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
  29 static int coroutine_fn GRAPH_RDLOCK
  30 snapshot_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
  42 static int coroutine_fn GRAPH_RDLOCK
  43 snapshot_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
  52 static int coroutine_fn GRAPH_RDLOCK
  53 snapshot_access_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
  54 {
  55     return bdrv_co_pdiscard_snapshot(bs->file->bs, offset, bytes);
  56 }
  57
  58 static int coroutine_fn
  59 snapshot_access_co_pwrite_zeroes(BlockDriverState *bs,
  60                                  int64_t offset, int64_t bytes,
  61                                  BdrvRequestFlags flags)
  62 {
  63     return -ENOTSUP;
  64 }
  65
  66 static coroutine_fn int
  67 snapshot_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
  76 static void snapshot_access_refresh_filename(BlockDriverState *bs)
  77 {
  78     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
  79             bs->file->bs->filename);
  80 }
  81
  82 static int snapshot_access_open(BlockDriverState *bs, QDict *options, int flags,
  83                                 Error **errp)
  84 {
  85     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
  97 static 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
 111 static BlockDriver 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
 127 static void snapshot_access_init(void)
 128 {
 129     bdrv_register(&bdrv_snapshot_access_drv);
 130 }
 131
 132 block_init(snapshot_access_init);