Merge tag 'block-6.9-20240405' of git://git.kernel.dk/linux

[thirdparty/linux.git] / drivers / block / loop.c

// 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);

        bw = vfs_iter_write(file, &i, ppos, 0);

        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);
        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 queue_limits *lim)
{
        struct file *file = lo->lo_backing_file;
        struct inode *inode = file->f_mapping->host;
        u32 granularity = 0, max_discard_sectors = 0;
        struct kstatfs sbuf;

        /*
         * 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 && !vfs_statfs(&file->f_path, &sbuf)) {
                max_discard_sectors = UINT_MAX >> 9;
                granularity = sbuf.f_bsize;
        }

        lim->max_hw_discard_sectors = max_discard_sectors;
        lim->max_write_zeroes_sectors = max_discard_sectors;
        if (max_discard_sectors)
                lim->discard_granularity = granularity;
        else
                lim->discard_granularity = 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_reconfigure_limits(struct loop_device *lo, unsigned short bsize,
                bool update_discard_settings)
{
        struct queue_limits lim;

        lim = queue_limits_start_update(lo->lo_queue);
        lim.logical_block_size = bsize;
        lim.physical_block_size = bsize;
        lim.io_min = bsize;
        if (update_discard_settings)
                loop_config_discard(lo, &lim);
        return queue_limits_commit_update(lo->lo_queue, &lim);
}

static int loop_configure(struct loop_device *lo, blk_mode_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 & BLK_OPEN_EXCL)) {
                error = bd_prepare_to_claim(bdev, loop_configure, NULL);
                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 & BLK_OPEN_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);
        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;

        error = loop_reconfigure_limits(lo, bsize, true);
        if (WARN_ON_ONCE(error))
                goto out_unlock;

        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 & BLK_OPEN_EXCL))
                bd_abort_claiming(bdev, loop_configure);

        return 0;

out_unlock:
        loop_global_unlock(lo, is_loop);
out_bdev:
        if (!(mode & BLK_OPEN_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);
        loop_reconfigure_limits(lo, 512, false);
        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);

        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);
        }

        /* 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);
        err = loop_reconfigure_limits(lo, arg, false);
        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, blk_mode_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 & BLK_OPEN_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 & BLK_OPEN_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 & BLK_OPEN_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, blk_mode_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)
{
        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);
        timer_shutdown_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 qd, ret;

        ret = kstrtoint(s, 0, &qd);
        if (ret < 0)
                return ret;
        if (qd < 1)
                return -EINVAL;
        hw_queue_depth = qd;
        return 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: " __stringify(LOOP_DEFAULT_HW_Q_DEPTH));

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 queue_limits lim = {
                /*
                 * Random number picked from the historic block max_sectors cap.
                 */
                .max_hw_sectors         = 2560u,
        };
        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, &lim, lo);
        if (IS_ERR(disk)) {
                err = PTR_ERR(disk);
                goto out_cleanup_tags;
        }
        lo->lo_queue = lo->lo_disk->queue;

        /*
         * 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