/*
 *  linux/drivers/block/loop.c
 *
 *  Written by Theodore Ts'o, 3/29/93
 * 
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU General Public License.
 *
 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
 *
 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
 *
 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
 *
 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
 *
 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
 *
 * Loadable modules and other fixes by AK, 1998
 *
 * Make real block number available to downstream transfer functions, enables
 * CBC (and relatives) mode encryption requiring unique IVs per data block. 
 * Reed H. Petty, rhp@draper.net
 *
 * Maximum number of loop devices now dynamic via max_loop module parameter.
 * Russell Kroll <rkroll@exploits.org> 19990701
 * 
 * Maximum number of loop devices when compiled-in now selectable by passing
 * max_loop=<1-255> to the kernel on boot.
 * Erik I. Bolsø, <eriki@himolde.no>, Oct 31, 1999
 *
 * Completely rewrite request handling to be make_request_fn style and
 * non blocking, pushing work to a helper thread. Lots of fixes from
 * Al Viro too.
 * Jens Axboe <axboe@suse.de>, Nov 2000
 *
 * Support up to 256 loop devices
 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
 *
 * Still To Fix:
 * - Advisory locking is ignored here. 
 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN 
 *
 * WARNING/FIXME:
 * - The block number as IV passing to low level transfer functions is broken:
 *   it passes the underlying device's block number instead of the
 *   offset. This makes it change for a given block when the file is 
 *   moved/restored/copied and also doesn't work over NFS. 
 * AV, Feb 12, 2000: we pass the logical block number now. It fixes the
 *   problem above. Encryption modules that used to rely on the old scheme
 *   should just call ->i_mapping->bmap() to calculate the physical block
 *   number.
 */ 

#include <linux/config.h>
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/major.h>
#include <linux/wait.h>
#include <linux/blk.h>
#include <linux/blkpg.h>
#include <linux/init.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/smp_lock.h>
#include <linux/swap.h>
#include <linux/slab.h>

#include <asm/uaccess.h>

#include <linux/loop.h>         

#define MAJOR_NR LOOP_MAJOR

static int max_loop = 8;
static struct loop_device *loop_dev;
static int *loop_sizes;
static int *loop_blksizes;
static devfs_handle_t devfs_handle;      /*  For the directory */

/*
 * Transfer functions
 */
static int transfer_none(struct loop_device *lo, int cmd, char *raw_buf,
                         char *loop_buf, int size, int real_block)
{
        if (raw_buf != loop_buf) {
                if (cmd == READ)
                        memcpy(loop_buf, raw_buf, size);
                else
                        memcpy(raw_buf, loop_buf, size);
        }

        return 0;
}

static int transfer_xor(struct loop_device *lo, int cmd, char *raw_buf,
                        char *loop_buf, int size, int real_block)
{
        char    *in, *out, *key;
        int     i, keysize;

        if (cmd == READ) {
                in = raw_buf;
                out = loop_buf;
        } else {
                in = loop_buf;
                out = raw_buf;
        }

        key = lo->lo_encrypt_key;
        keysize = lo->lo_encrypt_key_size;
        for (i = 0; i < size; i++)
                *out++ = *in++ ^ key[(i & 511) % keysize];
        return 0;
}

static int none_status(struct loop_device *lo, struct loop_info *info)
{
        lo->lo_flags |= LO_FLAGS_BH_REMAP;
        return 0;
}

static int xor_status(struct loop_device *lo, struct loop_info *info)
{
        if (info->lo_encrypt_key_size <= 0)
                return -EINVAL;
        return 0;
}

struct loop_func_table none_funcs = { 
        number: LO_CRYPT_NONE,
        transfer: transfer_none,
        init: none_status,
};      

struct loop_func_table xor_funcs = { 
        number: LO_CRYPT_XOR,
        transfer: transfer_xor,
        init: xor_status
};      

/* xfer_funcs[0] is special - its release function is never called */ 
struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
        &none_funcs,
        &xor_funcs  
};

#define MAX_DISK_SIZE 1024*1024*1024

static int compute_loop_size(struct loop_device *lo, struct dentry * lo_dentry, kdev_t lodev)
{
        if (S_ISREG(lo_dentry->d_inode->i_mode))
                return (lo_dentry->d_inode->i_size - lo->lo_offset) >> BLOCK_SIZE_BITS;
        if (blk_size[MAJOR(lodev)])
                return blk_size[MAJOR(lodev)][MINOR(lodev)] -
                                (lo->lo_offset >> BLOCK_SIZE_BITS);
        return MAX_DISK_SIZE;
}

static void figure_loop_size(struct loop_device *lo)
{
        loop_sizes[lo->lo_number] = compute_loop_size(lo,
                                        lo->lo_backing_file->f_dentry,
                                        lo->lo_device);
}

static int lo_send(struct loop_device *lo, struct buffer_head *bh, int bsize,
                   loff_t pos)
{
        struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
        struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
        struct address_space_operations *aops = mapping->a_ops;
        struct page *page;
        char *kaddr, *data;
        unsigned long index;
        unsigned size, offset;
        int len;

        down(&mapping->host->i_sem);
        index = pos >> PAGE_CACHE_SHIFT;
        offset = pos & (PAGE_CACHE_SIZE - 1);
        len = bh->b_size;
        data = bh->b_data;
        while (len > 0) {
                int IV = index * (PAGE_CACHE_SIZE/bsize) + offset/bsize;
                int transfer_result;

                size = PAGE_CACHE_SIZE - offset;
                if (size > len)
                        size = len;

                page = grab_cache_page(mapping, index);
                if (!page)
                        goto fail;
                kaddr = kmap(page);
                if (aops->prepare_write(file, page, offset, offset+size))
                        goto unlock;
                flush_dcache_page(page);
                transfer_result = lo_do_transfer(lo, WRITE, kaddr + offset, data, size, IV);
                if (transfer_result) {
                        /*
                         * The transfer failed, but we still write the data to
                         * keep prepare/commit calls balanced.
                         */
                        printk(KERN_ERR "loop: transfer error block %ld\n", index);
                        memset(kaddr + offset, 0, size);
                }
                if (aops->commit_write(file, page, offset, offset+size))
                        goto unlock;
                if (transfer_result)
                        goto unlock;
                kunmap(page);
                data += size;
                len -= size;
                offset = 0;
                index++;
                pos += size;
                UnlockPage(page);
                page_cache_release(page);
        }
        up(&mapping->host->i_sem);
        return 0;

unlock:
        kunmap(page);
        UnlockPage(page);
        page_cache_release(page);
fail:
        up(&mapping->host->i_sem);
        return -1;
}

struct lo_read_data {
        struct loop_device *lo;
        char *data;
        int bsize;
};

static int lo_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
{
        char *kaddr;
        unsigned long count = desc->count;
        struct lo_read_data *p = (struct lo_read_data*)desc->buf;
        struct loop_device *lo = p->lo;
        int IV = page->index * (PAGE_CACHE_SIZE/p->bsize) + offset/p->bsize;

        if (size > count)
                size = count;

        kaddr = kmap(page);
        if (lo_do_transfer(lo, READ, kaddr + offset, p->data, size, IV)) {
                size = 0;
                printk(KERN_ERR "loop: transfer error block %ld\n",page->index);
                desc->error = -EINVAL;
        }
        kunmap(page);
        
        desc->count = count - size;
        desc->written += size;
        p->data += size;
        return size;
}

static int lo_receive(struct loop_device *lo, struct buffer_head *bh, int bsize,
                      loff_t pos)
{
        struct lo_read_data cookie;
        read_descriptor_t desc;
        struct file *file;

        cookie.lo = lo;
        cookie.data = bh->b_data;
        cookie.bsize = bsize;
        desc.written = 0;
        desc.count = bh->b_size;
        desc.buf = (char*)&cookie;
        desc.error = 0;
        spin_lock_irq(&lo->lo_lock);
        file = lo->lo_backing_file;
        spin_unlock_irq(&lo->lo_lock);
        do_generic_file_read(file, &pos, &desc, lo_read_actor);
        return desc.error;
}

static inline int loop_get_bs(struct loop_device *lo)
{
        int bs = 0;

        if (blksize_size[MAJOR(lo->lo_device)])
                bs = blksize_size[MAJOR(lo->lo_device)][MINOR(lo->lo_device)];
        if (!bs)
                bs = BLOCK_SIZE;        

        return bs;
}

static inline unsigned long loop_get_iv(struct loop_device *lo,
                                        unsigned long sector)
{
        int bs = loop_get_bs(lo);
        unsigned long offset, IV;

        IV = sector / (bs >> 9) + lo->lo_offset / bs;
        offset = ((sector % (bs >> 9)) << 9) + lo->lo_offset % bs;
        if (offset >= bs)
                IV++;

        return IV;
}

static int do_bh_filebacked(struct loop_device *lo, struct buffer_head *bh, int rw)
{
        loff_t pos;
        int ret;

        pos = ((loff_t) bh->b_rsector << 9) + lo->lo_offset;

        if (rw == WRITE)
                ret = lo_send(lo, bh, loop_get_bs(lo), pos);
        else
                ret = lo_receive(lo, bh, loop_get_bs(lo), pos);

        return ret;
}

static void loop_end_io_transfer(struct buffer_head *bh, int uptodate);
static void loop_put_buffer(struct buffer_head *bh)
{
        /*
         * check b_end_io, may just be a remapped bh and not an allocated one
         */
        if (bh && bh->b_end_io == loop_end_io_transfer) {
                __free_page(bh->b_page);
                kmem_cache_free(bh_cachep, bh);
        }
}

/*
 * Add buffer_head to back of pending list
 */
static void loop_add_bh(struct loop_device *lo, struct buffer_head *bh)
{
        unsigned long flags;

        spin_lock_irqsave(&lo->lo_lock, flags);
        if (lo->lo_bhtail) {
                lo->lo_bhtail->b_reqnext = bh;
                lo->lo_bhtail = bh;
        } else
                lo->lo_bh = lo->lo_bhtail = bh;
        spin_unlock_irqrestore(&lo->lo_lock, flags);

        up(&lo->lo_bh_mutex);
}

/*
 * Grab first pending buffer
 */
static struct buffer_head *loop_get_bh(struct loop_device *lo)
{
        struct buffer_head *bh;

        spin_lock_irq(&lo->lo_lock);
        if ((bh = lo->lo_bh)) {
                if (bh == lo->lo_bhtail)
                        lo->lo_bhtail = NULL;
                lo->lo_bh = bh->b_reqnext;
                bh->b_reqnext = NULL;
        }
        spin_unlock_irq(&lo->lo_lock);

        return bh;
}

/*
 * when buffer i/o has completed. if BH_Dirty is set, this was a WRITE
 * and lo->transfer stuff has already been done. if not, it was a READ
 * so queue it for the loop thread and let it do the transfer out of
 * b_end_io context (we don't want to do decrypt of a page with irqs
 * disabled)
 */
static void loop_end_io_transfer(struct buffer_head *bh, int uptodate)
{
        struct loop_device *lo = &loop_dev[MINOR(bh->b_dev)];

        if (!uptodate || test_bit(BH_Dirty, &bh->b_state)) {
                struct buffer_head *rbh = bh->b_private;

                rbh->b_end_io(rbh, uptodate);
                if (atomic_dec_and_test(&lo->lo_pending))
                        up(&lo->lo_bh_mutex);
                loop_put_buffer(bh);
        } else
                loop_add_bh(lo, bh);
}

static struct buffer_head *loop_get_buffer(struct loop_device *lo,
                                           struct buffer_head *rbh)
{
        struct buffer_head *bh;

        /*
         * for xfer_funcs that can operate on the same bh, do that
         */
        if (lo->lo_flags & LO_FLAGS_BH_REMAP) {
                bh = rbh;
                goto out_bh;
        }

        do {
                bh = kmem_cache_alloc(bh_cachep, SLAB_NOIO);
                if (bh)
                        break;

                run_task_queue(&tq_disk);
                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(HZ);
        } while (1);
        memset(bh, 0, sizeof(*bh));

        bh->b_size = rbh->b_size;
        bh->b_dev = rbh->b_rdev;
        bh->b_state = (1 << BH_Req) | (1 << BH_Mapped) | (1 << BH_Lock);

        /*
         * easy way out, although it does waste some memory for < PAGE_SIZE
         * blocks... if highmem bounce buffering can get away with it,
         * so can we :-)
         */
        do {
                bh->b_page = alloc_page(GFP_NOIO);
                if (bh->b_page)
                        break;

                run_task_queue(&tq_disk);
                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(HZ);
        } while (1);

        bh->b_data = page_address(bh->b_page);
        bh->b_end_io = loop_end_io_transfer;
        bh->b_private = rbh;
        init_waitqueue_head(&bh->b_wait);

out_bh:
        bh->b_rsector = rbh->b_rsector + (lo->lo_offset >> 9);
        spin_lock_irq(&lo->lo_lock);
        bh->b_rdev = lo->lo_device;
        spin_unlock_irq(&lo->lo_lock);

        return bh;
}

static int loop_make_request(request_queue_t *q, int rw, struct buffer_head *rbh)
{
        struct buffer_head *bh = NULL;
        struct loop_device *lo;
        unsigned long IV;

        if (!buffer_locked(rbh))
                BUG();

        if (MINOR(rbh->b_rdev) >= max_loop)
                goto out;

        lo = &loop_dev[MINOR(rbh->b_rdev)];
        spin_lock_irq(&lo->lo_lock);
        if (lo->lo_state != Lo_bound)
                goto inactive;
        atomic_inc(&lo->lo_pending);
        spin_unlock_irq(&lo->lo_lock);

        if (rw == WRITE) {
                if (lo->lo_flags & LO_FLAGS_READ_ONLY)
                        goto err;
        } else if (rw == READA) {
                rw = READ;
        } else if (rw != READ) {
                printk(KERN_ERR "loop: unknown command (%d)\n", rw);
                goto err;
        }

        rbh = blk_queue_bounce(q, rw, rbh);

        /*
         * file backed, queue for loop_thread to handle
         */
        if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
                /*
                 * rbh locked at this point, noone else should clear
                 * the dirty flag
                 */
                if (rw == WRITE)
                        set_bit(BH_Dirty, &rbh->b_state);
                loop_add_bh(lo, rbh);
                return 0;
        }

        /*
         * piggy old buffer on original, and submit for I/O
         */
        bh = loop_get_buffer(lo, rbh);
        IV = loop_get_iv(lo, rbh->b_rsector);
        if (rw == WRITE) {
                set_bit(BH_Dirty, &bh->b_state);
                if (lo_do_transfer(lo, WRITE, bh->b_data, rbh->b_data,
                                   bh->b_size, IV))
                        goto err;
        }

        generic_make_request(rw, bh);
        return 0;

err:
        if (atomic_dec_and_test(&lo->lo_pending))
                up(&lo->lo_bh_mutex);
        loop_put_buffer(bh);
out:
        buffer_IO_error(rbh);
        return 0;
inactive:
        spin_unlock_irq(&lo->lo_lock);
        goto out;
}

static inline void loop_handle_bh(struct loop_device *lo,struct buffer_head *bh)
{
        int ret;

        /*
         * For block backed loop, we know this is a READ
         */
        if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
                int rw = !!test_and_clear_bit(BH_Dirty, &bh->b_state);

                ret = do_bh_filebacked(lo, bh, rw);
                bh->b_end_io(bh, !ret);
        } else {
                struct buffer_head *rbh = bh->b_private;
                unsigned long IV = loop_get_iv(lo, rbh->b_rsector);

                ret = lo_do_transfer(lo, READ, bh->b_data, rbh->b_data,
                                     bh->b_size, IV);

                rbh->b_end_io(rbh, !ret);
                loop_put_buffer(bh);
        }
}

/*
 * worker thread that handles reads/writes to file backed loop devices,
 * to avoid blocking in our make_request_fn. it also does loop decrypting
 * on reads for block backed loop, as that is too heavy to do from
 * b_end_io context where irqs may be disabled.
 */
static int loop_thread(void *data)
{
        struct loop_device *lo = data;
        struct buffer_head *bh;

        daemonize();
        exit_files(current);
        reparent_to_init();

        sprintf(current->comm, "loop%d", lo->lo_number);

        spin_lock_irq(&current->sigmask_lock);
        sigfillset(&current->blocked);
        flush_signals(current);
        spin_unlock_irq(&current->sigmask_lock);

        spin_lock_irq(&lo->lo_lock);
        lo->lo_state = Lo_bound;
        atomic_inc(&lo->lo_pending);
        spin_unlock_irq(&lo->lo_lock);

        current->flags |= PF_NOIO;

        /*
         * up sem, we are running
         */
        up(&lo->lo_sem);

        for (;;) {
                down_interruptible(&lo->lo_bh_mutex);
                /*
                 * could be upped because of tear-down, not because of
                 * pending work
                 */
                if (!atomic_read(&lo->lo_pending))
                        break;

                bh = loop_get_bh(lo);
                if (!bh) {
                        printk("loop: missing bh\n");
                        continue;
                }
                loop_handle_bh(lo, bh);

                /*
                 * upped both for pending work and tear-down, lo_pending
                 * will hit zero then
                 */
                if (atomic_dec_and_test(&lo->lo_pending))
                        break;
        }

        up(&lo->lo_sem);
        return 0;
}

static int loop_set_fd(struct loop_device *lo, struct file *lo_file, kdev_t dev,
                       unsigned int arg)
{
        struct file     *file;
        struct inode    *inode;
        kdev_t          lo_device;
        int             lo_flags = 0;
        int             error;
        int             bs;

        MOD_INC_USE_COUNT;

        error = -EBUSY;
        if (lo->lo_state != Lo_unbound)
                goto out;

        error = -EBADF;
        file = fget(arg);
        if (!file)
                goto out;

        error = -EINVAL;
        inode = file->f_dentry->d_inode;

        if (!(file->f_mode & FMODE_WRITE))
                lo_flags |= LO_FLAGS_READ_ONLY;

        if (S_ISBLK(inode->i_mode)) {
                lo_device = inode->i_rdev;
                if (lo_device == dev) {
                        error = -EBUSY;
                        goto out_putf;
                }
        } else if (S_ISREG(inode->i_mode)) {
                struct address_space_operations *aops = inode->i_mapping->a_ops;
                /*
                 * If we can't read - sorry. If we only can't write - well,
                 * it's going to be read-only.
                 */
                if (!aops->readpage)
                        goto out_putf;

                if (!aops->prepare_write || !aops->commit_write)
                        lo_flags |= LO_FLAGS_READ_ONLY;

                lo_device = inode->i_dev;
                lo_flags |= LO_FLAGS_DO_BMAP;
                error = 0;
        } else
                goto out_putf;

        get_file(file);

        if (IS_RDONLY (inode) || is_read_only(lo_device)
            || !(lo_file->f_mode & FMODE_WRITE))
                lo_flags |= LO_FLAGS_READ_ONLY;

        set_device_ro(dev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);

        lo->lo_device = lo_device;
        lo->lo_flags = lo_flags;
        lo->lo_backing_file = file;
        lo->transfer = NULL;
        lo->ioctl = NULL;
        figure_loop_size(lo);
        lo->old_gfp_mask = inode->i_mapping->gfp_mask;
        inode->i_mapping->gfp_mask &= ~(__GFP_IO|__GFP_FS);

        bs = 0;
        if (blksize_size[MAJOR(lo_device)])
                bs = blksize_size[MAJOR(lo_device)][MINOR(lo_device)];
        if (!bs)
                bs = BLOCK_SIZE;

        set_blocksize(dev, bs);

        lo->lo_bh = lo->lo_bhtail = NULL;
        kernel_thread(loop_thread, lo, CLONE_FS | CLONE_FILES | CLONE_SIGHAND);
        down(&lo->lo_sem);

        fput(file);
        return 0;

 out_putf:
        fput(file);
 out:
        MOD_DEC_USE_COUNT;
        return error;
}

static int loop_release_xfer(struct loop_device *lo)
{
        int err = 0; 
        if (lo->lo_encrypt_type) {
                struct loop_func_table *xfer= xfer_funcs[lo->lo_encrypt_type]; 
                if (xfer && xfer->release)
                        err = xfer->release(lo); 
                if (xfer && xfer->unlock)
                        xfer->unlock(lo); 
                lo->lo_encrypt_type = 0;
        }
        return err;
}

static int loop_init_xfer(struct loop_device *lo, int type,struct loop_info *i)
{
        int err = 0; 
        if (type) {
                struct loop_func_table *xfer = xfer_funcs[type]; 
                if (xfer->init)
                        err = xfer->init(lo, i);
                if (!err) { 
                        lo->lo_encrypt_type = type;
                        if (xfer->lock)
                                xfer->lock(lo);
                }
        }
        return err;
}  

static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
{
        struct file *filp = lo->lo_backing_file;
        int gfp = lo->old_gfp_mask;

        if (lo->lo_state != Lo_bound)
                return -ENXIO;
        if (lo->lo_refcnt > 1)  /* we needed one fd for the ioctl */
                return -EBUSY;
        if (filp==NULL)
                return -EINVAL;

        spin_lock_irq(&lo->lo_lock);
        lo->lo_state = Lo_rundown;
        if (atomic_dec_and_test(&lo->lo_pending))
                up(&lo->lo_bh_mutex);
        spin_unlock_irq(&lo->lo_lock);

        down(&lo->lo_sem);

        lo->lo_backing_file = NULL;

        loop_release_xfer(lo);
        lo->transfer = NULL;
        lo->ioctl = NULL;
        lo->lo_device = 0;
        lo->lo_encrypt_type = 0;
        lo->lo_offset = 0;
        lo->lo_encrypt_key_size = 0;
        lo->lo_flags = 0;
        memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
        memset(lo->lo_name, 0, LO_NAME_SIZE);
        loop_sizes[lo->lo_number] = 0;
        invalidate_bdev(bdev, 0);
        filp->f_dentry->d_inode->i_mapping->gfp_mask = gfp;
        lo->lo_state = Lo_unbound;
        fput(filp);
        MOD_DEC_USE_COUNT;
        return 0;
}

static int loop_set_status(struct loop_device *lo, struct loop_info *arg)
{
        struct loop_info info; 
        int err;
        unsigned int type;

        if (lo->lo_encrypt_key_size && lo->lo_key_owner != current->uid && 
            !capable(CAP_SYS_ADMIN))
                return -EPERM;
        if (lo->lo_state != Lo_bound)
                return -ENXIO;
        if (copy_from_user(&info, arg, sizeof (struct loop_info)))
                return -EFAULT; 
        if ((unsigned int) info.lo_encrypt_key_size > LO_KEY_SIZE)
                return -EINVAL;
        type = info.lo_encrypt_type; 
        if (type >= MAX_LO_CRYPT || xfer_funcs[type] == NULL)
                return -EINVAL;
        if (type == LO_CRYPT_XOR && info.lo_encrypt_key_size == 0)
                return -EINVAL;
        err = loop_release_xfer(lo);
        if (!err) 
                err = loop_init_xfer(lo, type, &info);
        if (err)
                return err;     

        lo->lo_offset = info.lo_offset;
        strncpy(lo->lo_name, info.lo_name, LO_NAME_SIZE);

        lo->transfer = xfer_funcs[type]->transfer;
        lo->ioctl = xfer_funcs[type]->ioctl;
        lo->lo_encrypt_key_size = info.lo_encrypt_key_size;
        lo->lo_init[0] = info.lo_init[0];
        lo->lo_init[1] = info.lo_init[1];
        if (info.lo_encrypt_key_size) {
                memcpy(lo->lo_encrypt_key, info.lo_encrypt_key, 
                       info.lo_encrypt_key_size);
                lo->lo_key_owner = current->uid; 
        }       
        figure_loop_size(lo);
        return 0;
}

static int loop_get_status(struct loop_device *lo, struct loop_info *arg)
{
        struct loop_info        info;
        struct file *file = lo->lo_backing_file;

        if (lo->lo_state != Lo_bound)
                return -ENXIO;
        if (!arg)
                return -EINVAL;
        memset(&info, 0, sizeof(info));
        info.lo_number = lo->lo_number;
        info.lo_device = kdev_t_to_nr(file->f_dentry->d_inode->i_dev);
        info.lo_inode = file->f_dentry->d_inode->i_ino;
        info.lo_rdevice = kdev_t_to_nr(lo->lo_device);
        info.lo_offset = lo->lo_offset;
        info.lo_flags = lo->lo_flags;
        strncpy(info.lo_name, lo->lo_name, LO_NAME_SIZE);
        info.lo_encrypt_type = lo->lo_encrypt_type;
        if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
                info.lo_encrypt_key_size = lo->lo_encrypt_key_size;
                memcpy(info.lo_encrypt_key, lo->lo_encrypt_key,
                       lo->lo_encrypt_key_size);
        }
        return copy_to_user(arg, &info, sizeof(info)) ? -EFAULT : 0;
}

static int lo_ioctl(struct inode * inode, struct file * file,
        unsigned int cmd, unsigned long arg)
{
        struct loop_device *lo;
        int dev, err;

        if (!inode)
                return -EINVAL;
        if (MAJOR(inode->i_rdev) != MAJOR_NR) {
                printk(KERN_WARNING "lo_ioctl: pseudo-major != %d\n",
                       MAJOR_NR);
                return -ENODEV;
        }
        dev = MINOR(inode->i_rdev);
        if (dev >= max_loop)
                return -ENODEV;
        lo = &loop_dev[dev];
        down(&lo->lo_ctl_mutex);
        switch (cmd) {
        case LOOP_SET_FD:
                err = loop_set_fd(lo, file, inode->i_rdev, arg);
                break;
        case LOOP_CLR_FD:
                err = loop_clr_fd(lo, inode->i_bdev);
                break;
        case LOOP_SET_STATUS:
                err = loop_set_status(lo, (struct loop_info *) arg);
                break;
        case LOOP_GET_STATUS:
                err = loop_get_status(lo, (struct loop_info *) arg);
                break;
        case BLKGETSIZE:
                if (lo->lo_state != Lo_bound) {
                        err = -ENXIO;
                        break;
                }
                err = put_user((unsigned long)loop_sizes[lo->lo_number] << 1, (unsigned long *) arg);
                break;
        case BLKGETSIZE64:
                if (lo->lo_state != Lo_bound) {
                        err = -ENXIO;
                        break;
                }
                err = put_user((u64)loop_sizes[lo->lo_number] << 10, (u64*)arg);
                break;
        case BLKBSZGET:
        case BLKBSZSET:
        case BLKSSZGET:
                err = blk_ioctl(inode->i_rdev, cmd, arg);
                break;
        default:
                err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
        }
        up(&lo->lo_ctl_mutex);
        return err;
}

static int lo_open(struct inode *inode, struct file *file)
{
        struct loop_device *lo;
        int     dev, type;

        if (!inode)
                return -EINVAL;
        if (MAJOR(inode->i_rdev) != MAJOR_NR) {
                printk(KERN_WARNING "lo_open: pseudo-major != %d\n", MAJOR_NR);
                return -ENODEV;
        }
        dev = MINOR(inode->i_rdev);
        if (dev >= max_loop)
                return -ENODEV;

        lo = &loop_dev[dev];
        MOD_INC_USE_COUNT;
        down(&lo->lo_ctl_mutex);

        type = lo->lo_encrypt_type; 
        if (type && xfer_funcs[type] && xfer_funcs[type]->lock)
                xfer_funcs[type]->lock(lo);
        lo->lo_refcnt++;
        up(&lo->lo_ctl_mutex);
        return 0;
}

static int lo_release(struct inode *inode, struct file *file)
{
        struct loop_device *lo;
        int     dev, type;

        if (!inode)
                return 0;
        if (MAJOR(inode->i_rdev) != MAJOR_NR) {
                printk(KERN_WARNING "lo_release: pseudo-major != %d\n",
                       MAJOR_NR);
                return 0;
        }
        dev = MINOR(inode->i_rdev);
        if (dev >= max_loop)
                return 0;

        lo = &loop_dev[dev];
        down(&lo->lo_ctl_mutex);
        type = lo->lo_encrypt_type;
        --lo->lo_refcnt;
        if (xfer_funcs[type] && xfer_funcs[type]->unlock)
                xfer_funcs[type]->unlock(lo);

        up(&lo->lo_ctl_mutex);
        MOD_DEC_USE_COUNT;
        return 0;
}

static struct block_device_operations lo_fops = {
        owner:          THIS_MODULE,
        open:           lo_open,
        release:        lo_release,
        ioctl:          lo_ioctl,
};

/*
 * And now the modules code and kernel interface.
 */
MODULE_PARM(max_loop, "i");
MODULE_PARM_DESC(max_loop, "Maximum number of loop devices (1-256)");
MODULE_LICENSE("GPL");

int loop_register_transfer(struct loop_func_table *funcs)
{
        if ((unsigned)funcs->number > MAX_LO_CRYPT || xfer_funcs[funcs->number])
                return -EINVAL;
        xfer_funcs[funcs->number] = funcs;
        return 0; 
}

int loop_unregister_transfer(int number)
{
        struct loop_device *lo; 

        if ((unsigned)number >= MAX_LO_CRYPT)
                return -EINVAL; 
        for (lo = &loop_dev[0]; lo < &loop_dev[max_loop]; lo++) { 
                int type = lo->lo_encrypt_type;
                if (type == number) { 
                        xfer_funcs[type]->release(lo);
                        lo->transfer = NULL; 
                        lo->lo_encrypt_type = 0; 
                }
        }
        xfer_funcs[number] = NULL; 
        return 0; 
}

EXPORT_SYMBOL(loop_register_transfer);
EXPORT_SYMBOL(loop_unregister_transfer);

int __init loop_init(void) 
{
        int     i;

        if ((max_loop < 1) || (max_loop > 256)) {
                printk(KERN_WARNING "loop: invalid max_loop (must be between"
                                    " 1 and 256), using default (8)\n");
                max_loop = 8;
        }

        if (devfs_register_blkdev(MAJOR_NR, "loop", &lo_fops)) {
                printk(KERN_WARNING "Unable to get major number %d for loop"
                                    " device\n", MAJOR_NR);
                return -EIO;
        }


        loop_dev = kmalloc(max_loop * sizeof(struct loop_device), GFP_KERNEL);
        if (!loop_dev)
                return -ENOMEM;

        loop_sizes = kmalloc(max_loop * sizeof(int), GFP_KERNEL);
        if (!loop_sizes)
                goto out_sizes;

        loop_blksizes = kmalloc(max_loop * sizeof(int), GFP_KERNEL);
        if (!loop_blksizes)
                goto out_blksizes;

        blk_queue_make_request(BLK_DEFAULT_QUEUE(MAJOR_NR), loop_make_request);

        for (i = 0; i < max_loop; i++) {
                struct loop_device *lo = &loop_dev[i];
                memset(lo, 0, sizeof(struct loop_device));
                init_MUTEX(&lo->lo_ctl_mutex);
                init_MUTEX_LOCKED(&lo->lo_sem);
                init_MUTEX_LOCKED(&lo->lo_bh_mutex);
                lo->lo_number = i;
                spin_lock_init(&lo->lo_lock);
        }

        memset(loop_sizes, 0, max_loop * sizeof(int));
        memset(loop_blksizes, 0, max_loop * sizeof(int));
        blk_size[MAJOR_NR] = loop_sizes;
        blksize_size[MAJOR_NR] = loop_blksizes;
        for (i = 0; i < max_loop; i++)
                register_disk(NULL, MKDEV(MAJOR_NR, i), 1, &lo_fops, 0);

        devfs_handle = devfs_mk_dir(NULL, "loop", NULL);
        devfs_register_series(devfs_handle, "%u", max_loop, DEVFS_FL_DEFAULT,
                              MAJOR_NR, 0,
                              S_IFBLK | S_IRUSR | S_IWUSR | S_IRGRP,
                              &lo_fops, NULL);

        printk(KERN_INFO "loop: loaded (max %d devices)\n", max_loop);
        return 0;

out_blksizes:
        kfree(loop_sizes);
out_sizes:
        kfree(loop_dev);
        if (devfs_unregister_blkdev(MAJOR_NR, "loop"))
                printk(KERN_WARNING "loop: cannot unregister blkdev\n");
        printk(KERN_ERR "loop: ran out of memory\n");
        return -ENOMEM;
}

void loop_exit(void) 
{
        devfs_unregister(devfs_handle);
        if (devfs_unregister_blkdev(MAJOR_NR, "loop"))
                printk(KERN_WARNING "loop: cannot unregister blkdev\n");
        kfree(loop_dev);
        kfree(loop_sizes);
        kfree(loop_blksizes);
}

module_init(loop_init);
module_exit(loop_exit);

#ifndef MODULE
static int __init max_loop_setup(char *str)
{
        max_loop = simple_strtol(str, NULL, 0);
        return 1;
}

__setup("max_loop=", max_loop_setup);
#endif