The Wednesday 27 Aug 2014 à 14:22:56 (+0800), Fam Zheng wrote :
> This is an analogue to Linux null_blk. It can be used for testing block
> device emulation and general block layer functionalities such as
> coroutines and throttling, where disk IO is not necessary or wanted.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> block/Makefile.objs | 1 +
> block/null.c | 172
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 173 insertions(+)
> create mode 100644 block/null.c
>
> diff --git a/block/Makefile.objs b/block/Makefile.objs
> index 858d2b3..087e281 100644
> --- a/block/Makefile.objs
> +++ b/block/Makefile.objs
> @@ -9,6 +9,7 @@ block-obj-y += snapshot.o qapi.o
> block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
> block-obj-$(CONFIG_POSIX) += raw-posix.o
> block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
> +block-obj-y += null.o
>
> ifeq ($(CONFIG_POSIX),y)
> block-obj-y += nbd.o nbd-client.o sheepdog.o
> diff --git a/block/null.c b/block/null.c
> new file mode 100644
> index 0000000..d93a24d
> --- /dev/null
> +++ b/block/null.c
> @@ -0,0 +1,172 @@
> +/*
> + * Null block driver
> + *
> + * Authors:
> + * Fam Zheng <f...@redhat.com>
> + *
> + * Copyright (C) 2014 Red Hat, Inc.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "block/block_int.h"
> +
> +typedef struct {
> + int64_t length;
> +} BDRVNullState;
> +
> +static QemuOptsList runtime_opts = {
> + .name = "null",
> + .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
> + .desc = {
> + {
> + .name = "filename",
> + .type = QEMU_OPT_STRING,
> + .help = "",
> + },
> + { /* end of list */ }
> + },
> +};
> +
> +static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
> + Error **errp)
> +{
> + QemuOpts *opts;
> +
> + opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
> + qemu_opts_absorb_qdict(opts, options, &error_abort);
> + qemu_opts_del(opts);
> + return 0;
> +}
> +
> +static void null_close(BlockDriverState *bs)
> +{
> +}
> +
> +static int64_t null_getlength(BlockDriverState *bs)
> +{
> + /* Size is not very relevant, let's report 1G for now */
> + return 1 << 30;
> +}
> +
> +#ifdef NULL_COROUTINE
Aren't you afraid that the conditional compilation will let parts of the code
bitrot ?
Best regards
Benoît
> +static coroutine_fn int null_co_read(BlockDriverState *bs, int64_t
> sector_num,
> + uint8_t *buf, int nb_sectors)
> +{
> + return 0;
> +}
> +
> +static coroutine_fn int null_co_write(BlockDriverState *bs, int64_t
> sector_num,
> + const uint8_t *buf, int nb_sectors)
> +{
> + return 0;
> +}
> +
> +static coroutine_fn int null_co_flush(BlockDriverState *bs)
> +{
> + return 0;
> +}
> +#else
> +
> +typedef struct {
> + BlockDriverAIOCB common;
> + QEMUBH *bh;
> +} NullAIOCB;
> +
> +typedef struct BlkdebugSuspendedReq {
> + Coroutine *co;
> + char *tag;
> + QLIST_ENTRY(BlkdebugSuspendedReq) next;
> +} BlkdebugSuspendedReq;
> +
> +static void null_aio_cancel(BlockDriverAIOCB *blockacb);
> +
> +static const AIOCBInfo null_aiocb_info = {
> + .aiocb_size = sizeof(NullAIOCB),
> + .cancel = null_aio_cancel,
> +};
> +
> +static void null_bh_cb(void *opaque)
> +{
> + NullAIOCB *acb = opaque;
> + acb->common.cb(acb->common.opaque, 0);
> + qemu_bh_delete(acb->bh);
> + qemu_aio_release(acb);
> +}
> +
> +static BlockDriverAIOCB *null_aio_readv(BlockDriverState *bs,
> + int64_t sector_num, QEMUIOVector
> *qiov,
> + int nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + NullAIOCB *acb;
> +
> + acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
> + acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
> + qemu_bh_schedule(acb->bh);
> + return &acb->common;
> +}
> +
> +static BlockDriverAIOCB *null_aio_writev(BlockDriverState *bs,
> + int64_t sector_num, QEMUIOVector
> *qiov,
> + int nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + NullAIOCB *acb;
> +
> + acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
> + acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
> + qemu_bh_schedule(acb->bh);
> + return &acb->common;
> +}
> +
> +static BlockDriverAIOCB *null_aio_flush(BlockDriverState *bs,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + NullAIOCB *acb;
> +
> + acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
> + acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
> + qemu_bh_schedule(acb->bh);
> + return &acb->common;
> +}
> +
> +static void null_aio_cancel(BlockDriverAIOCB *blockacb)
> +{
> + NullAIOCB *acb = container_of(blockacb, NullAIOCB, common);
> + qemu_bh_delete(acb->bh);
> + qemu_aio_release(acb);
> +}
> +
> +#endif
> +
> +static BlockDriver bdrv_null = {
> + .format_name = "null",
> + .protocol_name = "null",
> + .instance_size = sizeof(BDRVNullState),
> +
> + .bdrv_file_open = null_file_open,
> + .bdrv_close = null_close,
> + .bdrv_getlength = null_getlength,
> +
> +#ifdef NULL_COROUTINE
> + .bdrv_read = null_co_read,
> + .bdrv_write = null_co_write,
> + .bdrv_co_flush_to_disk = null_co_flush,
> +#else
> + .bdrv_aio_readv = null_aio_readv,
> + .bdrv_aio_writev = null_aio_writev,
> + .bdrv_aio_flush = null_aio_flush,
> +#endif
> +};
> +
> +static void bdrv_null_init(void)
> +{
> + bdrv_register(&bdrv_null);
> +}
> +
> +block_init(bdrv_null_init);
> --
> 2.1.0
>
>
