[Qemu-devel] [PATCH v2 0/3] null driver patches

[Qemu-devel] [PATCH v2 0/3] null driver patches

[Fam Zheng]

v2: Change patch 01 to use realtime clock, that way we don't need to check the
    VCPU state. [Stefan]
    Added Eric's rev-by in 2&3.
    Change title to "Null block driver" in 3. [Eric]

The second patch allows testing commit to a null image.

The third adds a stanza to MAINTAINERS.


Fam Zheng (3):
  block/null: Latency simulation by adding new option "latency-ns"
  block/null: Support reopen
  MAINTAINERS: Add Fam Zheng as Null block driver maintainer

 MAINTAINERS          |  6 +++++
 block/null.c         | 66 +++++++++++++++++++++++++++++++++++++++++++++++-----
 qapi/block-core.json |  5 +++-
 3 files changed, 70 insertions(+), 7 deletions(-)

-- 
1.9.3

[Qemu-devel] [PATCH v2 1/3] block/null: Latency simulation by adding new option "latency-ns"

[Fam Zheng]

Aio context switch should just work because the requests will be
drained, so the scheduled timer(s) on the old context will be freed.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 block/null.c         | 58 ++++++++++++++++++++++++++++++++++++++++++++++------
 qapi/block-core.json |  5 ++++-
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/block/null.c b/block/null.c
index ec2bd27..267d3e6 100644
--- a/block/null.c
+++ b/block/null.c
@@ -12,8 +12,11 @@
 
 #include "block/block_int.h"
 
+#define NULL_OPT_LATENCY "latency-ns"
+
 typedef struct {
     int64_t length;
+    int64_t latency_ns;
 } BDRVNullState;
 
 static QemuOptsList runtime_opts = {
@@ -30,6 +33,12 @@ static QemuOptsList runtime_opts = {
             .type = QEMU_OPT_SIZE,
             .help = "size of the null block",
         },
+        {
+            .name = NULL_OPT_LATENCY,
+            .type = QEMU_OPT_NUMBER,
+            .help = "nanoseconds (approximated) to wait "
+                    "before completing request",
+        },
         { /* end of list */ }
     },
 };
@@ -39,13 +48,20 @@ static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
 {
     QemuOpts *opts;
     BDRVNullState *s = bs->opaque;
+    int ret = 0;
 
     opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
     qemu_opts_absorb_qdict(opts, options, &error_abort);
     s->length =
         qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
+    s->latency_ns =
+        qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
+    if (s->latency_ns < 0) {
+        error_setg(errp, "latency-ns is invalid");
+        ret = -EINVAL;
+    }
     qemu_opts_del(opts);
-    return 0;
+    return ret;
 }
 
 static void null_close(BlockDriverState *bs)
@@ -58,28 +74,40 @@ static int64_t null_getlength(BlockDriverState *bs)
     return s->length;
 }
 
+static coroutine_fn int null_co_common(BlockDriverState *bs)
+{
+    BDRVNullState *s = bs->opaque;
+
+    if (s->latency_ns) {
+        co_aio_sleep_ns(bdrv_get_aio_context(bs), QEMU_CLOCK_REALTIME,
+                        s->latency_ns);
+    }
+    return 0;
+}
+
 static coroutine_fn int null_co_readv(BlockDriverState *bs,
                                       int64_t sector_num, int nb_sectors,
                                       QEMUIOVector *qiov)
 {
-    return 0;
+    return null_co_common(bs);
 }
 
 static coroutine_fn int null_co_writev(BlockDriverState *bs,
                                        int64_t sector_num, int nb_sectors,
                                        QEMUIOVector *qiov)
 {
-    return 0;
+    return null_co_common(bs);
 }
 
 static coroutine_fn int null_co_flush(BlockDriverState *bs)
 {
-    return 0;
+    return null_co_common(bs);
 }
 
 typedef struct {
     BlockAIOCB common;
     QEMUBH *bh;
+    QEMUTimer timer;
 } NullAIOCB;
 
 static const AIOCBInfo null_aiocb_info = {
@@ -94,15 +122,33 @@ static void null_bh_cb(void *opaque)
     qemu_aio_unref(acb);
 }
 
+static void null_timer_cb(void *opaque)
+{
+    NullAIOCB *acb = opaque;
+    acb->common.cb(acb->common.opaque, 0);
+    timer_deinit(&acb->timer);
+    qemu_aio_unref(acb);
+}
+
 static inline BlockAIOCB *null_aio_common(BlockDriverState *bs,
                                           BlockCompletionFunc *cb,
                                           void *opaque)
 {
     NullAIOCB *acb;
+    BDRVNullState *s = bs->opaque;
 
     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);
+    /* Only emulate latency after vcpu is running. */
+    if (s->latency_ns) {
+        aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
+                       QEMU_CLOCK_REALTIME, SCALE_NS,
+                       null_timer_cb, acb);
+        timer_mod_ns(&acb->timer,
+                     qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns);
+    } else {
+        acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
+        qemu_bh_schedule(acb->bh);
+    }
     return &acb->common;
 }
 
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 7873084..e158a7c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1310,11 +1310,14 @@
 # Driver specific block device options for the null backend.
 #
 # @size:    #optional size of the device in bytes.
+# @latency-ns: #optional emulated latency (in nanoseconds) in processing
+#              requests. Default to zero which completes requests immediately.
+#              (Since 2.4)
 #
 # Since: 2.2
 ##
 { 'type': 'BlockdevOptionsNull',
-  'data': { '*size': 'int' } }
+  'data': { '*size': 'int', '*latency-ns': 'uint64' } }
 
 ##
 # @BlockdevOptionsVVFAT
-- 
1.9.3

[Qemu-devel] [PATCH v2 2/3] block/null: Support reopen

[Fam Zheng]

Reopen is used in block-commit. With this always-succeed operation, it
is now possible to test committing to a null drive, by specifying
"null-aio://" or "null-co://" as the backing image when creating the
qcow2 image.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 block/null.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/block/null.c b/block/null.c
index 267d3e6..7d08323 100644
--- a/block/null.c
+++ b/block/null.c
@@ -177,6 +177,12 @@ static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
     return null_aio_common(bs, cb, opaque);
 }
 
+static int null_reopen_prepare(BDRVReopenState *reopen_state,
+                               BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
 static BlockDriver bdrv_null_co = {
     .format_name            = "null-co",
     .protocol_name          = "null-co",
@@ -189,6 +195,7 @@ static BlockDriver bdrv_null_co = {
     .bdrv_co_readv          = null_co_readv,
     .bdrv_co_writev         = null_co_writev,
     .bdrv_co_flush_to_disk  = null_co_flush,
+    .bdrv_reopen_prepare    = null_reopen_prepare,
 };
 
 static BlockDriver bdrv_null_aio = {
@@ -203,6 +210,7 @@ static BlockDriver bdrv_null_aio = {
     .bdrv_aio_readv         = null_aio_readv,
     .bdrv_aio_writev        = null_aio_writev,
     .bdrv_aio_flush         = null_aio_flush,
+    .bdrv_reopen_prepare    = null_reopen_prepare,
 };
 
 static void bdrv_null_init(void)
-- 
1.9.3

[Qemu-devel] [PATCH v2 3/3] MAINTAINERS: Add Fam Zheng as Null block driver maintainer

[Fam Zheng]

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 MAINTAINERS | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index d7e9ba2..56013b3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1172,6 +1172,12 @@ S: Supported
 F: block/gluster.c
 T: git git://github.com/codyprime/qemu-kvm-jtc.git block
 
+Null Block Driver
+M: Fam Zheng <famz@redhat.com>
+L: qemu-block@nongnu.org
+S: Supported
+F: block/null.c
+
 Bootdevice
 M: Gonglei <arei.gonglei@huawei.com>
 S: Maintained
-- 
1.9.3

Re: [Qemu-devel] [Qemu-block] [PATCH v2 0/3] null driver patches

[Stefan Hajnoczi]

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On Wed, Apr 01, 2015 at 09:45:37AM +0800, Fam Zheng wrote:
> v2: Change patch 01 to use realtime clock, that way we don't need to check the
>     VCPU state. [Stefan]
>     Added Eric's rev-by in 2&3.
>     Change title to "Null block driver" in 3. [Eric]
> 
> The second patch allows testing commit to a null image.
> 
> The third adds a stanza to MAINTAINERS.
> 
> 
> Fam Zheng (3):
>   block/null: Latency simulation by adding new option "latency-ns"
>   block/null: Support reopen
>   MAINTAINERS: Add Fam Zheng as Null block driver maintainer
> 
>  MAINTAINERS          |  6 +++++
>  block/null.c         | 66 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  qapi/block-core.json |  5 +++-
>  3 files changed, 70 insertions(+), 7 deletions(-)
> 
> -- 
> 1.9.3
> 
> 

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [Qemu-devel] [Qemu-block] [PATCH v2 0/3] null driver patches

[Stefan Hajnoczi]

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On Wed, Apr 01, 2015 at 09:45:37AM +0800, Fam Zheng wrote:
> v2: Change patch 01 to use realtime clock, that way we don't need to check the
>     VCPU state. [Stefan]
>     Added Eric's rev-by in 2&3.
>     Change title to "Null block driver" in 3. [Eric]
> 
> The second patch allows testing commit to a null image.
> 
> The third adds a stanza to MAINTAINERS.
> 
> 
> Fam Zheng (3):
>   block/null: Latency simulation by adding new option "latency-ns"
>   block/null: Support reopen
>   MAINTAINERS: Add Fam Zheng as Null block driver maintainer
> 
>  MAINTAINERS          |  6 +++++
>  block/null.c         | 66 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  qapi/block-core.json |  5 +++-
>  3 files changed, 70 insertions(+), 7 deletions(-)

Thanks, applied to my block-next tree:
https://github.com/stefanha/qemu/commits/block-next

Stefan

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