OSCL-LXR linux-6.0.1/​drivers/​block/​loop.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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);
 }
 
 static void __loop_update_dio(struct loop_device *lo, bool dio)
 {
     struct file *file = lo->lo_backing_file;
     struct address_space *mapping = file->f_mapping;
     struct inode *inode = mapping->host;
     unsigned short sb_bsize = 0;
     unsigned dio_align = 0;
     bool use_dio;
 
     if (inode->i_sb->s_bdev) {
         sb_bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
         dio_align = sb_bsize - 1;
     }
 
     /*
      * 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 the backing device's.
      *
      * TODO: the above condition may be loosed in the future, and
      * direct I/O may be switched runtime at that time because most
      * of requests in sane applications should be PAGE_SIZE aligned
      */
     if (dio) {
         if (queue_logical_block_size(lo->lo_queue) >= sb_bsize &&
             !(lo->lo_offset & dio_align) &&
             (file->f_mode & FMODE_CAN_ODIRECT))
             use_dio = true;
         else
             use_dio = false;
     } else {
         use_dio = false;
     }
 
     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, WRITE, 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, READ, &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, bool 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 == WRITE)
         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, WRITE);
         else
             return lo_write_simple(lo, rq, pos);
     case REQ_OP_READ:
         if (cmd->use_aio)
             return lo_rw_aio(lo, cmd, pos, READ);
         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;
     }
 
     lo->lo_offset = info->lo_offset;
     lo->lo_sizelimit = info->lo_sizelimit;
 
     /* loff_t vars have been assigned __u64 */
     if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
         return -EOVERFLOW;
 
     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);
 
     /* suppress uevents while reconfiguring the device */
     dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
 
     /*
      * 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;
         }
     }
 
     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);
 
     loop_global_unlock(lo, is_loop);
     if (partscan)
         loop_reread_partitions(lo);
     if (!(mode & FMODE_EXCL))
         bd_abort_claiming(bdev, loop_configure);
 
     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_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);
     goto done;
 }
 
 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.
  */
 static int max_loop;
 module_param(max_loop, int, 0444);
 MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
 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 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;
 
     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));
 
     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 (!cmd->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);
 }
 
 static void loop_probe(dev_t dev)
 {
     int idx = MINOR(dev) >> part_shift;
 
     if (max_loop && idx >= max_loop)
         return;
     loop_add(idx);
 }
 
 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, nr;
     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;
     }
 
     /*
      * If max_loop is specified, create that many devices upfront.
      * This also becomes a hard limit. If max_loop is not specified,
      * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
      * init time. Loop devices can be requested on-demand with the
      * /dev/loop-control interface, or be instantiated by accessing
      * a 'dead' device node.
      */
     if (max_loop)
         nr = max_loop;
     else
         nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
 
     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 < nr; 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);
     return 1;
 }
 
 __setup("max_loop=", max_loop_setup);
 #endif

This page was automatically generated by the 2.1.0 LXR engine. The LXR team