1 files changed, 1348 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
new file mode 100644
index 000000000000..6f011d0d8e97
--- /dev/null
+++ b/drivers/block/loop.c
@@ -0,0 +1,1348 @@
+/*
+ *  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. Bolsų, <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
+ *
+ * Support for falling back on the write file operation when the address space
+ * operations prepare_write and/or commit_write are not available on the
+ * backing filesystem.
+ * Anton Altaparmakov, 16 Feb 2005
+ *
+ * Still To Fix:
+ * - Advisory locking is ignored here.
+ * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/moduleparam.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/blkdev.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 <linux/completion.h>
+#include <linux/highmem.h>
+#include <linux/gfp.h>
+
+#include <asm/uaccess.h>
+
+static int max_loop = 8;
+static struct loop_device *loop_dev;
+static struct gendisk **disks;
+
+/*
+ * Transfer functions
+ */
+static int transfer_none(struct loop_device *lo, int cmd,
+                         struct page *raw_page, unsigned raw_off,
+                         struct page *loop_page, unsigned loop_off,
+                         int size, sector_t real_block)
+{
+        char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
+        char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
+
+        if (cmd == READ)
+                memcpy(loop_buf, raw_buf, size);
+        else
+                memcpy(raw_buf, loop_buf, size);
+
+        kunmap_atomic(raw_buf, KM_USER0);
+        kunmap_atomic(loop_buf, KM_USER1);
+        cond_resched();
+        return 0;
+}
+
+static int transfer_xor(struct loop_device *lo, int cmd,
+                        struct page *raw_page, unsigned raw_off,
+                        struct page *loop_page, unsigned loop_off,
+                        int size, sector_t real_block)
+{
+        char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
+        char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
+        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];
+
+        kunmap_atomic(raw_buf, KM_USER0);
+        kunmap_atomic(loop_buf, KM_USER1);
+        cond_resched();
+        return 0;
+}
+
+static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
+{
+        if (unlikely(info->lo_encrypt_key_size <= 0))
+                return -EINVAL;
+        return 0;
+}
+
+static struct loop_func_table none_funcs = {
+        .number = LO_CRYPT_NONE,
+        .transfer = transfer_none,
+};      
+
+static struct loop_func_table xor_funcs = {
+        .number = LO_CRYPT_XOR,
+        .transfer = transfer_xor,
+        .init = xor_init
+};      
+
+/* xfer_funcs[0] is special - its release function is never called */
+static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
+        &none_funcs,
+        &xor_funcs
+};
+
+static loff_t get_loop_size(struct loop_device *lo, struct file *file)
+{
+        loff_t size, offset, loopsize;
+
+        /* Compute loopsize in bytes */
+        size = i_size_read(file->f_mapping->host);
+        offset = lo->lo_offset;
+        loopsize = size - offset;
+        if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
+                loopsize = lo->lo_sizelimit;
+
+        /*
+         * Unfortunately, if we want to do I/O on the device,
+         * the number of 512-byte sectors has to fit into a sector_t.
+         */
+        return loopsize >> 9;
+}
+
+static int
+figure_loop_size(struct loop_device *lo)
+{
+        loff_t size = get_loop_size(lo, lo->lo_backing_file);
+        sector_t x = (sector_t)size;
+
+        if (unlikely((loff_t)x != size))
+                return -EFBIG;
+
+        set_capacity(disks[lo->lo_number], x);
+        return 0;                                       
+}
+
+static inline int
+lo_do_transfer(struct loop_device *lo, int cmd,
+               struct page *rpage, unsigned roffs,
+               struct page *lpage, unsigned loffs,
+               int size, sector_t rblock)
+{
+        if (unlikely(!lo->transfer))
+                return 0;
+
+        return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
+}
+
+/**
+ * do_lo_send_aops - helper for writing data to a loop device
+ *
+ * This is the fast version for backing filesystems which implement the address
+ * space operations prepare_write and commit_write.
+ */
+static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
+                int bsize, loff_t pos, struct page *page)
+{
+        struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
+        struct address_space *mapping = file->f_mapping;
+        struct address_space_operations *aops = mapping->a_ops;
+        pgoff_t index;
+        unsigned offset, bv_offs;
+        int len, ret = 0;
+
+        down(&mapping->host->i_sem);
+        index = pos >> PAGE_CACHE_SHIFT;
+        offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1);
+        bv_offs = bvec->bv_offset;
+        len = bvec->bv_len;
+        while (len > 0) {
+                sector_t IV;
+                unsigned size;
+                int transfer_result;
+
+                IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
+                size = PAGE_CACHE_SIZE - offset;
+                if (size > len)
+                        size = len;
+                page = grab_cache_page(mapping, index);
+                if (unlikely(!page))
+                        goto fail;
+                if (unlikely(aops->prepare_write(file, page, offset,
+                                offset + size)))
+                        goto unlock;
+                transfer_result = lo_do_transfer(lo, WRITE, page, offset,
+                                bvec->bv_page, bv_offs, size, IV);
+                if (unlikely(transfer_result)) {
+                        char *kaddr;
+
+                        /*
+                         * 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);
+                        kaddr = kmap_atomic(page, KM_USER0);
+                        memset(kaddr + offset, 0, size);
+                        kunmap_atomic(kaddr, KM_USER0);
+                }
+                flush_dcache_page(page);
+                if (unlikely(aops->commit_write(file, page, offset,
+                                offset + size)))
+                        goto unlock;
+                if (unlikely(transfer_result))
+                        goto unlock;
+                bv_offs += size;
+                len -= size;
+                offset = 0;
+                index++;
+                pos += size;
+                unlock_page(page);
+                page_cache_release(page);
+        }
+out:
+        up(&mapping->host->i_sem);
+        return ret;
+unlock:
+        unlock_page(page);
+        page_cache_release(page);
+fail:
+        ret = -1;
+        goto out;
+}
+
+/**
+ * __do_lo_send_write - helper for writing data to a loop device
+ *
+ * This helper just factors out common code between do_lo_send_direct_write()
+ * and do_lo_send_write().
+ */
+static inline int __do_lo_send_write(struct file *file,
+                u8 __user *buf, const int len, loff_t pos)
+{
+        ssize_t bw;
+        mm_segment_t old_fs = get_fs();
+
+        set_fs(get_ds());
+        bw = file->f_op->write(file, buf, len, &pos);
+        set_fs(old_fs);
+        if (likely(bw == len))
+                return 0;
+        printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.\n",
+                        (unsigned long long)pos, len);
+        if (bw >= 0)
+                bw = -EIO;
+        return bw;
+}
+
+/**
+ * do_lo_send_direct_write - helper for writing data to a loop device
+ *
+ * This is the fast, non-transforming version for backing filesystems which do
+ * not implement the address space operations prepare_write and commit_write.
+ * It uses the write file operation which should be present on all writeable
+ * filesystems.
+ */
+static int do_lo_send_direct_write(struct loop_device *lo,
+                struct bio_vec *bvec, int bsize, loff_t pos, struct page *page)
+{
+        ssize_t bw = __do_lo_send_write(lo->lo_backing_file,
+                        (u8 __user *)kmap(bvec->bv_page) + bvec->bv_offset,
+                        bvec->bv_len, pos);
+        kunmap(bvec->bv_page);
+        cond_resched();
+        return bw;
+}
+
+/**
+ * do_lo_send_write - helper for writing data to a loop device
+ *
+ * This is the slow, transforming version for filesystems which do not
+ * implement the address space operations prepare_write and commit_write.  It
+ * uses the write file operation which should be present on all writeable
+ * filesystems.
+ *
+ * Using fops->write is slower than using aops->{prepare,commit}_write in the
+ * transforming case because we need to double buffer the data as we cannot do
+ * the transformations in place as we do not have direct access to the
+ * destination pages of the backing file.
+ */
+static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec,
+                int bsize, loff_t pos, struct page *page)
+{
+        int ret = lo_do_transfer(lo, WRITE, page, 0, bvec->bv_page,
+                        bvec->bv_offset, bvec->bv_len, pos >> 9);
+        if (likely(!ret))
+                return __do_lo_send_write(lo->lo_backing_file,
+                                (u8 __user *)page_address(page), bvec->bv_len,
+                                pos);
+        printk(KERN_ERR "loop: Transfer error at byte offset %llu, "
+                        "length %i.\n", (unsigned long long)pos, bvec->bv_len);
+        if (ret > 0)
+                ret = -EIO;
+        return ret;
+}
+
+static int lo_send(struct loop_device *lo, struct bio *bio, int bsize,
+                loff_t pos)
+{
+        int (*do_lo_send)(struct loop_device *, struct bio_vec *, int, loff_t,
+                        struct page *page);
+        struct bio_vec *bvec;
+        struct page *page = NULL;
+        int i, ret = 0;
+
+        do_lo_send = do_lo_send_aops;
+        if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) {
+                do_lo_send = do_lo_send_direct_write;
+                if (lo->transfer != transfer_none) {
+                        page = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
+                        if (unlikely(!page))
+                                goto fail;
+                        kmap(page);
+                        do_lo_send = do_lo_send_write;
+                }
+        }
+        bio_for_each_segment(bvec, bio, i) {
+                ret = do_lo_send(lo, bvec, bsize, pos, page);
+                if (ret < 0)
+                        break;
+                pos += bvec->bv_len;
+        }
+        if (page) {
+                kunmap(page);
+                __free_page(page);
+        }
+out:
+        return ret;
+fail:
+        printk(KERN_ERR "loop: Failed to allocate temporary page for write.\n");
+        ret = -ENOMEM;
+        goto out;
+}
+
+struct lo_read_data {
+        struct loop_device *lo;
+        struct page *page;
+        unsigned offset;
+        int bsize;
+};
+
+static int
+lo_read_actor(read_descriptor_t *desc, struct page *page,
+              unsigned long offset, unsigned long size)
+{
+        unsigned long count = desc->count;
+        struct lo_read_data *p = desc->arg.data;
+        struct loop_device *lo = p->lo;
+        sector_t IV;
+
+        IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
+
+        if (size > count)
+                size = count;
+
+        if (lo_do_transfer(lo, READ, page, offset, p->page, p->offset, size, IV)) {
+                size = 0;
+                printk(KERN_ERR "loop: transfer error block %ld\n",
+                       page->index);
+                desc->error = -EINVAL;
+        }
+
+        flush_dcache_page(p->page);
+
+        desc->count = count - size;
+        desc->written += size;
+        p->offset += 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.page = bvec->bv_page;
+        cookie.offset = 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);
+        return (retval < 0)? retval: 0;
+}
+
+static int
+lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
+{
+        struct bio_vec *bvec;
+        int i, ret = 0;
+
+        bio_for_each_segment(bvec, bio, i) {
+                ret = do_lo_receive(lo, bvec, bsize, pos);
+                if (ret < 0)
+                        break;
+                pos += bvec->bv_len;
+        }
+        return ret;
+}
+
+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;
+        if (bio_rw(bio) == WRITE)
+                ret = lo_send(lo, bio, lo->lo_blocksize, pos);
+        else
+                ret = lo_receive(lo, bio, lo->lo_blocksize, pos);
+        return ret;
+}
+
+/*
+ * 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;
+}
+
+static int loop_make_request(request_queue_t *q, struct bio *old_bio)
+{
+        struct loop_device *lo = q->queuedata;
+        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;
+        }
+        loop_add_bio(lo, old_bio);
+        return 0;
+err:
+        if (atomic_dec_and_test(&lo->lo_pending))
+                up(&lo->lo_bh_mutex);
+out:
+        bio_io_error(old_bio, old_bio->bi_size);
+        return 0;
+inactive:
+        spin_unlock_irq(&lo->lo_lock);
+        goto out;
+}
+
+/*
+ * kick off io on the underlying address space
+ */
+static void loop_unplug(request_queue_t *q)
+{
+        struct loop_device *lo = q->queuedata;
+
+        clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
+        blk_run_address_space(lo->lo_backing_file->f_mapping);
+}
+
+struct switch_request {
+        struct file *file;
+        struct completion wait;
+};
+
+static void do_loop_switch(struct loop_device *, struct switch_request *);
+
+static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
+{
+        int ret;
+
+        if (unlikely(!bio->bi_bdev)) {
+                do_loop_switch(lo, bio->bi_private);
+                bio_put(bio);
+        } else {
+                ret = do_bio_filebacked(lo, bio);
+                bio_endio(bio, bio->bi_size, ret);
+        }
+}
+
+/*
+ * 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("loop%d", lo->lo_number);
+
+        /*
+         * loop can be used in an encrypted device,
+         * hence, it mustn't be stopped at all
+         * because it could be indirectly used during suspension
+         */
+        current->flags |= PF_NOFREEZE;
+
+        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;
+}
+
+/*
+ * loop_switch performs the hard work of switching a backing store.
+ * First it needs to flush existing IO, it does this by sending a magic
+ * BIO down the pipe. The completion of this BIO does the actual switch.
+ */
+static int loop_switch(struct loop_device *lo, struct file *file)
+{
+        struct switch_request w;
+        struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+        if (!bio)
+                return -ENOMEM;
+        init_completion(&w.wait);
+        w.file = file;
+        bio->bi_private = &w;
+        bio->bi_bdev = NULL;
+        loop_make_request(lo->lo_queue, bio);
+        wait_for_completion(&w.wait);
+        return 0;
+}
+
+/*
+ * Do the actual switch; called from the BIO completion routine
+ */
+static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
+{
+        struct file *file = p->file;
+        struct file *old_file = lo->lo_backing_file;
+        struct address_space *mapping = file->f_mapping;
+
+        mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
+        lo->lo_backing_file = file;
+        lo->lo_blocksize = mapping->host->i_blksize;
+        lo->old_gfp_mask = mapping_gfp_mask(mapping);
+        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+        complete(&p->wait);
+}
+
+
+/*
+ * loop_change_fd switched the backing store of a loopback device to
+ * a new file. This is useful for operating system installers to free up
+ * the original file and in High Availability environments to switch to
+ * an alternative location for the content in case of server meltdown.
+ * This can only work if the loop device is used read-only, and if the
+ * new backing store is the same size and type as the old backing store.
+ */
+static int loop_change_fd(struct loop_device *lo, struct file *lo_file,
+                       struct block_device *bdev, unsigned int arg)
+{
+        struct file     *file, *old_file;
+        struct inode    *inode;
+        int             error;
+
+        error = -ENXIO;
+        if (lo->lo_state != Lo_bound)
+                goto out;
+
+        /* the loop device has to be read-only */
+        error = -EINVAL;
+        if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
+                goto out;
+
+        error = -EBADF;
+        file = fget(arg);
+        if (!file)
+                goto out;
+
+        inode = file->f_mapping->host;
+        old_file = lo->lo_backing_file;
+
+        error = -EINVAL;
+
+        if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+                goto out_putf;
+
+        /* new backing store needs to support loop (eg sendfile) */
+        if (!inode->i_fop->sendfile)
+                goto out_putf;
+
+        /* size of the new backing store needs to be the same */
+        if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
+                goto out_putf;
+
+        /* and ... switch */
+        error = loop_switch(lo, file);
+        if (error)
+                goto out_putf;
+
+        fput(old_file);
+        return 0;
+
+ out_putf:
+        fput(file);
+ out:
+        return error;
+}
+
+static inline int is_loop_device(struct file *file)
+{
+        struct inode *i = file->f_mapping->host;
+
+        return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
+}
+
+static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
+                       struct block_device *bdev, unsigned int arg)
+{
+        struct file     *file, *f;
+        struct inode    *inode;
+        struct address_space *mapping;
+        unsigned lo_blocksize;
+        int             lo_flags = 0;
+        int             error;
+        loff_t          size;
+
+        /* This is safe, since we have a reference from open(). */
+        __module_get(THIS_MODULE);
+
+        error = -EBADF;
+        file = fget(arg);
+        if (!file)
+                goto out;
+
+        error = -EBUSY;
+        if (lo->lo_state != Lo_unbound)
+                goto out_putf;
+
+        /* Avoid recursion */
+        f = file;
+        while (is_loop_device(f)) {
+                struct loop_device *l;
+
+                if (f->f_mapping->host->i_rdev == lo_file->f_mapping->host->i_rdev)
+                        goto out_putf;
+
+                l = f->f_mapping->host->i_bdev->bd_disk->private_data;
+                if (l->lo_state == Lo_unbound) {
+                        error = -EINVAL;
+                        goto out_putf;
+                }
+                f = l->lo_backing_file;
+        }
+
+        mapping = file->f_mapping;
+        inode = mapping->host;
+
+        if (!(file->f_mode & FMODE_WRITE))
+                lo_flags |= LO_FLAGS_READ_ONLY;
+
+        error = -EINVAL;
+        if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
+                struct address_space_operations *aops = mapping->a_ops;
+                /*
+                 * If we can't read - sorry. If we only can't write - well,
+                 * it's going to be read-only.
+                 */
+                if (!file->f_op->sendfile)
+                        goto out_putf;
+                if (aops->prepare_write && aops->commit_write)
+                        lo_flags |= LO_FLAGS_USE_AOPS;
+                if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
+                        lo_flags |= LO_FLAGS_READ_ONLY;
+
+                lo_blocksize = inode->i_blksize;
+                error = 0;
+        } else {
+                goto out_putf;
+        }
+
+        size = get_loop_size(lo, file);
+
+        if ((loff_t)(sector_t)size != size) {
+                error = -EFBIG;
+                goto out_putf;
+        }
+
+        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 = bdev;
+        lo->lo_flags = lo_flags;
+        lo->lo_backing_file = file;
+        lo->transfer = NULL;
+        lo->ioctl = NULL;
+        lo->lo_sizelimit = 0;
+        lo->old_gfp_mask = mapping_gfp_mask(mapping);
+        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+
+        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);
+        lo->lo_queue->queuedata = lo;
+        lo->lo_queue->unplug_fn = loop_unplug;
+
+        set_capacity(disks[lo->lo_number], size);
+        bd_set_size(bdev, size << 9);
+
+        set_blocksize(bdev, lo_blocksize);
+
+        kernel_thread(loop_thread, lo, CLONE_KERNEL);
+        down(&lo->lo_sem);
+        return 0;
+
+ out_putf:
+        fput(file);
+ out:
+        /* This is safe: open() is still holding a reference. */
+        module_put(THIS_MODULE);
+        return error;
+}
+
+static int
+loop_release_xfer(struct loop_device *lo)
+{
+        int err = 0;
+        struct loop_func_table *xfer = lo->lo_encryption;
+
+        if (xfer) {
+                if (xfer->release)
+                        err = xfer->release(lo);
+                lo->transfer = NULL;
+                lo->lo_encryption = NULL;
+                module_put(xfer->owner);
+        }
+        return err;
+}
+
+static int
+loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
+               const struct loop_info64 *i)
+{
+        int err = 0;
+
+        if (xfer) {
+                struct module *owner = xfer->owner;
+
+                if (!try_module_get(owner))
+                        return -EINVAL;
+                if (xfer->init)
+                        err = xfer->init(lo, i);
+                if (err)
+                        module_put(owner);
+                else
+                        lo->lo_encryption = xfer;
+        }
+        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_encryption = NULL;
+        lo->lo_offset = 0;
+        lo->lo_sizelimit = 0;
+        lo->lo_encrypt_key_size = 0;
+        lo->lo_flags = 0;
+        memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
+        memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
+        memset(lo->lo_file_name, 0, LO_NAME_SIZE);
+        invalidate_bdev(bdev, 0);
+        set_capacity(disks[lo->lo_number], 0);
+        bd_set_size(bdev, 0);
+        mapping_set_gfp_mask(filp->f_mapping, gfp);
+        lo->lo_state = Lo_unbound;
+        fput(filp);
+        /* This is safe: open() is still holding a reference. */
+        module_put(THIS_MODULE);
+        return 0;
+}
+
+static int
+loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+{
+        int err;
+        struct loop_func_table *xfer;
+
+        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 ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
+                return -EINVAL;
+
+        err = loop_release_xfer(lo);
+        if (err)
+                return err;
+
+        if (info->lo_encrypt_type) {
+                unsigned int type = info->lo_encrypt_type;
+
+                if (type >= MAX_LO_CRYPT)
+                        return -EINVAL;
+                xfer = xfer_funcs[type];
+                if (xfer == NULL)
+                        return -EINVAL;
+        } else
+                xfer = NULL;
+
+        err = loop_init_xfer(lo, xfer, info);
+        if (err)
+                return err;
+
+        if (lo->lo_offset != info->lo_offset ||
+            lo->lo_sizelimit != info->lo_sizelimit) {
+                lo->lo_offset = info->lo_offset;
+                lo->lo_sizelimit = info->lo_sizelimit;
+                if (figure_loop_size(lo))
+                        return -EFBIG;
+        }
+
+        memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
+        memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
+        lo->lo_file_name[LO_NAME_SIZE-1] = 0;
+        lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
+
+        if (!xfer)
+                xfer = &none_funcs;
+        lo->transfer = xfer->transfer;
+        lo->ioctl = xfer->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_info64 *info)
+{
+        struct file *file = lo->lo_backing_file;
+        struct kstat stat;
+        int error;
+
+        if (lo->lo_state != Lo_bound)
+                return -ENXIO;
+        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 = huge_encode_dev(stat.dev);
+        info->lo_inode = stat.ino;
+        info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
+        info->lo_offset = lo->lo_offset;
+        info->lo_sizelimit = lo->lo_sizelimit;
+        info->lo_flags = lo->lo_flags;
+        memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
+        memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
+        info->lo_encrypt_type =
+                lo->lo_encryption ? lo->lo_encryption->number : 0;
+        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 0;
+}
+
+static void
+loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
+{
+        memset(info64, 0, sizeof(*info64));
+        info64->lo_number = info->lo_number;
+        info64->lo_device = info->lo_device;
+        info64->lo_inode = info->lo_inode;
+        info64->lo_rdevice = info->lo_rdevice;
+        info64->lo_offset = info->lo_offset;
+        info64->lo_sizelimit = 0;
+        info64->lo_encrypt_type = info->lo_encrypt_type;
+        info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
+        info64->lo_flags = info->lo_flags;
+        info64->lo_init[0] = info->lo_init[0];
+        info64->lo_init[1] = info->lo_init[1];
+        if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+                memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
+        else
+                memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
+        memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
+}
+
+static int
+loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
+{
+        memset(info, 0, sizeof(*info));
+        info->lo_number = info64->lo_number;
+        info->lo_device = info64->lo_device;
+        info->lo_inode = info64->lo_inode;
+        info->lo_rdevice = info64->lo_rdevice;
+        info->lo_offset = info64->lo_offset;
+        info->lo_encrypt_type = info64->lo_encrypt_type;
+        info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
+        info->lo_flags = info64->lo_flags;
+        info->lo_init[0] = info64->lo_init[0];
+        info->lo_init[1] = info64->lo_init[1];
+        if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+                memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
+        else
+                memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
+        memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
+
+        /* error in case values were truncated */
+        if (info->lo_device != info64->lo_device ||
+            info->lo_rdevice != info64->lo_rdevice ||
+            info->lo_inode != info64->lo_inode ||
+            info->lo_offset != info64->lo_offset)
+                return -EOVERFLOW;
+
+        return 0;
+}
+
+static int
+loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
+{
+        struct loop_info info;
+        struct loop_info64 info64;
+
+        if (copy_from_user(&info, arg, sizeof (struct loop_info)))
+                return -EFAULT;
+        loop_info64_from_old(&info, &info64);
+        return loop_set_status(lo, &info64);
+}
+
+static int
+loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
+{
+        struct loop_info64 info64;
+
+        if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
+                return -EFAULT;
+        return loop_set_status(lo, &info64);
+}
+
+static int
+loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
+        struct loop_info info;
+        struct loop_info64 info64;
+        int err = 0;
+
+        if (!arg)
+                err = -EINVAL;
+        if (!err)
+                err = loop_get_status(lo, &info64);
+        if (!err)
+                err = loop_info64_to_old(&info64, &info);
+        if (!err && copy_to_user(arg, &info, sizeof(info)))
+                err = -EFAULT;
+
+        return err;
+}
+
+static int
+loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
+        struct loop_info64 info64;
+        int err = 0;
+
+        if (!arg)
+                err = -EINVAL;
+        if (!err)
+                err = loop_get_status(lo, &info64);
+        if (!err && copy_to_user(arg, &info64, sizeof(info64)))
+                err = -EFAULT;
+
+        return err;
+}
+
+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_CHANGE_FD:
+                err = loop_change_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_old(lo, (struct loop_info __user *) arg);
+                break;
+        case LOOP_GET_STATUS:
+                err = loop_get_status_old(lo, (struct loop_info __user *) arg);
+                break;
+        case LOOP_SET_STATUS64:
+                err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
+                break;
+        case LOOP_GET_STATUS64:
+                err = loop_get_status64(lo, (struct loop_info64 __user *) 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;
+
+        down(&lo->lo_ctl_mutex);
+        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;
+
+        down(&lo->lo_ctl_mutex);
+        --lo->lo_refcnt;
+        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_param(max_loop, int, 0);
+MODULE_PARM_DESC(max_loop, "Maximum number of loop devices (1-256)");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
+
+int loop_register_transfer(struct loop_func_table *funcs)
+{
+        unsigned int n = funcs->number;
+
+        if (n >= MAX_LO_CRYPT || xfer_funcs[n])
+                return -EINVAL;
+        xfer_funcs[n] = funcs;
+        return 0;
+}
+
+int loop_unregister_transfer(int number)
+{
+        unsigned int n = number;
+        struct loop_device *lo;
+        struct loop_func_table *xfer;
+
+        if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
+                return -EINVAL;
+
+        xfer_funcs[n] = NULL;
+
+        for (lo = &loop_dev[0]; lo < &loop_dev[max_loop]; lo++) {
+                down(&lo->lo_ctl_mutex);
+
+                if (lo->lo_encryption == xfer)
+                        loop_release_xfer(lo);
+
+                up(&lo->lo_ctl_mutex);
+        }
+
+        return 0;
+}
+
+EXPORT_SYMBOL(loop_register_transfer);
+EXPORT_SYMBOL(loop_unregister_transfer);
+
+static 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(LOOP_MAJOR, "loop"))
+                return -EIO;
+
+        loop_dev = kmalloc(max_loop * sizeof(struct loop_device), GFP_KERNEL);
+        if (!loop_dev)
+                goto out_mem1;
+        memset(loop_dev, 0, max_loop * sizeof(struct loop_device));
+
+        disks = kmalloc(max_loop * sizeof(struct gendisk *), GFP_KERNEL);
+        if (!disks)
+                goto out_mem2;
+
+        for (i = 0; i < max_loop; i++) {
+                disks[i] = alloc_disk(1);
+                if (!disks[i])
+                        goto out_mem3;
+        }
+
+        devfs_mk_dir("loop");
+
+        for (i = 0; i < max_loop; i++) {
+                struct loop_device *lo = &loop_dev[i];
+                struct gendisk *disk = disks[i];
+
+                memset(lo, 0, sizeof(*lo));
+                lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
+                if (!lo->lo_queue)
+                        goto out_mem4;
+                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);
+                sprintf(disk->devfs_name, "loop/%d", i);
+                disk->private_data = lo;
+                disk->queue = lo->lo_queue;
+        }
+
+        /* We cannot fail after we call this, so another loop!*/
+        for (i = 0; i < max_loop; i++)
+                add_disk(disks[i]);
+        printk(KERN_INFO "loop: loaded (max %d devices)\n", max_loop);
+        return 0;
+
+out_mem4:
+        while (i--)
+                blk_put_queue(loop_dev[i].lo_queue);
+        devfs_remove("loop");
+        i = max_loop;
+out_mem3:
+        while (i--)
+                put_disk(disks[i]);
+        kfree(disks);
+out_mem2:
+        kfree(loop_dev);
+out_mem1:
+        unregister_blkdev(LOOP_MAJOR, "loop");
+        printk(KERN_ERR "loop: ran out of memory\n");
+        return -ENOMEM;
+}
+
+static void loop_exit(void)
+{
+        int i;
+
+        for (i = 0; i < max_loop; i++) {
+                del_gendisk(disks[i]);
+                blk_put_queue(loop_dev[i].lo_queue);
+                put_disk(disks[i]);
+        }
+        devfs_remove("loop");
+        if (unregister_blkdev(LOOP_MAJOR, "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