Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1348 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
new file mode 100644
index 0000000..6f011d0
--- /dev/null
+++ b/drivers/block/loop.c
@@ -0,0 +1,1348 @@
+/*
+ *  linux/drivers/block/loop.c
+ *
+ *  Written by Theodore Ts'o, 3/29/93
+ *
+ * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
+ * permitted under the GNU General Public License.
+ *
+ * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
+ * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
+ *
+ * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
+ * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
+ *
+ * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
+ *
+ * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
+ *
+ * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
+ *
+ * Loadable modules and other fixes by AK, 1998
+ *
+ * Make real block number available to downstream transfer functions, enables
+ * CBC (and relatives) mode encryption requiring unique IVs per data block.
+ * Reed H. Petty, rhp@draper.net
+ *
+ * Maximum number of loop devices now dynamic via max_loop module parameter.
+ * Russell Kroll <rkroll@exploits.org> 19990701
+ *
+ * Maximum number of loop devices when compiled-in now selectable by passing
+ * max_loop=<1-255> to the kernel on boot.
+ * Erik I. Bolsų, <eriki@himolde.no>, Oct 31, 1999
+ *
+ * Completely rewrite request handling to be make_request_fn style and
+ * non blocking, pushing work to a helper thread. Lots of fixes from
+ * Al Viro too.
+ * Jens Axboe <axboe@suse.de>, Nov 2000
+ *
+ * Support up to 256 loop devices
+ * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
+ *
+ * Support for falling back on the write file operation when the address space
+ * operations prepare_write and/or commit_write are not available on the
+ * backing filesystem.
+ * Anton Altaparmakov, 16 Feb 2005
+ *
+ * Still To Fix:
+ * - Advisory locking is ignored here.
+ * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/stat.h>
+#include <linux/errno.h>
+#include <linux/major.h>
+#include <linux/wait.h>
+#include <linux/blkdev.h>
+#include <linux/blkpg.h>
+#include <linux/init.h>
+#include <linux/devfs_fs_kernel.h>
+#include <linux/smp_lock.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+#include <linux/loop.h>
+#include <linux/suspend.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>		/* for invalidate_bdev() */
+#include <linux/completion.h>
+#include <linux/highmem.h>
+#include <linux/gfp.h>
+
+#include <asm/uaccess.h>
+
+static int max_loop = 8;
+static struct loop_device *loop_dev;
+static struct gendisk **disks;
+
+/*
+ * Transfer functions
+ */
+static int transfer_none(struct loop_device *lo, int cmd,
+			 struct page *raw_page, unsigned raw_off,
+			 struct page *loop_page, unsigned loop_off,
+			 int size, sector_t real_block)
+{
+	char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
+	char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
+
+	if (cmd == READ)
+		memcpy(loop_buf, raw_buf, size);
+	else
+		memcpy(raw_buf, loop_buf, size);
+
+	kunmap_atomic(raw_buf, KM_USER0);
+	kunmap_atomic(loop_buf, KM_USER1);
+	cond_resched();
+	return 0;
+}
+
+static int transfer_xor(struct loop_device *lo, int cmd,
+			struct page *raw_page, unsigned raw_off,
+			struct page *loop_page, unsigned loop_off,
+			int size, sector_t real_block)
+{
+	char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
+	char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
+	char *in, *out, *key;
+	int i, keysize;
+
+	if (cmd == READ) {
+		in = raw_buf;
+		out = loop_buf;
+	} else {
+		in = loop_buf;
+		out = raw_buf;
+	}
+
+	key = lo->lo_encrypt_key;
+	keysize = lo->lo_encrypt_key_size;
+	for (i = 0; i < size; i++)
+		*out++ = *in++ ^ key[(i & 511) % keysize];
+
+	kunmap_atomic(raw_buf, KM_USER0);
+	kunmap_atomic(loop_buf, KM_USER1);
+	cond_resched();
+	return 0;
+}
+
+static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
+{
+	if (unlikely(info->lo_encrypt_key_size <= 0))
+		return -EINVAL;
+	return 0;
+}
+
+static struct loop_func_table none_funcs = {
+	.number = LO_CRYPT_NONE,
+	.transfer = transfer_none,
+}; 	
+
+static struct loop_func_table xor_funcs = {
+	.number = LO_CRYPT_XOR,
+	.transfer = transfer_xor,
+	.init = xor_init
+}; 	
+
+/* xfer_funcs[0] is special - its release function is never called */
+static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
+	&none_funcs,
+	&xor_funcs
+};
+
+static loff_t get_loop_size(struct loop_device *lo, struct file *file)
+{
+	loff_t size, offset, loopsize;
+
+	/* Compute loopsize in bytes */
+	size = i_size_read(file->f_mapping->host);
+	offset = lo->lo_offset;
+	loopsize = size - offset;
+	if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
+		loopsize = lo->lo_sizelimit;
+
+	/*
+	 * Unfortunately, if we want to do I/O on the device,
+	 * the number of 512-byte sectors has to fit into a sector_t.
+	 */
+	return loopsize >> 9;
+}
+
+static int
+figure_loop_size(struct loop_device *lo)
+{
+	loff_t size = get_loop_size(lo, lo->lo_backing_file);
+	sector_t x = (sector_t)size;
+
+	if (unlikely((loff_t)x != size))
+		return -EFBIG;
+
+	set_capacity(disks[lo->lo_number], x);
+	return 0;					
+}
+
+static inline int
+lo_do_transfer(struct loop_device *lo, int cmd,
+	       struct page *rpage, unsigned roffs,
+	       struct page *lpage, unsigned loffs,
+	       int size, sector_t rblock)
+{
+	if (unlikely(!lo->transfer))
+		return 0;
+
+	return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
+}
+
+/**
+ * do_lo_send_aops - helper for writing data to a loop device
+ *
+ * This is the fast version for backing filesystems which implement the address
+ * space operations prepare_write and commit_write.
+ */
+static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
+		int bsize, loff_t pos, struct page *page)
+{
+	struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
+	struct address_space *mapping = file->f_mapping;
+	struct address_space_operations *aops = mapping->a_ops;
+	pgoff_t index;
+	unsigned offset, bv_offs;
+	int len, ret = 0;
+
+	down(&mapping->host->i_sem);
+	index = pos >> PAGE_CACHE_SHIFT;
+	offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1);
+	bv_offs = bvec->bv_offset;
+	len = bvec->bv_len;
+	while (len > 0) {
+		sector_t IV;
+		unsigned size;
+		int transfer_result;
+
+		IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
+		size = PAGE_CACHE_SIZE - offset;
+		if (size > len)
+			size = len;
+		page = grab_cache_page(mapping, index);
+		if (unlikely(!page))
+			goto fail;
+		if (unlikely(aops->prepare_write(file, page, offset,
+				offset + size)))
+			goto unlock;
+		transfer_result = lo_do_transfer(lo, WRITE, page, offset,
+				bvec->bv_page, bv_offs, size, IV);
+		if (unlikely(transfer_result)) {
+			char *kaddr;
+
+			/*
+			 * The transfer failed, but we still write the data to
+			 * keep prepare/commit calls balanced.
+			 */
+			printk(KERN_ERR "loop: transfer error block %llu\n",
+			       (unsigned long long)index);
+			kaddr = kmap_atomic(page, KM_USER0);
+			memset(kaddr + offset, 0, size);
+			kunmap_atomic(kaddr, KM_USER0);
+		}
+		flush_dcache_page(page);
+		if (unlikely(aops->commit_write(file, page, offset,
+				offset + size)))
+			goto unlock;
+		if (unlikely(transfer_result))
+			goto unlock;
+		bv_offs += size;
+		len -= size;
+		offset = 0;
+		index++;
+		pos += size;
+		unlock_page(page);
+		page_cache_release(page);
+	}
+out:
+	up(&mapping->host->i_sem);
+	return ret;
+unlock:
+	unlock_page(page);
+	page_cache_release(page);
+fail:
+	ret = -1;
+	goto out;
+}
+
+/**
+ * __do_lo_send_write - helper for writing data to a loop device
+ *
+ * This helper just factors out common code between do_lo_send_direct_write()
+ * and do_lo_send_write().
+ */
+static inline int __do_lo_send_write(struct file *file,
+		u8 __user *buf, const int len, loff_t pos)
+{
+	ssize_t bw;
+	mm_segment_t old_fs = get_fs();
+
+	set_fs(get_ds());
+	bw = file->f_op->write(file, buf, len, &pos);
+	set_fs(old_fs);
+	if (likely(bw == len))
+		return 0;
+	printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.\n",
+			(unsigned long long)pos, len);
+	if (bw >= 0)
+		bw = -EIO;
+	return bw;
+}
+
+/**
+ * do_lo_send_direct_write - helper for writing data to a loop device
+ *
+ * This is the fast, non-transforming version for backing filesystems which do
+ * not implement the address space operations prepare_write and commit_write.
+ * It uses the write file operation which should be present on all writeable
+ * filesystems.
+ */
+static int do_lo_send_direct_write(struct loop_device *lo,
+		struct bio_vec *bvec, int bsize, loff_t pos, struct page *page)
+{
+	ssize_t bw = __do_lo_send_write(lo->lo_backing_file,
+			(u8 __user *)kmap(bvec->bv_page) + bvec->bv_offset,
+			bvec->bv_len, pos);
+	kunmap(bvec->bv_page);
+	cond_resched();
+	return bw;
+}
+
+/**
+ * do_lo_send_write - helper for writing data to a loop device
+ *
+ * This is the slow, transforming version for filesystems which do not
+ * implement the address space operations prepare_write and commit_write.  It
+ * uses the write file operation which should be present on all writeable
+ * filesystems.
+ *
+ * Using fops->write is slower than using aops->{prepare,commit}_write in the
+ * transforming case because we need to double buffer the data as we cannot do
+ * the transformations in place as we do not have direct access to the
+ * destination pages of the backing file.
+ */
+static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec,
+		int bsize, loff_t pos, struct page *page)
+{
+	int ret = lo_do_transfer(lo, WRITE, page, 0, bvec->bv_page,
+			bvec->bv_offset, bvec->bv_len, pos >> 9);
+	if (likely(!ret))
+		return __do_lo_send_write(lo->lo_backing_file,
+				(u8 __user *)page_address(page), bvec->bv_len,
+				pos);
+	printk(KERN_ERR "loop: Transfer error at byte offset %llu, "
+			"length %i.\n", (unsigned long long)pos, bvec->bv_len);
+	if (ret > 0)
+		ret = -EIO;
+	return ret;
+}
+
+static int lo_send(struct loop_device *lo, struct bio *bio, int bsize,
+		loff_t pos)
+{
+	int (*do_lo_send)(struct loop_device *, struct bio_vec *, int, loff_t,
+			struct page *page);
+	struct bio_vec *bvec;
+	struct page *page = NULL;
+	int i, ret = 0;
+
+	do_lo_send = do_lo_send_aops;
+	if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) {
+		do_lo_send = do_lo_send_direct_write;
+		if (lo->transfer != transfer_none) {
+			page = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
+			if (unlikely(!page))
+				goto fail;
+			kmap(page);
+			do_lo_send = do_lo_send_write;
+		}
+	}
+	bio_for_each_segment(bvec, bio, i) {
+		ret = do_lo_send(lo, bvec, bsize, pos, page);
+		if (ret < 0)
+			break;
+		pos += bvec->bv_len;
+	}
+	if (page) {
+		kunmap(page);
+		__free_page(page);
+	}
+out:
+	return ret;
+fail:
+	printk(KERN_ERR "loop: Failed to allocate temporary page for write.\n");
+	ret = -ENOMEM;
+	goto out;
+}
+
+struct lo_read_data {
+	struct loop_device *lo;
+	struct page *page;
+	unsigned offset;
+	int bsize;
+};
+
+static int
+lo_read_actor(read_descriptor_t *desc, struct page *page,
+	      unsigned long offset, unsigned long size)
+{
+	unsigned long count = desc->count;
+	struct lo_read_data *p = desc->arg.data;
+	struct loop_device *lo = p->lo;
+	sector_t IV;
+
+	IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
+
+	if (size > count)
+		size = count;
+
+	if (lo_do_transfer(lo, READ, page, offset, p->page, p->offset, size, IV)) {
+		size = 0;
+		printk(KERN_ERR "loop: transfer error block %ld\n",
+		       page->index);
+		desc->error = -EINVAL;
+	}
+
+	flush_dcache_page(p->page);
+
+	desc->count = count - size;
+	desc->written += size;
+	p->offset += size;
+	return size;
+}
+
+static int
+do_lo_receive(struct loop_device *lo,
+	      struct bio_vec *bvec, int bsize, loff_t pos)
+{
+	struct lo_read_data cookie;
+	struct file *file;
+	int retval;
+
+	cookie.lo = lo;
+	cookie.page = bvec->bv_page;
+	cookie.offset = bvec->bv_offset;
+	cookie.bsize = bsize;
+	file = lo->lo_backing_file;
+	retval = file->f_op->sendfile(file, &pos, bvec->bv_len,
+			lo_read_actor, &cookie);
+	return (retval < 0)? retval: 0;
+}
+
+static int
+lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
+{
+	struct bio_vec *bvec;
+	int i, ret = 0;
+
+	bio_for_each_segment(bvec, bio, i) {
+		ret = do_lo_receive(lo, bvec, bsize, pos);
+		if (ret < 0)
+			break;
+		pos += bvec->bv_len;
+	}
+	return ret;
+}
+
+static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
+{
+	loff_t pos;
+	int ret;
+
+	pos = ((loff_t) bio->bi_sector << 9) + lo->lo_offset;
+	if (bio_rw(bio) == WRITE)
+		ret = lo_send(lo, bio, lo->lo_blocksize, pos);
+	else
+		ret = lo_receive(lo, bio, lo->lo_blocksize, pos);
+	return ret;
+}
+
+/*
+ * Add bio to back of pending list
+ */
+static void loop_add_bio(struct loop_device *lo, struct bio *bio)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&lo->lo_lock, flags);
+	if (lo->lo_biotail) {
+		lo->lo_biotail->bi_next = bio;
+		lo->lo_biotail = bio;
+	} else
+		lo->lo_bio = lo->lo_biotail = bio;
+	spin_unlock_irqrestore(&lo->lo_lock, flags);
+
+	up(&lo->lo_bh_mutex);
+}
+
+/*
+ * Grab first pending buffer
+ */
+static struct bio *loop_get_bio(struct loop_device *lo)
+{
+	struct bio *bio;
+
+	spin_lock_irq(&lo->lo_lock);
+	if ((bio = lo->lo_bio)) {
+		if (bio == lo->lo_biotail)
+			lo->lo_biotail = NULL;
+		lo->lo_bio = bio->bi_next;
+		bio->bi_next = NULL;
+	}
+	spin_unlock_irq(&lo->lo_lock);
+
+	return bio;
+}
+
+static int loop_make_request(request_queue_t *q, struct bio *old_bio)
+{
+	struct loop_device *lo = q->queuedata;
+	int rw = bio_rw(old_bio);
+
+	if (!lo)
+		goto out;
+
+	spin_lock_irq(&lo->lo_lock);
+	if (lo->lo_state != Lo_bound)
+		goto inactive;
+	atomic_inc(&lo->lo_pending);
+	spin_unlock_irq(&lo->lo_lock);
+
+	if (rw == WRITE) {
+		if (lo->lo_flags & LO_FLAGS_READ_ONLY)
+			goto err;
+	} else if (rw == READA) {
+		rw = READ;
+	} else if (rw != READ) {
+		printk(KERN_ERR "loop: unknown command (%x)\n", rw);
+		goto err;
+	}
+	loop_add_bio(lo, old_bio);
+	return 0;
+err:
+	if (atomic_dec_and_test(&lo->lo_pending))
+		up(&lo->lo_bh_mutex);
+out:
+	bio_io_error(old_bio, old_bio->bi_size);
+	return 0;
+inactive:
+	spin_unlock_irq(&lo->lo_lock);
+	goto out;
+}
+
+/*
+ * kick off io on the underlying address space
+ */
+static void loop_unplug(request_queue_t *q)
+{
+	struct loop_device *lo = q->queuedata;
+
+	clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
+	blk_run_address_space(lo->lo_backing_file->f_mapping);
+}
+
+struct switch_request {
+	struct file *file;
+	struct completion wait;
+};
+
+static void do_loop_switch(struct loop_device *, struct switch_request *);
+
+static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
+{
+	int ret;
+
+	if (unlikely(!bio->bi_bdev)) {
+		do_loop_switch(lo, bio->bi_private);
+		bio_put(bio);
+	} else {
+		ret = do_bio_filebacked(lo, bio);
+		bio_endio(bio, bio->bi_size, ret);
+	}
+}
+
+/*
+ * worker thread that handles reads/writes to file backed loop devices,
+ * to avoid blocking in our make_request_fn. it also does loop decrypting
+ * on reads for block backed loop, as that is too heavy to do from
+ * b_end_io context where irqs may be disabled.
+ */
+static int loop_thread(void *data)
+{
+	struct loop_device *lo = data;
+	struct bio *bio;
+
+	daemonize("loop%d", lo->lo_number);
+
+	/*
+	 * loop can be used in an encrypted device,
+	 * hence, it mustn't be stopped at all
+	 * because it could be indirectly used during suspension
+	 */
+	current->flags |= PF_NOFREEZE;
+
+	set_user_nice(current, -20);
+
+	lo->lo_state = Lo_bound;
+	atomic_inc(&lo->lo_pending);
+
+	/*
+	 * up sem, we are running
+	 */
+	up(&lo->lo_sem);
+
+	for (;;) {
+		down_interruptible(&lo->lo_bh_mutex);
+		/*
+		 * could be upped because of tear-down, not because of
+		 * pending work
+		 */
+		if (!atomic_read(&lo->lo_pending))
+			break;
+
+		bio = loop_get_bio(lo);
+		if (!bio) {
+			printk("loop: missing bio\n");
+			continue;
+		}
+		loop_handle_bio(lo, bio);
+
+		/*
+		 * upped both for pending work and tear-down, lo_pending
+		 * will hit zero then
+		 */
+		if (atomic_dec_and_test(&lo->lo_pending))
+			break;
+	}
+
+	up(&lo->lo_sem);
+	return 0;
+}
+
+/*
+ * loop_switch performs the hard work of switching a backing store.
+ * First it needs to flush existing IO, it does this by sending a magic
+ * BIO down the pipe. The completion of this BIO does the actual switch.
+ */
+static int loop_switch(struct loop_device *lo, struct file *file)
+{
+	struct switch_request w;
+	struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+	if (!bio)
+		return -ENOMEM;
+	init_completion(&w.wait);
+	w.file = file;
+	bio->bi_private = &w;
+	bio->bi_bdev = NULL;
+	loop_make_request(lo->lo_queue, bio);
+	wait_for_completion(&w.wait);
+	return 0;
+}
+
+/*
+ * Do the actual switch; called from the BIO completion routine
+ */
+static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
+{
+	struct file *file = p->file;
+	struct file *old_file = lo->lo_backing_file;
+	struct address_space *mapping = file->f_mapping;
+
+	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
+	lo->lo_backing_file = file;
+	lo->lo_blocksize = mapping->host->i_blksize;
+	lo->old_gfp_mask = mapping_gfp_mask(mapping);
+	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+	complete(&p->wait);
+}
+
+
+/*
+ * loop_change_fd switched the backing store of a loopback device to
+ * a new file. This is useful for operating system installers to free up
+ * the original file and in High Availability environments to switch to
+ * an alternative location for the content in case of server meltdown.
+ * This can only work if the loop device is used read-only, and if the
+ * new backing store is the same size and type as the old backing store.
+ */
+static int loop_change_fd(struct loop_device *lo, struct file *lo_file,
+		       struct block_device *bdev, unsigned int arg)
+{
+	struct file	*file, *old_file;
+	struct inode	*inode;
+	int		error;
+
+	error = -ENXIO;
+	if (lo->lo_state != Lo_bound)
+		goto out;
+
+	/* the loop device has to be read-only */
+	error = -EINVAL;
+	if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
+		goto out;
+
+	error = -EBADF;
+	file = fget(arg);
+	if (!file)
+		goto out;
+
+	inode = file->f_mapping->host;
+	old_file = lo->lo_backing_file;
+
+	error = -EINVAL;
+
+	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+		goto out_putf;
+
+	/* new backing store needs to support loop (eg sendfile) */
+	if (!inode->i_fop->sendfile)
+		goto out_putf;
+
+	/* size of the new backing store needs to be the same */
+	if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
+		goto out_putf;
+
+	/* and ... switch */
+	error = loop_switch(lo, file);
+	if (error)
+		goto out_putf;
+
+	fput(old_file);
+	return 0;
+
+ out_putf:
+	fput(file);
+ out:
+	return error;
+}
+
+static inline int is_loop_device(struct file *file)
+{
+	struct inode *i = file->f_mapping->host;
+
+	return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
+}
+
+static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
+		       struct block_device *bdev, unsigned int arg)
+{
+	struct file	*file, *f;
+	struct inode	*inode;
+	struct address_space *mapping;
+	unsigned lo_blocksize;
+	int		lo_flags = 0;
+	int		error;
+	loff_t		size;
+
+	/* This is safe, since we have a reference from open(). */
+	__module_get(THIS_MODULE);
+
+	error = -EBADF;
+	file = fget(arg);
+	if (!file)
+		goto out;
+
+	error = -EBUSY;
+	if (lo->lo_state != Lo_unbound)
+		goto out_putf;
+
+	/* Avoid recursion */
+	f = file;
+	while (is_loop_device(f)) {
+		struct loop_device *l;
+
+		if (f->f_mapping->host->i_rdev == lo_file->f_mapping->host->i_rdev)
+			goto out_putf;
+
+		l = f->f_mapping->host->i_bdev->bd_disk->private_data;
+		if (l->lo_state == Lo_unbound) {
+			error = -EINVAL;
+			goto out_putf;
+		}
+		f = l->lo_backing_file;
+	}
+
+	mapping = file->f_mapping;
+	inode = mapping->host;
+
+	if (!(file->f_mode & FMODE_WRITE))
+		lo_flags |= LO_FLAGS_READ_ONLY;
+
+	error = -EINVAL;
+	if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
+		struct address_space_operations *aops = mapping->a_ops;
+		/*
+		 * If we can't read - sorry. If we only can't write - well,
+		 * it's going to be read-only.
+		 */
+		if (!file->f_op->sendfile)
+			goto out_putf;
+		if (aops->prepare_write && aops->commit_write)
+			lo_flags |= LO_FLAGS_USE_AOPS;
+		if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
+			lo_flags |= LO_FLAGS_READ_ONLY;
+
+		lo_blocksize = inode->i_blksize;
+		error = 0;
+	} else {
+		goto out_putf;
+	}
+
+	size = get_loop_size(lo, file);
+
+	if ((loff_t)(sector_t)size != size) {
+		error = -EFBIG;
+		goto out_putf;
+	}
+
+	if (!(lo_file->f_mode & FMODE_WRITE))
+		lo_flags |= LO_FLAGS_READ_ONLY;
+
+	set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
+
+	lo->lo_blocksize = lo_blocksize;
+	lo->lo_device = bdev;
+	lo->lo_flags = lo_flags;
+	lo->lo_backing_file = file;
+	lo->transfer = NULL;
+	lo->ioctl = NULL;
+	lo->lo_sizelimit = 0;
+	lo->old_gfp_mask = mapping_gfp_mask(mapping);
+	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+
+	lo->lo_bio = lo->lo_biotail = NULL;
+
+	/*
+	 * set queue make_request_fn, and add limits based on lower level
+	 * device
+	 */
+	blk_queue_make_request(lo->lo_queue, loop_make_request);
+	lo->lo_queue->queuedata = lo;
+	lo->lo_queue->unplug_fn = loop_unplug;
+
+	set_capacity(disks[lo->lo_number], size);
+	bd_set_size(bdev, size << 9);
+
+	set_blocksize(bdev, lo_blocksize);
+
+	kernel_thread(loop_thread, lo, CLONE_KERNEL);
+	down(&lo->lo_sem);
+	return 0;
+
+ out_putf:
+	fput(file);
+ out:
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	return error;
+}
+
+static int
+loop_release_xfer(struct loop_device *lo)
+{
+	int err = 0;
+	struct loop_func_table *xfer = lo->lo_encryption;
+
+	if (xfer) {
+		if (xfer->release)
+			err = xfer->release(lo);
+		lo->transfer = NULL;
+		lo->lo_encryption = NULL;
+		module_put(xfer->owner);
+	}
+	return err;
+}
+
+static int
+loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
+	       const struct loop_info64 *i)
+{
+	int err = 0;
+
+	if (xfer) {
+		struct module *owner = xfer->owner;
+
+		if (!try_module_get(owner))
+			return -EINVAL;
+		if (xfer->init)
+			err = xfer->init(lo, i);
+		if (err)
+			module_put(owner);
+		else
+			lo->lo_encryption = xfer;
+	}
+	return err;
+}
+
+static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
+{
+	struct file *filp = lo->lo_backing_file;
+	int gfp = lo->old_gfp_mask;
+
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+
+	if (lo->lo_refcnt > 1)	/* we needed one fd for the ioctl */
+		return -EBUSY;
+
+	if (filp == NULL)
+		return -EINVAL;
+
+	spin_lock_irq(&lo->lo_lock);
+	lo->lo_state = Lo_rundown;
+	if (atomic_dec_and_test(&lo->lo_pending))
+		up(&lo->lo_bh_mutex);
+	spin_unlock_irq(&lo->lo_lock);
+
+	down(&lo->lo_sem);
+
+	lo->lo_backing_file = NULL;
+
+	loop_release_xfer(lo);
+	lo->transfer = NULL;
+	lo->ioctl = NULL;
+	lo->lo_device = NULL;
+	lo->lo_encryption = NULL;
+	lo->lo_offset = 0;
+	lo->lo_sizelimit = 0;
+	lo->lo_encrypt_key_size = 0;
+	lo->lo_flags = 0;
+	memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
+	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
+	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
+	invalidate_bdev(bdev, 0);
+	set_capacity(disks[lo->lo_number], 0);
+	bd_set_size(bdev, 0);
+	mapping_set_gfp_mask(filp->f_mapping, gfp);
+	lo->lo_state = Lo_unbound;
+	fput(filp);
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	return 0;
+}
+
+static int
+loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+{
+	int err;
+	struct loop_func_table *xfer;
+
+	if (lo->lo_encrypt_key_size && lo->lo_key_owner != current->uid &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+	if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
+		return -EINVAL;
+
+	err = loop_release_xfer(lo);
+	if (err)
+		return err;
+
+	if (info->lo_encrypt_type) {
+		unsigned int type = info->lo_encrypt_type;
+
+		if (type >= MAX_LO_CRYPT)
+			return -EINVAL;
+		xfer = xfer_funcs[type];
+		if (xfer == NULL)
+			return -EINVAL;
+	} else
+		xfer = NULL;
+
+	err = loop_init_xfer(lo, xfer, info);
+	if (err)
+		return err;
+
+	if (lo->lo_offset != info->lo_offset ||
+	    lo->lo_sizelimit != info->lo_sizelimit) {
+		lo->lo_offset = info->lo_offset;
+		lo->lo_sizelimit = info->lo_sizelimit;
+		if (figure_loop_size(lo))
+			return -EFBIG;
+	}
+
+	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
+	memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
+	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
+	lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
+
+	if (!xfer)
+		xfer = &none_funcs;
+	lo->transfer = xfer->transfer;
+	lo->ioctl = xfer->ioctl;
+
+	lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
+	lo->lo_init[0] = info->lo_init[0];
+	lo->lo_init[1] = info->lo_init[1];
+	if (info->lo_encrypt_key_size) {
+		memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
+		       info->lo_encrypt_key_size);
+		lo->lo_key_owner = current->uid;
+	}	
+
+	return 0;
+}
+
+static int
+loop_get_status(struct loop_device *lo, struct loop_info64 *info)
+{
+	struct file *file = lo->lo_backing_file;
+	struct kstat stat;
+	int error;
+
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+	error = vfs_getattr(file->f_vfsmnt, file->f_dentry, &stat);
+	if (error)
+		return error;
+	memset(info, 0, sizeof(*info));
+	info->lo_number = lo->lo_number;
+	info->lo_device = huge_encode_dev(stat.dev);
+	info->lo_inode = stat.ino;
+	info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
+	info->lo_offset = lo->lo_offset;
+	info->lo_sizelimit = lo->lo_sizelimit;
+	info->lo_flags = lo->lo_flags;
+	memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
+	info->lo_encrypt_type =
+		lo->lo_encryption ? lo->lo_encryption->number : 0;
+	if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
+		info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
+		memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
+		       lo->lo_encrypt_key_size);
+	}
+	return 0;
+}
+
+static void
+loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
+{
+	memset(info64, 0, sizeof(*info64));
+	info64->lo_number = info->lo_number;
+	info64->lo_device = info->lo_device;
+	info64->lo_inode = info->lo_inode;
+	info64->lo_rdevice = info->lo_rdevice;
+	info64->lo_offset = info->lo_offset;
+	info64->lo_sizelimit = 0;
+	info64->lo_encrypt_type = info->lo_encrypt_type;
+	info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
+	info64->lo_flags = info->lo_flags;
+	info64->lo_init[0] = info->lo_init[0];
+	info64->lo_init[1] = info->lo_init[1];
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
+	else
+		memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
+	memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
+}
+
+static int
+loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
+{
+	memset(info, 0, sizeof(*info));
+	info->lo_number = info64->lo_number;
+	info->lo_device = info64->lo_device;
+	info->lo_inode = info64->lo_inode;
+	info->lo_rdevice = info64->lo_rdevice;
+	info->lo_offset = info64->lo_offset;
+	info->lo_encrypt_type = info64->lo_encrypt_type;
+	info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
+	info->lo_flags = info64->lo_flags;
+	info->lo_init[0] = info64->lo_init[0];
+	info->lo_init[1] = info64->lo_init[1];
+	if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
+		memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
+	else
+		memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
+	memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
+
+	/* error in case values were truncated */
+	if (info->lo_device != info64->lo_device ||
+	    info->lo_rdevice != info64->lo_rdevice ||
+	    info->lo_inode != info64->lo_inode ||
+	    info->lo_offset != info64->lo_offset)
+		return -EOVERFLOW;
+
+	return 0;
+}
+
+static int
+loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
+{
+	struct loop_info info;
+	struct loop_info64 info64;
+
+	if (copy_from_user(&info, arg, sizeof (struct loop_info)))
+		return -EFAULT;
+	loop_info64_from_old(&info, &info64);
+	return loop_set_status(lo, &info64);
+}
+
+static int
+loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
+{
+	struct loop_info64 info64;
+
+	if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
+		return -EFAULT;
+	return loop_set_status(lo, &info64);
+}
+
+static int
+loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
+	struct loop_info info;
+	struct loop_info64 info64;
+	int err = 0;
+
+	if (!arg)
+		err = -EINVAL;
+	if (!err)
+		err = loop_get_status(lo, &info64);
+	if (!err)
+		err = loop_info64_to_old(&info64, &info);
+	if (!err && copy_to_user(arg, &info, sizeof(info)))
+		err = -EFAULT;
+
+	return err;
+}
+
+static int
+loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
+	struct loop_info64 info64;
+	int err = 0;
+
+	if (!arg)
+		err = -EINVAL;
+	if (!err)
+		err = loop_get_status(lo, &info64);
+	if (!err && copy_to_user(arg, &info64, sizeof(info64)))
+		err = -EFAULT;
+
+	return err;
+}
+
+static int lo_ioctl(struct inode * inode, struct file * file,
+	unsigned int cmd, unsigned long arg)
+{
+	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
+	int err;
+
+	down(&lo->lo_ctl_mutex);
+	switch (cmd) {
+	case LOOP_SET_FD:
+		err = loop_set_fd(lo, file, inode->i_bdev, arg);
+		break;
+	case LOOP_CHANGE_FD:
+		err = loop_change_fd(lo, file, inode->i_bdev, arg);
+		break;
+	case LOOP_CLR_FD:
+		err = loop_clr_fd(lo, inode->i_bdev);
+		break;
+	case LOOP_SET_STATUS:
+		err = loop_set_status_old(lo, (struct loop_info __user *) arg);
+		break;
+	case LOOP_GET_STATUS:
+		err = loop_get_status_old(lo, (struct loop_info __user *) arg);
+		break;
+	case LOOP_SET_STATUS64:
+		err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
+		break;
+	case LOOP_GET_STATUS64:
+		err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
+		break;
+	default:
+		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
+	}
+	up(&lo->lo_ctl_mutex);
+	return err;
+}
+
+static int lo_open(struct inode *inode, struct file *file)
+{
+	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
+
+	down(&lo->lo_ctl_mutex);
+	lo->lo_refcnt++;
+	up(&lo->lo_ctl_mutex);
+
+	return 0;
+}
+
+static int lo_release(struct inode *inode, struct file *file)
+{
+	struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
+
+	down(&lo->lo_ctl_mutex);
+	--lo->lo_refcnt;
+	up(&lo->lo_ctl_mutex);
+
+	return 0;
+}
+
+static struct block_device_operations lo_fops = {
+	.owner =	THIS_MODULE,
+	.open =		lo_open,
+	.release =	lo_release,
+	.ioctl =	lo_ioctl,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+module_param(max_loop, int, 0);
+MODULE_PARM_DESC(max_loop, "Maximum number of loop devices (1-256)");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
+
+int loop_register_transfer(struct loop_func_table *funcs)
+{
+	unsigned int n = funcs->number;
+
+	if (n >= MAX_LO_CRYPT || xfer_funcs[n])
+		return -EINVAL;
+	xfer_funcs[n] = funcs;
+	return 0;
+}
+
+int loop_unregister_transfer(int number)
+{
+	unsigned int n = number;
+	struct loop_device *lo;
+	struct loop_func_table *xfer;
+
+	if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
+		return -EINVAL;
+
+	xfer_funcs[n] = NULL;
+
+	for (lo = &loop_dev[0]; lo < &loop_dev[max_loop]; lo++) {
+		down(&lo->lo_ctl_mutex);
+
+		if (lo->lo_encryption == xfer)
+			loop_release_xfer(lo);
+
+		up(&lo->lo_ctl_mutex);
+	}
+
+	return 0;
+}
+
+EXPORT_SYMBOL(loop_register_transfer);
+EXPORT_SYMBOL(loop_unregister_transfer);
+
+static int __init loop_init(void)
+{
+	int	i;
+
+	if (max_loop < 1 || max_loop > 256) {
+		printk(KERN_WARNING "loop: invalid max_loop (must be between"
+				    " 1 and 256), using default (8)\n");
+		max_loop = 8;
+	}
+
+	if (register_blkdev(LOOP_MAJOR, "loop"))
+		return -EIO;
+
+	loop_dev = kmalloc(max_loop * sizeof(struct loop_device), GFP_KERNEL);
+	if (!loop_dev)
+		goto out_mem1;
+	memset(loop_dev, 0, max_loop * sizeof(struct loop_device));
+
+	disks = kmalloc(max_loop * sizeof(struct gendisk *), GFP_KERNEL);
+	if (!disks)
+		goto out_mem2;
+
+	for (i = 0; i < max_loop; i++) {
+		disks[i] = alloc_disk(1);
+		if (!disks[i])
+			goto out_mem3;
+	}
+
+	devfs_mk_dir("loop");
+
+	for (i = 0; i < max_loop; i++) {
+		struct loop_device *lo = &loop_dev[i];
+		struct gendisk *disk = disks[i];
+
+		memset(lo, 0, sizeof(*lo));
+		lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
+		if (!lo->lo_queue)
+			goto out_mem4;
+		init_MUTEX(&lo->lo_ctl_mutex);
+		init_MUTEX_LOCKED(&lo->lo_sem);
+		init_MUTEX_LOCKED(&lo->lo_bh_mutex);
+		lo->lo_number = i;
+		spin_lock_init(&lo->lo_lock);
+		disk->major = LOOP_MAJOR;
+		disk->first_minor = i;
+		disk->fops = &lo_fops;
+		sprintf(disk->disk_name, "loop%d", i);
+		sprintf(disk->devfs_name, "loop/%d", i);
+		disk->private_data = lo;
+		disk->queue = lo->lo_queue;
+	}
+
+	/* We cannot fail after we call this, so another loop!*/
+	for (i = 0; i < max_loop; i++)
+		add_disk(disks[i]);
+	printk(KERN_INFO "loop: loaded (max %d devices)\n", max_loop);
+	return 0;
+
+out_mem4:
+	while (i--)
+		blk_put_queue(loop_dev[i].lo_queue);
+	devfs_remove("loop");
+	i = max_loop;
+out_mem3:
+	while (i--)
+		put_disk(disks[i]);
+	kfree(disks);
+out_mem2:
+	kfree(loop_dev);
+out_mem1:
+	unregister_blkdev(LOOP_MAJOR, "loop");
+	printk(KERN_ERR "loop: ran out of memory\n");
+	return -ENOMEM;
+}
+
+static void loop_exit(void)
+{
+	int i;
+
+	for (i = 0; i < max_loop; i++) {
+		del_gendisk(disks[i]);
+		blk_put_queue(loop_dev[i].lo_queue);
+		put_disk(disks[i]);
+	}
+	devfs_remove("loop");
+	if (unregister_blkdev(LOOP_MAJOR, "loop"))
+		printk(KERN_WARNING "loop: cannot unregister blkdev\n");
+
+	kfree(disks);
+	kfree(loop_dev);
+}
+
+module_init(loop_init);
+module_exit(loop_exit);
+
+#ifndef MODULE
+static int __init max_loop_setup(char *str)
+{
+	max_loop = simple_strtol(str, NULL, 0);
+	return 1;
+}
+
+__setup("max_loop=", max_loop_setup);
+#endif