text: /*
   * Copy-on-read filter block driver
   *
   * Copyright (c) 2018 Red Hat, Inc.
   *
   * Author:
   *   Max Reitz <mreitz@redhat.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation; either version 2 or
   * (at your option) version 3 of the License.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, see <http://www.gnu.org/licenses/>.
   */
  
  #include "qemu/osdep.h"
  #include "block/block_int.h"
  
  
  static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
  {
      bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file, false,
                                 errp);
      if (!bs->file) {
          return -EINVAL;
      }
  
      bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
          (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
  
      bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
          ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
              bs->file->bs->supported_zero_flags);
  
      return 0;
  }
  
  
  #define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \
                            | BLK_PERM_WRITE \
                            | BLK_PERM_RESIZE)
  #define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH)
  
  static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
                             const BdrvChildRole *role,
                             BlockReopenQueue *reopen_queue,
                             uint64_t perm, uint64_t shared,
                             uint64_t *nperm, uint64_t *nshared)
  {
      if (c == NULL) {
          *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED;
          *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
          return;
      }
  
      *nperm = (perm & PERM_PASSTHROUGH) |
               (c->perm & PERM_UNCHANGED);
      *nshared = (shared & PERM_PASSTHROUGH) |
                 (c->shared_perm & PERM_UNCHANGED);
  }
  
  
  static int64_t cor_getlength(BlockDriverState *bs)
  {
      return bdrv_getlength(bs->file->bs);
  }
  
  
  static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset,
                                          PreallocMode prealloc, Error **errp)
  {
      return bdrv_co_truncate(bs->file, offset, prealloc, errp);
  }
  
  
  static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
                                        uint64_t offset, uint64_t bytes,
                                        QEMUIOVector *qiov, int flags)
  {
      return bdrv_co_preadv(bs->file, offset, bytes, qiov,
                            flags | BDRV_REQ_COPY_ON_READ);
  }
  
  
  static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
                                         uint64_t offset, uint64_t bytes,
                                         QEMUIOVector *qiov, int flags)
  {
  
      return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
  }
  
  
  static int coroutine_fn cor_co_pwrite_zeroes(BlockDriverState *bs,
                                               int64_t offset, int bytes,
                                               BdrvRequestFlags flags)
  {
      return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
  }
  
  
  static int coroutine_fn cor_co_pdiscard(BlockDriverState *bs,
                                          int64_t offset, int bytes)
  {
      return bdrv_co_pdiscard(bs->file, offset, bytes);
  }
  
  
  static void cor_eject(BlockDriverState *bs, bool eject_flag)
  {
      bdrv_eject(bs->file->bs, eject_flag);
  }
  
  
  static void cor_lock_medium(BlockDriverState *bs, bool locked)
  {
      bdrv_lock_medium(bs->file->bs, locked);
  }
  
  
  static bool cor_recurse_is_first_non_filter(BlockDriverState *bs,
                                              BlockDriverState *candidate)
  {
      return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate);
  }
  
  
  static BlockDriver bdrv_copy_on_read = {
      .format_name                        = "copy-on-read",
  
      .bdrv_open                          = cor_open,
      .bdrv_child_perm                    = cor_child_perm,
  
      .bdrv_getlength                     = cor_getlength,
      .bdrv_co_truncate                   = cor_co_truncate,
  
      .bdrv_co_preadv                     = cor_co_preadv,
      .bdrv_co_pwritev                    = cor_co_pwritev,
      .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
      .bdrv_co_pdiscard                   = cor_co_pdiscard,
  
      .bdrv_eject                         = cor_eject,
      .bdrv_lock_medium                   = cor_lock_medium,
  
      .bdrv_co_block_status               = bdrv_co_block_status_from_file,
  
      .bdrv_recurse_is_first_non_filter   = cor_recurse_is_first_non_filter,
  
      .has_variable_length                = true,
      .is_filter                          = true,
  };
  
  static void bdrv_copy_on_read_init(void)
  {
      bdrv_register(&bdrv_copy_on_read);
  }
  
  block_init(bdrv_copy_on_read_init);
  