/*
   *  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
   *
   * Support for falling back on the write file operation when the address space
   * operations write_begin is 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/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/swap.h>
  #include <linux/slab.h>
  #include <linux/compat.h>
  #include <linux/suspend.h>
  #include <linux/freezer.h>
  #include <linux/mutex.h>
  #include <linux/writeback.h>
  #include <linux/completion.h>
  #include <linux/highmem.h>
  #include <linux/kthread.h>
  #include <linux/splice.h>
  #include <linux/sysfs.h>
  #include <linux/miscdevice.h>
  #include <linux/falloc.h>
  #include "loop.h"
  
  #include <asm/uaccess.h>
  
  static DEFINE_IDR(loop_index_idr);
  static DEFINE_MUTEX(loop_index_mutex);
  
  static int max_part;
  static int part_shift;
  
  /*
   * 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) + raw_off;
  	char *loop_buf = kmap_atomic(loop_page) + loop_off;
  
  	if (cmd == READ)
  		memcpy(loop_buf, raw_buf, size);
  	else
  		memcpy(raw_buf, loop_buf, size);
  
  	kunmap_atomic(loop_buf);
  	kunmap_atomic(raw_buf);
  	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) + raw_off;
  	char *loop_buf = kmap_atomic(loop_page) + 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(loop_buf);
  	kunmap_atomic(raw_buf);
  	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_size(loff_t offset, loff_t sizelimit, struct file *file)
  {
  	loff_t loopsize;
  
  	/* Compute loopsize in bytes */
  	loopsize = i_size_read(file->f_mapping->host);
  	if (offset > 0)
  		loopsize -= offset;
  	/* offset is beyond i_size, weird but possible */
  	if (loopsize < 0)
  		return 0;
  
  	if (sizelimit > 0 && sizelimit < loopsize)
  		loopsize = 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 loff_t get_loop_size(struct loop_device *lo, struct file *file)
  {
  	return get_size(lo->lo_offset, lo->lo_sizelimit, file);
  }
  
  static int
  figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
  {
  	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
  	sector_t x = (sector_t)size;
  	struct block_device *bdev = lo->lo_device;
  
  	if (unlikely((loff_t)x != size))
  		return -EFBIG;
  	if (lo->lo_offset != offset)
  		lo->lo_offset = offset;
  	if (lo->lo_sizelimit != sizelimit)
  		lo->lo_sizelimit = sizelimit;
  	set_capacity(lo->lo_disk, x);
  	bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
  	/* let user-space know about the new size */
  	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
  	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_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 int __do_lo_send_write(struct file *file,
  		u8 *buf, const int len, loff_t pos)
  {
  	ssize_t bw;
  	mm_segment_t old_fs = get_fs();
  
  	file_start_write(file);
  	set_fs(get_ds());
  	bw = file->f_op->write(file, buf, len, &pos);
  	set_fs(old_fs);
  	file_end_write(file);
  	if (likely(bw == len))
  		return 0;
  	printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.
  ",
  			(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 that does not need double
   * buffering.
   */
  static int do_lo_send_direct_write(struct loop_device *lo,
  		struct bio_vec *bvec, loff_t pos, struct page *page)
  {
  	ssize_t bw = __do_lo_send_write(lo->lo_backing_file,
  			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 that needs to double buffer the
   * data as it cannot do the transformations in place without having direct
   * access to the destination pages of the backing file.
   */
  static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec,
  		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,
  				page_address(page), bvec->bv_len,
  				pos);
  	printk(KERN_ERR "loop: Transfer error at byte offset %llu, "
  			"length %i.
  ", (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, loff_t pos)
  {
  	int (*do_lo_send)(struct loop_device *, struct bio_vec *, loff_t,
  			struct page *page);
  	struct bio_vec bvec;
  	struct bvec_iter iter;
  	struct page *page = NULL;
  	int ret = 0;
  
  	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;
  	} else {
  		do_lo_send = do_lo_send_direct_write;
  	}
  
  	bio_for_each_segment(bvec, bio, iter) {
  		ret = do_lo_send(lo, &bvec, 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.
  ");
  	ret = -ENOMEM;
  	goto out;
  }
  
  struct lo_read_data {
  	struct loop_device *lo;
  	struct page *page;
  	unsigned offset;
  	int bsize;
  };
  
  static int
  lo_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
  		struct splice_desc *sd)
  {
  	struct lo_read_data *p = sd->u.data;
  	struct loop_device *lo = p->lo;
  	struct page *page = buf->page;
  	sector_t IV;
  	int size;
  
  	IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9)) +
  							(buf->offset >> 9);
  	size = sd->len;
  	if (size > p->bsize)
  		size = p->bsize;
  
  	if (lo_do_transfer(lo, READ, page, buf->offset, p->page, p->offset, size, IV)) {
  		printk(KERN_ERR "loop: transfer error block %ld
  ",
  		       page->index);
  		size = -EINVAL;
  	}
  
  	flush_dcache_page(p->page);
  
  	if (size > 0)
  		p->offset += size;
  
  	return size;
  }
  
  static int
  lo_direct_splice_actor(struct pipe_inode_info *pipe, struct splice_desc *sd)
  {
  	return __splice_from_pipe(pipe, sd, lo_splice_actor);
  }
  
  static ssize_t
  do_lo_receive(struct loop_device *lo,
  	      struct bio_vec *bvec, int bsize, loff_t pos)
  {
  	struct lo_read_data cookie;
  	struct splice_desc sd;
  	struct file *file;
  	ssize_t retval;
  
  	cookie.lo = lo;
  	cookie.page = bvec->bv_page;
  	cookie.offset = bvec->bv_offset;
  	cookie.bsize = bsize;
  
  	sd.len = 0;
  	sd.total_len = bvec->bv_len;
  	sd.flags = 0;
  	sd.pos = pos;
  	sd.u.data = &cookie;
  
  	file = lo->lo_backing_file;
  	retval = splice_direct_to_actor(file, &sd, lo_direct_splice_actor);
  
  	return retval;
  }
  
  static int
  lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
  {
  	struct bio_vec bvec;
  	struct bvec_iter iter;
  	ssize_t s;
  
  	bio_for_each_segment(bvec, bio, iter) {
  		s = do_lo_receive(lo, &bvec, bsize, pos);
  		if (s < 0)
  			return s;
  
  		if (s != bvec.bv_len) {
  			zero_fill_bio(bio);
  			break;
  		}
  		pos += bvec.bv_len;
  	}
  	return 0;
  }
  
  static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
  {
  	loff_t pos;
  	int ret;
  
  	pos = ((loff_t) bio->bi_iter.bi_sector << 9) + lo->lo_offset;
  
  	if (bio_rw(bio) == WRITE) {
  		struct file *file = lo->lo_backing_file;
  
  		if (bio->bi_rw & REQ_FLUSH) {
  			ret = vfs_fsync(file, 0);
  			if (unlikely(ret && ret != -EINVAL)) {
  				ret = -EIO;
  				goto out;
  			}
  		}
  
  		/*
  		 * We use punch hole to reclaim the free space used by the
  		 * image a.k.a. discard. However we do not support discard if
  		 * encryption is enabled, because it may give an attacker
  		 * useful information.
  		 */
  		if (bio->bi_rw & REQ_DISCARD) {
  			struct file *file = lo->lo_backing_file;
  			int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
  
  			if ((!file->f_op->fallocate) ||
  			    lo->lo_encrypt_key_size) {
  				ret = -EOPNOTSUPP;
  				goto out;
  			}
  			ret = file->f_op->fallocate(file, mode, pos,
  						    bio->bi_iter.bi_size);
  			if (unlikely(ret && ret != -EINVAL &&
  				     ret != -EOPNOTSUPP))
  				ret = -EIO;
  			goto out;
  		}
  
  		ret = lo_send(lo, bio, pos);
  
  		if ((bio->bi_rw & REQ_FUA) && !ret) {
  			ret = vfs_fsync(file, 0);
  			if (unlikely(ret && ret != -EINVAL))
  				ret = -EIO;
  		}
  	} else
  		ret = lo_receive(lo, bio, lo->lo_blocksize, pos);
  
  out:
  	return ret;
  }
  
  /*
   * Add bio to back of pending list
   */
  static void loop_add_bio(struct loop_device *lo, struct bio *bio)
  {
  	lo->lo_bio_count++;
  	bio_list_add(&lo->lo_bio_list, bio);
  }
  
  /*
   * Grab first pending buffer
   */
  static struct bio *loop_get_bio(struct loop_device *lo)
  {
  	lo->lo_bio_count--;
  	return bio_list_pop(&lo->lo_bio_list);
  }
  
  static void loop_make_request(struct request_queue *q, struct bio *old_bio)
  {
  	struct loop_device *lo = q->queuedata;
  	int rw = bio_rw(old_bio);
  
  	if (rw == READA)
  		rw = READ;
  
  	BUG_ON(!lo || (rw != READ && rw != WRITE));
  
  	spin_lock_irq(&lo->lo_lock);
  	if (lo->lo_state != Lo_bound)
  		goto out;
  	if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
  		goto out;
  	if (lo->lo_bio_count >= q->nr_congestion_on)
  		wait_event_lock_irq(lo->lo_req_wait,
  				    lo->lo_bio_count < q->nr_congestion_off,
  				    lo->lo_lock);
  	loop_add_bio(lo, old_bio);
  	wake_up(&lo->lo_event);
  	spin_unlock_irq(&lo->lo_lock);
  	return;
  
  out:
  	spin_unlock_irq(&lo->lo_lock);
  	bio_io_error(old_bio);
  }
  
  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)
  {
  	if (unlikely(!bio->bi_bdev)) {
  		do_loop_switch(lo, bio->bi_private);
  		bio_put(bio);
  	} else {
  		int ret = do_bio_filebacked(lo, bio);
  		bio_endio(bio, 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.
   *
   * Loop explanation:  loop_clr_fd() sets lo_state to Lo_rundown before
   * calling kthread_stop().  Therefore once kthread_should_stop() is
   * true, make_request will not place any more requests.  Therefore
   * once kthread_should_stop() is true and lo_bio is NULL, we are
   * done with the loop.
   */
  static int loop_thread(void *data)
  {
  	struct loop_device *lo = data;
  	struct bio *bio;
  
  	set_user_nice(current, -20);
  
  	while (!kthread_should_stop() || !bio_list_empty(&lo->lo_bio_list)) {
  
  		wait_event_interruptible(lo->lo_event,
  				!bio_list_empty(&lo->lo_bio_list) ||
  				kthread_should_stop());
  
  		if (bio_list_empty(&lo->lo_bio_list))
  			continue;
  		spin_lock_irq(&lo->lo_lock);
  		bio = loop_get_bio(lo);
  		if (lo->lo_bio_count < lo->lo_queue->nr_congestion_off)
  			wake_up(&lo->lo_req_wait);
  		spin_unlock_irq(&lo->lo_lock);
  
  		BUG_ON(!bio);
  		loop_handle_bio(lo, bio);
  	}
  
  	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, 0);
  	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;
  }
  
  /*
   * Helper to flush the IOs in loop, but keeping loop thread running
   */
  static int loop_flush(struct loop_device *lo)
  {
  	/* loop not yet configured, no running thread, nothing to flush */
  	if (!lo->lo_thread)
  		return 0;
  
  	return loop_switch(lo, NULL);
  }
  
  /*
   * 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;
  
  	/* if no new file, only flush of queued bios requested */
  	if (!file)
  		goto out;
  
  	mapping = file->f_mapping;
  	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
  	lo->lo_backing_file = file;
  	lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
  		mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
  	lo->old_gfp_mask = mapping_gfp_mask(mapping);
  	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
  out:
  	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 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;
  
  	/* 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);
  	if (lo->lo_flags & LO_FLAGS_PARTSCAN)
  		ioctl_by_bdev(bdev, BLKRRPART, 0);
  	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;
  }
  
  /* loop sysfs attributes */
  
  static ssize_t loop_attr_show(struct device *dev, char *page,
  			      ssize_t (*callback)(struct loop_device *, char *))
  {
  	struct gendisk *disk = dev_to_disk(dev);
  	struct loop_device *lo = disk->private_data;
  
  	return callback(lo, page);
  }
  
  #define LOOP_ATTR_RO(_name)						\
  static ssize_t loop_attr_##_name##_show(struct loop_device *, char *);	\
  static ssize_t loop_attr_do_show_##_name(struct device *d,		\
  				struct device_attribute *attr, char *b)	\
  {									\
  	return loop_attr_show(d, b, loop_attr_##_name##_show);		\
  }									\
  static struct device_attribute loop_attr_##_name =			\
  	__ATTR(_name, S_IRUGO, loop_attr_do_show_##_name, NULL);
  
  static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
  {
  	ssize_t ret;
  	char *p = NULL;
  
  	spin_lock_irq(&lo->lo_lock);
  	if (lo->lo_backing_file)
  		p = d_path(&lo->lo_backing_file->f_path, buf, PAGE_SIZE - 1);
  	spin_unlock_irq(&lo->lo_lock);
  
  	if (IS_ERR_OR_NULL(p))
  		ret = PTR_ERR(p);
  	else {
  		ret = strlen(p);
  		memmove(buf, p, ret);
  		buf[ret++] = '
  ';
  		buf[ret] = 0;
  	}
  
  	return ret;
  }
  
  static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
  {
  	return sprintf(buf, "%llu
  ", (unsigned long long)lo->lo_offset);
  }
  
  static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
  {
  	return sprintf(buf, "%llu
  ", (unsigned long long)lo->lo_sizelimit);
  }
  
  static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
  {
  	int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
  
  	return sprintf(buf, "%s
  ", autoclear ? "1" : "0");
  }
  
  static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
  {
  	int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
  
  	return sprintf(buf, "%s
  ", partscan ? "1" : "0");
  }
  
  LOOP_ATTR_RO(backing_file);
  LOOP_ATTR_RO(offset);
  LOOP_ATTR_RO(sizelimit);
  LOOP_ATTR_RO(autoclear);
  LOOP_ATTR_RO(partscan);
  
  static struct attribute *loop_attrs[] = {
  	&loop_attr_backing_file.attr,
  	&loop_attr_offset.attr,
  	&loop_attr_sizelimit.attr,
  	&loop_attr_autoclear.attr,
  	&loop_attr_partscan.attr,
  	NULL,
  };
  
  static struct attribute_group loop_attribute_group = {
  	.name = "loop",
  	.attrs= loop_attrs,
  };
  
  static int loop_sysfs_init(struct loop_device *lo)
  {
  	return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
  				  &loop_attribute_group);
  }
  
  static void loop_sysfs_exit(struct loop_device *lo)
  {
  	sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
  			   &loop_attribute_group);
  }
  
  static void loop_config_discard(struct loop_device *lo)
  {
  	struct file *file = lo->lo_backing_file;
  	struct inode *inode = file->f_mapping->host;
  	struct request_queue *q = lo->lo_queue;
  
  	/*
  	 * We use punch hole to reclaim the free space used by the
  	 * image a.k.a. discard. However we do not support discard if
  	 * encryption is enabled, because it may give an attacker
  	 * useful information.
  	 */
  	if ((!file->f_op->fallocate) ||
  	    lo->lo_encrypt_key_size) {
  		q->limits.discard_granularity = 0;
  		q->limits.discard_alignment = 0;
  		q->limits.max_discard_sectors = 0;
  		q->limits.discard_zeroes_data = 0;
  		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
  		return;
  	}
  
  	q->limits.discard_granularity = inode->i_sb->s_blocksize;
  	q->limits.discard_alignment = 0;
  	q->limits.max_discard_sectors = UINT_MAX >> 9;
  	q->limits.discard_zeroes_data = 1;
  	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
  }
  
  static int loop_set_fd(struct loop_device *lo, fmode_t mode,
  		       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_bdev == bdev)
  			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;
  
  	error = -EINVAL;
  	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
  		goto out_putf;
  
  	if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
  	    !file->f_op->write)
  		lo_flags |= LO_FLAGS_READ_ONLY;
  
  	lo_blocksize = S_ISBLK(inode->i_mode) ?
  		inode->i_bdev->bd_block_size : PAGE_SIZE;
  
  	error = -EFBIG;
  	size = get_loop_size(lo, file);
  	if ((loff_t)(sector_t)size != size)
  		goto out_putf;
  
  	error = 0;
  
  	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 = transfer_none;
  	lo->ioctl = NULL;
  	lo->lo_sizelimit = 0;
  	lo->lo_bio_count = 0;
  	lo->old_gfp_mask = mapping_gfp_mask(mapping);
  	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
  
  	bio_list_init(&lo->lo_bio_list);
  
  	if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
  		blk_queue_flush(lo->lo_queue, REQ_FLUSH);
  
  	set_capacity(lo->lo_disk, size);
  	bd_set_size(bdev, size << 9);
  	loop_sysfs_init(lo);
  	/* let user-space know about the new size */
  	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
  
  	set_blocksize(bdev, lo_blocksize);
  
  	lo->lo_thread = kthread_create(loop_thread, lo, "loop%d",
  						lo->lo_number);
  	if (IS_ERR(lo->lo_thread)) {
  		error = PTR_ERR(lo->lo_thread);
  		goto out_clr;
  	}
  	lo->lo_state = Lo_bound;
  	wake_up_process(lo->lo_thread);
  	if (part_shift)
  		lo->lo_flags |= LO_FLAGS_PARTSCAN;
  	if (lo->lo_flags & LO_FLAGS_PARTSCAN)
  		ioctl_by_bdev(bdev, BLKRRPART, 0);
  
  	/* Grab the block_device to prevent its destruction after we
  	 * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
  	 */
  	bdgrab(bdev);
  	return 0;
  
  out_clr:
  	loop_sysfs_exit(lo);
  	lo->lo_thread = NULL;
  	lo->lo_device = NULL;
  	lo->lo_backing_file = NULL;
  	lo->lo_flags = 0;
  	set_capacity(lo->lo_disk, 0);
  	invalidate_bdev(bdev);
  	bd_set_size(bdev, 0);
  	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
  	mapping_set_gfp_mask(mapping, lo->old_gfp_mask);
  	lo->lo_state = Lo_unbound;
   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 file *filp = lo->lo_backing_file;
  	gfp_t gfp = lo->old_gfp_mask;
  	struct block_device *bdev = lo->lo_device;
  
  	if (lo->lo_state != Lo_bound)
  		return -ENXIO;
  
  	/*
  	 * If we've explicitly asked to tear down the loop device,
  	 * and it has an elevated reference count, set it for auto-teardown when
  	 * the last reference goes away. This stops $!~#$@ udev from
  	 * preventing teardown because it decided that it needs to run blkid on
  	 * the loopback device whenever they appear. xfstests is notorious for
  	 * failing tests because blkid via udev races with a losetup
  	 * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
  	 * command to fail with EBUSY.
  	 */
  	if (lo->lo_refcnt > 1) {
  		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
  		mutex_unlock(&lo->lo_ctl_mutex);
  		return 0;
  	}
  
  	if (filp == NULL)
  		return -EINVAL;
  
  	spin_lock_irq(&lo->lo_lock);
  	lo->lo_state = Lo_rundown;
  	spin_unlock_irq(&lo->lo_lock);
  
  	kthread_stop(lo->lo_thread);
  
  	spin_lock_irq(&lo->lo_lock);
  	lo->lo_backing_file = NULL;
  	spin_unlock_irq(&lo->lo_lock);
  
  	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_thread = NULL;
  	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);
  	if (bdev) {
  		bdput(bdev);
  		invalidate_bdev(bdev);
  	}
  	set_capacity(lo->lo_disk, 0);
  	loop_sysfs_exit(lo);
  	if (bdev) {
  		bd_set_size(bdev, 0);
  		/* let user-space know about this change */
  		kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
  	}
  	mapping_set_gfp_mask(filp->f_mapping, gfp);
  	lo->lo_state = Lo_unbound;
  	/* This is safe: open() is still holding a reference. */
  	module_put(THIS_MODULE);
  	if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
  		ioctl_by_bdev(bdev, BLKRRPART, 0);
  	lo->lo_flags = 0;
  	if (!part_shift)
  		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
  	mutex_unlock(&lo->lo_ctl_mutex);
  	/*
  	 * Need not hold lo_ctl_mutex to fput backing file.
  	 * Calling fput holding lo_ctl_mutex triggers a circular
  	 * lock dependency possibility warning as fput can take
  	 * bd_mutex which is usually taken before lo_ctl_mutex.
  	 */
  	fput(filp);
  	return 0;
  }
  
  static int
  loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
  {
  	int err;
  	struct loop_func_table *xfer;
  	kuid_t uid = current_uid();
  
  	if (lo->lo_encrypt_key_size &&
  	    !uid_eq(lo->lo_key_owner, 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)
  		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
  			return -EFBIG;
  
  	loop_config_discard(lo);
  
  	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;
  
  	if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
  	     (info->lo_flags & LO_FLAGS_AUTOCLEAR))
  		lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
  
  	if ((info->lo_flags & LO_FLAGS_PARTSCAN) &&
  	     !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
  		lo->lo_flags |= LO_FLAGS_PARTSCAN;
  		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
  		ioctl_by_bdev(lo->lo_device, BLKRRPART, 0);
  	}
  
  	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 = 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_path, &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 loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
  {
  	if (unlikely(lo->lo_state != Lo_bound))
  		return -ENXIO;
  
  	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
  }
  
  static int lo_ioctl(struct block_device *bdev, fmode_t mode,
  	unsigned int cmd, unsigned long arg)
  {
  	struct loop_device *lo = bdev->bd_disk->private_data;
  	int err;
  
  	mutex_lock_nested(&lo->lo_ctl_mutex, 1);
  	switch (cmd) {
  	case LOOP_SET_FD:
  		err = loop_set_fd(lo, mode, bdev, arg);
  		break;
  	case LOOP_CHANGE_FD:
  		err = loop_change_fd(lo, bdev, arg);
  		break;
  	case LOOP_CLR_FD:
  		/* loop_clr_fd would have unlocked lo_ctl_mutex on success */
  		err = loop_clr_fd(lo);
  		if (!err)
  			goto out_unlocked;
  		break;
  	case LOOP_SET_STATUS:
  		err = -EPERM;
  		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
  			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 = -EPERM;
  		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
  			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;
  	case LOOP_SET_CAPACITY:
  		err = -EPERM;
  		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
  			err = loop_set_capacity(lo, bdev);
  		break;
  	default:
  		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
  	}
  	mutex_unlock(&lo->lo_ctl_mutex);
  
  out_unlocked:
  	return err;
  }
  
  #ifdef CONFIG_COMPAT
  struct compat_loop_info {
  	compat_int_t	lo_number;      /* ioctl r/o */
  	compat_dev_t	lo_device;      /* ioctl r/o */
  	compat_ulong_t	lo_inode;       /* ioctl r/o */
  	compat_dev_t	lo_rdevice;     /* ioctl r/o */
  	compat_int_t	lo_offset;
  	compat_int_t	lo_encrypt_type;
  	compat_int_t	lo_encrypt_key_size;    /* ioctl w/o */
  	compat_int_t	lo_flags;       /* ioctl r/o */
  	char		lo_name[LO_NAME_SIZE];
  	unsigned char	lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
  	compat_ulong_t	lo_init[2];
  	char		reserved[4];
  };
  
  /*
   * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
   * - noinlined to reduce stack space usage in main part of driver
   */
  static noinline int
  loop_info64_from_compat(const struct compat_loop_info __user *arg,
  			struct loop_info64 *info64)
  {
  	struct compat_loop_info info;
  
  	if (copy_from_user(&info, arg, sizeof(info)))
  		return -EFAULT;
  
  	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);
  	return 0;
  }
  
  /*
   * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
   * - noinlined to reduce stack space usage in main part of driver
   */
  static noinline int
  loop_info64_to_compat(const struct loop_info64 *info64,
  		      struct compat_loop_info __user *arg)
  {
  	struct compat_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 ||
  	    info.lo_init[0] != info64->lo_init[0] ||
  	    info.lo_init[1] != info64->lo_init[1])
  		return -EOVERFLOW;
  
  	if (copy_to_user(arg, &info, sizeof(info)))
  		return -EFAULT;
  	return 0;
  }
  
  static int
  loop_set_status_compat(struct loop_device *lo,
  		       const struct compat_loop_info __user *arg)
  {
  	struct loop_info64 info64;
  	int ret;
  
  	ret = loop_info64_from_compat(arg, &info64);
  	if (ret < 0)
  		return ret;
  	return loop_set_status(lo, &info64);
  }
  
  static int
  loop_get_status_compat(struct loop_device *lo,
  		       struct compat_loop_info __user *arg)
  {
  	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_compat(&info64, arg);
  	return err;
  }
  
  static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
  			   unsigned int cmd, unsigned long arg)
  {
  	struct loop_device *lo = bdev->bd_disk->private_data;
  	int err;
  
  	switch(cmd) {
  	case LOOP_SET_STATUS:
  		mutex_lock(&lo->lo_ctl_mutex);
  		err = loop_set_status_compat(
  			lo, (const struct compat_loop_info __user *) arg);
  		mutex_unlock(&lo->lo_ctl_mutex);
  		break;
  	case LOOP_GET_STATUS:
  		mutex_lock(&lo->lo_ctl_mutex);
  		err = loop_get_status_compat(
  			lo, (struct compat_loop_info __user *) arg);
  		mutex_unlock(&lo->lo_ctl_mutex);
  		break;
  	case LOOP_SET_CAPACITY:
  	case LOOP_CLR_FD:
  	case LOOP_GET_STATUS64:
  	case LOOP_SET_STATUS64:
  		arg = (unsigned long) compat_ptr(arg);
  	case LOOP_SET_FD:
  	case LOOP_CHANGE_FD:
  		err = lo_ioctl(bdev, mode, cmd, arg);
  		break;
  	default:
  		err = -ENOIOCTLCMD;
  		break;
  	}
  	return err;
  }
  #endif
  
  static int lo_open(struct block_device *bdev, fmode_t mode)
  {
  	struct loop_device *lo;
  	int err = 0;
  
  	mutex_lock(&loop_index_mutex);
  	lo = bdev->bd_disk->private_data;
  	if (!lo) {
  		err = -ENXIO;
  		goto out;
  	}
  
  	mutex_lock(&lo->lo_ctl_mutex);
  	lo->lo_refcnt++;
  	mutex_unlock(&lo->lo_ctl_mutex);
  out:
  	mutex_unlock(&loop_index_mutex);
  	return err;
  }
  
  static void lo_release(struct gendisk *disk, fmode_t mode)
  {
  	struct loop_device *lo = disk->private_data;
  	int err;
  
  	mutex_lock(&lo->lo_ctl_mutex);
  
  	if (--lo->lo_refcnt)
  		goto out;
  
  	if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
  		/*
  		 * In autoclear mode, stop the loop thread
  		 * and remove configuration after last close.
  		 */
  		err = loop_clr_fd(lo);
  		if (!err)
  			return;
  	} else {
  		/*
  		 * Otherwise keep thread (if running) and config,
  		 * but flush possible ongoing bios in thread.
  		 */
  		loop_flush(lo);
  	}
  
  out:
  	mutex_unlock(&lo->lo_ctl_mutex);
  }
  
  static const struct block_device_operations lo_fops = {
  	.owner =	THIS_MODULE,
  	.open =		lo_open,
  	.release =	lo_release,
  	.ioctl =	lo_ioctl,
  #ifdef CONFIG_COMPAT
  	.compat_ioctl =	lo_compat_ioctl,
  #endif
  };
  
  /*
   * And now the modules code and kernel interface.
   */
  static int max_loop;
  module_param(max_loop, int, S_IRUGO);
  MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
  module_param(max_part, int, S_IRUGO);
  MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
  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;
  }
  
  static int unregister_transfer_cb(int id, void *ptr, void *data)
  {
  	struct loop_device *lo = ptr;
  	struct loop_func_table *xfer = data;
  
  	mutex_lock(&lo->lo_ctl_mutex);
  	if (lo->lo_encryption == xfer)
  		loop_release_xfer(lo);
  	mutex_unlock(&lo->lo_ctl_mutex);
  	return 0;
  }
  
  int loop_unregister_transfer(int number)
  {
  	unsigned int n = number;
  	struct loop_func_table *xfer;
  
  	if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
  		return -EINVAL;
  
  	xfer_funcs[n] = NULL;
  	idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
  	return 0;
  }
  
  EXPORT_SYMBOL(loop_register_transfer);
  EXPORT_SYMBOL(loop_unregister_transfer);
  
  static int loop_add(struct loop_device **l, int i)
  {
  	struct loop_device *lo;
  	struct gendisk *disk;
  	int err;
  
  	err = -ENOMEM;
  	lo = kzalloc(sizeof(*lo), GFP_KERNEL);
  	if (!lo)
  		goto out;
  
  	lo->lo_state = Lo_unbound;
  
  	/* allocate id, if @id >= 0, we're requesting that specific id */
  	if (i >= 0) {
  		err = idr_alloc(&loop_index_idr, lo, i, i + 1, GFP_KERNEL);
  		if (err == -ENOSPC)
  			err = -EEXIST;
  	} else {
  		err = idr_alloc(&loop_index_idr, lo, 0, 0, GFP_KERNEL);
  	}
  	if (err < 0)
  		goto out_free_dev;
  	i = err;
  
  	err = -ENOMEM;
  	lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
  	if (!lo->lo_queue)
  		goto out_free_idr;
  
  	/*
  	 * set queue make_request_fn
  	 */
  	blk_queue_make_request(lo->lo_queue, loop_make_request);
  	lo->lo_queue->queuedata = lo;
  
  	disk = lo->lo_disk = alloc_disk(1 << part_shift);
  	if (!disk)
  		goto out_free_queue;
  
  	/*
  	 * Disable partition scanning by default. The in-kernel partition
  	 * scanning can be requested individually per-device during its
  	 * setup. Userspace can always add and remove partitions from all
  	 * devices. The needed partition minors are allocated from the
  	 * extended minor space, the main loop device numbers will continue
  	 * to match the loop minors, regardless of the number of partitions
  	 * used.
  	 *
  	 * If max_part is given, partition scanning is globally enabled for
  	 * all loop devices. The minors for the main loop devices will be
  	 * multiples of max_part.
  	 *
  	 * Note: Global-for-all-devices, set-only-at-init, read-only module
  	 * parameteters like 'max_loop' and 'max_part' make things needlessly
  	 * complicated, are too static, inflexible and may surprise
  	 * userspace tools. Parameters like this in general should be avoided.
  	 */
  	if (!part_shift)
  		disk->flags |= GENHD_FL_NO_PART_SCAN;
  	disk->flags |= GENHD_FL_EXT_DEVT;
  	mutex_init(&lo->lo_ctl_mutex);
  	lo->lo_number		= i;
  	lo->lo_thread		= NULL;
  	init_waitqueue_head(&lo->lo_event);
  	init_waitqueue_head(&lo->lo_req_wait);
  	spin_lock_init(&lo->lo_lock);
  	disk->major		= LOOP_MAJOR;
  	disk->first_minor	= i << part_shift;
  	disk->fops		= &lo_fops;
  	disk->private_data	= lo;
  	disk->queue		= lo->lo_queue;
  	sprintf(disk->disk_name, "loop%d", i);
  	add_disk(disk);
  	*l = lo;
  	return lo->lo_number;
  
  out_free_queue:
  	blk_cleanup_queue(lo->lo_queue);
  out_free_idr:
  	idr_remove(&loop_index_idr, i);
  out_free_dev:
  	kfree(lo);
  out:
  	return err;
  }
  
  static void loop_remove(struct loop_device *lo)
  {
  	del_gendisk(lo->lo_disk);
  	blk_cleanup_queue(lo->lo_queue);
  	put_disk(lo->lo_disk);
  	kfree(lo);
  }
  
  static int find_free_cb(int id, void *ptr, void *data)
  {
  	struct loop_device *lo = ptr;
  	struct loop_device **l = data;
  
  	if (lo->lo_state == Lo_unbound) {
  		*l = lo;
  		return 1;
  	}
  	return 0;
  }
  
  static int loop_lookup(struct loop_device **l, int i)
  {
  	struct loop_device *lo;
  	int ret = -ENODEV;
  
  	if (i < 0) {
  		int err;
  
  		err = idr_for_each(&loop_index_idr, &find_free_cb, &lo);
  		if (err == 1) {
  			*l = lo;
  			ret = lo->lo_number;
  		}
  		goto out;
  	}
  
  	/* lookup and return a specific i */
  	lo = idr_find(&loop_index_idr, i);
  	if (lo) {
  		*l = lo;
  		ret = lo->lo_number;
  	}
  out:
  	return ret;
  }
  
  static struct kobject *loop_probe(dev_t dev, int *part, void *data)
  {
  	struct loop_device *lo;
  	struct kobject *kobj;
  	int err;
  
  	mutex_lock(&loop_index_mutex);
  	err = loop_lookup(&lo, MINOR(dev) >> part_shift);
  	if (err < 0)
  		err = loop_add(&lo, MINOR(dev) >> part_shift);
  	if (err < 0)
  		kobj = NULL;
  	else
  		kobj = get_disk(lo->lo_disk);
  	mutex_unlock(&loop_index_mutex);
  
  	*part = 0;
  	return kobj;
  }
  
  static long loop_control_ioctl(struct file *file, unsigned int cmd,
  			       unsigned long parm)
  {
  	struct loop_device *lo;
  	int ret = -ENOSYS;
  
  	mutex_lock(&loop_index_mutex);
  	switch (cmd) {
  	case LOOP_CTL_ADD:
  		ret = loop_lookup(&lo, parm);
  		if (ret >= 0) {
  			ret = -EEXIST;
  			break;
  		}
  		ret = loop_add(&lo, parm);
  		break;
  	case LOOP_CTL_REMOVE:
  		ret = loop_lookup(&lo, parm);
  		if (ret < 0)
  			break;
  		mutex_lock(&lo->lo_ctl_mutex);
  		if (lo->lo_state != Lo_unbound) {
  			ret = -EBUSY;
  			mutex_unlock(&lo->lo_ctl_mutex);
  			break;
  		}
  		if (lo->lo_refcnt > 0) {
  			ret = -EBUSY;
  			mutex_unlock(&lo->lo_ctl_mutex);
  			break;
  		}
  		lo->lo_disk->private_data = NULL;
  		mutex_unlock(&lo->lo_ctl_mutex);
  		idr_remove(&loop_index_idr, lo->lo_number);
  		loop_remove(lo);
  		break;
  	case LOOP_CTL_GET_FREE:
  		ret = loop_lookup(&lo, -1);
  		if (ret >= 0)
  			break;
  		ret = loop_add(&lo, -1);
  	}
  	mutex_unlock(&loop_index_mutex);
  
  	return ret;
  }
  
  static const struct file_operations loop_ctl_fops = {
  	.open		= nonseekable_open,
  	.unlocked_ioctl	= loop_control_ioctl,
  	.compat_ioctl	= loop_control_ioctl,
  	.owner		= THIS_MODULE,
  	.llseek		= noop_llseek,
  };
  
  static struct miscdevice loop_misc = {
  	.minor		= LOOP_CTRL_MINOR,
  	.name		= "loop-control",
  	.fops		= &loop_ctl_fops,
  };
  
  MODULE_ALIAS_MISCDEV(LOOP_CTRL_MINOR);
  MODULE_ALIAS("devname:loop-control");
  
  static int __init loop_init(void)
  {
  	int i, nr;
  	unsigned long range;
  	struct loop_device *lo;
  	int err;
  
  	err = misc_register(&loop_misc);
  	if (err < 0)
  		return err;
  
  	part_shift = 0;
  	if (max_part > 0) {
  		part_shift = fls(max_part);
  
  		/*
  		 * Adjust max_part according to part_shift as it is exported
  		 * to user space so that user can decide correct minor number
  		 * if [s]he want to create more devices.
  		 *
  		 * Note that -1 is required because partition 0 is reserved
  		 * for the whole disk.
  		 */
  		max_part = (1UL << part_shift) - 1;
  	}
  
  	if ((1UL << part_shift) > DISK_MAX_PARTS) {
  		err = -EINVAL;
  		goto misc_out;
  	}
  
  	if (max_loop > 1UL << (MINORBITS - part_shift)) {
  		err = -EINVAL;
  		goto misc_out;
  	}
  
  	/*
  	 * If max_loop is specified, create that many devices upfront.
  	 * This also becomes a hard limit. If max_loop is not specified,
  	 * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
  	 * init time. Loop devices can be requested on-demand with the
  	 * /dev/loop-control interface, or be instantiated by accessing
  	 * a 'dead' device node.
  	 */
  	if (max_loop) {
  		nr = max_loop;
  		range = max_loop << part_shift;
  	} else {
  		nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
  		range = 1UL << MINORBITS;
  	}
  
  	if (register_blkdev(LOOP_MAJOR, "loop")) {
  		err = -EIO;
  		goto misc_out;
  	}
  
  	blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
  				  THIS_MODULE, loop_probe, NULL, NULL);
  
  	/* pre-create number of devices given by config or max_loop */
  	mutex_lock(&loop_index_mutex);
  	for (i = 0; i < nr; i++)
  		loop_add(&lo, i);
  	mutex_unlock(&loop_index_mutex);
  
  	printk(KERN_INFO "loop: module loaded
  ");
  	return 0;
  
  misc_out:
  	misc_deregister(&loop_misc);
  	return err;
  }
  
  static int loop_exit_cb(int id, void *ptr, void *data)
  {
  	struct loop_device *lo = ptr;
  
  	loop_remove(lo);
  	return 0;
  }
  
  static void __exit loop_exit(void)
  {
  	unsigned long range;
  
  	range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
  
  	idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
  	idr_destroy(&loop_index_idr);
  
  	blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
  	unregister_blkdev(LOOP_MAJOR, "loop");
  
  	misc_deregister(&loop_misc);
  }
  
  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