LXR qemu/block/snapshot-access.c

   1/*
   2 * snapshot_access block driver
   3 *
   4 * Copyright (c) 2022 Virtuozzo International GmbH.
   5 *
   6 * Author:
   7 *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
   8 *
   9 * This program is free software; you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License as published by
  11 * the Free Software Foundation; either version 2 of the License, or
  12 * (at your option) any later version.
  13 *
  14 * This program is distributed in the hope that it will be useful,
  15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 * GNU General Public License for more details.
  18 *
  19 * You should have received a copy of the GNU General Public License
  20 * along with this program. If not, see <http://www.gnu.org/licenses/>.
  21 */
  22
  23#include "qemu/osdep.h"
  24
  25#include "sysemu/block-backend.h"
  26#include "qemu/cutils.h"
  27#include "block/block_int.h"
  28
  29static coroutine_fn int
  30snapshot_access_co_preadv_part(BlockDriverState *bs,
  31                               int64_t offset, int64_t bytes,
  32                               QEMUIOVector *qiov, size_t qiov_offset,
  33                               BdrvRequestFlags flags)
  34{
  35    if (flags) {
  36        return -ENOTSUP;
  37    }
  38
  39    return bdrv_co_preadv_snapshot(bs->file, offset, bytes, qiov, qiov_offset);
  40}
  41
  42static int coroutine_fn
  43snapshot_access_co_block_status(BlockDriverState *bs,
  44                                bool want_zero, int64_t offset,
  45                                int64_t bytes, int64_t *pnum,
  46                                int64_t *map, BlockDriverState **file)
  47{
  48    return bdrv_co_snapshot_block_status(bs->file->bs, want_zero, offset,
  49                                         bytes, pnum, map, file);
  50}
  51
  52static int coroutine_fn snapshot_access_co_pdiscard(BlockDriverState *bs,
  53                                             int64_t offset, int64_t bytes)
  54{
  55    return bdrv_co_pdiscard_snapshot(bs->file->bs, offset, bytes);
  56}
  57
  58static int coroutine_fn
  59snapshot_access_co_pwrite_zeroes(BlockDriverState *bs,
  60                                 int64_t offset, int64_t bytes,
  61                                 BdrvRequestFlags flags)
  62{
  63    return -ENOTSUP;
  64}
  65
  66static coroutine_fn int
  67snapshot_access_co_pwritev_part(BlockDriverState *bs,
  68                                int64_t offset, int64_t bytes,
  69                                QEMUIOVector *qiov, size_t qiov_offset,
  70                                BdrvRequestFlags flags)
  71{
  72    return -ENOTSUP;
  73}
  74
  75
  76static void snapshot_access_refresh_filename(BlockDriverState *bs)
  77{
  78    pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
  79            bs->file->bs->filename);
  80}
  81
  82static int snapshot_access_open(BlockDriverState *bs, QDict *options, int flags,
  83                                Error **errp)
  84{
  85    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
  86                               BDRV_CHILD_DATA | BDRV_CHILD_PRIMARY,
  87                               false, errp);
  88    if (!bs->file) {
  89        return -EINVAL;
  90    }
  91
  92    bs->total_sectors = bs->file->bs->total_sectors;
  93
  94    return 0;
  95}
  96
  97static void snapshot_access_child_perm(BlockDriverState *bs, BdrvChild *c,
  98                                BdrvChildRole role,
  99                                BlockReopenQueue *reopen_queue,
 100                                uint64_t perm, uint64_t shared,
 101                                uint64_t *nperm, uint64_t *nshared)
 102{
 103    /*
 104     * Currently, we don't need any permissions. If bs->file provides
 105     * snapshot-access API, we can use it.
 106     */
 107    *nperm = 0;
 108    *nshared = BLK_PERM_ALL;
 109}
 110
 111BlockDriver bdrv_snapshot_access_drv = {
 112    .format_name = "snapshot-access",
 113
 114    .bdrv_open                  = snapshot_access_open,
 115
 116    .bdrv_co_preadv_part        = snapshot_access_co_preadv_part,
 117    .bdrv_co_pwritev_part       = snapshot_access_co_pwritev_part,
 118    .bdrv_co_pwrite_zeroes      = snapshot_access_co_pwrite_zeroes,
 119    .bdrv_co_pdiscard           = snapshot_access_co_pdiscard,
 120    .bdrv_co_block_status       = snapshot_access_co_block_status,
 121
 122    .bdrv_refresh_filename      = snapshot_access_refresh_filename,
 123
 124    .bdrv_child_perm            = snapshot_access_child_perm,
 125};
 126
 127static void snapshot_access_init(void)
 128{
 129    bdrv_register(&bdrv_snapshot_access_drv);
 130}
 131
 132block_init(snapshot_access_init);
 133