1 /* 2 * Null block driver 3 * 4 * Authors: 5 * Fam Zheng <famz@redhat.com> 6 * 7 * Copyright (C) 2014 Red Hat, Inc. 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #include "block/block_int.h" 14 15 typedef struct { 16 int64_t length; 17 } BDRVNullState; 18 19 static QemuOptsList runtime_opts = { 20 .name = "null", 21 .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head), 22 .desc = { 23 { 24 .name = "filename", 25 .type = QEMU_OPT_STRING, 26 .help = "", 27 }, 28 { 29 .name = BLOCK_OPT_SIZE, 30 .type = QEMU_OPT_SIZE, 31 .help = "size of the null block", 32 }, 33 { /* end of list */ } 34 }, 35 }; 36 37 static int null_file_open(BlockDriverState *bs, QDict *options, int flags, 38 Error **errp) 39 { 40 QemuOpts *opts; 41 BDRVNullState *s = bs->opaque; 42 43 opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort); 44 qemu_opts_absorb_qdict(opts, options, &error_abort); 45 s->length = 46 qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30); 47 qemu_opts_del(opts); 48 return 0; 49 } 50 51 static void null_close(BlockDriverState *bs) 52 { 53 } 54 55 static int64_t null_getlength(BlockDriverState *bs) 56 { 57 BDRVNullState *s = bs->opaque; 58 return s->length; 59 } 60 61 static coroutine_fn int null_co_readv(BlockDriverState *bs, 62 int64_t sector_num, int nb_sectors, 63 QEMUIOVector *qiov) 64 { 65 return 0; 66 } 67 68 static coroutine_fn int null_co_writev(BlockDriverState *bs, 69 int64_t sector_num, int nb_sectors, 70 QEMUIOVector *qiov) 71 { 72 return 0; 73 } 74 75 static coroutine_fn int null_co_flush(BlockDriverState *bs) 76 { 77 return 0; 78 } 79 80 typedef struct { 81 BlockDriverAIOCB common; 82 QEMUBH *bh; 83 } NullAIOCB; 84 85 static const AIOCBInfo null_aiocb_info = { 86 .aiocb_size = sizeof(NullAIOCB), 87 }; 88 89 static void null_bh_cb(void *opaque) 90 { 91 NullAIOCB *acb = opaque; 92 acb->common.cb(acb->common.opaque, 0); 93 qemu_bh_delete(acb->bh); 94 qemu_aio_unref(acb); 95 } 96 97 static inline BlockDriverAIOCB *null_aio_common(BlockDriverState *bs, 98 BlockDriverCompletionFunc *cb, 99 void *opaque) 100 { 101 NullAIOCB *acb; 102 103 acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque); 104 acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb); 105 qemu_bh_schedule(acb->bh); 106 return &acb->common; 107 } 108 109 static BlockDriverAIOCB *null_aio_readv(BlockDriverState *bs, 110 int64_t sector_num, QEMUIOVector *qiov, 111 int nb_sectors, 112 BlockDriverCompletionFunc *cb, 113 void *opaque) 114 { 115 return null_aio_common(bs, cb, opaque); 116 } 117 118 static BlockDriverAIOCB *null_aio_writev(BlockDriverState *bs, 119 int64_t sector_num, QEMUIOVector *qiov, 120 int nb_sectors, 121 BlockDriverCompletionFunc *cb, 122 void *opaque) 123 { 124 return null_aio_common(bs, cb, opaque); 125 } 126 127 static BlockDriverAIOCB *null_aio_flush(BlockDriverState *bs, 128 BlockDriverCompletionFunc *cb, 129 void *opaque) 130 { 131 return null_aio_common(bs, cb, opaque); 132 } 133 134 static BlockDriver bdrv_null_co = { 135 .format_name = "null-co", 136 .protocol_name = "null-co", 137 .instance_size = sizeof(BDRVNullState), 138 139 .bdrv_file_open = null_file_open, 140 .bdrv_close = null_close, 141 .bdrv_getlength = null_getlength, 142 143 .bdrv_co_readv = null_co_readv, 144 .bdrv_co_writev = null_co_writev, 145 .bdrv_co_flush_to_disk = null_co_flush, 146 }; 147 148 static BlockDriver bdrv_null_aio = { 149 .format_name = "null-aio", 150 .protocol_name = "null-aio", 151 .instance_size = sizeof(BDRVNullState), 152 153 .bdrv_file_open = null_file_open, 154 .bdrv_close = null_close, 155 .bdrv_getlength = null_getlength, 156 157 .bdrv_aio_readv = null_aio_readv, 158 .bdrv_aio_writev = null_aio_writev, 159 .bdrv_aio_flush = null_aio_flush, 160 }; 161 162 static void bdrv_null_init(void) 163 { 164 bdrv_register(&bdrv_null_co); 165 bdrv_register(&bdrv_null_aio); 166 } 167 168 block_init(bdrv_null_init); 169