* [Qemu-devel] [PATCH] block: Introduce "null" driver
@ 2014-08-27 6:22 Fam Zheng
2014-08-27 12:49 ` Eric Blake
2014-08-27 14:33 ` Benoît Canet
0 siblings, 2 replies; 4+ messages in thread
From: Fam Zheng @ 2014-08-27 6:22 UTC (permalink / raw)
To: qemu-devel; +Cc: Kevin Wolf, Stefan Hajnoczi
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 <famz@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 <famz@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
+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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [Qemu-devel] [PATCH] block: Introduce "null" driver
2014-08-27 6:22 [Qemu-devel] [PATCH] block: Introduce "null" driver Fam Zheng
@ 2014-08-27 12:49 ` Eric Blake
2014-08-27 13:27 ` Markus Armbruster
2014-08-27 14:33 ` Benoît Canet
1 sibling, 1 reply; 4+ messages in thread
From: Eric Blake @ 2014-08-27 12:49 UTC (permalink / raw)
To: Fam Zheng, qemu-devel; +Cc: Kevin Wolf, Stefan Hajnoczi
[-- Attachment #1: Type: text/plain, Size: 855 bytes --]
On 08/27/2014 12:22 AM, 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 <famz@redhat.com>
> ---
> block/Makefile.objs | 1 +
> block/null.c | 172 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 173 insertions(+)
> create mode 100644 block/null.c
Worth also adding it to BlockdevOptions in qapi/block-core.json to allow
hotplug of this driver? (Not that libvirt will ever hotplug one, but I
really want to move towards being feature-complete on letting QMP drive
all block types)
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] block: Introduce "null" driver
2014-08-27 12:49 ` Eric Blake
@ 2014-08-27 13:27 ` Markus Armbruster
0 siblings, 0 replies; 4+ messages in thread
From: Markus Armbruster @ 2014-08-27 13:27 UTC (permalink / raw)
To: Eric Blake; +Cc: Kevin Wolf, Fam Zheng, qemu-devel, Stefan Hajnoczi
Eric Blake <eblake@redhat.com> writes:
> On 08/27/2014 12:22 AM, 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 <famz@redhat.com>
>> ---
>> block/Makefile.objs | 1 +
>> block/null.c | 172
>> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 173 insertions(+)
>> create mode 100644 block/null.c
>
> Worth also adding it to BlockdevOptions in qapi/block-core.json to allow
> hotplug of this driver? (Not that libvirt will ever hotplug one, but I
> really want to move towards being feature-complete on letting QMP drive
> all block types)
I'd support a policy of "no new block drivers outside QAPI".
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] block: Introduce "null" driver
2014-08-27 6:22 [Qemu-devel] [PATCH] block: Introduce "null" driver Fam Zheng
2014-08-27 12:49 ` Eric Blake
@ 2014-08-27 14:33 ` Benoît Canet
1 sibling, 0 replies; 4+ messages in thread
From: Benoît Canet @ 2014-08-27 14:33 UTC (permalink / raw)
To: Fam Zheng; +Cc: Kevin Wolf, qemu-devel, Stefan Hajnoczi
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 <famz@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 <famz@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
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2014-08-27 6:22 [Qemu-devel] [PATCH] block: Introduce "null" driver Fam Zheng
2014-08-27 12:49 ` Eric Blake
2014-08-27 13:27 ` Markus Armbruster
2014-08-27 14:33 ` Benoît Canet
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