MOXA linux-2.6.x / linux-2.6.9-uc0 from sdlinux-moxaart.tgz

[linux-2.6.9-moxart.git] / arch / um / drivers / ubd_kern.c

/* 
 * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
 * Licensed under the GPL
 */

/* 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 MAJOR_NR UBD_MAJOR
#define UBD_SHIFT 4

#include "linux/config.h"
#include "linux/module.h"
#include "linux/blkdev.h"
#include "linux/hdreg.h"
#include "linux/init.h"
#include "linux/devfs_fs_kernel.h"
#include "linux/cdrom.h"
#include "linux/proc_fs.h"
#include "linux/ctype.h"
#include "linux/capability.h"
#include "linux/mm.h"
#include "linux/vmalloc.h"
#include "linux/blkpg.h"
#include "linux/genhd.h"
#include "linux/spinlock.h"
#include "asm/segment.h"
#include "asm/uaccess.h"
#include "asm/irq.h"
#include "asm/types.h"
#include "asm/tlbflush.h"
#include "user_util.h"
#include "mem_user.h"
#include "kern_util.h"
#include "kern.h"
#include "mconsole_kern.h"
#include "init.h"
#include "irq_user.h"
#include "irq_kern.h"
#include "ubd_user.h"
#include "2_5compat.h"
#include "os.h"
#include "mem.h"
#include "mem_kern.h"

static spinlock_t ubd_io_lock = SPIN_LOCK_UNLOCKED;
static spinlock_t ubd_lock = SPIN_LOCK_UNLOCKED;

static void (*do_ubd)(void);

static int ubd_open(struct inode * inode, struct file * filp);
static int ubd_release(struct inode * inode, struct file * file);
static int ubd_ioctl(struct inode * inode, struct file * file,
                     unsigned int cmd, unsigned long arg);

#define MAX_DEV (8)

/* Changed in early boot */
static int ubd_do_mmap = 0;
#define UBD_MMAP_BLOCK_SIZE PAGE_SIZE

static struct block_device_operations ubd_blops = {
        .owner          = THIS_MODULE,
        .open           = ubd_open,
        .release        = ubd_release,
        .ioctl          = ubd_ioctl,
};

/* Protected by the queue_lock */
static request_queue_t *ubd_queue;

/* Protected by ubd_lock */
static int fake_major = MAJOR_NR;

static struct gendisk *ubd_gendisk[MAX_DEV];
static struct gendisk *fake_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

/* Not protected - changed only in ubd_setup_common and then only to
 * to enable O_SYNC.
 */
static struct openflags global_openflags = OPEN_FLAGS;

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

struct ubd {
        char *file;
        int count;
        int fd;
        __u64 size;
        struct openflags boot_openflags;
        struct openflags openflags;
        int no_cow;
        struct cow cow;

        int map_writes;
        int map_reads;
        int nomap_writes;
        int nomap_reads;
        int write_maps;
};

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

#define DEFAULT_UBD { \
        .file =                 NULL, \
        .count =                0, \
        .fd =                   -1, \
        .size =                 -1, \
        .boot_openflags =       OPEN_FLAGS, \
        .openflags =            OPEN_FLAGS, \
        .no_cow =               0, \
        .cow =                  DEFAULT_COW, \
        .map_writes             = 0, \
        .map_reads              = 0, \
        .nomap_writes           = 0, \
        .nomap_reads            = 0, \
        .write_maps             = 0, \
}

struct ubd ubd_dev[MAX_DEV] = { [ 0 ... MAX_DEV - 1 ] = DEFAULT_UBD };

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

        if(dev->file == NULL)
                dev->file = "root_fs";
        return(0);
}

__initcall(ubd0_init);

/* Only changed by fake_ide_setup which is a setup */
static int fake_ide = 0;
static struct proc_dir_entry *proc_ide_root = NULL;
static struct proc_dir_entry *proc_ide = NULL;

static void make_proc_ide(void)
{
        proc_ide_root = proc_mkdir("ide", 0);
        proc_ide = proc_mkdir("ide0", proc_ide_root);
}

static int proc_ide_read_media(char *page, char **start, off_t off, int count,
                               int *eof, void *data)
{
        int len;

        strcpy(page, "disk\n");
        len = strlen("disk\n");
        len -= off;
        if (len < count){
                *eof = 1;
                if (len <= 0) return 0;
        }
        else len = count;
        *start = page + off;
        return len;
}

static void make_ide_entries(char *dev_name)
{
        struct proc_dir_entry *dir, *ent;
        char name[64];

        if(proc_ide_root == NULL) make_proc_ide();

        dir = proc_mkdir(dev_name, proc_ide);
        if(!dir) return;

        ent = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
        if(!ent) return;
        ent->nlink = 1;
        ent->data = NULL;
        ent->read_proc = proc_ide_read_media;
        ent->write_proc = NULL;
        sprintf(name,"ide0/%s", dev_name);
        proc_symlink(dev_name, proc_ide_root, name);
}

static int fake_ide_setup(char *str)
{
        fake_ide = 1;
        return(1);
}

__setup("fake_ide", fake_ide_setup);

__uml_help(fake_ide_setup,
"fake_ide\n"
"    Create ide0 entries that map onto ubd devices.\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 <= 'h')) {
                n = *str - 'a';
                str++;
                *ptr = str;
        }
        return(n);
}

static int ubd_setup_common(char *str, int *index_out)
{
        struct ubd *dev;
        struct openflags flags = global_openflags;
        char *backing_file;
        int n, err;

        if(index_out) *index_out = -1;
        n = *str;
        if(n == '='){
                char *end;
                int major;

                str++;
                if(!strcmp(str, "mmap")){
                        CHOOSE_MODE(printk("mmap not supported by the ubd "
                                           "driver in tt mode\n"),
                                    ubd_do_mmap = 1);
                        return(0);
                }

                if(!strcmp(str, "sync")){
                        global_openflags.s = 1;
                        return(0);
                }
                major = simple_strtoul(str, &end, 0);
                if((*end != '\0') || (end == str)){
                        printk(KERN_ERR 
                               "ubd_setup : didn't parse major number\n");
                        return(1);
                }

                err = 1;
                spin_lock(&ubd_lock);
                if(fake_major != MAJOR_NR){
                        printk(KERN_ERR "Can't assign a fake major twice\n");
                        goto out1;
                }
 
                fake_major = major;

                printk(KERN_INFO "Setting extra ubd major number to %d\n",
                       major);
                err = 0;
        out1:
                spin_unlock(&ubd_lock);
                return(err);
        }

        n = parse_unit(&str);
        if(n < 0){
                printk(KERN_ERR "ubd_setup : couldn't parse unit number "
                       "'%s'\n", str);
                return(1);
        }
        if(n >= MAX_DEV){
                printk(KERN_ERR "ubd_setup : index %d out of range "
                       "(%d devices, from 0 to %d)\n", n, MAX_DEV, MAX_DEV - 1);
                return(1);
        }

        err = 1;
        spin_lock(&ubd_lock);

        dev = &ubd_dev[n];
        if(dev->file != NULL){
                printk(KERN_ERR "ubd_setup : device already configured\n");
                goto out2;
        }

        if(index_out) *index_out = n;

        if (*str == 'r'){
                flags.w = 0;
                str++;
        }
        if (*str == 's'){
                flags.s = 1;
                str++;
        }
        if (*str == 'd'){
                dev->no_cow = 1;
                str++;
        }

        if(*str++ != '='){
                printk(KERN_ERR "ubd_setup : Expected '='\n");
                goto out2;
        }

        err = 0;
        backing_file = strchr(str, ',');
        if(backing_file){
                if(dev->no_cow)
                        printk(KERN_ERR "Can't specify both 'd' and a "
                               "cow file\n");
                else {
                        *backing_file = '\0';
                        backing_file++;
                }
        }
        dev->file = str;
        dev->cow.file = backing_file;
        dev->boot_openflags = flags;
 out2:
        spin_unlock(&ubd_lock);
        return(err);
}

static int ubd_setup(char *str)
{
        ubd_setup_common(str, NULL);
        return(1);
}

__setup("ubd", ubd_setup);
__uml_help(ubd_setup,
"ubd<n>=<filename>\n"
"    This is used to associate a device with a file in the underlying\n"
"    filesystem. 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' (has to be _after_ 'r', if there is one) will cause data\n"
"    to be written to disk on the host immediately.\n\n"
);

static int fakehd_set = 0;
static int fakehd(char *str)
{
        printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
        fakehd_set = 1;
        return 1;
}

__setup("fakehd", fakehd);
__uml_help(fakehd,
"fakehd\n"
"    Change the ubd device name to \"hd\".\n\n"
);

static void do_ubd_request(request_queue_t * q);

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

/* Changed by ubd_handler, which is serialized because interrupts only
 * happen on CPU 0.
 */
int intr_count = 0;

/* call ubd_finish if you need to serialize */
static void __ubd_finish(struct request *req, int error)
{
        int nsect;

        if(error){
                end_request(req, 0);
                return;
        }
        nsect = req->current_nr_sectors;
        req->sector += nsect;
        req->buffer += nsect << 9;
        req->errors = 0;
        req->nr_sectors -= nsect;
        req->current_nr_sectors = 0;
        end_request(req, 1);
}

static inline void ubd_finish(struct request *req, int error)
{
        spin_lock(&ubd_io_lock);
        __ubd_finish(req, error);
        spin_unlock(&ubd_io_lock);
}

/* Called without ubd_io_lock held */
static void ubd_handler(void)
{
        struct io_thread_req req;
        struct request *rq = elv_next_request(ubd_queue);
        int n, err;

        do_ubd = NULL;
        intr_count++;
        n = read_ubd_fs(thread_fd, &req, sizeof(req));
        if(n != sizeof(req)){
                printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
                       "err = %d\n", os_getpid(), -n);
                spin_lock(&ubd_io_lock);
                end_request(rq, 0);
                spin_unlock(&ubd_io_lock);
                return;
        }
        
        if((req.op != UBD_MMAP) &&
           ((req.offset != ((__u64) (rq->sector)) << 9) ||
            (req.length != (rq->current_nr_sectors) << 9)))
                panic("I/O op mismatch");
        
        if(req.map_fd != -1){
                err = physmem_subst_mapping(req.buffer, req.map_fd,
                                            req.map_offset, 1);
                if(err)
                        printk("ubd_handler - physmem_subst_mapping failed, "
                               "err = %d\n", -err);
        }

        ubd_finish(rq, req.error);
        reactivate_fd(thread_fd, UBD_IRQ);      
        do_ubd_request(ubd_queue);
}

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

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

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

__uml_exitcall(kill_io_thread);

static int ubd_file_size(struct ubd *dev, __u64 *size_out)
{
        char *file;

        file = dev->cow.file ? dev->cow.file : dev->file;
        return(os_file_size(file, size_out));
}

static void ubd_close(struct ubd *dev)
{
        if(ubd_do_mmap)
                physmem_forget_descriptor(dev->fd);
        os_close_file(dev->fd);
        if(dev->cow.file == NULL)
                return;

        if(ubd_do_mmap)
                physmem_forget_descriptor(dev->cow.fd);
        os_close_file(dev->cow.fd);
        vfree(dev->cow.bitmap);
        dev->cow.bitmap = NULL;
}

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

        dev->openflags = dev->boot_openflags;
        create_cow = 0;
        create_ptr = (dev->cow.file != NULL) ? &create_cow : NULL;
        back_ptr = dev->no_cow ? NULL : &dev->cow.file;
        dev->fd = open_ubd_file(dev->file, &dev->openflags, back_ptr,
                                &dev->cow.bitmap_offset, &dev->cow.bitmap_len, 
                                &dev->cow.data_offset, create_ptr);

        if((dev->fd == -ENOENT) && create_cow){
                dev->fd = create_cow_file(dev->file, dev->cow.file, 
                                          dev->openflags, 1 << 9, PAGE_SIZE,
                                          &dev->cow.bitmap_offset, 
                                          &dev->cow.bitmap_len,
                                          &dev->cow.data_offset);
                if(dev->fd >= 0){
                        printk(KERN_INFO "Creating \"%s\" as COW file for "
                               "\"%s\"\n", dev->file, dev->cow.file);
                }
        }

        if(dev->fd < 0) return(dev->fd);

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

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

                flags = dev->openflags;
                flags.w = 0;
                err = open_ubd_file(dev->cow.file, &flags, NULL, NULL, NULL, 
                                    NULL, NULL);
                if(err < 0) goto error;
                dev->cow.fd = err;
        }
        return(0);
 error:
        os_close_file(dev->fd);
        return(err);
}

static int ubd_new_disk(int major, u64 size, int unit,
                        struct gendisk **disk_out)
                        
{
        struct gendisk *disk;
        char from[sizeof("ubd/nnnnn\0")], to[sizeof("discnnnnn/disc\0")];
        int err;

        disk = alloc_disk(1 << UBD_SHIFT);
        if(disk == NULL)
                return(-ENOMEM);

        disk->major = major;
        disk->first_minor = unit << UBD_SHIFT;
        disk->fops = &ubd_blops;
        set_capacity(disk, size / 512);
        if(major == MAJOR_NR){
                sprintf(disk->disk_name, "ubd%c", 'a' + unit);
                sprintf(disk->devfs_name, "ubd/disc%d", unit);
                sprintf(from, "ubd/%d", unit);
                sprintf(to, "disc%d/disc", unit);
                err = devfs_mk_symlink(from, to);
                if(err)
                        printk("ubd_new_disk failed to make link from %s to "
                               "%s, error = %d\n", from, to, err);
        }
        else {
                sprintf(disk->disk_name, "ubd_fake%d", unit);
                sprintf(disk->devfs_name, "ubd_fake/disc%d", unit);
        }

        disk->private_data = &ubd_dev[unit];
        disk->queue = ubd_queue;
        add_disk(disk);

        *disk_out = disk;
        return 0;
}

static int ubd_add(int n)
{
        struct ubd *dev = &ubd_dev[n];
        int err;

        if(dev->file == NULL)
                return(-ENODEV);

        if (ubd_open_dev(dev))
                return(-ENODEV);

        err = ubd_file_size(dev, &dev->size);
        if(err < 0)
                return(err);

        err = ubd_new_disk(MAJOR_NR, dev->size, n, &ubd_gendisk[n]);
        if(err) 
                return(err);
 
        if(fake_major != MAJOR_NR)
                ubd_new_disk(fake_major, dev->size, n, 
                             &fake_gendisk[n]);

        /* perhaps this should also be under the "if (fake_major)" above */
        /* using the fake_disk->disk_name and also the fakehd_set name */
        if (fake_ide)
                make_ide_entries(ubd_gendisk[n]->disk_name);

        ubd_close(dev);
        return 0;
}

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

        str = uml_strdup(str);
        if(str == NULL){
                printk(KERN_ERR "ubd_config failed to strdup string\n");
                return(1);
        }
        err = ubd_setup_common(str, &n);
        if(err){
                kfree(str);
                return(-1);
        }
        if(n == -1) return(0);

        spin_lock(&ubd_lock);
        err = ubd_add(n);
        if(err)
                ubd_dev[n].file = NULL;
        spin_unlock(&ubd_lock);

        return(err);
}

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

        n = simple_strtoul(name, &end, 0);
        if((*end != '\0') || (end == name)){
                *error_out = "ubd_get_config : didn't parse device number";
                return(-1);
        }

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

        dev = &ubd_dev[n];
        spin_lock(&ubd_lock);

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

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

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

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

static int ubd_remove(char *str)
{
        struct ubd *dev;
        int n, err = -ENODEV;

        n = parse_unit(&str);

        if((n < 0) || (n >= MAX_DEV))
                return(err);

        dev = &ubd_dev[n];
        if(dev->count > 0)
                return(-EBUSY); /* you cannot remove a open disk */

        err = 0;
        spin_lock(&ubd_lock);

        if(ubd_gendisk[n] == NULL)
                goto out;

        del_gendisk(ubd_gendisk[n]);
        put_disk(ubd_gendisk[n]);
        ubd_gendisk[n] = NULL;

        if(fake_gendisk[n] != NULL){
                del_gendisk(fake_gendisk[n]);
                put_disk(fake_gendisk[n]);
                fake_gendisk[n] = NULL;
        }

        *dev = ((struct ubd) DEFAULT_UBD);
        err = 0;
 out:
        spin_unlock(&ubd_lock);
        return(err);
}

static struct mc_device ubd_mc = {
        .name           = "ubd",
        .config         = ubd_config,
        .get_config     = ubd_get_config,
        .remove         = ubd_remove,
};

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

__initcall(ubd_mc_init);

int ubd_init(void)
{
        int i;

        devfs_mk_dir("ubd");
        if (register_blkdev(MAJOR_NR, "ubd"))
                return -1;

        ubd_queue = blk_init_queue(do_ubd_request, &ubd_io_lock);
        if (!ubd_queue) {
                unregister_blkdev(MAJOR_NR, "ubd");
                return -1;
        }
                
        if (fake_major != MAJOR_NR) {
                char name[sizeof("ubd_nnn\0")];

                snprintf(name, sizeof(name), "ubd_%d", fake_major);
                devfs_mk_dir(name);
                if (register_blkdev(fake_major, "ubd"))
                        return -1;
        }
        for (i = 0; i < MAX_DEV; i++) 
                ubd_add(i);
        return 0;
}

late_initcall(ubd_init);

int 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 - sizeof(void *), 
                                 &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, 
                             SA_INTERRUPT, "ubd", ubd_dev);
        if(err != 0)
                printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
        return(err);
}

device_initcall(ubd_driver_init);

static int ubd_open(struct inode *inode, struct file *filp)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ubd *dev = disk->private_data;
        int err = 0;

        if(dev->count == 0){
                err = ubd_open_dev(dev);
                if(err){
                        printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
                               disk->disk_name, dev->file, -err);
                        goto out;
                }
        }
        dev->count++;
        if((filp->f_mode & FMODE_WRITE) && !dev->openflags.w){
                if(--dev->count == 0) ubd_close(dev);
                err = -EROFS;
        }
 out:
        return(err);
}

static int ubd_release(struct inode * inode, struct file * file)
{
        struct gendisk *disk = inode->i_bdev->bd_disk;
        struct ubd *dev = disk->private_data;

        if(--dev->count == 0)
                ubd_close(dev);
        return(0);
}

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 >> 9;
        int i, update_bitmap = 0;

        for(i = 0; i < length >> 9; 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 == ((bitmap_len + sizeof(unsigned long) - 1) /
                           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, unsigned long *bitmap,
                       __u64 bitmap_offset, __u64 bitmap_len)
{
        __u64 sector = req->offset >> 9;
        int i;

        if(req->length > (sizeof(req->sector_mask) * 8) << 9)
                panic("Operation too long");

        if(req->op == UBD_READ) {
                for(i = 0; i < req->length >> 9; i++){
                        if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
                                ubd_set_bit(i, (unsigned char *) 
                                            &req->sector_mask);
                }
        }
        else cowify_bitmap(req->offset, req->length, &req->sector_mask,
                           &req->cow_offset, bitmap, bitmap_offset,
                           req->bitmap_words, bitmap_len);
}

static int mmap_fd(struct request *req, struct ubd *dev, __u64 offset)
{
        __u64 sector;
        unsigned char *bitmap;
        int bit, i;

        /* mmap must have been requested on the command line */
        if(!ubd_do_mmap)
                return(-1);

        /* The buffer must be page aligned */
        if(((unsigned long) req->buffer % UBD_MMAP_BLOCK_SIZE) != 0)
                return(-1);

        /* The request must be a page long */
        if((req->current_nr_sectors << 9) != PAGE_SIZE)
                return(-1);

        if(dev->cow.file == NULL)
                return(dev->fd);

        sector = offset >> 9;
        bitmap = (unsigned char *) dev->cow.bitmap;
        bit = ubd_test_bit(sector, bitmap);

        for(i = 1; i < req->current_nr_sectors; i++){
                if(ubd_test_bit(sector + i, bitmap) != bit)
                        return(-1);
        }

        if(bit || (rq_data_dir(req) == WRITE))
                offset += dev->cow.data_offset;

        /* The data on disk must be page aligned */
        if((offset % UBD_MMAP_BLOCK_SIZE) != 0)
                return(-1);

        return(bit ? dev->fd : dev->cow.fd);
}

static int prepare_mmap_request(struct ubd *dev, int fd, __u64 offset,
                                struct request *req,
                                struct io_thread_req *io_req)
{
        int err;

        if(rq_data_dir(req) == WRITE){
                /* Writes are almost no-ops since the new data is already in the
                 * host page cache
                 */
                dev->map_writes++;
                if(dev->cow.file != NULL)
                        cowify_bitmap(io_req->offset, io_req->length,
                                      &io_req->sector_mask, &io_req->cow_offset,
                                      dev->cow.bitmap, dev->cow.bitmap_offset,
                                      io_req->bitmap_words,
                                      dev->cow.bitmap_len);
        }
        else {
                int w;

                if((dev->cow.file != NULL) && (fd == dev->cow.fd))
                        w = 0;
                else w = dev->openflags.w;

                if((dev->cow.file != NULL) && (fd == dev->fd))
                        offset += dev->cow.data_offset;

                err = physmem_subst_mapping(req->buffer, fd, offset, w);
                if(err){
                        printk("physmem_subst_mapping failed, err = %d\n",
                               -err);
                        return(1);
                }
                dev->map_reads++;
        }
        io_req->op = UBD_MMAP;
        io_req->buffer = req->buffer;
        return(0);
}

/* Called with ubd_io_lock held */
static int prepare_request(struct request *req, struct io_thread_req *io_req)
{
        struct gendisk *disk = req->rq_disk;
        struct ubd *dev = disk->private_data;
        __u64 offset;
        int len, fd;

        if(req->rq_status == RQ_INACTIVE) return(1);

        if((rq_data_dir(req) == WRITE) && !dev->openflags.w){
                printk("Write attempted on readonly ubd device %s\n", 
                       disk->disk_name);
                end_request(req, 0);
                return(1);
        }

        offset = ((__u64) req->sector) << 9;
        len = req->current_nr_sectors << 9;

        io_req->fds[0] = (dev->cow.file != NULL) ? dev->cow.fd : dev->fd;
        io_req->fds[1] = dev->fd;
        io_req->map_fd = -1;
        io_req->cow_offset = -1;
        io_req->offset = offset;
        io_req->length = len;
        io_req->error = 0;
        io_req->sector_mask = 0;

        fd = mmap_fd(req, dev, io_req->offset);
        if(fd > 0){
                /* If mmapping is otherwise OK, but the first access to the
                 * page is a write, then it's not mapped in yet.  So we have
                 * to write the data to disk first, then we can map the disk
                 * page in and continue normally from there.
                 */
                if((rq_data_dir(req) == WRITE) && !is_remapped(req->buffer)){
                        io_req->map_fd = dev->fd;
                        io_req->map_offset = io_req->offset +
                                dev->cow.data_offset;
                        dev->write_maps++;
                }
                else return(prepare_mmap_request(dev, fd, io_req->offset, req,
                                                 io_req));
        }

        if(rq_data_dir(req) == READ)
                dev->nomap_reads++;
        else dev->nomap_writes++;

        io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
        io_req->offsets[0] = 0;
        io_req->offsets[1] = dev->cow.data_offset;
        io_req->buffer = req->buffer;
        io_req->sectorsize = 1 << 9;

        if(dev->cow.file != NULL)
                cowify_req(io_req, dev->cow.bitmap, dev->cow.bitmap_offset,
                           dev->cow.bitmap_len);

        return(0);
}

/* Called with ubd_io_lock held */
static void do_ubd_request(request_queue_t *q)
{
        struct io_thread_req io_req;
        struct request *req;
        int err, n;

        if(thread_fd == -1){
                while((req = elv_next_request(q)) != NULL){
                        err = prepare_request(req, &io_req);
                        if(!err){
                                do_io(&io_req);
                                __ubd_finish(req, io_req.error);
                        }
                }
        }
        else {
                if(do_ubd || (req = elv_next_request(q)) == NULL)
                        return;
                err = prepare_request(req, &io_req);
                if(!err){
                        do_ubd = ubd_handler;
                        n = write_ubd_fs(thread_fd, (char *) &io_req, 
                                         sizeof(io_req));
                        if(n != sizeof(io_req))
                                printk("write to io thread failed, "
                                       "errno = %d\n", -n);
                }
        }
}

static int ubd_ioctl(struct inode * inode, struct file * file,
                     unsigned int cmd, unsigned long arg)
{
        struct hd_geometry *loc = (struct hd_geometry *) arg;
        struct ubd *dev = inode->i_bdev->bd_disk->private_data;
        struct hd_driveid ubd_id = {
                .cyls           = 0,
                .heads          = 128,
                .sectors        = 32,
        };

        switch (cmd) {
                struct hd_geometry g;
                struct cdrom_volctrl volume;
        case HDIO_GETGEO:
                if(!loc) return(-EINVAL);
                g.heads = 128;
                g.sectors = 32;
                g.cylinders = dev->size / (128 * 32 * 512);
                g.start = get_start_sect(inode->i_bdev);
                return(copy_to_user(loc, &g, sizeof(g)) ? -EFAULT : 0);

        case HDIO_GET_IDENTITY:
                ubd_id.cyls = dev->size / (128 * 32 * 512);
                if(copy_to_user((char *) arg, (char *) &ubd_id, 
                                 sizeof(ubd_id)))
                        return(-EFAULT);
                return(0);
                
        case CDROMVOLREAD:
                if(copy_from_user(&volume, (char *) arg, sizeof(volume)))
                        return(-EFAULT);
                volume.channel0 = 255;
                volume.channel1 = 255;
                volume.channel2 = 255;
                volume.channel3 = 255;
                if(copy_to_user((char *) arg, &volume, sizeof(volume)))
                        return(-EFAULT);
                return(0);
        }
        return(-EINVAL);
}

static int ubd_check_remapped(int fd, unsigned long address, int is_write,
                              __u64 offset)
{
        __u64 bitmap_offset;
        unsigned long new_bitmap[2];
        int i, err, n;

        /* If it's not a write access, we can't do anything about it */
        if(!is_write)
                return(0);

        /* We have a write */
        for(i = 0; i < sizeof(ubd_dev) / sizeof(ubd_dev[0]); i++){
                struct ubd *dev = &ubd_dev[i];

                if((dev->fd != fd) && (dev->cow.fd != fd))
                        continue;

                /* It's a write to a ubd device */

                if(!dev->openflags.w){
                        /* It's a write access on a read-only device - probably
                         * shouldn't happen.  If the kernel is trying to change
                         * something with no intention of writing it back out,
                         * then this message will clue us in that this needs
                         * fixing
                         */
                        printk("Write access to mapped page from readonly ubd "
                               "device %d\n", i);
                        return(0);
                }

                /* It's a write to a writeable ubd device - it must be COWed
                 * because, otherwise, the page would have been mapped in
                 * writeable
                 */

                if(!dev->cow.file)
                        panic("Write fault on writeable non-COW ubd device %d",
                              i);

                /* It should also be an access to the backing file since the
                 * COW pages should be mapped in read-write
                 */

                if(fd == dev->fd)
                        panic("Write fault on a backing page of ubd "
                              "device %d\n", i);

                /* So, we do the write, copying the backing data to the COW
                 * file...
                 */

                err = os_seek_file(dev->fd, offset + dev->cow.data_offset);
                if(err < 0)
                        panic("Couldn't seek to %lld in COW file of ubd "
                              "device %d, err = %d",
                              offset + dev->cow.data_offset, i, -err);

                n = os_write_file(dev->fd, (void *) address, PAGE_SIZE);
                if(n != PAGE_SIZE)
                        panic("Couldn't copy data to COW file of ubd "
                              "device %d, err = %d", i, -n);

                /* ... updating the COW bitmap... */

                cowify_bitmap(offset, PAGE_SIZE, NULL, &bitmap_offset,
                              dev->cow.bitmap, dev->cow.bitmap_offset,
                              new_bitmap, dev->cow.bitmap_len);

                err = os_seek_file(dev->fd, bitmap_offset);
                if(err < 0)
                        panic("Couldn't seek to %lld in COW file of ubd "
                              "device %d, err = %d", bitmap_offset, i, -err);

                n = os_write_file(dev->fd, new_bitmap, sizeof(new_bitmap));
                if(n != sizeof(new_bitmap))
                        panic("Couldn't update bitmap  of ubd device %d, "
                              "err = %d", i, -n);

                /* Maybe we can map the COW page in, and maybe we can't.  If
                 * it is a pre-V3 COW file, we can't, since the alignment will
                 * be wrong.  If it is a V3 or later COW file which has been
                 * moved to a system with a larger page size, then maybe we
                 * can't, depending on the exact location of the page.
                 */

                offset += dev->cow.data_offset;

                /* Remove the remapping, putting the original anonymous page
                 * back.  If the COW file can be mapped in, that is done.
                 * Otherwise, the COW page is read in.
                 */

                if(!physmem_remove_mapping((void *) address))
                        panic("Address 0x%lx not remapped by ubd device %d",
                              address, i);
                if((offset % UBD_MMAP_BLOCK_SIZE) == 0)
                        physmem_subst_mapping((void *) address, dev->fd,
                                              offset, 1);
                else {
                        err = os_seek_file(dev->fd, offset);
                        if(err < 0)
                                panic("Couldn't seek to %lld in COW file of "
                                      "ubd device %d, err = %d", offset, i,
                                      -err);

                        n = os_read_file(dev->fd, (void *) address, PAGE_SIZE);
                        if(n != PAGE_SIZE)
                                panic("Failed to read page from offset %llx of "
                                      "COW file of ubd device %d, err = %d",
                                      offset, i, -n);
                }

                return(1);
        }

        /* It's not a write on a ubd device */
        return(0);
}

static struct remapper ubd_remapper = {
        .list   = LIST_HEAD_INIT(ubd_remapper.list),
        .proc   = ubd_check_remapped,
};

static int ubd_remapper_setup(void)
{
        if(ubd_do_mmap)
                register_remapper(&ubd_remapper);

        return(0);
}

__initcall(ubd_remapper_setup);

/*
 * Overrides for Emacs so that we follow Linus's tabbing style.
 * Emacs will notice this stuff at the end of the file and automatically
 * adjust the settings for this buffer only.  This must remain at the end
 * of the file.
 * ---------------------------------------------------------------------------
 * Local variables:
 * c-file-style: "linux"
 * End:
 */