[T106][ZXW-22]7520V3SCV2.01.01.02P42U09_VEC_V0.8_AP_VEC origin source commit

Change-Id: Ic6e05d89ecd62fc34f82b23dcf306c93764aec4b
diff --git a/ap/os/linux/linux-3.4.x/drivers/block/loop.c b/ap/os/linux/linux-3.4.x/drivers/block/loop.c
new file mode 100644
index 0000000..462fd18
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/drivers/block/loop.c
@@ -0,0 +1,1930 @@
+/*
+ *  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/loop.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 <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 size, loopsize;
+
+	/* Compute loopsize in bytes */
+	size = i_size_read(file->f_mapping->host);
+	loopsize = size - offset;
+	/* offset is beyond i_size, wierd 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;
+
+	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);
+	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();
+
+	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 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.\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, loff_t pos)
+{
+	int (*do_lo_send)(struct loop_device *, struct bio_vec *, loff_t,
+			struct page *page);
+	struct bio_vec *bvec;
+	struct page *page = NULL;
+	int i, 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, i) {
+		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.\n");
+	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\n",
+		       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;
+	ssize_t s;
+	int i;
+
+	bio_for_each_segment(bvec, bio, i) {
+		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_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_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)
+{
+	bio_list_add(&lo->lo_bio_list, bio);
+}
+
+/*
+ * Grab first pending buffer
+ */
+static struct bio *loop_get_bio(struct loop_device *lo)
+{
+	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;
+	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);
+		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++] = '\n';
+		buf[ret] = 0;
+	}
+
+	return ret;
+}
+
+static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
+{
+	return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
+}
+
+static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
+{
+	return sprintf(buf, "%llu\n", (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\n", 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\n", 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 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->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);
+
+	/*
+	 * 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;
+
+	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 (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;
+	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;
+	uid_t uid = current_uid();
+
+	if (lo->lo_encrypt_key_size &&
+	    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.mnt, file->f_path.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 loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
+{
+	int err;
+	sector_t sec;
+	loff_t sz;
+
+	err = -ENXIO;
+	if (unlikely(lo->lo_state != Lo_bound))
+		goto out;
+	err = figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
+	if (unlikely(err))
+		goto out;
+	sec = get_capacity(lo->lo_disk);
+	/* the width of sector_t may be narrow for bit-shift */
+	sz = sec;
+	sz <<= 9;
+	bd_set_size(bdev, sz);
+	/* let user-space know about the new size */
+	kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+
+ out:
+	return err;
+}
+
+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 int 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)
+			goto out_unlocked;
+	} 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);
+out_unlocked:
+	return 0;
+}
+
+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;
+
+	lo = kzalloc(sizeof(*lo), GFP_KERNEL);
+	if (!lo) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	err = idr_pre_get(&loop_index_idr, GFP_KERNEL);
+	if (err < 0)
+		goto out_free_dev;
+
+	if (i >= 0) {
+		int m;
+
+		/* create specific i in the index */
+		err = idr_get_new_above(&loop_index_idr, lo, i, &m);
+		if (err >= 0 && i != m) {
+			idr_remove(&loop_index_idr, m);
+			err = -EEXIST;
+		}
+	} else if (i == -1) {
+		int m;
+
+		/* get next free nr */
+		err = idr_get_new(&loop_index_idr, lo, &m);
+		if (err >= 0)
+			i = m;
+	} else {
+		err = -EINVAL;
+	}
+	if (err < 0)
+		goto out_free_dev;
+
+	lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
+	if (!lo->lo_queue)
+		goto out_free_idr;
+
+	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);
+	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\n");
+	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_remove_all(&loop_index_idr);
+	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