Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2318 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
new file mode 100644
index 000000000..12ff6f58b
--- /dev/null
+++ b/drivers/block/loop.c
@@ -0,0 +1,2318 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 1993 by Theodore Ts'o.
+ */
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/stat.h>
+#include <linux/errno.h>
+#include <linux/major.h>
+#include <linux/wait.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/splice.h>
+#include <linux/sysfs.h>
+#include <linux/miscdevice.h>
+#include <linux/falloc.h>
+#include <linux/uio.h>
+#include <linux/ioprio.h>
+#include <linux/blk-cgroup.h>
+#include <linux/sched/mm.h>
+#include <linux/statfs.h>
+#include <linux/uaccess.h>
+#include <linux/blk-mq.h>
+#include <linux/spinlock.h>
+#include <uapi/linux/loop.h>
+
+/* Possible states of device */
+enum {
+	Lo_unbound,
+	Lo_bound,
+	Lo_rundown,
+	Lo_deleting,
+};
+
+struct loop_func_table;
+
+struct loop_device {
+	int		lo_number;
+	loff_t		lo_offset;
+	loff_t		lo_sizelimit;
+	int		lo_flags;
+	char		lo_file_name[LO_NAME_SIZE];
+
+	struct file *	lo_backing_file;
+	struct block_device *lo_device;
+
+	gfp_t		old_gfp_mask;
+
+	spinlock_t		lo_lock;
+	int			lo_state;
+	spinlock_t              lo_work_lock;
+	struct workqueue_struct *workqueue;
+	struct work_struct      rootcg_work;
+	struct list_head        rootcg_cmd_list;
+	struct list_head        idle_worker_list;
+	struct rb_root          worker_tree;
+	struct timer_list       timer;
+	bool			use_dio;
+	bool			sysfs_inited;
+
+	struct request_queue	*lo_queue;
+	struct blk_mq_tag_set	tag_set;
+	struct gendisk		*lo_disk;
+	struct mutex		lo_mutex;
+	bool			idr_visible;
+};
+
+struct loop_cmd {
+	struct list_head list_entry;
+	bool use_aio; /* use AIO interface to handle I/O */
+	atomic_t ref; /* only for aio */
+	long ret;
+	struct kiocb iocb;
+	struct bio_vec *bvec;
+	struct cgroup_subsys_state *blkcg_css;
+	struct cgroup_subsys_state *memcg_css;
+};
+
+#define LOOP_IDLE_WORKER_TIMEOUT (60 * HZ)
+#define LOOP_DEFAULT_HW_Q_DEPTH (128)
+
+static DEFINE_IDR(loop_index_idr);
+static DEFINE_MUTEX(loop_ctl_mutex);
+static DEFINE_MUTEX(loop_validate_mutex);
+
+/**
+ * loop_global_lock_killable() - take locks for safe loop_validate_file() test
+ *
+ * @lo: struct loop_device
+ * @global: true if @lo is about to bind another "struct loop_device", false otherwise
+ *
+ * Returns 0 on success, -EINTR otherwise.
+ *
+ * Since loop_validate_file() traverses on other "struct loop_device" if
+ * is_loop_device() is true, we need a global lock for serializing concurrent
+ * loop_configure()/loop_change_fd()/__loop_clr_fd() calls.
+ */
+static int loop_global_lock_killable(struct loop_device *lo, bool global)
+{
+	int err;
+
+	if (global) {
+		err = mutex_lock_killable(&loop_validate_mutex);
+		if (err)
+			return err;
+	}
+	err = mutex_lock_killable(&lo->lo_mutex);
+	if (err && global)
+		mutex_unlock(&loop_validate_mutex);
+	return err;
+}
+
+/**
+ * loop_global_unlock() - release locks taken by loop_global_lock_killable()
+ *
+ * @lo: struct loop_device
+ * @global: true if @lo was about to bind another "struct loop_device", false otherwise
+ */
+static void loop_global_unlock(struct loop_device *lo, bool global)
+{
+	mutex_unlock(&lo->lo_mutex);
+	if (global)
+		mutex_unlock(&loop_validate_mutex);
+}
+
+static int max_part;
+static int part_shift;
+
+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);
+}
+
+/*
+ * We support direct I/O only if lo_offset is aligned with the logical I/O size
+ * of backing device, and the logical block size of loop is bigger than that of
+ * the backing device.
+ */
+static bool lo_bdev_can_use_dio(struct loop_device *lo,
+		struct block_device *backing_bdev)
+{
+	unsigned short sb_bsize = bdev_logical_block_size(backing_bdev);
+
+	if (queue_logical_block_size(lo->lo_queue) < sb_bsize)
+		return false;
+	if (lo->lo_offset & (sb_bsize - 1))
+		return false;
+	return true;
+}
+
+static void __loop_update_dio(struct loop_device *lo, bool dio)
+{
+	struct file *file = lo->lo_backing_file;
+	struct inode *inode = file->f_mapping->host;
+	struct block_device *backing_bdev = NULL;
+	bool use_dio;
+
+	if (S_ISBLK(inode->i_mode))
+		backing_bdev = I_BDEV(inode);
+	else if (inode->i_sb->s_bdev)
+		backing_bdev = inode->i_sb->s_bdev;
+
+	use_dio = dio && (file->f_mode & FMODE_CAN_ODIRECT) &&
+		(!backing_bdev || lo_bdev_can_use_dio(lo, backing_bdev));
+
+	if (lo->use_dio == use_dio)
+		return;
+
+	/* flush dirty pages before changing direct IO */
+	vfs_fsync(file, 0);
+
+	/*
+	 * The flag of LO_FLAGS_DIRECT_IO is handled similarly with
+	 * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup
+	 * will get updated by ioctl(LOOP_GET_STATUS)
+	 */
+	if (lo->lo_state == Lo_bound)
+		blk_mq_freeze_queue(lo->lo_queue);
+	lo->use_dio = use_dio;
+	if (use_dio) {
+		blk_queue_flag_clear(QUEUE_FLAG_NOMERGES, lo->lo_queue);
+		lo->lo_flags |= LO_FLAGS_DIRECT_IO;
+	} else {
+		blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_queue);
+		lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
+	}
+	if (lo->lo_state == Lo_bound)
+		blk_mq_unfreeze_queue(lo->lo_queue);
+}
+
+/**
+ * loop_set_size() - sets device size and notifies userspace
+ * @lo: struct loop_device to set the size for
+ * @size: new size of the loop device
+ *
+ * Callers must validate that the size passed into this function fits into
+ * a sector_t, eg using loop_validate_size()
+ */
+static void loop_set_size(struct loop_device *lo, loff_t size)
+{
+	if (!set_capacity_and_notify(lo->lo_disk, size))
+		kobject_uevent(&disk_to_dev(lo->lo_disk)->kobj, KOBJ_CHANGE);
+}
+
+static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos)
+{
+	struct iov_iter i;
+	ssize_t bw;
+
+	iov_iter_bvec(&i, ITER_SOURCE, bvec, 1, bvec->bv_len);
+
+	file_start_write(file);
+	bw = vfs_iter_write(file, &i, ppos, 0);
+	file_end_write(file);
+
+	if (likely(bw ==  bvec->bv_len))
+		return 0;
+
+	printk_ratelimited(KERN_ERR
+		"loop: Write error at byte offset %llu, length %i.\n",
+		(unsigned long long)*ppos, bvec->bv_len);
+	if (bw >= 0)
+		bw = -EIO;
+	return bw;
+}
+
+static int lo_write_simple(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec;
+	struct req_iterator iter;
+	int ret = 0;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		ret = lo_write_bvec(lo->lo_backing_file, &bvec, &pos);
+		if (ret < 0)
+			break;
+		cond_resched();
+	}
+
+	return ret;
+}
+
+static int lo_read_simple(struct loop_device *lo, struct request *rq,
+		loff_t pos)
+{
+	struct bio_vec bvec;
+	struct req_iterator iter;
+	struct iov_iter i;
+	ssize_t len;
+
+	rq_for_each_segment(bvec, rq, iter) {
+		iov_iter_bvec(&i, ITER_DEST, &bvec, 1, bvec.bv_len);
+		len = vfs_iter_read(lo->lo_backing_file, &i, &pos, 0);
+		if (len < 0)
+			return len;
+
+		flush_dcache_page(bvec.bv_page);
+
+		if (len != bvec.bv_len) {
+			struct bio *bio;
+
+			__rq_for_each_bio(bio, rq)
+				zero_fill_bio(bio);
+			break;
+		}
+		cond_resched();
+	}
+
+	return 0;
+}
+
+static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
+			int mode)
+{
+	/*
+	 * We use fallocate to manipulate the space mappings used by the image
+	 * a.k.a. discard/zerorange.
+	 */
+	struct file *file = lo->lo_backing_file;
+	int ret;
+
+	mode |= FALLOC_FL_KEEP_SIZE;
+
+	if (!bdev_max_discard_sectors(lo->lo_device))
+		return -EOPNOTSUPP;
+
+	ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
+	if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
+		return -EIO;
+	return ret;
+}
+
+static int lo_req_flush(struct loop_device *lo, struct request *rq)
+{
+	int ret = vfs_fsync(lo->lo_backing_file, 0);
+	if (unlikely(ret && ret != -EINVAL))
+		ret = -EIO;
+
+	return ret;
+}
+
+static void lo_complete_rq(struct request *rq)
+{
+	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
+	blk_status_t ret = BLK_STS_OK;
+
+	if (!cmd->use_aio || cmd->ret < 0 || cmd->ret == blk_rq_bytes(rq) ||
+	    req_op(rq) != REQ_OP_READ) {
+		if (cmd->ret < 0)
+			ret = errno_to_blk_status(cmd->ret);
+		goto end_io;
+	}
+
+	/*
+	 * Short READ - if we got some data, advance our request and
+	 * retry it. If we got no data, end the rest with EIO.
+	 */
+	if (cmd->ret) {
+		blk_update_request(rq, BLK_STS_OK, cmd->ret);
+		cmd->ret = 0;
+		blk_mq_requeue_request(rq, true);
+	} else {
+		if (cmd->use_aio) {
+			struct bio *bio = rq->bio;
+
+			while (bio) {
+				zero_fill_bio(bio);
+				bio = bio->bi_next;
+			}
+		}
+		ret = BLK_STS_IOERR;
+end_io:
+		blk_mq_end_request(rq, ret);
+	}
+}
+
+static void lo_rw_aio_do_completion(struct loop_cmd *cmd)
+{
+	struct request *rq = blk_mq_rq_from_pdu(cmd);
+
+	if (!atomic_dec_and_test(&cmd->ref))
+		return;
+	kfree(cmd->bvec);
+	cmd->bvec = NULL;
+	if (likely(!blk_should_fake_timeout(rq->q)))
+		blk_mq_complete_request(rq);
+}
+
+static void lo_rw_aio_complete(struct kiocb *iocb, long ret)
+{
+	struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
+
+	cmd->ret = ret;
+	lo_rw_aio_do_completion(cmd);
+}
+
+static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
+		     loff_t pos, int rw)
+{
+	struct iov_iter iter;
+	struct req_iterator rq_iter;
+	struct bio_vec *bvec;
+	struct request *rq = blk_mq_rq_from_pdu(cmd);
+	struct bio *bio = rq->bio;
+	struct file *file = lo->lo_backing_file;
+	struct bio_vec tmp;
+	unsigned int offset;
+	int nr_bvec = 0;
+	int ret;
+
+	rq_for_each_bvec(tmp, rq, rq_iter)
+		nr_bvec++;
+
+	if (rq->bio != rq->biotail) {
+
+		bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
+				     GFP_NOIO);
+		if (!bvec)
+			return -EIO;
+		cmd->bvec = bvec;
+
+		/*
+		 * The bios of the request may be started from the middle of
+		 * the 'bvec' because of bio splitting, so we can't directly
+		 * copy bio->bi_iov_vec to new bvec. The rq_for_each_bvec
+		 * API will take care of all details for us.
+		 */
+		rq_for_each_bvec(tmp, rq, rq_iter) {
+			*bvec = tmp;
+			bvec++;
+		}
+		bvec = cmd->bvec;
+		offset = 0;
+	} else {
+		/*
+		 * Same here, this bio may be started from the middle of the
+		 * 'bvec' because of bio splitting, so offset from the bvec
+		 * must be passed to iov iterator
+		 */
+		offset = bio->bi_iter.bi_bvec_done;
+		bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+	}
+	atomic_set(&cmd->ref, 2);
+
+	iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
+	iter.iov_offset = offset;
+
+	cmd->iocb.ki_pos = pos;
+	cmd->iocb.ki_filp = file;
+	cmd->iocb.ki_complete = lo_rw_aio_complete;
+	cmd->iocb.ki_flags = IOCB_DIRECT;
+	cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+
+	if (rw == ITER_SOURCE)
+		ret = call_write_iter(file, &cmd->iocb, &iter);
+	else
+		ret = call_read_iter(file, &cmd->iocb, &iter);
+
+	lo_rw_aio_do_completion(cmd);
+
+	if (ret != -EIOCBQUEUED)
+		lo_rw_aio_complete(&cmd->iocb, ret);
+	return 0;
+}
+
+static int do_req_filebacked(struct loop_device *lo, struct request *rq)
+{
+	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
+	loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
+
+	/*
+	 * lo_write_simple and lo_read_simple should have been covered
+	 * by io submit style function like lo_rw_aio(), one blocker
+	 * is that lo_read_simple() need to call flush_dcache_page after
+	 * the page is written from kernel, and it isn't easy to handle
+	 * this in io submit style function which submits all segments
+	 * of the req at one time. And direct read IO doesn't need to
+	 * run flush_dcache_page().
+	 */
+	switch (req_op(rq)) {
+	case REQ_OP_FLUSH:
+		return lo_req_flush(lo, rq);
+	case REQ_OP_WRITE_ZEROES:
+		/*
+		 * If the caller doesn't want deallocation, call zeroout to
+		 * write zeroes the range.  Otherwise, punch them out.
+		 */
+		return lo_fallocate(lo, rq, pos,
+			(rq->cmd_flags & REQ_NOUNMAP) ?
+				FALLOC_FL_ZERO_RANGE :
+				FALLOC_FL_PUNCH_HOLE);
+	case REQ_OP_DISCARD:
+		return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
+	case REQ_OP_WRITE:
+		if (cmd->use_aio)
+			return lo_rw_aio(lo, cmd, pos, ITER_SOURCE);
+		else
+			return lo_write_simple(lo, rq, pos);
+	case REQ_OP_READ:
+		if (cmd->use_aio)
+			return lo_rw_aio(lo, cmd, pos, ITER_DEST);
+		else
+			return lo_read_simple(lo, rq, pos);
+	default:
+		WARN_ON_ONCE(1);
+		return -EIO;
+	}
+}
+
+static inline void loop_update_dio(struct loop_device *lo)
+{
+	__loop_update_dio(lo, (lo->lo_backing_file->f_flags & O_DIRECT) |
+				lo->use_dio);
+}
+
+static void loop_reread_partitions(struct loop_device *lo)
+{
+	int rc;
+
+	mutex_lock(&lo->lo_disk->open_mutex);
+	rc = bdev_disk_changed(lo->lo_disk, false);
+	mutex_unlock(&lo->lo_disk->open_mutex);
+	if (rc)
+		pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
+			__func__, lo->lo_number, lo->lo_file_name, rc);
+}
+
+static inline int is_loop_device(struct file *file)
+{
+	struct inode *i = file->f_mapping->host;
+
+	return i && S_ISBLK(i->i_mode) && imajor(i) == LOOP_MAJOR;
+}
+
+static int loop_validate_file(struct file *file, struct block_device *bdev)
+{
+	struct inode	*inode = file->f_mapping->host;
+	struct file	*f = file;
+
+	/* Avoid recursion */
+	while (is_loop_device(f)) {
+		struct loop_device *l;
+
+		lockdep_assert_held(&loop_validate_mutex);
+		if (f->f_mapping->host->i_rdev == bdev->bd_dev)
+			return -EBADF;
+
+		l = I_BDEV(f->f_mapping->host)->bd_disk->private_data;
+		if (l->lo_state != Lo_bound)
+			return -EINVAL;
+		/* Order wrt setting lo->lo_backing_file in loop_configure(). */
+		rmb();
+		f = l->lo_backing_file;
+	}
+	if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
+		return -EINVAL;
+	return 0;
+}
+
+/*
+ * 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 = fget(arg);
+	struct file *old_file;
+	int error;
+	bool partscan;
+	bool is_loop;
+
+	if (!file)
+		return -EBADF;
+
+	/* suppress uevents while reconfiguring the device */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
+
+	is_loop = is_loop_device(file);
+	error = loop_global_lock_killable(lo, is_loop);
+	if (error)
+		goto out_putf;
+	error = -ENXIO;
+	if (lo->lo_state != Lo_bound)
+		goto out_err;
+
+	/* the loop device has to be read-only */
+	error = -EINVAL;
+	if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
+		goto out_err;
+
+	error = loop_validate_file(file, bdev);
+	if (error)
+		goto out_err;
+
+	old_file = lo->lo_backing_file;
+
+	error = -EINVAL;
+
+	/* 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_err;
+
+	/* and ... switch */
+	disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
+	blk_mq_freeze_queue(lo->lo_queue);
+	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
+	lo->lo_backing_file = file;
+	lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
+	mapping_set_gfp_mask(file->f_mapping,
+			     lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+	loop_update_dio(lo);
+	blk_mq_unfreeze_queue(lo->lo_queue);
+	partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
+	loop_global_unlock(lo, is_loop);
+
+	/*
+	 * Flush loop_validate_file() before fput(), for l->lo_backing_file
+	 * might be pointing at old_file which might be the last reference.
+	 */
+	if (!is_loop) {
+		mutex_lock(&loop_validate_mutex);
+		mutex_unlock(&loop_validate_mutex);
+	}
+	/*
+	 * We must drop file reference outside of lo_mutex as dropping
+	 * the file ref can take open_mutex which creates circular locking
+	 * dependency.
+	 */
+	fput(old_file);
+	if (partscan)
+		loop_reread_partitions(lo);
+
+	error = 0;
+done:
+	/* enable and uncork uevent now that we are done */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
+	return error;
+
+out_err:
+	loop_global_unlock(lo, is_loop);
+out_putf:
+	fput(file);
+	goto done;
+}
+
+/* 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, 0444, 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 = file_path(lo->lo_backing_file, 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 sysfs_emit(buf, "%llu\n", (unsigned long long)lo->lo_offset);
+}
+
+static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
+{
+	return sysfs_emit(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 sysfs_emit(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 sysfs_emit(buf, "%s\n", partscan ? "1" : "0");
+}
+
+static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf)
+{
+	int dio = (lo->lo_flags & LO_FLAGS_DIRECT_IO);
+
+	return sysfs_emit(buf, "%s\n", dio ? "1" : "0");
+}
+
+LOOP_ATTR_RO(backing_file);
+LOOP_ATTR_RO(offset);
+LOOP_ATTR_RO(sizelimit);
+LOOP_ATTR_RO(autoclear);
+LOOP_ATTR_RO(partscan);
+LOOP_ATTR_RO(dio);
+
+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,
+	&loop_attr_dio.attr,
+	NULL,
+};
+
+static struct attribute_group loop_attribute_group = {
+	.name = "loop",
+	.attrs= loop_attrs,
+};
+
+static void loop_sysfs_init(struct loop_device *lo)
+{
+	lo->sysfs_inited = !sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
+						&loop_attribute_group);
+}
+
+static void loop_sysfs_exit(struct loop_device *lo)
+{
+	if (lo->sysfs_inited)
+		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;
+	u32 granularity, max_discard_sectors;
+
+	/*
+	 * If the backing device is a block device, mirror its zeroing
+	 * capability. Set the discard sectors to the block device's zeroing
+	 * capabilities because loop discards result in blkdev_issue_zeroout(),
+	 * not blkdev_issue_discard(). This maintains consistent behavior with
+	 * file-backed loop devices: discarded regions read back as zero.
+	 */
+	if (S_ISBLK(inode->i_mode)) {
+		struct request_queue *backingq = bdev_get_queue(I_BDEV(inode));
+
+		max_discard_sectors = backingq->limits.max_write_zeroes_sectors;
+		granularity = bdev_discard_granularity(I_BDEV(inode)) ?:
+			queue_physical_block_size(backingq);
+
+	/*
+	 * We use punch hole to reclaim the free space used by the
+	 * image a.k.a. discard.
+	 */
+	} else if (!file->f_op->fallocate) {
+		max_discard_sectors = 0;
+		granularity = 0;
+
+	} else {
+		struct kstatfs sbuf;
+
+		max_discard_sectors = UINT_MAX >> 9;
+		if (!vfs_statfs(&file->f_path, &sbuf))
+			granularity = sbuf.f_bsize;
+		else
+			max_discard_sectors = 0;
+	}
+
+	if (max_discard_sectors) {
+		q->limits.discard_granularity = granularity;
+		blk_queue_max_discard_sectors(q, max_discard_sectors);
+		blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
+	} else {
+		q->limits.discard_granularity = 0;
+		blk_queue_max_discard_sectors(q, 0);
+		blk_queue_max_write_zeroes_sectors(q, 0);
+	}
+}
+
+struct loop_worker {
+	struct rb_node rb_node;
+	struct work_struct work;
+	struct list_head cmd_list;
+	struct list_head idle_list;
+	struct loop_device *lo;
+	struct cgroup_subsys_state *blkcg_css;
+	unsigned long last_ran_at;
+};
+
+static void loop_workfn(struct work_struct *work);
+
+#ifdef CONFIG_BLK_CGROUP
+static inline int queue_on_root_worker(struct cgroup_subsys_state *css)
+{
+	return !css || css == blkcg_root_css;
+}
+#else
+static inline int queue_on_root_worker(struct cgroup_subsys_state *css)
+{
+	return !css;
+}
+#endif
+
+static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
+{
+	struct rb_node **node, *parent = NULL;
+	struct loop_worker *cur_worker, *worker = NULL;
+	struct work_struct *work;
+	struct list_head *cmd_list;
+
+	spin_lock_irq(&lo->lo_work_lock);
+
+	if (queue_on_root_worker(cmd->blkcg_css))
+		goto queue_work;
+
+	node = &lo->worker_tree.rb_node;
+
+	while (*node) {
+		parent = *node;
+		cur_worker = container_of(*node, struct loop_worker, rb_node);
+		if (cur_worker->blkcg_css == cmd->blkcg_css) {
+			worker = cur_worker;
+			break;
+		} else if ((long)cur_worker->blkcg_css < (long)cmd->blkcg_css) {
+			node = &(*node)->rb_left;
+		} else {
+			node = &(*node)->rb_right;
+		}
+	}
+	if (worker)
+		goto queue_work;
+
+	worker = kzalloc(sizeof(struct loop_worker), GFP_NOWAIT | __GFP_NOWARN);
+	/*
+	 * In the event we cannot allocate a worker, just queue on the
+	 * rootcg worker and issue the I/O as the rootcg
+	 */
+	if (!worker) {
+		cmd->blkcg_css = NULL;
+		if (cmd->memcg_css)
+			css_put(cmd->memcg_css);
+		cmd->memcg_css = NULL;
+		goto queue_work;
+	}
+
+	worker->blkcg_css = cmd->blkcg_css;
+	css_get(worker->blkcg_css);
+	INIT_WORK(&worker->work, loop_workfn);
+	INIT_LIST_HEAD(&worker->cmd_list);
+	INIT_LIST_HEAD(&worker->idle_list);
+	worker->lo = lo;
+	rb_link_node(&worker->rb_node, parent, node);
+	rb_insert_color(&worker->rb_node, &lo->worker_tree);
+queue_work:
+	if (worker) {
+		/*
+		 * We need to remove from the idle list here while
+		 * holding the lock so that the idle timer doesn't
+		 * free the worker
+		 */
+		if (!list_empty(&worker->idle_list))
+			list_del_init(&worker->idle_list);
+		work = &worker->work;
+		cmd_list = &worker->cmd_list;
+	} else {
+		work = &lo->rootcg_work;
+		cmd_list = &lo->rootcg_cmd_list;
+	}
+	list_add_tail(&cmd->list_entry, cmd_list);
+	queue_work(lo->workqueue, work);
+	spin_unlock_irq(&lo->lo_work_lock);
+}
+
+static void loop_set_timer(struct loop_device *lo)
+{
+	timer_reduce(&lo->timer, jiffies + LOOP_IDLE_WORKER_TIMEOUT);
+}
+
+static void loop_free_idle_workers(struct loop_device *lo, bool delete_all)
+{
+	struct loop_worker *pos, *worker;
+
+	spin_lock_irq(&lo->lo_work_lock);
+	list_for_each_entry_safe(worker, pos, &lo->idle_worker_list,
+				idle_list) {
+		if (!delete_all &&
+		    time_is_after_jiffies(worker->last_ran_at +
+					  LOOP_IDLE_WORKER_TIMEOUT))
+			break;
+		list_del(&worker->idle_list);
+		rb_erase(&worker->rb_node, &lo->worker_tree);
+		css_put(worker->blkcg_css);
+		kfree(worker);
+	}
+	if (!list_empty(&lo->idle_worker_list))
+		loop_set_timer(lo);
+	spin_unlock_irq(&lo->lo_work_lock);
+}
+
+static void loop_free_idle_workers_timer(struct timer_list *timer)
+{
+	struct loop_device *lo = container_of(timer, struct loop_device, timer);
+
+	return loop_free_idle_workers(lo, false);
+}
+
+static void loop_update_rotational(struct loop_device *lo)
+{
+	struct file *file = lo->lo_backing_file;
+	struct inode *file_inode = file->f_mapping->host;
+	struct block_device *file_bdev = file_inode->i_sb->s_bdev;
+	struct request_queue *q = lo->lo_queue;
+	bool nonrot = true;
+
+	/* not all filesystems (e.g. tmpfs) have a sb->s_bdev */
+	if (file_bdev)
+		nonrot = bdev_nonrot(file_bdev);
+
+	if (nonrot)
+		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
+	else
+		blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
+}
+
+/**
+ * loop_set_status_from_info - configure device from loop_info
+ * @lo: struct loop_device to configure
+ * @info: struct loop_info64 to configure the device with
+ *
+ * Configures the loop device parameters according to the passed
+ * in loop_info64 configuration.
+ */
+static int
+loop_set_status_from_info(struct loop_device *lo,
+			  const struct loop_info64 *info)
+{
+	if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
+		return -EINVAL;
+
+	switch (info->lo_encrypt_type) {
+	case LO_CRYPT_NONE:
+		break;
+	case LO_CRYPT_XOR:
+		pr_warn("support for the xor transformation has been removed.\n");
+		return -EINVAL;
+	case LO_CRYPT_CRYPTOAPI:
+		pr_warn("support for cryptoloop has been removed.  Use dm-crypt instead.\n");
+		return -EINVAL;
+	default:
+		return -EINVAL;
+	}
+
+	/* Avoid assigning overflow values */
+	if (info->lo_offset > LLONG_MAX || info->lo_sizelimit > LLONG_MAX)
+		return -EOVERFLOW;
+
+	lo->lo_offset = info->lo_offset;
+	lo->lo_sizelimit = info->lo_sizelimit;
+
+	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
+	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
+	lo->lo_flags = info->lo_flags;
+	return 0;
+}
+
+static int loop_configure(struct loop_device *lo, fmode_t mode,
+			  struct block_device *bdev,
+			  const struct loop_config *config)
+{
+	struct file *file = fget(config->fd);
+	struct inode *inode;
+	struct address_space *mapping;
+	int error;
+	loff_t size;
+	bool partscan;
+	unsigned short bsize;
+	bool is_loop;
+
+	if (!file)
+		return -EBADF;
+	is_loop = is_loop_device(file);
+
+	/* This is safe, since we have a reference from open(). */
+	__module_get(THIS_MODULE);
+
+	/*
+	 * If we don't hold exclusive handle for the device, upgrade to it
+	 * here to avoid changing device under exclusive owner.
+	 */
+	if (!(mode & FMODE_EXCL)) {
+		error = bd_prepare_to_claim(bdev, loop_configure);
+		if (error)
+			goto out_putf;
+	}
+
+	error = loop_global_lock_killable(lo, is_loop);
+	if (error)
+		goto out_bdev;
+
+	error = -EBUSY;
+	if (lo->lo_state != Lo_unbound)
+		goto out_unlock;
+
+	error = loop_validate_file(file, bdev);
+	if (error)
+		goto out_unlock;
+
+	mapping = file->f_mapping;
+	inode = mapping->host;
+
+	if ((config->info.lo_flags & ~LOOP_CONFIGURE_SETTABLE_FLAGS) != 0) {
+		error = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (config->block_size) {
+		error = blk_validate_block_size(config->block_size);
+		if (error)
+			goto out_unlock;
+	}
+
+	error = loop_set_status_from_info(lo, &config->info);
+	if (error)
+		goto out_unlock;
+
+	if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
+	    !file->f_op->write_iter)
+		lo->lo_flags |= LO_FLAGS_READ_ONLY;
+
+	if (!lo->workqueue) {
+		lo->workqueue = alloc_workqueue("loop%d",
+						WQ_UNBOUND | WQ_FREEZABLE,
+						0, lo->lo_number);
+		if (!lo->workqueue) {
+			error = -ENOMEM;
+			goto out_unlock;
+		}
+	}
+
+	/* suppress uevents while reconfiguring the device */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
+
+	disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
+	set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
+
+	lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
+	lo->lo_device = bdev;
+	lo->lo_backing_file = file;
+	lo->old_gfp_mask = mapping_gfp_mask(mapping);
+	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+
+	if (!(lo->lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
+		blk_queue_write_cache(lo->lo_queue, true, false);
+
+	if (config->block_size)
+		bsize = config->block_size;
+	else if ((lo->lo_backing_file->f_flags & O_DIRECT) && inode->i_sb->s_bdev)
+		/* In case of direct I/O, match underlying block size */
+		bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
+	else
+		bsize = 512;
+
+	blk_queue_logical_block_size(lo->lo_queue, bsize);
+	blk_queue_physical_block_size(lo->lo_queue, bsize);
+	blk_queue_io_min(lo->lo_queue, bsize);
+
+	loop_config_discard(lo);
+	loop_update_rotational(lo);
+	loop_update_dio(lo);
+	loop_sysfs_init(lo);
+
+	size = get_loop_size(lo, file);
+	loop_set_size(lo, size);
+
+	/* Order wrt reading lo_state in loop_validate_file(). */
+	wmb();
+
+	lo->lo_state = Lo_bound;
+	if (part_shift)
+		lo->lo_flags |= LO_FLAGS_PARTSCAN;
+	partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
+	if (partscan)
+		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
+
+	/* enable and uncork uevent now that we are done */
+	dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
+
+	loop_global_unlock(lo, is_loop);
+	if (partscan)
+		loop_reread_partitions(lo);
+
+	if (!(mode & FMODE_EXCL))
+		bd_abort_claiming(bdev, loop_configure);
+
+	return 0;
+
+out_unlock:
+	loop_global_unlock(lo, is_loop);
+out_bdev:
+	if (!(mode & FMODE_EXCL))
+		bd_abort_claiming(bdev, loop_configure);
+out_putf:
+	fput(file);
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	return error;
+}
+
+static void __loop_clr_fd(struct loop_device *lo, bool release)
+{
+	struct file *filp;
+	gfp_t gfp = lo->old_gfp_mask;
+
+	if (test_bit(QUEUE_FLAG_WC, &lo->lo_queue->queue_flags))
+		blk_queue_write_cache(lo->lo_queue, false, false);
+
+	/*
+	 * Freeze the request queue when unbinding on a live file descriptor and
+	 * thus an open device.  When called from ->release we are guaranteed
+	 * that there is no I/O in progress already.
+	 */
+	if (!release)
+		blk_mq_freeze_queue(lo->lo_queue);
+
+	spin_lock_irq(&lo->lo_lock);
+	filp = lo->lo_backing_file;
+	lo->lo_backing_file = NULL;
+	spin_unlock_irq(&lo->lo_lock);
+
+	lo->lo_device = NULL;
+	lo->lo_offset = 0;
+	lo->lo_sizelimit = 0;
+	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
+	blk_queue_logical_block_size(lo->lo_queue, 512);
+	blk_queue_physical_block_size(lo->lo_queue, 512);
+	blk_queue_io_min(lo->lo_queue, 512);
+	invalidate_disk(lo->lo_disk);
+	loop_sysfs_exit(lo);
+	/* let user-space know about this change */
+	kobject_uevent(&disk_to_dev(lo->lo_disk)->kobj, KOBJ_CHANGE);
+	mapping_set_gfp_mask(filp->f_mapping, gfp);
+	/* This is safe: open() is still holding a reference. */
+	module_put(THIS_MODULE);
+	if (!release)
+		blk_mq_unfreeze_queue(lo->lo_queue);
+
+	disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
+
+	if (lo->lo_flags & LO_FLAGS_PARTSCAN) {
+		int err;
+
+		/*
+		 * open_mutex has been held already in release path, so don't
+		 * acquire it if this function is called in such case.
+		 *
+		 * If the reread partition isn't from release path, lo_refcnt
+		 * must be at least one and it can only become zero when the
+		 * current holder is released.
+		 */
+		if (!release)
+			mutex_lock(&lo->lo_disk->open_mutex);
+		err = bdev_disk_changed(lo->lo_disk, false);
+		if (!release)
+			mutex_unlock(&lo->lo_disk->open_mutex);
+		if (err)
+			pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
+				__func__, lo->lo_number, err);
+		/* Device is gone, no point in returning error */
+	}
+
+	/*
+	 * lo->lo_state is set to Lo_unbound here after above partscan has
+	 * finished. There cannot be anybody else entering __loop_clr_fd() as
+	 * Lo_rundown state protects us from all the other places trying to
+	 * change the 'lo' device.
+	 */
+	lo->lo_flags = 0;
+	if (!part_shift)
+		set_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
+	mutex_lock(&lo->lo_mutex);
+	lo->lo_state = Lo_unbound;
+	mutex_unlock(&lo->lo_mutex);
+
+	/*
+	 * Need not hold lo_mutex to fput backing file. Calling fput holding
+	 * lo_mutex triggers a circular lock dependency possibility warning as
+	 * fput can take open_mutex which is usually taken before lo_mutex.
+	 */
+	fput(filp);
+}
+
+static int loop_clr_fd(struct loop_device *lo)
+{
+	int err;
+
+	/*
+	 * Since lo_ioctl() is called without locks held, it is possible that
+	 * loop_configure()/loop_change_fd() and loop_clr_fd() run in parallel.
+	 *
+	 * Therefore, use global lock when setting Lo_rundown state in order to
+	 * make sure that loop_validate_file() will fail if the "struct file"
+	 * which loop_configure()/loop_change_fd() found via fget() was this
+	 * loop device.
+	 */
+	err = loop_global_lock_killable(lo, true);
+	if (err)
+		return err;
+	if (lo->lo_state != Lo_bound) {
+		loop_global_unlock(lo, true);
+		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 (disk_openers(lo->lo_disk) > 1) {
+		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
+		loop_global_unlock(lo, true);
+		return 0;
+	}
+	lo->lo_state = Lo_rundown;
+	loop_global_unlock(lo, true);
+
+	__loop_clr_fd(lo, false);
+	return 0;
+}
+
+static int
+loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
+{
+	int err;
+	int prev_lo_flags;
+	bool partscan = false;
+	bool size_changed = false;
+
+	err = mutex_lock_killable(&lo->lo_mutex);
+	if (err)
+		return err;
+	if (lo->lo_state != Lo_bound) {
+		err = -ENXIO;
+		goto out_unlock;
+	}
+
+	if (lo->lo_offset != info->lo_offset ||
+	    lo->lo_sizelimit != info->lo_sizelimit) {
+		size_changed = true;
+		sync_blockdev(lo->lo_device);
+		invalidate_bdev(lo->lo_device);
+	}
+
+	/* I/O need to be drained during transfer transition */
+	blk_mq_freeze_queue(lo->lo_queue);
+
+	prev_lo_flags = lo->lo_flags;
+
+	err = loop_set_status_from_info(lo, info);
+	if (err)
+		goto out_unfreeze;
+
+	/* Mask out flags that can't be set using LOOP_SET_STATUS. */
+	lo->lo_flags &= LOOP_SET_STATUS_SETTABLE_FLAGS;
+	/* For those flags, use the previous values instead */
+	lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_SETTABLE_FLAGS;
+	/* For flags that can't be cleared, use previous values too */
+	lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_CLEARABLE_FLAGS;
+
+	if (size_changed) {
+		loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
+					   lo->lo_backing_file);
+		loop_set_size(lo, new_size);
+	}
+
+	loop_config_discard(lo);
+
+	/* update dio if lo_offset or transfer is changed */
+	__loop_update_dio(lo, lo->use_dio);
+
+out_unfreeze:
+	blk_mq_unfreeze_queue(lo->lo_queue);
+
+	if (!err && (lo->lo_flags & LO_FLAGS_PARTSCAN) &&
+	     !(prev_lo_flags & LO_FLAGS_PARTSCAN)) {
+		clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
+		partscan = true;
+	}
+out_unlock:
+	mutex_unlock(&lo->lo_mutex);
+	if (partscan)
+		loop_reread_partitions(lo);
+
+	return err;
+}
+
+static int
+loop_get_status(struct loop_device *lo, struct loop_info64 *info)
+{
+	struct path path;
+	struct kstat stat;
+	int ret;
+
+	ret = mutex_lock_killable(&lo->lo_mutex);
+	if (ret)
+		return ret;
+	if (lo->lo_state != Lo_bound) {
+		mutex_unlock(&lo->lo_mutex);
+		return -ENXIO;
+	}
+
+	memset(info, 0, sizeof(*info));
+	info->lo_number = lo->lo_number;
+	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);
+
+	/* Drop lo_mutex while we call into the filesystem. */
+	path = lo->lo_backing_file->f_path;
+	path_get(&path);
+	mutex_unlock(&lo->lo_mutex);
+	ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT);
+	if (!ret) {
+		info->lo_device = huge_encode_dev(stat.dev);
+		info->lo_inode = stat.ino;
+		info->lo_rdevice = huge_encode_dev(stat.rdev);
+	}
+	path_put(&path);
+	return ret;
+}
+
+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_flags = info->lo_flags;
+	memcpy(info64->lo_file_name, info->lo_name, LO_NAME_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_flags = info64->lo_flags;
+	memcpy(info->lo_name, info64->lo_file_name, LO_NAME_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;
+
+	if (!arg)
+		return -EINVAL;
+	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;
+
+	if (!arg)
+		return -EINVAL;
+	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)
+{
+	loff_t size;
+
+	if (unlikely(lo->lo_state != Lo_bound))
+		return -ENXIO;
+
+	size = get_loop_size(lo, lo->lo_backing_file);
+	loop_set_size(lo, size);
+
+	return 0;
+}
+
+static int loop_set_dio(struct loop_device *lo, unsigned long arg)
+{
+	int error = -ENXIO;
+	if (lo->lo_state != Lo_bound)
+		goto out;
+
+	__loop_update_dio(lo, !!arg);
+	if (lo->use_dio == !!arg)
+		return 0;
+	error = -EINVAL;
+ out:
+	return error;
+}
+
+static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
+{
+	int err = 0;
+
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
+
+	err = blk_validate_block_size(arg);
+	if (err)
+		return err;
+
+	if (lo->lo_queue->limits.logical_block_size == arg)
+		return 0;
+
+	sync_blockdev(lo->lo_device);
+	invalidate_bdev(lo->lo_device);
+
+	blk_mq_freeze_queue(lo->lo_queue);
+	blk_queue_logical_block_size(lo->lo_queue, arg);
+	blk_queue_physical_block_size(lo->lo_queue, arg);
+	blk_queue_io_min(lo->lo_queue, arg);
+	loop_update_dio(lo);
+	blk_mq_unfreeze_queue(lo->lo_queue);
+
+	return err;
+}
+
+static int lo_simple_ioctl(struct loop_device *lo, unsigned int cmd,
+			   unsigned long arg)
+{
+	int err;
+
+	err = mutex_lock_killable(&lo->lo_mutex);
+	if (err)
+		return err;
+	switch (cmd) {
+	case LOOP_SET_CAPACITY:
+		err = loop_set_capacity(lo);
+		break;
+	case LOOP_SET_DIRECT_IO:
+		err = loop_set_dio(lo, arg);
+		break;
+	case LOOP_SET_BLOCK_SIZE:
+		err = loop_set_block_size(lo, arg);
+		break;
+	default:
+		err = -EINVAL;
+	}
+	mutex_unlock(&lo->lo_mutex);
+	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;
+	void __user *argp = (void __user *) arg;
+	int err;
+
+	switch (cmd) {
+	case LOOP_SET_FD: {
+		/*
+		 * Legacy case - pass in a zeroed out struct loop_config with
+		 * only the file descriptor set , which corresponds with the
+		 * default parameters we'd have used otherwise.
+		 */
+		struct loop_config config;
+
+		memset(&config, 0, sizeof(config));
+		config.fd = arg;
+
+		return loop_configure(lo, mode, bdev, &config);
+	}
+	case LOOP_CONFIGURE: {
+		struct loop_config config;
+
+		if (copy_from_user(&config, argp, sizeof(config)))
+			return -EFAULT;
+
+		return loop_configure(lo, mode, bdev, &config);
+	}
+	case LOOP_CHANGE_FD:
+		return loop_change_fd(lo, bdev, arg);
+	case LOOP_CLR_FD:
+		return loop_clr_fd(lo);
+	case LOOP_SET_STATUS:
+		err = -EPERM;
+		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) {
+			err = loop_set_status_old(lo, argp);
+		}
+		break;
+	case LOOP_GET_STATUS:
+		return loop_get_status_old(lo, argp);
+	case LOOP_SET_STATUS64:
+		err = -EPERM;
+		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) {
+			err = loop_set_status64(lo, argp);
+		}
+		break;
+	case LOOP_GET_STATUS64:
+		return loop_get_status64(lo, argp);
+	case LOOP_SET_CAPACITY:
+	case LOOP_SET_DIRECT_IO:
+	case LOOP_SET_BLOCK_SIZE:
+		if (!(mode & FMODE_WRITE) && !capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		fallthrough;
+	default:
+		err = lo_simple_ioctl(lo, cmd, arg);
+		break;
+	}
+
+	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;        /* obsolete, ignored */
+	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_flags = info.lo_flags;
+	memcpy(info64->lo_file_name, info.lo_name, LO_NAME_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_flags = info64->lo_flags;
+	memcpy(info.lo_name, info64->lo_file_name, LO_NAME_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;
+
+	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;
+
+	if (!arg)
+		return -EINVAL;
+	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:
+		err = loop_set_status_compat(lo,
+			     (const struct compat_loop_info __user *)arg);
+		break;
+	case LOOP_GET_STATUS:
+		err = loop_get_status_compat(lo,
+				     (struct compat_loop_info __user *)arg);
+		break;
+	case LOOP_SET_CAPACITY:
+	case LOOP_CLR_FD:
+	case LOOP_GET_STATUS64:
+	case LOOP_SET_STATUS64:
+	case LOOP_CONFIGURE:
+		arg = (unsigned long) compat_ptr(arg);
+		fallthrough;
+	case LOOP_SET_FD:
+	case LOOP_CHANGE_FD:
+	case LOOP_SET_BLOCK_SIZE:
+	case LOOP_SET_DIRECT_IO:
+		err = lo_ioctl(bdev, mode, cmd, arg);
+		break;
+	default:
+		err = -ENOIOCTLCMD;
+		break;
+	}
+	return err;
+}
+#endif
+
+static void lo_release(struct gendisk *disk, fmode_t mode)
+{
+	struct loop_device *lo = disk->private_data;
+
+	if (disk_openers(disk) > 0)
+		return;
+
+	mutex_lock(&lo->lo_mutex);
+	if (lo->lo_state == Lo_bound && (lo->lo_flags & LO_FLAGS_AUTOCLEAR)) {
+		lo->lo_state = Lo_rundown;
+		mutex_unlock(&lo->lo_mutex);
+		/*
+		 * In autoclear mode, stop the loop thread
+		 * and remove configuration after last close.
+		 */
+		__loop_clr_fd(lo, true);
+		return;
+	}
+	mutex_unlock(&lo->lo_mutex);
+}
+
+static void lo_free_disk(struct gendisk *disk)
+{
+	struct loop_device *lo = disk->private_data;
+
+	if (lo->workqueue)
+		destroy_workqueue(lo->workqueue);
+	loop_free_idle_workers(lo, true);
+	del_timer_sync(&lo->timer);
+	mutex_destroy(&lo->lo_mutex);
+	kfree(lo);
+}
+
+static const struct block_device_operations lo_fops = {
+	.owner =	THIS_MODULE,
+	.release =	lo_release,
+	.ioctl =	lo_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl =	lo_compat_ioctl,
+#endif
+	.free_disk =	lo_free_disk,
+};
+
+/*
+ * And now the modules code and kernel interface.
+ */
+
+/*
+ * If max_loop is specified, create that many devices upfront.
+ * This also becomes a hard limit. If max_loop is not specified,
+ * the default isn't a hard limit (as before commit 85c50197716c
+ * changed the default value from 0 for max_loop=0 reasons), just
+ * 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.
+ */
+static int max_loop = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
+
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
+static bool max_loop_specified;
+
+static int max_loop_param_set_int(const char *val,
+				  const struct kernel_param *kp)
+{
+	int ret;
+
+	ret = param_set_int(val, kp);
+	if (ret < 0)
+		return ret;
+
+	max_loop_specified = true;
+	return 0;
+}
+
+static const struct kernel_param_ops max_loop_param_ops = {
+	.set = max_loop_param_set_int,
+	.get = param_get_int,
+};
+
+module_param_cb(max_loop, &max_loop_param_ops, &max_loop, 0444);
+MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
+#else
+module_param(max_loop, int, 0444);
+MODULE_PARM_DESC(max_loop, "Initial number of loop devices");
+#endif
+
+module_param(max_part, int, 0444);
+MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
+
+static int hw_queue_depth = LOOP_DEFAULT_HW_Q_DEPTH;
+
+static int loop_set_hw_queue_depth(const char *s, const struct kernel_param *p)
+{
+	int ret = kstrtoint(s, 10, &hw_queue_depth);
+
+	return (ret || (hw_queue_depth < 1)) ? -EINVAL : 0;
+}
+
+static const struct kernel_param_ops loop_hw_qdepth_param_ops = {
+	.set	= loop_set_hw_queue_depth,
+	.get	= param_get_int,
+};
+
+device_param_cb(hw_queue_depth, &loop_hw_qdepth_param_ops, &hw_queue_depth, 0444);
+MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 128");
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
+
+static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
+		const struct blk_mq_queue_data *bd)
+{
+	struct request *rq = bd->rq;
+	struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
+	struct loop_device *lo = rq->q->queuedata;
+
+	blk_mq_start_request(rq);
+
+	if (lo->lo_state != Lo_bound)
+		return BLK_STS_IOERR;
+
+	switch (req_op(rq)) {
+	case REQ_OP_FLUSH:
+	case REQ_OP_DISCARD:
+	case REQ_OP_WRITE_ZEROES:
+		cmd->use_aio = false;
+		break;
+	default:
+		cmd->use_aio = lo->use_dio;
+		break;
+	}
+
+	/* always use the first bio's css */
+	cmd->blkcg_css = NULL;
+	cmd->memcg_css = NULL;
+#ifdef CONFIG_BLK_CGROUP
+	if (rq->bio) {
+		cmd->blkcg_css = bio_blkcg_css(rq->bio);
+#ifdef CONFIG_MEMCG
+		if (cmd->blkcg_css) {
+			cmd->memcg_css =
+				cgroup_get_e_css(cmd->blkcg_css->cgroup,
+						&memory_cgrp_subsys);
+		}
+#endif
+	}
+#endif
+	loop_queue_work(lo, cmd);
+
+	return BLK_STS_OK;
+}
+
+static void loop_handle_cmd(struct loop_cmd *cmd)
+{
+	struct cgroup_subsys_state *cmd_blkcg_css = cmd->blkcg_css;
+	struct cgroup_subsys_state *cmd_memcg_css = cmd->memcg_css;
+	struct request *rq = blk_mq_rq_from_pdu(cmd);
+	const bool write = op_is_write(req_op(rq));
+	struct loop_device *lo = rq->q->queuedata;
+	int ret = 0;
+	struct mem_cgroup *old_memcg = NULL;
+	const bool use_aio = cmd->use_aio;
+
+	if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
+		ret = -EIO;
+		goto failed;
+	}
+
+	if (cmd_blkcg_css)
+		kthread_associate_blkcg(cmd_blkcg_css);
+	if (cmd_memcg_css)
+		old_memcg = set_active_memcg(
+			mem_cgroup_from_css(cmd_memcg_css));
+
+	/*
+	 * do_req_filebacked() may call blk_mq_complete_request() synchronously
+	 * or asynchronously if using aio. Hence, do not touch 'cmd' after
+	 * do_req_filebacked() has returned unless we are sure that 'cmd' has
+	 * not yet been completed.
+	 */
+	ret = do_req_filebacked(lo, rq);
+
+	if (cmd_blkcg_css)
+		kthread_associate_blkcg(NULL);
+
+	if (cmd_memcg_css) {
+		set_active_memcg(old_memcg);
+		css_put(cmd_memcg_css);
+	}
+ failed:
+	/* complete non-aio request */
+	if (!use_aio || ret) {
+		if (ret == -EOPNOTSUPP)
+			cmd->ret = ret;
+		else
+			cmd->ret = ret ? -EIO : 0;
+		if (likely(!blk_should_fake_timeout(rq->q)))
+			blk_mq_complete_request(rq);
+	}
+}
+
+static void loop_process_work(struct loop_worker *worker,
+			struct list_head *cmd_list, struct loop_device *lo)
+{
+	int orig_flags = current->flags;
+	struct loop_cmd *cmd;
+
+	current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
+	spin_lock_irq(&lo->lo_work_lock);
+	while (!list_empty(cmd_list)) {
+		cmd = container_of(
+			cmd_list->next, struct loop_cmd, list_entry);
+		list_del(cmd_list->next);
+		spin_unlock_irq(&lo->lo_work_lock);
+
+		loop_handle_cmd(cmd);
+		cond_resched();
+
+		spin_lock_irq(&lo->lo_work_lock);
+	}
+
+	/*
+	 * We only add to the idle list if there are no pending cmds
+	 * *and* the worker will not run again which ensures that it
+	 * is safe to free any worker on the idle list
+	 */
+	if (worker && !work_pending(&worker->work)) {
+		worker->last_ran_at = jiffies;
+		list_add_tail(&worker->idle_list, &lo->idle_worker_list);
+		loop_set_timer(lo);
+	}
+	spin_unlock_irq(&lo->lo_work_lock);
+	current->flags = orig_flags;
+}
+
+static void loop_workfn(struct work_struct *work)
+{
+	struct loop_worker *worker =
+		container_of(work, struct loop_worker, work);
+	loop_process_work(worker, &worker->cmd_list, worker->lo);
+}
+
+static void loop_rootcg_workfn(struct work_struct *work)
+{
+	struct loop_device *lo =
+		container_of(work, struct loop_device, rootcg_work);
+	loop_process_work(NULL, &lo->rootcg_cmd_list, lo);
+}
+
+static const struct blk_mq_ops loop_mq_ops = {
+	.queue_rq       = loop_queue_rq,
+	.complete	= lo_complete_rq,
+};
+
+static int loop_add(int i)
+{
+	struct loop_device *lo;
+	struct gendisk *disk;
+	int err;
+
+	err = -ENOMEM;
+	lo = kzalloc(sizeof(*lo), GFP_KERNEL);
+	if (!lo)
+		goto out;
+	lo->worker_tree = RB_ROOT;
+	INIT_LIST_HEAD(&lo->idle_worker_list);
+	timer_setup(&lo->timer, loop_free_idle_workers_timer, TIMER_DEFERRABLE);
+	lo->lo_state = Lo_unbound;
+
+	err = mutex_lock_killable(&loop_ctl_mutex);
+	if (err)
+		goto out_free_dev;
+
+	/* 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);
+	}
+	mutex_unlock(&loop_ctl_mutex);
+	if (err < 0)
+		goto out_free_dev;
+	i = err;
+
+	lo->tag_set.ops = &loop_mq_ops;
+	lo->tag_set.nr_hw_queues = 1;
+	lo->tag_set.queue_depth = hw_queue_depth;
+	lo->tag_set.numa_node = NUMA_NO_NODE;
+	lo->tag_set.cmd_size = sizeof(struct loop_cmd);
+	lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING |
+		BLK_MQ_F_NO_SCHED_BY_DEFAULT;
+	lo->tag_set.driver_data = lo;
+
+	err = blk_mq_alloc_tag_set(&lo->tag_set);
+	if (err)
+		goto out_free_idr;
+
+	disk = lo->lo_disk = blk_mq_alloc_disk(&lo->tag_set, lo);
+	if (IS_ERR(disk)) {
+		err = PTR_ERR(disk);
+		goto out_cleanup_tags;
+	}
+	lo->lo_queue = lo->lo_disk->queue;
+
+	blk_queue_max_hw_sectors(lo->lo_queue, BLK_DEF_MAX_SECTORS);
+
+	/*
+	 * By default, we do buffer IO, so it doesn't make sense to enable
+	 * merge because the I/O submitted to backing file is handled page by
+	 * page. For directio mode, merge does help to dispatch bigger request
+	 * to underlayer disk. We will enable merge once directio is enabled.
+	 */
+	blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_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)
+		set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
+	mutex_init(&lo->lo_mutex);
+	lo->lo_number		= i;
+	spin_lock_init(&lo->lo_lock);
+	spin_lock_init(&lo->lo_work_lock);
+	INIT_WORK(&lo->rootcg_work, loop_rootcg_workfn);
+	INIT_LIST_HEAD(&lo->rootcg_cmd_list);
+	disk->major		= LOOP_MAJOR;
+	disk->first_minor	= i << part_shift;
+	disk->minors		= 1 << part_shift;
+	disk->fops		= &lo_fops;
+	disk->private_data	= lo;
+	disk->queue		= lo->lo_queue;
+	disk->events		= DISK_EVENT_MEDIA_CHANGE;
+	disk->event_flags	= DISK_EVENT_FLAG_UEVENT;
+	sprintf(disk->disk_name, "loop%d", i);
+	/* Make this loop device reachable from pathname. */
+	err = add_disk(disk);
+	if (err)
+		goto out_cleanup_disk;
+
+	/* Show this loop device. */
+	mutex_lock(&loop_ctl_mutex);
+	lo->idr_visible = true;
+	mutex_unlock(&loop_ctl_mutex);
+
+	return i;
+
+out_cleanup_disk:
+	put_disk(disk);
+out_cleanup_tags:
+	blk_mq_free_tag_set(&lo->tag_set);
+out_free_idr:
+	mutex_lock(&loop_ctl_mutex);
+	idr_remove(&loop_index_idr, i);
+	mutex_unlock(&loop_ctl_mutex);
+out_free_dev:
+	kfree(lo);
+out:
+	return err;
+}
+
+static void loop_remove(struct loop_device *lo)
+{
+	/* Make this loop device unreachable from pathname. */
+	del_gendisk(lo->lo_disk);
+	blk_mq_free_tag_set(&lo->tag_set);
+
+	mutex_lock(&loop_ctl_mutex);
+	idr_remove(&loop_index_idr, lo->lo_number);
+	mutex_unlock(&loop_ctl_mutex);
+
+	put_disk(lo->lo_disk);
+}
+
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
+static void loop_probe(dev_t dev)
+{
+	int idx = MINOR(dev) >> part_shift;
+
+	if (max_loop_specified && max_loop && idx >= max_loop)
+		return;
+	loop_add(idx);
+}
+#else
+#define loop_probe NULL
+#endif /* !CONFIG_BLOCK_LEGACY_AUTOLOAD */
+
+static int loop_control_remove(int idx)
+{
+	struct loop_device *lo;
+	int ret;
+
+	if (idx < 0) {
+		pr_warn_once("deleting an unspecified loop device is not supported.\n");
+		return -EINVAL;
+	}
+		
+	/* Hide this loop device for serialization. */
+	ret = mutex_lock_killable(&loop_ctl_mutex);
+	if (ret)
+		return ret;
+	lo = idr_find(&loop_index_idr, idx);
+	if (!lo || !lo->idr_visible)
+		ret = -ENODEV;
+	else
+		lo->idr_visible = false;
+	mutex_unlock(&loop_ctl_mutex);
+	if (ret)
+		return ret;
+
+	/* Check whether this loop device can be removed. */
+	ret = mutex_lock_killable(&lo->lo_mutex);
+	if (ret)
+		goto mark_visible;
+	if (lo->lo_state != Lo_unbound || disk_openers(lo->lo_disk) > 0) {
+		mutex_unlock(&lo->lo_mutex);
+		ret = -EBUSY;
+		goto mark_visible;
+	}
+	/* Mark this loop device as no more bound, but not quite unbound yet */
+	lo->lo_state = Lo_deleting;
+	mutex_unlock(&lo->lo_mutex);
+
+	loop_remove(lo);
+	return 0;
+
+mark_visible:
+	/* Show this loop device again. */
+	mutex_lock(&loop_ctl_mutex);
+	lo->idr_visible = true;
+	mutex_unlock(&loop_ctl_mutex);
+	return ret;
+}
+
+static int loop_control_get_free(int idx)
+{
+	struct loop_device *lo;
+	int id, ret;
+
+	ret = mutex_lock_killable(&loop_ctl_mutex);
+	if (ret)
+		return ret;
+	idr_for_each_entry(&loop_index_idr, lo, id) {
+		/* Hitting a race results in creating a new loop device which is harmless. */
+		if (lo->idr_visible && data_race(lo->lo_state) == Lo_unbound)
+			goto found;
+	}
+	mutex_unlock(&loop_ctl_mutex);
+	return loop_add(-1);
+found:
+	mutex_unlock(&loop_ctl_mutex);
+	return id;
+}
+
+static long loop_control_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long parm)
+{
+	switch (cmd) {
+	case LOOP_CTL_ADD:
+		return loop_add(parm);
+	case LOOP_CTL_REMOVE:
+		return loop_control_remove(parm);
+	case LOOP_CTL_GET_FREE:
+		return loop_control_get_free(parm);
+	default:
+		return -ENOSYS;
+	}
+}
+
+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;
+	int 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 err_out;
+	}
+
+	if (max_loop > 1UL << (MINORBITS - part_shift)) {
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	err = misc_register(&loop_misc);
+	if (err < 0)
+		goto err_out;
+
+
+	if (__register_blkdev(LOOP_MAJOR, "loop", loop_probe)) {
+		err = -EIO;
+		goto misc_out;
+	}
+
+	/* pre-create number of devices given by config or max_loop */
+	for (i = 0; i < max_loop; i++)
+		loop_add(i);
+
+	printk(KERN_INFO "loop: module loaded\n");
+	return 0;
+
+misc_out:
+	misc_deregister(&loop_misc);
+err_out:
+	return err;
+}
+
+static void __exit loop_exit(void)
+{
+	struct loop_device *lo;
+	int id;
+
+	unregister_blkdev(LOOP_MAJOR, "loop");
+	misc_deregister(&loop_misc);
+
+	/*
+	 * There is no need to use loop_ctl_mutex here, for nobody else can
+	 * access loop_index_idr when this module is unloading (unless forced
+	 * module unloading is requested). If this is not a clean unloading,
+	 * we have no means to avoid kernel crash.
+	 */
+	idr_for_each_entry(&loop_index_idr, lo, id)
+		loop_remove(lo);
+
+	idr_destroy(&loop_index_idr);
+}
+
+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);
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
+	max_loop_specified = true;
+#endif
+	return 1;
+}
+
+__setup("max_loop=", max_loop_setup);
+#endif