Merge with Linux 2.5.48.

[linux-2.6/linux-mips.git] / drivers / block / loop.c

/*
 *  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/bio.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 <linux/loop.h>
#include <linux/suspend.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>          /* for invalidate_bdev() */

#include <asm/uaccess.h>

#define MAJOR_NR LOOP_MAJOR

static int max_loop = 8;
static struct loop_device *loop_dev;
static struct gendisk **disks;
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, sector_t 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, sector_t 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  
};

static int figure_loop_size(struct loop_device *lo)
{
        loff_t size = lo->lo_backing_file->f_dentry->d_inode->i_mapping->host->i_size;
        sector_t x;
        /*
         * Unfortunately, if we want to do I/O on the device,
         * the number of 512-byte sectors has to fit into a sector_t.
         */
        size = (size - lo->lo_offset) >> 9;
        x = (sector_t)size;
        if ((loff_t)x != size)
                return -EFBIG;

        set_capacity(disks[lo->lo_number], size);
        return 0;                                       
}

static inline int lo_do_transfer(struct loop_device *lo, int cmd, char *rbuf,
                                 char *lbuf, int size, sector_t rblock)
{
        if (!lo->transfer)
                return 0;

        return lo->transfer(lo, cmd, rbuf, lbuf, size, rblock);
}

static int
do_lo_send(struct loop_device *lo, struct bio_vec *bvec, 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;
        pgoff_t index;
        unsigned size, offset;
        int len;
        int ret = 0;

        down(&mapping->host->i_sem);
        index = pos >> PAGE_CACHE_SHIFT;
        offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1);
        data = kmap(bvec->bv_page) + bvec->bv_offset;
        len = bvec->bv_len;
        while (len > 0) {
                sector_t 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;
                if (aops->prepare_write(file, page, offset, offset+size))
                        goto unlock;
                kaddr = kmap(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 %llu\n", (unsigned long long)index);
                        memset(kaddr + offset, 0, size);
                }
                flush_dcache_page(page);
                kunmap(page);
                if (aops->commit_write(file, page, offset, offset+size))
                        goto unlock;
                if (transfer_result)
                        goto unlock;
                data += size;
                len -= size;
                offset = 0;
                index++;
                pos += size;
                unlock_page(page);
                page_cache_release(page);
        }
        up(&mapping->host->i_sem);
out:
        kunmap(bvec->bv_page);
        balance_dirty_pages(mapping);
        return ret;

unlock:
        unlock_page(page);
        page_cache_release(page);
fail:
        up(&mapping->host->i_sem);
        ret = -1;
        goto out;
}

static int
lo_send(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
{
        unsigned vecnr;
        int ret = 0;

        for (vecnr = 0; vecnr < bio->bi_vcnt; vecnr++) {
                struct bio_vec *bvec = &bio->bi_io_vec[vecnr];

                ret = do_lo_send(lo, bvec, bsize, pos);
                if (ret < 0)
                        break;
                pos += bvec->bv_len;
        }
        return ret;
}

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
do_lo_receive(struct loop_device *lo,
                struct bio_vec *bvec, int bsize, loff_t pos)
{
        struct lo_read_data cookie;
        struct file *file;
        int retval;

        cookie.lo = lo;
        cookie.data = kmap(bvec->bv_page) + bvec->bv_offset;
        cookie.bsize = bsize;
        file = lo->lo_backing_file;
        retval = file->f_op->sendfile(file, &pos, bvec->bv_len,
                        lo_read_actor, &cookie);
        kunmap(bvec->bv_page);
        return (retval < 0)? retval: 0;
}

static int
lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
{
        unsigned vecnr;
        int ret = 0;

        for (vecnr = 0; vecnr < bio->bi_vcnt; vecnr++) {
                struct bio_vec *bvec = &bio->bi_io_vec[vecnr];

                ret = do_lo_receive(lo, bvec, bsize, pos);
                if (ret < 0)
                        break;
                pos += bvec->bv_len;
        }
        return ret;
}

static inline unsigned long loop_get_iv(struct loop_device *lo,
                                        unsigned long sector)
{
        int bs = lo->lo_blocksize;
        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_bio_filebacked(struct loop_device *lo, struct bio *bio)
{
        loff_t pos;
        int ret;

        pos = ((loff_t) bio->bi_sector << 9) + lo->lo_offset;

        do {
                if (bio_rw(bio) == WRITE)
                        ret = lo_send(lo, bio, lo->lo_blocksize, pos);
                else
                        ret = lo_receive(lo, bio, lo->lo_blocksize, pos);

        } while (++bio->bi_idx < bio->bi_vcnt);

        return ret;
}

static int loop_end_io_transfer(struct bio *, unsigned int, int);
static void loop_put_buffer(struct bio *bio)
{
        /*
         * check bi_end_io, may just be a remapped bio
         */
        if (bio && bio->bi_end_io == loop_end_io_transfer) {
                int i;

                for (i = 0; i < bio->bi_vcnt; i++)
                        __free_page(bio->bi_io_vec[i].bv_page);

                bio_put(bio);
        }
}

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

        spin_lock_irqsave(&lo->lo_lock, flags);
        if (lo->lo_biotail) {
                lo->lo_biotail->bi_next = bio;
                lo->lo_biotail = bio;
        } else
                lo->lo_bio = lo->lo_biotail = bio;
        spin_unlock_irqrestore(&lo->lo_lock, flags);

        up(&lo->lo_bh_mutex);
}

/*
 * Grab first pending buffer
 */
static struct bio *loop_get_bio(struct loop_device *lo)
{
        struct bio *bio;

        spin_lock_irq(&lo->lo_lock);
        if ((bio = lo->lo_bio)) {
                if (bio == lo->lo_biotail)
                        lo->lo_biotail = NULL;
                lo->lo_bio = bio->bi_next;
                bio->bi_next = NULL;
        }
        spin_unlock_irq(&lo->lo_lock);

        return bio;
}

/*
 * if this was a WRITE lo->transfer stuff has already been done. for READs,
 * queue it for the loop thread and let it do the transfer out of
 * bi_end_io context (we don't want to do decrypt of a page with irqs
 * disabled)
 */
static int loop_end_io_transfer(struct bio *bio, unsigned int bytes_done, int err)
{
        struct bio *rbh = bio->bi_private;
        struct loop_device *lo = rbh->bi_bdev->bd_disk->private_data;

        if (bio->bi_size)
                return 1;

        if (err || bio_rw(bio) == WRITE) {
                bio_endio(rbh, rbh->bi_size, err);
                if (atomic_dec_and_test(&lo->lo_pending))
                        up(&lo->lo_bh_mutex);
                loop_put_buffer(bio);
        } else
                loop_add_bio(lo, bio);

        return 0;
}

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

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

        bio = bio_copy(rbh, GFP_NOIO, rbh->bi_rw & WRITE);

        bio->bi_end_io = loop_end_io_transfer;
        bio->bi_private = rbh;

out_bh:
        bio->bi_sector = rbh->bi_sector + (lo->lo_offset >> 9);
        bio->bi_rw = rbh->bi_rw;
        bio->bi_bdev = lo->lo_device;

        return bio;
}

static int
bio_transfer(struct loop_device *lo, struct bio *to_bio,
                              struct bio *from_bio)
{
        unsigned long IV = loop_get_iv(lo, from_bio->bi_sector);
        struct bio_vec *from_bvec, *to_bvec;
        char *vto, *vfrom;
        int ret = 0, i;

        __bio_for_each_segment(from_bvec, from_bio, i, 0) {
                to_bvec = &to_bio->bi_io_vec[i];

                kmap(from_bvec->bv_page);
                kmap(to_bvec->bv_page);
                vfrom = page_address(from_bvec->bv_page) + from_bvec->bv_offset;
                vto = page_address(to_bvec->bv_page) + to_bvec->bv_offset;
                ret |= lo_do_transfer(lo, bio_data_dir(to_bio), vto, vfrom,
                                        from_bvec->bv_len, IV);
                kunmap(from_bvec->bv_page);
                kunmap(to_bvec->bv_page);
        }

        return ret;
}
                
static int loop_make_request(request_queue_t *q, struct bio *old_bio)
{
        struct bio *new_bio = NULL;
        struct loop_device *lo = q->queuedata;
        unsigned long IV;
        int rw = bio_rw(old_bio);

        if (!lo)
                goto out;

        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 (%x)\n", rw);
                goto err;
        }

        blk_queue_bounce(q, &old_bio);

        /*
         * file backed, queue for loop_thread to handle
         */
        if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
                loop_add_bio(lo, old_bio);
                return 0;
        }

        /*
         * piggy old buffer on original, and submit for I/O
         */
        new_bio = loop_get_buffer(lo, old_bio);
        IV = loop_get_iv(lo, old_bio->bi_sector);
        if (rw == WRITE) {
                if (bio_transfer(lo, new_bio, old_bio))
                        goto err;
        }

        generic_make_request(new_bio);
        return 0;

err:
        if (atomic_dec_and_test(&lo->lo_pending))
                up(&lo->lo_bh_mutex);
        loop_put_buffer(new_bio);
out:
        bio_io_error(old_bio, old_bio->bi_size);
        return 0;
inactive:
        spin_unlock_irq(&lo->lo_lock);
        goto out;
}

static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
{
        int ret;

        /*
         * For block backed loop, we know this is a READ
         */
        if (lo->lo_flags & LO_FLAGS_DO_BMAP) {
                ret = do_bio_filebacked(lo, bio);
                bio_endio(bio, bio->bi_size, ret);
        } else {
                struct bio *rbh = bio->bi_private;

                ret = bio_transfer(lo, bio, rbh);

                bio_endio(rbh, rbh->bi_size, ret);
                loop_put_buffer(bio);
        }
}

/*
 * 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 bio *bio;

        daemonize();

        sprintf(current->comm, "loop%d", lo->lo_number);
        current->flags |= PF_IOTHREAD;  /* loop can be used in an encrypted device
                                           hence, it mustn't be stopped at all because it could
                                           be indirectly used during suspension */

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

        set_user_nice(current, -20);

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

        /*
         * 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;

                bio = loop_get_bio(lo);
                if (!bio) {
                        printk("loop: missing bio\n");
                        continue;
                }
                loop_handle_bio(lo, bio);

                /*
                 * 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,
                       struct block_device *bdev, unsigned int arg)
{
        struct file     *file;
        struct inode    *inode;
        struct block_device *lo_device = NULL;
        unsigned lo_blocksize;
        int             lo_flags = 0;
        int             error;

        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_bdev;
                if (lo_device == bdev) {
                        error = -EBUSY;
                        goto out;
                }
                lo_blocksize = block_size(lo_device);
                if (bdev_read_only(lo_device))
                        lo_flags |= LO_FLAGS_READ_ONLY;
        } 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 (!inode->i_fop->sendfile)
                        goto out_putf;

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

                lo_blocksize = inode->i_blksize;
                lo_flags |= LO_FLAGS_DO_BMAP;
                error = 0;
        } else
                goto out_putf;

        get_file(file);

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

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

        lo->lo_blocksize = lo_blocksize;
        lo->lo_device = lo_device;
        lo->lo_flags = lo_flags;
        lo->lo_backing_file = file;
        lo->transfer = NULL;
        lo->ioctl = NULL;
        if (figure_loop_size(lo)) {
                error = -EFBIG;
                fput(file);
                goto out_putf;
        }
        lo->old_gfp_mask = inode->i_mapping->gfp_mask;
        inode->i_mapping->gfp_mask = GFP_NOIO;

        set_blocksize(bdev, lo_blocksize);

        lo->lo_bio = lo->lo_biotail = NULL;

        /*
         * set queue make_request_fn, and add limits based on lower level
         * device
         */
        blk_queue_make_request(&lo->lo_queue, loop_make_request);
        blk_queue_bounce_limit(&lo->lo_queue, BLK_BOUNCE_HIGH);
        lo->lo_queue.queuedata = lo;

        /*
         * we remap to a block device, make sure we correctly stack limits
         */
        if (S_ISBLK(inode->i_mode)) {
                request_queue_t *q = bdev_get_queue(lo_device);

                blk_queue_max_sectors(&lo->lo_queue, q->max_sectors);
                blk_queue_max_phys_segments(&lo->lo_queue,q->max_phys_segments);
                blk_queue_max_hw_segments(&lo->lo_queue, q->max_hw_segments);
                blk_queue_max_segment_size(&lo->lo_queue, q->max_segment_size);
                blk_queue_segment_boundary(&lo->lo_queue, q->seg_boundary_mask);
                blk_queue_merge_bvec(&lo->lo_queue, q->merge_bvec_fn);
        }

        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 = NULL;
        lo->lo_encrypt_type = 0;
        lo->lo_offset = 0;
        lo->lo_encrypt_key_size = 0;
        lo->lo_flags = 0;
        lo->lo_queue.queuedata = NULL;
        memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
        memset(lo->lo_name, 0, LO_NAME_SIZE);
        invalidate_bdev(bdev, 0);
        set_capacity(disks[lo->lo_number], 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;
        loff_t offset;

        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);

        offset = lo->lo_offset;
        if (offset != info.lo_offset) {
                lo->lo_offset = info.lo_offset;
                if (figure_loop_size(lo)){
                        err = -EFBIG;
                        lo->lo_offset = offset;
                }
        }

        if (err)
                return err;     

        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; 
        }       

        return 0;
}

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

        if (lo->lo_state != Lo_bound)
                return -ENXIO;
        if (!arg)
                return -EINVAL;
        error = vfs_getattr(file->f_vfsmnt, file->f_dentry, &stat);
        if (error)
                return error;
        memset(&info, 0, sizeof(info));
        info.lo_number = lo->lo_number;
        info.lo_device = stat.dev;
        info.lo_inode = stat.ino;
        info.lo_rdevice = lo->lo_device ? stat.rdev : stat.dev;
        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 = inode->i_bdev->bd_disk->private_data;
        int err;

        down(&lo->lo_ctl_mutex);
        switch (cmd) {
        case LOOP_SET_FD:
                err = loop_set_fd(lo, file, inode->i_bdev, 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;
        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 = inode->i_bdev->bd_disk->private_data;
        int type;

        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 = inode->i_bdev->bd_disk->private_data;
        int type;

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

        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);

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

        disks = kmalloc(max_loop * sizeof(struct gendisk *), GFP_KERNEL);
        if (!disks)
                goto out_mem;

        for (i = 0; i < max_loop; i++) {
                disks[i] = alloc_disk(1);
                if (!disks[i])
                        goto out_mem2;
        }

        for (i = 0; i < max_loop; i++) {
                struct loop_device *lo = &loop_dev[i];
                struct gendisk *disk = disks[i];
                memset(lo, 0, sizeof(*lo));
                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);
                disk->major = LOOP_MAJOR;
                disk->first_minor = i;
                disk->fops = &lo_fops;
                sprintf(disk->disk_name, "loop%d", i);
                disk->private_data = lo;
                disk->queue = &lo->lo_queue;
                add_disk(disk);
        }
        printk(KERN_INFO "loop: loaded (max %d devices)\n", max_loop);
        return 0;

out_mem2:
        while (i--)
                put_disk(disks[i]);
        kfree(disks);
out_mem:
        kfree(loop_dev);
        printk(KERN_ERR "loop: ran out of memory\n");
        return -ENOMEM;
}

void loop_exit(void) 
{
        int i;
        for (i = 0; i < max_loop; i++) {
                del_gendisk(disks[i]);
                put_disk(disks[i]);
        }
        devfs_unregister(devfs_handle);
        if (unregister_blkdev(MAJOR_NR, "loop"))
                printk(KERN_WARNING "loop: cannot unregister blkdev\n");

        kfree(disks);
        kfree(loop_dev);
}

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