1 << UBD_SHIFT;
        disk->fops = &ubd_blops;
        set_capacity(disk, size / 512);
        sprintf(disk->disk_name, "ubd%c", 'a' + unit);

        ubd_devs[unit].pdev.id   = unit;
        ubd_devs[unit].pdev.name = DRIVER_NAME;
        ubd_devs[unit].pdev.dev.release = ubd_device_release;
        dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
        platform_device_register(&ubd_devs[unit].pdev);

        disk->private_data = &ubd_devs[unit];
        disk->queue = ubd_devs[unit].queue;
        device_add_disk(&ubd_devs[unit].pdev.dev, disk, ubd_attr_groups);
}

#define ROUND_BLOCK(n) ((n + (SECTOR_SIZE - 1)) & (-SECTOR_SIZE))

static const struct blk_mq_ops ubd_mq_ops = {
        .queue_rq = ubd_queue_rq,
};

static int ubd_add(int n, char **error_out)
{
        struct ubd *ubd_dev = &ubd_devs[n];
        struct gendisk *disk;
        int err = 0;

        if(ubd_dev->file == NULL)
                goto out;

        err = ubd_file_size(ubd_dev, &ubd_dev->size);
        if(err < 0){
                *error_out = "Couldn't determine size of device's file";
                goto out;
        }

        ubd_dev->size = ROUND_BLOCK(ubd_dev->size);

        ubd_dev->tag_set.ops = &ubd_mq_ops;
        ubd_dev->tag_set.queue_depth = 64;
        ubd_dev->tag_set.numa_node = NUMA_NO_NODE;
        ubd_dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
        ubd_dev->tag_set.driver_data = ubd_dev;
        ubd_dev->tag_set.nr_hw_queues = 1;

        err = blk_mq_alloc_tag_set(&ubd_dev->tag_set);
        if (err)
                goto out;

        disk = blk_mq_alloc_disk(&ubd_dev->tag_set, ubd_dev);
        if (IS_ERR(disk)) {
                err = PTR_ERR(disk);
                goto out_cleanup_tags;
        }
        ubd_dev->queue = disk->queue;

        blk_queue_write_cache(ubd_dev->queue, true, false);
        blk_queue_max_segments(ubd_dev->queue, MAX_SG);
        blk_queue_segment_boundary(ubd_dev->queue, PAGE_SIZE - 1);
        ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, disk);
        ubd_gendisk[n] = disk;
        return 0;

out_cleanup_tags:
        blk_mq_free_tag_set(&ubd_dev->tag_set);
out:
        return err;
}

static int ubd_config(char *str, char **error_out)
{
        int n, ret;

        /* This string is possibly broken up and stored, so it's only
         * freed if ubd_setup_common fails, or if only general options
         * were set.
         */
        str = kstrdup(str, GFP_KERNEL);
        if (str == NULL) {
                *error_out = "Failed to allocate memory";
                return -ENOMEM;
        }

        ret = ubd_setup_common(str, &n, error_out);
        if (ret)
                goto err_free;

        if (n == -1) {
                ret = 0;
                goto err_free;
        }

        mutex_lock(&ubd_lock);
        ret = ubd_add(n, error_out);
        if (ret)
                ubd_devs[n].file = NULL;
        mutex_unlock(&ubd_lock);

out:
        return ret;

err_free:
        kfree(str);
        goto out;
}

static int ubd_get_config(char *name, char *str, int size, char **error_out)
{
        struct ubd *ubd_dev;
        int n, len = 0;

        n = parse_unit(&name);
        if((n >= MAX_DEV) || (n < 0)){
                *error_out = "ubd_get_config : device number out of range";
                return -1;
        }

        ubd_dev = &ubd_devs[n];
        mutex_lock(&ubd_lock);

        if(ubd_dev->file == NULL){
                CONFIG_CHUNK(str, size, len, "", 1);
                goto out;
        }

        CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);

        if(ubd_dev->cow.file != NULL){
                CONFIG_CHUNK(str, size, len, ",", 0);
                CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
        }
        else CONFIG_CHUNK(str, size, len, "", 1);

 out:
        mutex_unlock(&ubd_lock);
        return len;
}

static int ubd_id(char **str, int *start_out, int *end_out)
{
        int n;

        n = parse_unit(str);
        *start_out = 0;
        *end_out = MAX_DEV - 1;
        return n;
}

static int ubd_remove(int n, char **error_out)
{
        struct gendisk *disk = ubd_gendisk[n];
        struct ubd *ubd_dev;
        int err = -ENODEV;

        mutex_lock(&ubd_lock);

        ubd_dev = &ubd_devs[n];

        if(ubd_dev->file == NULL)
                goto out;

        /* you cannot remove a open disk */
        err = -EBUSY;
        if(ubd_dev->count > 0)
                goto out;

        ubd_gendisk[n] = NULL;
        if(disk != NULL){
                del_gendisk(disk);
                blk_cleanup_disk(disk);
        }

        err = 0;
        platform_device_unregister(&ubd_dev->pdev);
out:
        mutex_unlock(&ubd_lock);
        return err;
}

/* All these are called by mconsole in process context and without
 * ubd-specific locks.  The structure itself is const except for .list.
 */
static struct mc_device ubd_mc = {
        .list           = LIST_HEAD_INIT(ubd_mc.list),
        .name           = "ubd",
        .config         = ubd_config,
        .get_config     = ubd_get_config,
        .id             = ubd_id,
        .remove         = ubd_remove,
};

static int __init ubd_mc_init(void)
{
        mconsole_register_dev(&ubd_mc);
        return 0;
}

__initcall(ubd_mc_init);

static int __init ubd0_init(void)
{
        struct ubd *ubd_dev = &ubd_devs[0];

        mutex_lock(&ubd_lock);
        if(ubd_dev->file == NULL)
                ubd_dev->file = "root_fs";
        mutex_unlock(&ubd_lock);

        return 0;
}

__initcall(ubd0_init);

/* Used in ubd_init, which is an initcall */
static struct platform_driver ubd_driver = {
        .driver = {
                .name  = DRIVER_NAME,
        },
};

static int __init ubd_init(void)
{
        char *error;
        int i, err;

        if (register_blkdev(UBD_MAJOR, "ubd"))
                return -1;

        irq_req_buffer = kmalloc_array(UBD_REQ_BUFFER_SIZE,
                                       sizeof(struct io_thread_req *),
                                       GFP_KERNEL
                );
        irq_remainder = 0;

        if (irq_req_buffer == NULL) {
                printk(KERN_ERR "Failed to initialize ubd buffering\n");
                return -1;
        }
        io_req_buffer = kmalloc_array(UBD_REQ_BUFFER_SIZE,
                                      sizeof(struct io_thread_req *),
                                      GFP_KERNEL
                );

        io_remainder = 0;

        if (io_req_buffer == NULL) {
                printk(KERN_ERR "Failed to initialize ubd buffering\n");
                return -1;
        }
        platform_driver_register(&ubd_driver);
        mutex_lock(&ubd_lock);
        for (i = 0; i < MAX_DEV; i++){
                err = ubd_add(i, &error);
                if(err)
                        printk(KERN_ERR "Failed to initialize ubd device %d :"
                               "%s\n", i, error);
        }
        mutex_unlock(&ubd_lock);
        return 0;
}

late_initcall(ubd_init);

static int __init ubd_driver_init(void){
        unsigned long stack;
        int err;

        /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
        if(global_openflags.s){
                printk(KERN_INFO "ubd: Synchronous mode\n");
                /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
                 * enough. So use anyway the io thread. */
        }
        stack = alloc_stack(0, 0);
        io_pid = start_io_thread(stack + PAGE_SIZE, &thread_fd);
        if(io_pid < 0){
                printk(KERN_ERR
                       "ubd : Failed to start I/O thread (errno = %d) - "
                       "falling back to synchronous I/O\n", -io_pid);
                io_pid = -1;
                return 0;
        }
        err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
                             0, "ubd", ubd_devs);
        if(err < 0)
                printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
        return 0;
}

device_initcall(ubd_driver_init);

static int ubd_open(struct block_device *bdev, fmode_t mode)
{
        struct gendisk *disk = bdev->bd_disk;
        struct ubd *ubd_dev = disk->private_data;
        int err = 0;

        mutex_lock(&ubd_mutex);
        if(ubd_dev->count == 0){
                err = ubd_open_dev(ubd_dev);
                if(err){
                        printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
                               disk->disk_name, ubd_dev->file, -err);
                        goto out;
                }
        }
        ubd_dev->count++;
        set_disk_ro(disk, !ubd_dev->openflags.w);

        /* This should no more be needed. And it didn't work anyway to exclude
         * read-write remounting of filesystems.*/
        /*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
                if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
                err = -EROFS;
        }*/
out:
        mutex_unlock(&ubd_mutex);
        return err;
}

static void ubd_release(struct gendisk *disk, fmode_t mode)
{
        struct ubd *ubd_dev = disk->private_data;

        mutex_lock(&ubd_mutex);
        if(--ubd_dev->count == 0)
                ubd_close_dev(ubd_dev);
        mutex_unlock(&ubd_mutex);
}

static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
                          __u64 *cow_offset, unsigned long *bitmap,
                          __u64 bitmap_offset, unsigned long *bitmap_words,
                          __u64 bitmap_len)
{
        __u64 sector = io_offset >> SECTOR_SHIFT;
        int i, update_bitmap = 0;

        for (i = 0; i < length >> SECTOR_SHIFT; i++) {
                if(cow_mask != NULL)
                        ubd_set_bit(i, (unsigned char *) cow_mask);
                if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
                        continue;

                update_bitmap = 1;
                ubd_set_bit(sector + i, (unsigned char *) bitmap);
        }

        if(!update_bitmap)
                return;

        *cow_offset = sector / (sizeof(unsigned long) * 8);

        /* This takes care of the case where we're exactly at the end of the
         * device, and *cow_offset + 1 is off the end.  So, just back it up
         * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
         * for the original diagnosis.
         */
        if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
                                         sizeof(unsigned long)) - 1))
                (*cow_offset)--;

        bitmap_words[0] = bitmap[*cow_offset];
        bitmap_words[1] = bitmap[*cow_offset + 1];

        *cow_offset *= sizeof(unsigned long);
        *cow_offset += bitmap_offset;
}

static void cowify_req(struct io_thread_req *req, struct io_desc *segment,
                       unsigned long offset, unsigned long *bitmap,
                       __u64 bitmap_offset, __u64 bitmap_len)
{
        __u64 sector = offset >> SECTOR_SHIFT;
        int i;

        if (segment->length > (sizeof(segment->sector_mask) * 8) << SECTOR_SHIFT)
                panic("Operation too long");

        if (req_op(req->req) == REQ_OP_READ) {
                for (i = 0; i < segment->length >> SECTOR_SHIFT; i++) {
                        if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
                                ubd_set_bit(i, (unsigned char *)
                                            &segment->sector_mask);
                }
        } else {
                cowify_bitmap(offset, segment->length, &segment->sector_mask,
                              &segment->cow_offset, bitmap, bitmap_offset,
                              segment->bitmap_words, bitmap_len);
        }
}

static void ubd_map_req(struct ubd *dev, struct io_thread_req *io_req,
                        struct request *req)
{
        struct bio_vec bvec;
        struct req_iterator iter;
        int i = 0;
        unsigned long byte_offset = io_req->offset;
        int op = req_op(req);

        if (op == REQ_OP_WRITE_ZEROES || op == REQ_OP_DISCARD) {
                io_req->io_desc[0].buffer = NULL;
                io_req->io_desc[0].length = blk_rq_bytes(req);
        } else {
                rq_for_each_segment(bvec, req, iter) {
                        BUG_ON(i >= io_req->desc_cnt);

                        io_req->io_desc[i].buffer =
                                page_address(bvec.bv_page) + bvec.bv_offset;
                        io_req->io_desc[i].length = bvec.bv_len;
                        i++;
                }
        }

        if (dev->cow.file) {
                for (i = 0; i < io_req->desc_cnt; i++) {
                        cowify_req(io_req, &io_req->io_desc[i], byte_offset,
                                   dev->cow.bitmap, dev->cow.bitmap_offset,
                                   dev->cow.bitmap_len);
                        byte_offset += io_req->io_desc[i].length;
                }

        }
}

static struct io_thread_req *ubd_alloc_req(struct ubd *dev, struct request *req,
                                           int desc_cnt)
{
        struct io_thread_req *io_req;
        int i;

        io_req = kmalloc(sizeof(*io_req) +
                         (desc_cnt * sizeof(struct io_desc)),
                         GFP_ATOMIC);
        if (!io_req)
                return NULL;

        io_req->req = req;
        if (dev->cow.file)
                io_req->fds[0] = dev->cow.fd;
        else
                io_req->fds[0] = dev->fd;
        io_req->error = 0;
        io_req->sectorsize = SECTOR_SIZE;
        io_req->fds[1] = dev->fd;
        io_req->offset = (u64) blk_rq_pos(req) << SECTOR_SHIFT;
        io_req->offsets[0] = 0;
        io_req->offsets[1] = dev->cow.data_offset;

        for (i = 0 ; i < desc_cnt; i++) {
                io_req->io_desc[i].sector_mask = 0;
                io_req->io_desc[i].cow_offset = -1;
        }

        return io_req;
}

static int ubd_submit_request(struct ubd *dev, struct request *req)
{
        int segs = 0;
        struct io_thread_req *io_req;
        int ret;
        int op = req_op(req);

        if (op == REQ_OP_FLUSH)
                segs = 0;
        else if (op == REQ_OP_WRITE_ZEROES || op == REQ_OP_DISCARD)
                segs = 1;
        else
                segs = blk_rq_nr_phys_segments(req);

        io_req = ubd_alloc_req(dev, req, segs);
        if (!io_req)
                return -ENOMEM;

        io_req->desc_cnt = segs;
        if (segs)
                ubd_map_req(dev, io_req, req);

        ret = os_write_file(thread_fd, &io_req, sizeof(io_req));
        if (ret != sizeof(io_req)) {
                if (ret != -EAGAIN)
                        pr_err("write to io thread failed: %d\n", -ret);
                kfree(io_req);
        }
        return ret;
}

static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
                                 const struct blk_mq_queue_data *bd)
{
        struct ubd *ubd_dev = hctx->queue->queuedata;
        struct request *req = bd->rq;
        int ret = 0, res = BLK_STS_OK;

        blk_mq_start_request(req);

        spin_lock_irq(&ubd_dev->lock);

        switch (req_op(req)) {
        case REQ_OP_FLUSH:
        case REQ_OP_READ:
        case REQ_OP_WRITE:
        case REQ_OP_DISCARD:
        case REQ_OP_WRITE_ZEROES:
                ret = ubd_submit_request(ubd_dev, req);
                break;
        default:
                WARN_ON_ONCE(1);
                res = BLK_STS_NOTSUPP;
        }

        spin_unlock_irq(&ubd_dev->lock);

        if (ret < 0) {
                if (ret == -ENOMEM)
                        res = BLK_STS_RESOURCE;
                else
                        res = BLK_STS_DEV_RESOURCE;
        }

        return res;
}

static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
        struct ubd *ubd_dev = bdev->bd_disk->private_data;

        geo->heads = 128;
        geo->sectors = 32;
        geo->cylinders = ubd_dev->size / (128 * 32 * 512);
        return 0;
}

static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
                     unsigned int cmd, unsigned long arg)
{
        struct ubd *ubd_dev = bdev->bd_disk->private_data;
        u16 ubd_id[ATA_ID_WORDS];

        switch (cmd) {
                struct cdrom_volctrl volume;
        case HDIO_GET_IDENTITY:
                memset(&ubd_id, 0, ATA_ID_WORDS * 2);
                ubd_id[ATA_ID_CYLS]     = ubd_dev->size / (128 * 32 * 512);
                ubd_id[ATA_ID_HEADS]    = 128;
                ubd_id[ATA_ID_SECTORS]  = 32;
                if(copy_to_user((char __user *) arg, (char *) &ubd_id,
                                 sizeof(ubd_id)))
                        return -EFAULT;
                return 0;

        case CDROMVOLREAD:
                if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
                        return -EFAULT;
                volume.channel0 = 255;
                volume.channel1 = 255;
                volume.channel2 = 255;
                volume.channel3 = 255;
                if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
                        return -EFAULT;
                return 0;
        }
        return -EINVAL;
}

static int map_error(int error_code)
{
        switch (error_code) {
        case 0:
                return BLK_STS_OK;
        case ENOSYS:
        case EOPNOTSUPP:
                return BLK_STS_NOTSUPP;
        case ENOSPC:
                return BLK_STS_NOSPC;
        }
        return BLK_STS_IOERR;
}

/*
 * Everything from here onwards *IS NOT PART OF THE KERNEL*
 *
 * The following functions are part of UML hypervisor code.
 * All functions from here onwards are executed as a helper
 * thread and are not allowed to execute any kernel functions.
 *
 * Any communication must occur strictly via shared memory and IPC.
 *
 * Do not add printks, locks, kernel memory operations, etc - it
 * will result in unpredictable behaviour and/or crashes.
 */

static int update_bitmap(struct io_thread_req *req, struct io_desc *segment)
{
        int n;

        if (segment->cow_offset == -1)
                return map_error(0);

        n = os_pwrite_file(req->fds[1], &segment->bitmap_words,
                          sizeof(segment->bitmap_words), segment->cow_offset);
        if (n != sizeof(segment->bitmap_words))
                return map_error(-n);

        return map_error(0);
}

static void do_io(struct io_thread_req *req, struct io_desc *desc)
{
        char *buf = NULL;
        unsigned long len;
        int n, nsectors, start, end, bit;
        __u64 off;

        /* FLUSH is really a special case, we cannot "case" it with others */

        if (req_op(req->req) == REQ_OP_FLUSH) {
                /* fds[0] is always either the rw image or our cow file */
                req->error = map_error(-os_sync_file(req->fds[0]));
                return;
        }

        nsectors = desc->length / req->sectorsize;
        start = 0;
        do {
                bit = ubd_test_bit(start, (unsigned char *) &desc->sector_mask);
                end = start;
                while((end < nsectors) &&
                      (ubd_test_bit(end, (unsigned char *) &desc->sector_mask) == bit))
                        end++;

                off = req->offset + req->offsets[bit] +
                        start * req->sectorsize;
                len = (end - start) * req->sectorsize;
                if (desc->buffer != NULL)
                        buf = &desc->buffer[start * req->sectorsize];

                switch (req_op(req->req)) {
                case REQ_OP_READ:
                        n = 0;
                        do {
                                buf = &buf[n];
                                len -= n;
                                n = os_pread_file(req->fds[bit], buf, len, off);
                                if (n < 0) {
                                        req->error = map_error(-n);
                                        return;
                                }
                        } while((n < len) && (n != 0));
                        if (n < len) memset(&buf[n], 0, len - n);
                        break;
                case REQ_OP_WRITE:
                        n = os_pwrite_file(req->fds[bit], buf, len, off);
                        if(n != len){
                                req->error = map_error(-n);
                                return;
                        }
                        break;
                case REQ_OP_DISCARD:
                case REQ_OP_WRITE_ZEROES:
                        n = os_falloc_punch(req->fds[bit], off, len);
                        if (n) {
                                req->error = map_error(-n);
                                return;
                        }
                        break;
                default:
                        WARN_ON_ONCE(1);
                        req->error = BLK_STS_NOTSUPP;
                        return;
                }

                start = end;
        } while(start < nsectors);

        req->offset += len;
        req->error = update_bitmap(req, desc);
}

/* Changed in start_io_thread, which is serialized by being called only
 * from ubd_init, which is an initcall.
 */
int kernel_fd = -1;

/* Only changed by the io thread. XXX: currently unused. */
static int io_count = 0;

int io_thread(void *arg)
{
        int n, count, written, res;

        os_fix_helper_signals();

        while(1){
                n = bulk_req_safe_read(
                        kernel_fd,
                        io_req_buffer,
                        &io_remainder,
                        &io_remainder_size,
                        UBD_REQ_BUFFER_SIZE
                );
                if (n <= 0) {
                        if (n == -EAGAIN)
                                ubd_read_poll(-1);

                        continue;
                }

                for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
                        struct io_thread_req *req = (*io_req_buffer)[count];
                        int i;

                        io_count++;
                        for (i = 0; !req->error && i < req->desc_cnt; i++)
                                do_io(req, &(req->io_desc[i]));

                }

                written = 0;

                do {
                        res = os_write_file(kernel_fd,
                                            ((char *) io_req_buffer) + written,
                                            n - written);
                        if (res >= 0) {
                                written += res;
                        }
                        if (written < n) {
                                ubd_write_poll(-1);
                        }
                } while (written < n);
        }

        return 0;
}