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loop.c

/*
 *  linux/drivers/block/loop.c
 *
 *  Written by Theodore Ts'o, 3/29/93
 *
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU General Public License.
 *
 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
 *
 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
 *
 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
 *
 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
 *
 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
 *
 * Loadable modules and other fixes by AK, 1998
 *
 * Make real block number available to downstream transfer functions, enables
 * CBC (and relatives) mode encryption requiring unique IVs per data block.
 * Reed H. Petty, rhp@draper.net
 *
 * Maximum number of loop devices now dynamic via max_loop module parameter.
 * Russell Kroll <rkroll@exploits.org> 19990701
 *
 * Maximum number of loop devices when compiled-in now selectable by passing
 * max_loop=<1-255> to the kernel on boot.
 * Erik I. Bolsø, <eriki@himolde.no>, Oct 31, 1999
 *
 * Completely rewrite request handling to be make_request_fn style and
 * non blocking, pushing work to a helper thread. Lots of fixes from
 * Al Viro too.
 * Jens Axboe <axboe@suse.de>, Nov 2000
 *
 * Support up to 256 loop devices
 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
 *
 * Support for falling back on the write file operation when the address space
 * operations prepare_write and/or commit_write are not available on the
 * backing filesystem.
 * Anton Altaparmakov, 16 Feb 2005
 *
 * Still To Fix:
 * - Advisory locking is ignored here.
 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
 *
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/major.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
#include <linux/blkpg.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/loop.h>
#include <linux/compat.h>
#include <linux/suspend.h>
#include <linux/freezer.h>
#include <linux/writeback.h>
#include <linux/buffer_head.h>            /* for invalidate_bdev() */
#include <linux/completion.h>
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/kthread.h>
#include <linux/splice.h>

#include <asm/uaccess.h>

static LIST_HEAD(loop_devices);
static DEFINE_MUTEX(loop_devices_mutex);

/*
 * Transfer functions
 */
static int transfer_none(struct loop_device *lo, int cmd,
                   struct page *raw_page, unsigned raw_off,
                   struct page *loop_page, unsigned loop_off,
                   int size, sector_t real_block)
{
      char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
      char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;

      if (cmd == READ)
            memcpy(loop_buf, raw_buf, size);
      else
            memcpy(raw_buf, loop_buf, size);

      kunmap_atomic(raw_buf, KM_USER0);
      kunmap_atomic(loop_buf, KM_USER1);
      cond_resched();
      return 0;
}

static int transfer_xor(struct loop_device *lo, int cmd,
                  struct page *raw_page, unsigned raw_off,
                  struct page *loop_page, unsigned loop_off,
                  int size, sector_t real_block)
{
      char *raw_buf = kmap_atomic(raw_page, KM_USER0) + raw_off;
      char *loop_buf = kmap_atomic(loop_page, KM_USER1) + loop_off;
      char *in, *out, *key;
      int i, keysize;

      if (cmd == READ) {
            in = raw_buf;
            out = loop_buf;
      } else {
            in = loop_buf;
            out = raw_buf;
      }

      key = lo->lo_encrypt_key;
      keysize = lo->lo_encrypt_key_size;
      for (i = 0; i < size; i++)
            *out++ = *in++ ^ key[(i & 511) % keysize];

      kunmap_atomic(raw_buf, KM_USER0);
      kunmap_atomic(loop_buf, KM_USER1);
      cond_resched();
      return 0;
}

static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
{
      if (unlikely(info->lo_encrypt_key_size <= 0))
            return -EINVAL;
      return 0;
}

static struct loop_func_table none_funcs = {
      .number = LO_CRYPT_NONE,
      .transfer = transfer_none,
};    

static struct loop_func_table xor_funcs = {
      .number = LO_CRYPT_XOR,
      .transfer = transfer_xor,
      .init = xor_init
};    

/* xfer_funcs[0] is special - its release function is never called */
static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
      &none_funcs,
      &xor_funcs
};

static loff_t get_loop_size(struct loop_device *lo, struct file *file)
{
      loff_t size, offset, loopsize;

      /* Compute loopsize in bytes */
      size = i_size_read(file->f_mapping->host);
      offset = lo->lo_offset;
      loopsize = size - offset;
      if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
            loopsize = lo->lo_sizelimit;

      /*
       * Unfortunately, if we want to do I/O on the device,
       * the number of 512-byte sectors has to fit into a sector_t.
       */
      return loopsize >> 9;
}

static int
figure_loop_size(struct loop_device *lo)
{
      loff_t size = get_loop_size(lo, lo->lo_backing_file);
      sector_t x = (sector_t)size;

      if (unlikely((loff_t)x != size))
            return -EFBIG;

      set_capacity(lo->lo_disk, x);
      return 0;                           
}

static inline int
lo_do_transfer(struct loop_device *lo, int cmd,
             struct page *rpage, unsigned roffs,
             struct page *lpage, unsigned loffs,
             int size, sector_t rblock)
{
      if (unlikely(!lo->transfer))
            return 0;

      return lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
}

/**
 * do_lo_send_aops - helper for writing data to a loop device
 *
 * This is the fast version for backing filesystems which implement the address
 * space operations write_begin and write_end.
 */
static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
            int bsize, loff_t pos, struct page *unused)
{
      struct file *file = lo->lo_backing_file; /* kudos to NFsckingS */
      struct address_space *mapping = file->f_mapping;
      pgoff_t index;
      unsigned offset, bv_offs;
      int len, ret;

      mutex_lock(&mapping->host->i_mutex);
      index = pos >> PAGE_CACHE_SHIFT;
      offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1);
      bv_offs = bvec->bv_offset;
      len = bvec->bv_len;
      while (len > 0) {
            sector_t IV;
            unsigned size, copied;
            int transfer_result;
            struct page *page;
            void *fsdata;

            IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
            size = PAGE_CACHE_SIZE - offset;
            if (size > len)
                  size = len;

            ret = pagecache_write_begin(file, mapping, pos, size, 0,
                                          &page, &fsdata);
            if (ret)
                  goto fail;

            transfer_result = lo_do_transfer(lo, WRITE, page, offset,
                        bvec->bv_page, bv_offs, size, IV);
            copied = size;
            if (unlikely(transfer_result))
                  copied = 0;

            ret = pagecache_write_end(file, mapping, pos, size, copied,
                                          page, fsdata);
            if (ret < 0 || ret != copied)
                  goto fail;

            if (unlikely(transfer_result))
                  goto fail;

            bv_offs += copied;
            len -= copied;
            offset = 0;
            index++;
            pos += copied;
      }
      ret = 0;
out:
      mutex_unlock(&mapping->host->i_mutex);
      return ret;
fail:
      ret = -1;
      goto out;
}

/**
 * __do_lo_send_write - helper for writing data to a loop device
 *
 * This helper just factors out common code between do_lo_send_direct_write()
 * and do_lo_send_write().
 */
static int __do_lo_send_write(struct file *file,
            u8 *buf, const int len, loff_t pos)
{
      ssize_t bw;
      mm_segment_t old_fs = get_fs();

      set_fs(get_ds());
      bw = file->f_op->write(file, buf, len, &pos);
      set_fs(old_fs);
      if (likely(bw == len))
            return 0;
      printk(KERN_ERR "loop: Write error at byte offset %llu, length %i.\n",
                  (unsigned long long)pos, len);
      if (bw >= 0)
            bw = -EIO;
      return bw;
}

/**
 * do_lo_send_direct_write - helper for writing data to a loop device
 *
 * This is the fast, non-transforming version for backing filesystems which do
 * not implement the address space operations write_begin and write_end.
 * It uses the write file operation which should be present on all writeable
 * filesystems.
 */
static int do_lo_send_direct_write(struct loop_device *lo,
            struct bio_vec *bvec, int bsize, loff_t pos, struct page *page)
{
      ssize_t bw = __do_lo_send_write(lo->lo_backing_file,
                  kmap(bvec->bv_page) + bvec->bv_offset,
                  bvec->bv_len, pos);
      kunmap(bvec->bv_page);
      cond_resched();
      return bw;
}

/**
 * do_lo_send_write - helper for writing data to a loop device
 *
 * This is the slow, transforming version for filesystems which do not
 * implement the address space operations write_begin and write_end.  It
 * uses the write file operation which should be present on all writeable
 * filesystems.
 *
 * Using fops->write is slower than using aops->{prepare,commit}_write in the
 * transforming case because we need to double buffer the data as we cannot do
 * the transformations in place as we do not have direct access to the
 * destination pages of the backing file.
 */
static int do_lo_send_write(struct loop_device *lo, struct bio_vec *bvec,
            int bsize, loff_t pos, struct page *page)
{
      int ret = lo_do_transfer(lo, WRITE, page, 0, bvec->bv_page,
                  bvec->bv_offset, bvec->bv_len, pos >> 9);
      if (likely(!ret))
            return __do_lo_send_write(lo->lo_backing_file,
                        page_address(page), bvec->bv_len,
                        pos);
      printk(KERN_ERR "loop: Transfer error at byte offset %llu, "
                  "length %i.\n", (unsigned long long)pos, bvec->bv_len);
      if (ret > 0)
            ret = -EIO;
      return ret;
}

static int lo_send(struct loop_device *lo, struct bio *bio, int bsize,
            loff_t pos)
{
      int (*do_lo_send)(struct loop_device *, struct bio_vec *, int, loff_t,
                  struct page *page);
      struct bio_vec *bvec;
      struct page *page = NULL;
      int i, ret = 0;

      do_lo_send = do_lo_send_aops;
      if (!(lo->lo_flags & LO_FLAGS_USE_AOPS)) {
            do_lo_send = do_lo_send_direct_write;
            if (lo->transfer != transfer_none) {
                  page = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
                  if (unlikely(!page))
                        goto fail;
                  kmap(page);
                  do_lo_send = do_lo_send_write;
            }
      }
      bio_for_each_segment(bvec, bio, i) {
            ret = do_lo_send(lo, bvec, bsize, pos, page);
            if (ret < 0)
                  break;
            pos += bvec->bv_len;
      }
      if (page) {
            kunmap(page);
            __free_page(page);
      }
out:
      return ret;
fail:
      printk(KERN_ERR "loop: Failed to allocate temporary page for write.\n");
      ret = -ENOMEM;
      goto out;
}

struct lo_read_data {
      struct loop_device *lo;
      struct page *page;
      unsigned offset;
      int bsize;
};

static int
lo_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
            struct splice_desc *sd)
{
      struct lo_read_data *p = sd->u.data;
      struct loop_device *lo = p->lo;
      struct page *page = buf->page;
      sector_t IV;
      size_t size;
      int ret;

      ret = buf->ops->confirm(pipe, buf);
      if (unlikely(ret))
            return ret;

      IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9)) +
                                          (buf->offset >> 9);
      size = sd->len;
      if (size > p->bsize)
            size = p->bsize;

      if (lo_do_transfer(lo, READ, page, buf->offset, p->page, p->offset, size, IV)) {
            printk(KERN_ERR "loop: transfer error block %ld\n",
                   page->index);
            size = -EINVAL;
      }

      flush_dcache_page(p->page);

      if (size > 0)
            p->offset += size;

      return size;
}

static int
lo_direct_splice_actor(struct pipe_inode_info *pipe, struct splice_desc *sd)
{
      return __splice_from_pipe(pipe, sd, lo_splice_actor);
}

static int
do_lo_receive(struct loop_device *lo,
            struct bio_vec *bvec, int bsize, loff_t pos)
{
      struct lo_read_data cookie;
      struct splice_desc sd;
      struct file *file;
      long retval;

      cookie.lo = lo;
      cookie.page = bvec->bv_page;
      cookie.offset = bvec->bv_offset;
      cookie.bsize = bsize;

      sd.len = 0;
      sd.total_len = bvec->bv_len;
      sd.flags = 0;
      sd.pos = pos;
      sd.u.data = &cookie;

      file = lo->lo_backing_file;
      retval = splice_direct_to_actor(file, &sd, lo_direct_splice_actor);

      if (retval < 0)
            return retval;

      return 0;
}

static int
lo_receive(struct loop_device *lo, struct bio *bio, int bsize, loff_t pos)
{
      struct bio_vec *bvec;
      int i, ret = 0;

      bio_for_each_segment(bvec, bio, i) {
            ret = do_lo_receive(lo, bvec, bsize, pos);
            if (ret < 0)
                  break;
            pos += bvec->bv_len;
      }
      return ret;
}

static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
{
      loff_t pos;
      int ret;

      pos = ((loff_t) bio->bi_sector << 9) + lo->lo_offset;
      if (bio_rw(bio) == WRITE)
            ret = lo_send(lo, bio, lo->lo_blocksize, pos);
      else
            ret = lo_receive(lo, bio, lo->lo_blocksize, pos);
      return ret;
}

/*
 * Add bio to back of pending list
 */
static void loop_add_bio(struct loop_device *lo, struct bio *bio)
{
      if (lo->lo_biotail) {
            lo->lo_biotail->bi_next = bio;
            lo->lo_biotail = bio;
      } else
            lo->lo_bio = lo->lo_biotail = bio;
}

/*
 * Grab first pending buffer
 */
static struct bio *loop_get_bio(struct loop_device *lo)
{
      struct bio *bio;

      if ((bio = lo->lo_bio)) {
            if (bio == lo->lo_biotail)
                  lo->lo_biotail = NULL;
            lo->lo_bio = bio->bi_next;
            bio->bi_next = NULL;
      }

      return bio;
}

static int loop_make_request(struct request_queue *q, struct bio *old_bio)
{
      struct loop_device *lo = q->queuedata;
      int rw = bio_rw(old_bio);

      if (rw == READA)
            rw = READ;

      BUG_ON(!lo || (rw != READ && rw != WRITE));

      spin_lock_irq(&lo->lo_lock);
      if (lo->lo_state != Lo_bound)
            goto out;
      if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
            goto out;
      loop_add_bio(lo, old_bio);
      wake_up(&lo->lo_event);
      spin_unlock_irq(&lo->lo_lock);
      return 0;

out:
      spin_unlock_irq(&lo->lo_lock);
      bio_io_error(old_bio);
      return 0;
}

/*
 * kick off io on the underlying address space
 */
static void loop_unplug(struct request_queue *q)
{
      struct loop_device *lo = q->queuedata;

      clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
      blk_run_address_space(lo->lo_backing_file->f_mapping);
}

struct switch_request {
      struct file *file;
      struct completion wait;
};

static void do_loop_switch(struct loop_device *, struct switch_request *);

static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
{
      if (unlikely(!bio->bi_bdev)) {
            do_loop_switch(lo, bio->bi_private);
            bio_put(bio);
      } else {
            int ret = do_bio_filebacked(lo, bio);
            bio_endio(bio, ret);
      }
}

/*
 * worker thread that handles reads/writes to file backed loop devices,
 * to avoid blocking in our make_request_fn. it also does loop decrypting
 * on reads for block backed loop, as that is too heavy to do from
 * b_end_io context where irqs may be disabled.
 *
 * Loop explanation:  loop_clr_fd() sets lo_state to Lo_rundown before
 * calling kthread_stop().  Therefore once kthread_should_stop() is
 * true, make_request will not place any more requests.  Therefore
 * once kthread_should_stop() is true and lo_bio is NULL, we are
 * done with the loop.
 */
static int loop_thread(void *data)
{
      struct loop_device *lo = data;
      struct bio *bio;

      set_user_nice(current, -20);

      while (!kthread_should_stop() || lo->lo_bio) {

            wait_event_interruptible(lo->lo_event,
                        lo->lo_bio || kthread_should_stop());

            if (!lo->lo_bio)
                  continue;
            spin_lock_irq(&lo->lo_lock);
            bio = loop_get_bio(lo);
            spin_unlock_irq(&lo->lo_lock);

            BUG_ON(!bio);
            loop_handle_bio(lo, bio);
      }

      return 0;
}

/*
 * loop_switch performs the hard work of switching a backing store.
 * First it needs to flush existing IO, it does this by sending a magic
 * BIO down the pipe. The completion of this BIO does the actual switch.
 */
static int loop_switch(struct loop_device *lo, struct file *file)
{
      struct switch_request w;
      struct bio *bio = bio_alloc(GFP_KERNEL, 0);
      if (!bio)
            return -ENOMEM;
      init_completion(&w.wait);
      w.file = file;
      bio->bi_private = &w;
      bio->bi_bdev = NULL;
      loop_make_request(lo->lo_queue, bio);
      wait_for_completion(&w.wait);
      return 0;
}

/*
 * Do the actual switch; called from the BIO completion routine
 */
static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
{
      struct file *file = p->file;
      struct file *old_file = lo->lo_backing_file;
      struct address_space *mapping = file->f_mapping;

      mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
      lo->lo_backing_file = file;
      lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
            mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
      lo->old_gfp_mask = mapping_gfp_mask(mapping);
      mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
      complete(&p->wait);
}


/*
 * loop_change_fd switched the backing store of a loopback device to
 * a new file. This is useful for operating system installers to free up
 * the original file and in High Availability environments to switch to
 * an alternative location for the content in case of server meltdown.
 * This can only work if the loop device is used read-only, and if the
 * new backing store is the same size and type as the old backing store.
 */
static int loop_change_fd(struct loop_device *lo, struct file *lo_file,
                   struct block_device *bdev, unsigned int arg)
{
      struct file *file, *old_file;
      struct inode      *inode;
      int         error;

      error = -ENXIO;
      if (lo->lo_state != Lo_bound)
            goto out;

      /* the loop device has to be read-only */
      error = -EINVAL;
      if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
            goto out;

      error = -EBADF;
      file = fget(arg);
      if (!file)
            goto out;

      inode = file->f_mapping->host;
      old_file = lo->lo_backing_file;

      error = -EINVAL;

      if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
            goto out_putf;

      /* new backing store needs to support loop (eg splice_read) */
      if (!inode->i_fop->splice_read)
            goto out_putf;

      /* size of the new backing store needs to be the same */
      if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
            goto out_putf;

      /* and ... switch */
      error = loop_switch(lo, file);
      if (error)
            goto out_putf;

      fput(old_file);
      return 0;

 out_putf:
      fput(file);
 out:
      return error;
}

static inline int is_loop_device(struct file *file)
{
      struct inode *i = file->f_mapping->host;

      return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
}

static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
                   struct block_device *bdev, unsigned int arg)
{
      struct file *file, *f;
      struct inode      *inode;
      struct address_space *mapping;
      unsigned lo_blocksize;
      int         lo_flags = 0;
      int         error;
      loff_t            size;

      /* This is safe, since we have a reference from open(). */
      __module_get(THIS_MODULE);

      error = -EBADF;
      file = fget(arg);
      if (!file)
            goto out;

      error = -EBUSY;
      if (lo->lo_state != Lo_unbound)
            goto out_putf;

      /* Avoid recursion */
      f = file;
      while (is_loop_device(f)) {
            struct loop_device *l;

            if (f->f_mapping->host->i_rdev == lo_file->f_mapping->host->i_rdev)
                  goto out_putf;

            l = f->f_mapping->host->i_bdev->bd_disk->private_data;
            if (l->lo_state == Lo_unbound) {
                  error = -EINVAL;
                  goto out_putf;
            }
            f = l->lo_backing_file;
      }

      mapping = file->f_mapping;
      inode = mapping->host;

      if (!(file->f_mode & FMODE_WRITE))
            lo_flags |= LO_FLAGS_READ_ONLY;

      error = -EINVAL;
      if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
            const struct address_space_operations *aops = mapping->a_ops;
            /*
             * If we can't read - sorry. If we only can't write - well,
             * it's going to be read-only.
             */
            if (!file->f_op->splice_read)
                  goto out_putf;
            if (aops->prepare_write || aops->write_begin)
                  lo_flags |= LO_FLAGS_USE_AOPS;
            if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
                  lo_flags |= LO_FLAGS_READ_ONLY;

            lo_blocksize = S_ISBLK(inode->i_mode) ?
                  inode->i_bdev->bd_block_size : PAGE_SIZE;

            error = 0;
      } else {
            goto out_putf;
      }

      size = get_loop_size(lo, file);

      if ((loff_t)(sector_t)size != size) {
            error = -EFBIG;
            goto out_putf;
      }

      if (!(lo_file->f_mode & FMODE_WRITE))
            lo_flags |= LO_FLAGS_READ_ONLY;

      set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);

      lo->lo_blocksize = lo_blocksize;
      lo->lo_device = bdev;
      lo->lo_flags = lo_flags;
      lo->lo_backing_file = file;
      lo->transfer = transfer_none;
      lo->ioctl = NULL;
      lo->lo_sizelimit = 0;
      lo->old_gfp_mask = mapping_gfp_mask(mapping);
      mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));

      lo->lo_bio = lo->lo_biotail = NULL;

      /*
       * set queue make_request_fn, and add limits based on lower level
       * device
       */
      blk_queue_make_request(lo->lo_queue, loop_make_request);
      lo->lo_queue->queuedata = lo;
      lo->lo_queue->unplug_fn = loop_unplug;

      set_capacity(lo->lo_disk, size);
      bd_set_size(bdev, size << 9);

      set_blocksize(bdev, lo_blocksize);

      lo->lo_thread = kthread_create(loop_thread, lo, "loop%d",
                                    lo->lo_number);
      if (IS_ERR(lo->lo_thread)) {
            error = PTR_ERR(lo->lo_thread);
            goto out_clr;
      }
      lo->lo_state = Lo_bound;
      wake_up_process(lo->lo_thread);
      return 0;

out_clr:
      lo->lo_thread = NULL;
      lo->lo_device = NULL;
      lo->lo_backing_file = NULL;
      lo->lo_flags = 0;
      set_capacity(lo->lo_disk, 0);
      invalidate_bdev(bdev);
      bd_set_size(bdev, 0);
      mapping_set_gfp_mask(mapping, lo->old_gfp_mask);
      lo->lo_state = Lo_unbound;
 out_putf:
      fput(file);
 out:
      /* This is safe: open() is still holding a reference. */
      module_put(THIS_MODULE);
      return error;
}

static int
loop_release_xfer(struct loop_device *lo)
{
      int err = 0;
      struct loop_func_table *xfer = lo->lo_encryption;

      if (xfer) {
            if (xfer->release)
                  err = xfer->release(lo);
            lo->transfer = NULL;
            lo->lo_encryption = NULL;
            module_put(xfer->owner);
      }
      return err;
}

static int
loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
             const struct loop_info64 *i)
{
      int err = 0;

      if (xfer) {
            struct module *owner = xfer->owner;

            if (!try_module_get(owner))
                  return -EINVAL;
            if (xfer->init)
                  err = xfer->init(lo, i);
            if (err)
                  module_put(owner);
            else
                  lo->lo_encryption = xfer;
      }
      return err;
}

static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
{
      struct file *filp = lo->lo_backing_file;
      gfp_t gfp = lo->old_gfp_mask;

      if (lo->lo_state != Lo_bound)
            return -ENXIO;

      if (lo->lo_refcnt > 1)  /* we needed one fd for the ioctl */
            return -EBUSY;

      if (filp == NULL)
            return -EINVAL;

      spin_lock_irq(&lo->lo_lock);
      lo->lo_state = Lo_rundown;
      spin_unlock_irq(&lo->lo_lock);

      kthread_stop(lo->lo_thread);

      lo->lo_backing_file = NULL;

      loop_release_xfer(lo);
      lo->transfer = NULL;
      lo->ioctl = NULL;
      lo->lo_device = NULL;
      lo->lo_encryption = NULL;
      lo->lo_offset = 0;
      lo->lo_sizelimit = 0;
      lo->lo_encrypt_key_size = 0;
      lo->lo_flags = 0;
      lo->lo_thread = NULL;
      memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
      memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
      memset(lo->lo_file_name, 0, LO_NAME_SIZE);
      invalidate_bdev(bdev);
      set_capacity(lo->lo_disk, 0);
      bd_set_size(bdev, 0);
      mapping_set_gfp_mask(filp->f_mapping, gfp);
      lo->lo_state = Lo_unbound;
      fput(filp);
      /* This is safe: open() is still holding a reference. */
      module_put(THIS_MODULE);
      return 0;
}

static int
loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
{
      int err;
      struct loop_func_table *xfer;

      if (lo->lo_encrypt_key_size && lo->lo_key_owner != current->uid &&
          !capable(CAP_SYS_ADMIN))
            return -EPERM;
      if (lo->lo_state != Lo_bound)
            return -ENXIO;
      if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
            return -EINVAL;

      err = loop_release_xfer(lo);
      if (err)
            return err;

      if (info->lo_encrypt_type) {
            unsigned int type = info->lo_encrypt_type;

            if (type >= MAX_LO_CRYPT)
                  return -EINVAL;
            xfer = xfer_funcs[type];
            if (xfer == NULL)
                  return -EINVAL;
      } else
            xfer = NULL;

      err = loop_init_xfer(lo, xfer, info);
      if (err)
            return err;

      if (lo->lo_offset != info->lo_offset ||
          lo->lo_sizelimit != info->lo_sizelimit) {
            lo->lo_offset = info->lo_offset;
            lo->lo_sizelimit = info->lo_sizelimit;
            if (figure_loop_size(lo))
                  return -EFBIG;
      }

      memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
      memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
      lo->lo_file_name[LO_NAME_SIZE-1] = 0;
      lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;

      if (!xfer)
            xfer = &none_funcs;
      lo->transfer = xfer->transfer;
      lo->ioctl = xfer->ioctl;

      lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
      lo->lo_init[0] = info->lo_init[0];
      lo->lo_init[1] = info->lo_init[1];
      if (info->lo_encrypt_key_size) {
            memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
                   info->lo_encrypt_key_size);
            lo->lo_key_owner = current->uid;
      }     

      return 0;
}

static int
loop_get_status(struct loop_device *lo, struct loop_info64 *info)
{
      struct file *file = lo->lo_backing_file;
      struct kstat stat;
      int error;

      if (lo->lo_state != Lo_bound)
            return -ENXIO;
      error = vfs_getattr(file->f_path.mnt, file->f_path.dentry, &stat);
      if (error)
            return error;
      memset(info, 0, sizeof(*info));
      info->lo_number = lo->lo_number;
      info->lo_device = huge_encode_dev(stat.dev);
      info->lo_inode = stat.ino;
      info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
      info->lo_offset = lo->lo_offset;
      info->lo_sizelimit = lo->lo_sizelimit;
      info->lo_flags = lo->lo_flags;
      memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
      memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
      info->lo_encrypt_type =
            lo->lo_encryption ? lo->lo_encryption->number : 0;
      if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
            info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
            memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
                   lo->lo_encrypt_key_size);
      }
      return 0;
}

static void
loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
{
      memset(info64, 0, sizeof(*info64));
      info64->lo_number = info->lo_number;
      info64->lo_device = info->lo_device;
      info64->lo_inode = info->lo_inode;
      info64->lo_rdevice = info->lo_rdevice;
      info64->lo_offset = info->lo_offset;
      info64->lo_sizelimit = 0;
      info64->lo_encrypt_type = info->lo_encrypt_type;
      info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
      info64->lo_flags = info->lo_flags;
      info64->lo_init[0] = info->lo_init[0];
      info64->lo_init[1] = info->lo_init[1];
      if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
            memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
      else
            memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
      memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
}

static int
loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
{
      memset(info, 0, sizeof(*info));
      info->lo_number = info64->lo_number;
      info->lo_device = info64->lo_device;
      info->lo_inode = info64->lo_inode;
      info->lo_rdevice = info64->lo_rdevice;
      info->lo_offset = info64->lo_offset;
      info->lo_encrypt_type = info64->lo_encrypt_type;
      info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
      info->lo_flags = info64->lo_flags;
      info->lo_init[0] = info64->lo_init[0];
      info->lo_init[1] = info64->lo_init[1];
      if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
            memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
      else
            memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
      memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);

      /* error in case values were truncated */
      if (info->lo_device != info64->lo_device ||
          info->lo_rdevice != info64->lo_rdevice ||
          info->lo_inode != info64->lo_inode ||
          info->lo_offset != info64->lo_offset)
            return -EOVERFLOW;

      return 0;
}

static int
loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
{
      struct loop_info info;
      struct loop_info64 info64;

      if (copy_from_user(&info, arg, sizeof (struct loop_info)))
            return -EFAULT;
      loop_info64_from_old(&info, &info64);
      return loop_set_status(lo, &info64);
}

static int
loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
{
      struct loop_info64 info64;

      if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
            return -EFAULT;
      return loop_set_status(lo, &info64);
}

static int
loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
      struct loop_info info;
      struct loop_info64 info64;
      int err = 0;

      if (!arg)
            err = -EINVAL;
      if (!err)
            err = loop_get_status(lo, &info64);
      if (!err)
            err = loop_info64_to_old(&info64, &info);
      if (!err && copy_to_user(arg, &info, sizeof(info)))
            err = -EFAULT;

      return err;
}

static int
loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
      struct loop_info64 info64;
      int err = 0;

      if (!arg)
            err = -EINVAL;
      if (!err)
            err = loop_get_status(lo, &info64);
      if (!err && copy_to_user(arg, &info64, sizeof(info64)))
            err = -EFAULT;

      return err;
}

static int lo_ioctl(struct inode * inode, struct file * file,
      unsigned int cmd, unsigned long arg)
{
      struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
      int err;

      mutex_lock(&lo->lo_ctl_mutex);
      switch (cmd) {
      case LOOP_SET_FD:
            err = loop_set_fd(lo, file, inode->i_bdev, arg);
            break;
      case LOOP_CHANGE_FD:
            err = loop_change_fd(lo, file, inode->i_bdev, arg);
            break;
      case LOOP_CLR_FD:
            err = loop_clr_fd(lo, inode->i_bdev);
            break;
      case LOOP_SET_STATUS:
            err = loop_set_status_old(lo, (struct loop_info __user *) arg);
            break;
      case LOOP_GET_STATUS:
            err = loop_get_status_old(lo, (struct loop_info __user *) arg);
            break;
      case LOOP_SET_STATUS64:
            err = loop_set_status64(lo, (struct loop_info64 __user *) arg);
            break;
      case LOOP_GET_STATUS64:
            err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
            break;
      default:
            err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
      }
      mutex_unlock(&lo->lo_ctl_mutex);
      return err;
}

#ifdef CONFIG_COMPAT
struct compat_loop_info {
      compat_int_t      lo_number;      /* ioctl r/o */
      compat_dev_t      lo_device;      /* ioctl r/o */
      compat_ulong_t    lo_inode;       /* ioctl r/o */
      compat_dev_t      lo_rdevice;     /* ioctl r/o */
      compat_int_t      lo_offset;
      compat_int_t      lo_encrypt_type;
      compat_int_t      lo_encrypt_key_size;    /* ioctl w/o */
      compat_int_t      lo_flags;       /* ioctl r/o */
      char        lo_name[LO_NAME_SIZE];
      unsigned char     lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
      compat_ulong_t    lo_init[2];
      char        reserved[4];
};

/*
 * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
 * - noinlined to reduce stack space usage in main part of driver
 */
static noinline int
loop_info64_from_compat(const struct compat_loop_info __user *arg,
                  struct loop_info64 *info64)
{
      struct compat_loop_info info;

      if (copy_from_user(&info, arg, sizeof(info)))
            return -EFAULT;

      memset(info64, 0, sizeof(*info64));
      info64->lo_number = info.lo_number;
      info64->lo_device = info.lo_device;
      info64->lo_inode = info.lo_inode;
      info64->lo_rdevice = info.lo_rdevice;
      info64->lo_offset = info.lo_offset;
      info64->lo_sizelimit = 0;
      info64->lo_encrypt_type = info.lo_encrypt_type;
      info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
      info64->lo_flags = info.lo_flags;
      info64->lo_init[0] = info.lo_init[0];
      info64->lo_init[1] = info.lo_init[1];
      if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
            memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
      else
            memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
      memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
      return 0;
}

/*
 * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
 * - noinlined to reduce stack space usage in main part of driver
 */
static noinline int
loop_info64_to_compat(const struct loop_info64 *info64,
                  struct compat_loop_info __user *arg)
{
      struct compat_loop_info info;

      memset(&info, 0, sizeof(info));
      info.lo_number = info64->lo_number;
      info.lo_device = info64->lo_device;
      info.lo_inode = info64->lo_inode;
      info.lo_rdevice = info64->lo_rdevice;
      info.lo_offset = info64->lo_offset;
      info.lo_encrypt_type = info64->lo_encrypt_type;
      info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
      info.lo_flags = info64->lo_flags;
      info.lo_init[0] = info64->lo_init[0];
      info.lo_init[1] = info64->lo_init[1];
      if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
            memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
      else
            memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
      memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);

      /* error in case values were truncated */
      if (info.lo_device != info64->lo_device ||
          info.lo_rdevice != info64->lo_rdevice ||
          info.lo_inode != info64->lo_inode ||
          info.lo_offset != info64->lo_offset ||
          info.lo_init[0] != info64->lo_init[0] ||
          info.lo_init[1] != info64->lo_init[1])
            return -EOVERFLOW;

      if (copy_to_user(arg, &info, sizeof(info)))
            return -EFAULT;
      return 0;
}

static int
loop_set_status_compat(struct loop_device *lo,
                   const struct compat_loop_info __user *arg)
{
      struct loop_info64 info64;
      int ret;

      ret = loop_info64_from_compat(arg, &info64);
      if (ret < 0)
            return ret;
      return loop_set_status(lo, &info64);
}

static int
loop_get_status_compat(struct loop_device *lo,
                   struct compat_loop_info __user *arg)
{
      struct loop_info64 info64;
      int err = 0;

      if (!arg)
            err = -EINVAL;
      if (!err)
            err = loop_get_status(lo, &info64);
      if (!err)
            err = loop_info64_to_compat(&info64, arg);
      return err;
}

static long lo_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
      struct inode *inode = file->f_path.dentry->d_inode;
      struct loop_device *lo = inode->i_bdev->bd_disk->private_data;
      int err;

      switch(cmd) {
      case LOOP_SET_STATUS:
            mutex_lock(&lo->lo_ctl_mutex);
            err = loop_set_status_compat(
                  lo, (const struct compat_loop_info __user *) arg);
            mutex_unlock(&lo->lo_ctl_mutex);
            break;
      case LOOP_GET_STATUS:
            mutex_lock(&lo->lo_ctl_mutex);
            err = loop_get_status_compat(
                  lo, (struct compat_loop_info __user *) arg);
            mutex_unlock(&lo->lo_ctl_mutex);
            break;
      case LOOP_CLR_FD:
      case LOOP_GET_STATUS64:
      case LOOP_SET_STATUS64:
            arg = (unsigned long) compat_ptr(arg);
      case LOOP_SET_FD:
      case LOOP_CHANGE_FD:
            err = lo_ioctl(inode, file, cmd, arg);
            break;
      default:
            err = -ENOIOCTLCMD;
            break;
      }
      return err;
}
#endif

static int lo_open(struct inode *inode, struct file *file)
{
      struct loop_device *lo = inode->i_bdev->bd_disk->private_data;

      mutex_lock(&lo->lo_ctl_mutex);
      lo->lo_refcnt++;
      mutex_unlock(&lo->lo_ctl_mutex);

      return 0;
}

static int lo_release(struct inode *inode, struct file *file)
{
      struct loop_device *lo = inode->i_bdev->bd_disk->private_data;

      mutex_lock(&lo->lo_ctl_mutex);
      --lo->lo_refcnt;
      mutex_unlock(&lo->lo_ctl_mutex);

      return 0;
}

static struct block_device_operations lo_fops = {
      .owner =    THIS_MODULE,
      .open =           lo_open,
      .release =  lo_release,
      .ioctl =    lo_ioctl,
#ifdef CONFIG_COMPAT
      .compat_ioctl =   lo_compat_ioctl,
#endif
};

/*
 * And now the modules code and kernel interface.
 */
static int max_loop;
module_param(max_loop, int, 0);
MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);

int loop_register_transfer(struct loop_func_table *funcs)
{
      unsigned int n = funcs->number;

      if (n >= MAX_LO_CRYPT || xfer_funcs[n])
            return -EINVAL;
      xfer_funcs[n] = funcs;
      return 0;
}

int loop_unregister_transfer(int number)
{
      unsigned int n = number;
      struct loop_device *lo;
      struct loop_func_table *xfer;

      if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
            return -EINVAL;

      xfer_funcs[n] = NULL;

      list_for_each_entry(lo, &loop_devices, lo_list) {
            mutex_lock(&lo->lo_ctl_mutex);

            if (lo->lo_encryption == xfer)
                  loop_release_xfer(lo);

            mutex_unlock(&lo->lo_ctl_mutex);
      }

      return 0;
}

EXPORT_SYMBOL(loop_register_transfer);
EXPORT_SYMBOL(loop_unregister_transfer);

static struct loop_device *loop_alloc(int i)
{
      struct loop_device *lo;
      struct gendisk *disk;

      lo = kzalloc(sizeof(*lo), GFP_KERNEL);
      if (!lo)
            goto out;

      lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
      if (!lo->lo_queue)
            goto out_free_dev;

      disk = lo->lo_disk = alloc_disk(1);
      if (!disk)
            goto out_free_queue;

      mutex_init(&lo->lo_ctl_mutex);
      lo->lo_number           = i;
      lo->lo_thread           = NULL;
      init_waitqueue_head(&lo->lo_event);
      spin_lock_init(&lo->lo_lock);
      disk->major       = LOOP_MAJOR;
      disk->first_minor = i;
      disk->fops        = &lo_fops;
      disk->private_data      = lo;
      disk->queue       = lo->lo_queue;
      sprintf(disk->disk_name, "loop%d", i);
      return lo;

out_free_queue:
      blk_cleanup_queue(lo->lo_queue);
out_free_dev:
      kfree(lo);
out:
      return NULL;
}

static void loop_free(struct loop_device *lo)
{
      blk_cleanup_queue(lo->lo_queue);
      put_disk(lo->lo_disk);
      list_del(&lo->lo_list);
      kfree(lo);
}

static struct loop_device *loop_init_one(int i)
{
      struct loop_device *lo;

      list_for_each_entry(lo, &loop_devices, lo_list) {
            if (lo->lo_number == i)
                  return lo;
      }

      lo = loop_alloc(i);
      if (lo) {
            add_disk(lo->lo_disk);
            list_add_tail(&lo->lo_list, &loop_devices);
      }
      return lo;
}

static void loop_del_one(struct loop_device *lo)
{
      del_gendisk(lo->lo_disk);
      loop_free(lo);
}

static struct kobject *loop_probe(dev_t dev, int *part, void *data)
{
      struct loop_device *lo;
      struct kobject *kobj;

      mutex_lock(&loop_devices_mutex);
      lo = loop_init_one(dev & MINORMASK);
      kobj = lo ? get_disk(lo->lo_disk) : ERR_PTR(-ENOMEM);
      mutex_unlock(&loop_devices_mutex);

      *part = 0;
      return kobj;
}

static int __init loop_init(void)
{
      int i, nr;
      unsigned long range;
      struct loop_device *lo, *next;

      /*
       * loop module now has a feature to instantiate underlying device
       * structure on-demand, provided that there is an access dev node.
       * However, this will not work well with user space tool that doesn't
       * know about such "feature".  In order to not break any existing
       * tool, we do the following:
       *
       * (1) if max_loop is specified, create that many upfront, and this
       *     also becomes a hard limit.
       * (2) if max_loop is not specified, create 8 loop device on module
       *     load, user can further extend loop device by create dev node
       *     themselves and have kernel automatically instantiate actual
       *     device on-demand.
       */
      if (max_loop > 1UL << MINORBITS)
            return -EINVAL;

      if (max_loop) {
            nr = max_loop;
            range = max_loop;
      } else {
            nr = 8;
            range = 1UL << MINORBITS;
      }

      if (register_blkdev(LOOP_MAJOR, "loop"))
            return -EIO;

      for (i = 0; i < nr; i++) {
            lo = loop_alloc(i);
            if (!lo)
                  goto Enomem;
            list_add_tail(&lo->lo_list, &loop_devices);
      }

      /* point of no return */

      list_for_each_entry(lo, &loop_devices, lo_list)
            add_disk(lo->lo_disk);

      blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
                          THIS_MODULE, loop_probe, NULL, NULL);

      printk(KERN_INFO "loop: module loaded\n");
      return 0;

Enomem:
      printk(KERN_INFO "loop: out of memory\n");

      list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
            loop_free(lo);

      unregister_blkdev(LOOP_MAJOR, "loop");
      return -ENOMEM;
}

static void __exit loop_exit(void)
{
      unsigned long range;
      struct loop_device *lo, *next;

      range = max_loop ? max_loop :  1UL << MINORBITS;

      list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
            loop_del_one(lo);

      blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
      unregister_blkdev(LOOP_MAJOR, "loop");
}

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

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