[Qemu-devel] [PATCH v2 0/6] nbd export qmp interface

[Qemu-devel] [PATCH v2 0/6] nbd export qmp interface

[Vladimir Sementsov-Ogievskiy]

v2:
01: tweak comment
    add Eric's r-b
02: new patch
03: rewritten, to move form 'bool force' flag to 'enum mode' parameter
04: add Eric's r-b
05: improve commit message
    tweak comment
06: rebase on 03 changes
    make PEP8 happy
    some other tweaks
    I've left nbd_port variable hard-set to 10900. I think all such things
    should be fixed together, and it is simple to change in future
    nbd_port = '10900'
    to
    nbd_port = iotests.get_free_port()
    if needed.

[Unfortunately, qmp query-nbd-server is not finished yet, coming soon,
 but may be after my vocation on the next week]

Vladimir Sementsov-Ogievskiy (6):
  qapi: add name parameter to nbd-server-add
  hmp: add name parameter to nbd_server_add
  qapi: add nbd-server-remove
  iotest 147: add cases to test new @name parameter of nbd-server-add
  iotests: implement QemuIoInteractive class
  iotest 201: new test for qmp nbd-server-remove

 qapi/block.json               |  54 +++++++++++++-
 include/block/nbd.h           |   1 +
 blockdev-nbd.c                |  38 ++++++++--
 hmp.c                         |   6 +-
 nbd/server.c                  |  21 ++++++
 hmp-commands.hx               |   9 +--
 tests/qemu-iotests/147        |  68 ++++++++++++++----
 tests/qemu-iotests/147.out    |   4 +-
 tests/qemu-iotests/201        | 159 ++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/201.out    |   5 ++
 tests/qemu-iotests/group      |   1 +
 tests/qemu-iotests/iotests.py |  38 ++++++++++
 12 files changed, 376 insertions(+), 28 deletions(-)
 create mode 100644 tests/qemu-iotests/201
 create mode 100644 tests/qemu-iotests/201.out

-- 
2.11.1

[Qemu-devel] [PATCH v2 1/6] qapi: add name parameter to nbd-server-add

[Vladimir Sementsov-Ogievskiy]

Allow user to specify name for new export, to not reuse internal
node name and to not show it to clients.

This also allows creating several exports per device.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 qapi/block.json |  9 +++++++--
 blockdev-nbd.c  | 14 +++++++++-----
 hmp.c           |  5 +++--
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/qapi/block.json b/qapi/block.json
index f093fa3f27..353e3a45bd 100644
--- a/qapi/block.json
+++ b/qapi/block.json
@@ -213,14 +213,19 @@
 #
 # @device: The device name or node name of the node to be exported
 #
+# @name: Export name. If unspecified, the @device parameter is used as the
+#        export name. (Since 2.12)
+#
 # @writable: Whether clients should be able to write to the device via the
 #     NBD connection (default false).
 #
-# Returns: error if the device is already marked for export.
+# Returns: error if the server is not running, or export with the same name
+#          already exists.
 #
 # Since: 1.3.0
 ##
-{ 'command': 'nbd-server-add', 'data': {'device': 'str', '*writable': 'bool'} }
+{ 'command': 'nbd-server-add',
+  'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
 
 ##
 # @nbd-server-stop:
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 9e3c22109c..104789e521 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -140,8 +140,8 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr,
     qapi_free_SocketAddress(addr_flat);
 }
 
-void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
-                        Error **errp)
+void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
+                        bool has_writable, bool writable, Error **errp)
 {
     BlockDriverState *bs = NULL;
     BlockBackend *on_eject_blk;
@@ -152,8 +152,12 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         return;
     }
 
-    if (nbd_export_find(device)) {
-        error_setg(errp, "NBD server already exporting device '%s'", device);
+    if (!has_name) {
+        name = device;
+    }
+
+    if (nbd_export_find(name)) {
+        error_setg(errp, "NBD server already has export named '%s'", name);
         return;
     }
 
@@ -177,7 +181,7 @@ void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
         return;
     }
 
-    nbd_export_set_name(exp, device);
+    nbd_export_set_name(exp, name);
 
     /* The list of named exports has a strong reference to this export now and
      * our only way of accessing it is through nbd_export_find(), so we can drop
diff --git a/hmp.c b/hmp.c
index c6bab5373b..37972f8322 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2218,7 +2218,8 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
             continue;
         }
 
-        qmp_nbd_server_add(info->value->device, true, writable, &local_err);
+        qmp_nbd_server_add(info->value->device, false, NULL,
+                           true, writable, &local_err);
 
         if (local_err != NULL) {
             qmp_nbd_server_stop(NULL);
@@ -2238,7 +2239,7 @@ void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
     bool writable = qdict_get_try_bool(qdict, "writable", false);
     Error *local_err = NULL;
 
-    qmp_nbd_server_add(device, true, writable, &local_err);
+    qmp_nbd_server_add(device, false, NULL, true, writable, &local_err);
 
     if (local_err != NULL) {
         hmp_handle_error(mon, &local_err);
-- 
2.11.1

[Qemu-devel] [PATCH v2 2/6] hmp: add name parameter to nbd_server_add

[Vladimir Sementsov-Ogievskiy]

Support name parameter for HMP too.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 hmp.c           | 3 ++-
 hmp-commands.hx | 9 +++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/hmp.c b/hmp.c
index 37972f8322..964cff8aed 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2236,10 +2236,11 @@ exit:
 void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
 {
     const char *device = qdict_get_str(qdict, "device");
+    const char *name = qdict_get_try_str(qdict, "name");
     bool writable = qdict_get_try_bool(qdict, "writable", false);
     Error *local_err = NULL;
 
-    qmp_nbd_server_add(device, false, NULL, true, writable, &local_err);
+    qmp_nbd_server_add(device, name != NULL, name, true, writable, &local_err);
 
     if (local_err != NULL) {
         hmp_handle_error(mon, &local_err);
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 6d5ebdf6ab..cad9a9a238 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1553,8 +1553,8 @@ ETEXI
 
     {
         .name       = "nbd_server_add",
-        .args_type  = "writable:-w,device:B",
-        .params     = "nbd_server_add [-w] device",
+        .args_type  = "name:-n,writable:-w,device:B",
+        .params     = "nbd_server_add [-n] [-w] device",
         .help       = "export a block device via NBD",
         .cmd        = hmp_nbd_server_add,
     },
@@ -1562,8 +1562,9 @@ STEXI
 @item nbd_server_add @var{device}
 @findex nbd_server_add
 Export a block device through QEMU's NBD server, which must be started
-beforehand with @command{nbd_server_start}.  The @option{-w} option makes the
-exported device writable too.
+beforehand with @command{nbd_server_start}. The @option{-n} option sets export
+name. If @option{-n} option is unspecified, the @var{device} parameter is used.
+The @option{-w} option makes the exported device writable too.
 ETEXI
 
     {
-- 
2.11.1

Re: [Qemu-devel] [PATCH v2 2/6] hmp: add name parameter to nbd_server_add

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1207 bytes --]

On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
> Support name parameter for HMP too.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  hmp.c           | 3 ++-
>  hmp-commands.hx | 9 +++++----
>  2 files changed, 7 insertions(+), 5 deletions(-)
> 

> +++ b/hmp-commands.hx
> @@ -1553,8 +1553,8 @@ ETEXI
>  
>      {
>          .name       = "nbd_server_add",
> -        .args_type  = "writable:-w,device:B",
> -        .params     = "nbd_server_add [-w] device",
> +        .args_type  = "name:-n,writable:-w,device:B",
> +        .params     = "nbd_server_add [-n] [-w] device",

Doesn't quite look like my proposal:
https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg01639.html

-        .args_type  = "writable:-w,device:B",
-        .params     = "nbd_server_add [-w] device",
+        .args_type  = "writable:-w,device:B,name:s?",
+        .params     = "nbd_server_add [-w] device [name]",

In fact, using -n is not quite right, because that's just a boolean flag
rather than a string.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 2/6] hmp: add name parameter to nbd_server_add

[Vladimir Sementsov-Ogievskiy]

19.01.2018 00:08, Eric Blake wrote:
> On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
>> Support name parameter for HMP too.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   hmp.c           | 3 ++-
>>   hmp-commands.hx | 9 +++++----
>>   2 files changed, 7 insertions(+), 5 deletions(-)
>>
>> +++ b/hmp-commands.hx
>> @@ -1553,8 +1553,8 @@ ETEXI
>>   
>>       {
>>           .name       = "nbd_server_add",
>> -        .args_type  = "writable:-w,device:B",
>> -        .params     = "nbd_server_add [-w] device",
>> +        .args_type  = "name:-n,writable:-w,device:B",
>> +        .params     = "nbd_server_add [-n] [-w] device",
> Doesn't quite look like my proposal:
> https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg01639.html
>
> -        .args_type  = "writable:-w,device:B",
> -        .params     = "nbd_server_add [-w] device",
> +        .args_type  = "writable:-w,device:B,name:s?",
> +        .params     = "nbd_server_add [-w] device [name]",
>
> In fact, using -n is not quite right, because that's just a boolean flag
> rather than a string.
>

Strange, I don't have your letter. Let's use yours, of course.

-- 
Best regards,
Vladimir

[Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

Add command for export removing. It is needed for cases when we
don't want to keep export after the operation on it was completed.
The other example is temporary node, created with blockdev-add.
If we want to delete it we should firstly remove corresponding
NBD export.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qapi/block.json     | 45 +++++++++++++++++++++++++++++++++++++++++++++
 include/block/nbd.h |  1 +
 blockdev-nbd.c      | 24 ++++++++++++++++++++++++
 nbd/server.c        | 21 +++++++++++++++++++++
 4 files changed, 91 insertions(+)

diff --git a/qapi/block.json b/qapi/block.json
index 353e3a45bd..ddf73932ce 100644
--- a/qapi/block.json
+++ b/qapi/block.json
@@ -228,6 +228,51 @@
   'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
 
 ##
+# @NbdServerRemoveMode:
+#
+# Mode of NBD export removing.
+#
+# @safe: Remove export if there are no existing connections, fail otherwise.
+#
+# @hard: Drop all connections immediately and remove export.
+#
+# Postponed, not realized yet modes:
+#
+# hide: Just hide export from new clients, leave existing connections as is.
+#       Remove export after all clients are disconnected. nbd-server-remove
+#       with mode=soft or mode=hard may be called after nbd-server-remove
+#       with mode=hide.
+#
+# soft: Hide export from new clients, answer with ESHUTDOWN for all further
+#       requests from existing clients. Remove export after all clients are
+#       disconnected. nbd-server-requests with mode=hard may be called after
+#       nbd-server-remove with mode=soft
+#
+# Since: 2.12
+##
+{'enum': 'NbdServerRemoveMode', 'data': ['safe', 'hard']}
+
+##
+# @nbd-server-remove:
+#
+# Remove NBD export by name.
+#
+# @name: Export name.
+#
+# @mode: Mode of command operation. See @NbdServerRemoveMode description.
+#        Default is 'safe'.
+#
+# Returns: error if
+#            - the server is not running
+#            - export is not found
+#            - mode is 'safe' and there are existing connections
+#
+# Since: 2.12
+##
+{ 'command': 'nbd-server-remove',
+  'data': {'name': 'str', '*mode': 'NbdServerRemoveMode'} }
+
+##
 # @nbd-server-stop:
 #
 # Stop QEMU's embedded NBD server, and unregister all devices previously
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 978e443366..ee74ec391a 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -261,6 +261,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
                           bool writethrough, BlockBackend *on_eject_blk,
                           Error **errp);
 void nbd_export_close(NBDExport *exp);
+void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
 void nbd_export_get(NBDExport *exp);
 void nbd_export_put(NBDExport *exp);
 
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 104789e521..a9f79c6778 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -189,6 +189,30 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
     nbd_export_put(exp);
 }
 
+void qmp_nbd_server_remove(const char *name,
+                           bool has_mode, NbdServerRemoveMode mode,
+                           Error **errp)
+{
+    NBDExport *exp;
+
+    if (!nbd_server) {
+        error_setg(errp, "NBD server not running");
+        return;
+    }
+
+    exp = nbd_export_find(name);
+    if (exp == NULL) {
+        error_setg(errp, "Export '%s' is not found", name);
+        return;
+    }
+
+    if (!has_mode) {
+        mode = NBD_SERVER_REMOVE_MODE_SAFE;
+    }
+
+    nbd_export_remove(exp, mode, errp);
+}
+
 void qmp_nbd_server_stop(Error **errp)
 {
     nbd_export_close_all();
diff --git a/nbd/server.c b/nbd/server.c
index 6cf2eeb2c1..fdb6be7016 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1177,6 +1177,27 @@ void nbd_export_close(NBDExport *exp)
     nbd_export_put(exp);
 }
 
+void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp)
+{
+    NBDClient *client;
+    int nb_clients = 0;
+
+    if (mode == NBD_SERVER_REMOVE_MODE_HARD || QTAILQ_EMPTY(&exp->clients)) {
+        nbd_export_close(exp);
+        return;
+    }
+
+    assert(mode == NBD_SERVER_REMOVE_MODE_SAFE);
+
+    QTAILQ_FOREACH(client, &exp->clients, next) {
+        nb_clients++;
+    }
+
+    error_setg(errp, "NBD export '%s' has %d active connection%s. To force "
+               "remove it (and hard disconnect clients) use mode='hard'",
+               exp->name, nb_clients, nb_clients == 1 ? "" : "s");
+}
+
 void nbd_export_get(NBDExport *exp)
 {
     assert(exp->refcount > 0);
-- 
2.11.1

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 4300 bytes --]

On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
> Add command for export removing. It is needed for cases when we

s/export removing/removing an export/

> don't want to keep export after the operation on it was completed.
> The other example is temporary node, created with blockdev-add.
> If we want to delete it we should firstly remove corresponding
> NBD export.
> 

No HMP counterpart? I can give a quick shot at that, as a followup patch.

> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  qapi/block.json     | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  include/block/nbd.h |  1 +
>  blockdev-nbd.c      | 24 ++++++++++++++++++++++++
>  nbd/server.c        | 21 +++++++++++++++++++++
>  4 files changed, 91 insertions(+)
> 
> diff --git a/qapi/block.json b/qapi/block.json
> index 353e3a45bd..ddf73932ce 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -228,6 +228,51 @@
>    'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
>  
>  ##
> +# @NbdServerRemoveMode:
> +#
> +# Mode of NBD export removing.

Mode for removing an NBD export.

> +#
> +# @safe: Remove export if there are no existing connections, fail otherwise.
> +#
> +# @hard: Drop all connections immediately and remove export.
> +#
> +# Postponed, not realized yet modes:

Maybe:

Potential additional modes to be added in the future:

> +#
> +# hide: Just hide export from new clients, leave existing connections as is.
> +#       Remove export after all clients are disconnected. nbd-server-remove
> +#       with mode=soft or mode=hard may be called after nbd-server-remove
> +#       with mode=hide.

mode=safe could also be called; I don't see that this last sentence adds
much.

> +#
> +# soft: Hide export from new clients, answer with ESHUTDOWN for all further
> +#       requests from existing clients. Remove export after all clients are
> +#       disconnected. nbd-server-requests with mode=hard may be called after
> +#       nbd-server-remove with mode=soft

Again, the last sentence doesn't add mouch (I guess you're arguing that
requesting a hide doesn't make much sense after a soft disconnect has
already started; but I don't see any harm in permitting it as a no-op).

> +#
> +# Since: 2.12
> +##
> +{'enum': 'NbdServerRemoveMode', 'data': ['safe', 'hard']}
> +
> +##
> +# @nbd-server-remove:
> +#
> +# Remove NBD export by name.
> +#
> +# @name: Export name.
> +#
> +# @mode: Mode of command operation. See @NbdServerRemoveMode description.
> +#        Default is 'safe'.
> +#
> +# Returns: error if
> +#            - the server is not running
> +#            - export is not found
> +#            - mode is 'safe' and there are existing connections
> +#
> +# Since: 2.12
> +##
> +{ 'command': 'nbd-server-remove',
> +  'data': {'name': 'str', '*mode': 'NbdServerRemoveMode'} }

Looks reasonable.


> +++ b/nbd/server.c
> @@ -1177,6 +1177,27 @@ void nbd_export_close(NBDExport *exp)
>      nbd_export_put(exp);
>  }
>  
> +void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp)
> +{
> +    NBDClient *client;
> +    int nb_clients = 0;
> +
> +    if (mode == NBD_SERVER_REMOVE_MODE_HARD || QTAILQ_EMPTY(&exp->clients)) {
> +        nbd_export_close(exp);
> +        return;
> +    }
> +
> +    assert(mode == NBD_SERVER_REMOVE_MODE_SAFE);
> +
> +    QTAILQ_FOREACH(client, &exp->clients, next) {
> +        nb_clients++;
> +    }
> +
> +    error_setg(errp, "NBD export '%s' has %d active connection%s. To force "
> +               "remove it (and hard disconnect clients) use mode='hard'",
> +               exp->name, nb_clients, nb_clients == 1 ? "" : "s");

Playing games with English pluralization doesn't work too well in error
messages, if we ever want to allow translations; does the number of
active clients actually matter?  Also, error_setg() recommends against
using '.' or more than one sentence.  Better might be:

error_setg(errp, "export '%s' still in use");
error_append_hint(errp, "Use mode='hard' to force client disconnect\n");

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

[Qemu-devel] [PATCH v2 4/6] iotest 147: add cases to test new @name parameter of nbd-server-add

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 tests/qemu-iotests/147     | 68 +++++++++++++++++++++++++++++++++++++---------
 tests/qemu-iotests/147.out |  4 +--
 2 files changed, 57 insertions(+), 15 deletions(-)

diff --git a/tests/qemu-iotests/147 b/tests/qemu-iotests/147
index 90f40ed245..d2081df84b 100755
--- a/tests/qemu-iotests/147
+++ b/tests/qemu-iotests/147
@@ -38,8 +38,8 @@ def flatten_sock_addr(crumpled_address):
 
 
 class NBDBlockdevAddBase(iotests.QMPTestCase):
-    def blockdev_add_options(self, address, export=None):
-        options = { 'node-name': 'nbd-blockdev',
+    def blockdev_add_options(self, address, export, node_name):
+        options = { 'node-name': node_name,
                     'driver': 'raw',
                     'file': {
                         'driver': 'nbd',
@@ -50,23 +50,28 @@ class NBDBlockdevAddBase(iotests.QMPTestCase):
             options['file']['export'] = export
         return options
 
-    def client_test(self, filename, address, export=None):
-        bao = self.blockdev_add_options(address, export)
+    def client_test(self, filename, address, export=None,
+                    node_name='nbd-blockdev', delete=True):
+        bao = self.blockdev_add_options(address, export, node_name)
         result = self.vm.qmp('blockdev-add', **bao)
         self.assert_qmp(result, 'return', {})
 
+        found = False
         result = self.vm.qmp('query-named-block-nodes')
         for node in result['return']:
-            if node['node-name'] == 'nbd-blockdev':
+            if node['node-name'] == node_name:
+                found = True
                 if isinstance(filename, str):
                     self.assert_qmp(node, 'image/filename', filename)
                 else:
                     self.assert_json_filename_equal(node['image']['filename'],
                                                     filename)
                 break
+        self.assertTrue(found)
 
-        result = self.vm.qmp('blockdev-del', node_name='nbd-blockdev')
-        self.assert_qmp(result, 'return', {})
+        if delete:
+            result = self.vm.qmp('blockdev-del', node_name=node_name)
+            self.assert_qmp(result, 'return', {})
 
 
 class QemuNBD(NBDBlockdevAddBase):
@@ -125,26 +130,63 @@ class BuiltinNBD(NBDBlockdevAddBase):
         except OSError:
             pass
 
-    def _server_up(self, address):
+    def _server_up(self, address, export_name=None, export_name2=None):
         result = self.server.qmp('nbd-server-start', addr=address)
         self.assert_qmp(result, 'return', {})
 
-        result = self.server.qmp('nbd-server-add', device='nbd-export')
+        if export_name is None:
+            result = self.server.qmp('nbd-server-add', device='nbd-export')
+        else:
+            result = self.server.qmp('nbd-server-add', device='nbd-export',
+                                     name=export_name)
         self.assert_qmp(result, 'return', {})
 
+        if export_name2 is not None:
+            result = self.server.qmp('nbd-server-add', device='nbd-export',
+                                     name=export_name2)
+            self.assert_qmp(result, 'return', {})
+
+
     def _server_down(self):
         result = self.server.qmp('nbd-server-stop')
         self.assert_qmp(result, 'return', {})
 
-    def test_inet(self):
+    def do_test_inet(self, export_name=None):
         address = { 'type': 'inet',
                     'data': {
                         'host': 'localhost',
                         'port': str(NBD_PORT)
                     } }
-        self._server_up(address)
-        self.client_test('nbd://localhost:%i/nbd-export' % NBD_PORT,
-                         flatten_sock_addr(address), 'nbd-export')
+        self._server_up(address, export_name)
+        export_name = export_name or 'nbd-export'
+        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, export_name),
+                         flatten_sock_addr(address), export_name)
+        self._server_down()
+
+    def test_inet_default_export_name(self):
+        self.do_test_inet()
+
+    def test_inet_same_export_name(self):
+        self.do_test_inet('nbd-export')
+
+    def test_inet_different_export_name(self):
+        self.do_test_inet('shadow')
+
+    def test_inet_two_exports(self):
+        address = { 'type': 'inet',
+                    'data': {
+                        'host': 'localhost',
+                        'port': str(NBD_PORT)
+                    } }
+        self._server_up(address, 'exp1', 'exp2')
+        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, 'exp1'),
+                         flatten_sock_addr(address), 'exp1', 'node1', False)
+        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, 'exp2'),
+                         flatten_sock_addr(address), 'exp2', 'node2', False)
+        result = self.vm.qmp('blockdev-del', node_name='node1')
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp('blockdev-del', node_name='node2')
+        self.assert_qmp(result, 'return', {})
         self._server_down()
 
     def test_inet6(self):
diff --git a/tests/qemu-iotests/147.out b/tests/qemu-iotests/147.out
index 3f8a935a08..dae404e278 100644
--- a/tests/qemu-iotests/147.out
+++ b/tests/qemu-iotests/147.out
@@ -1,5 +1,5 @@
-......
+.........
 ----------------------------------------------------------------------
-Ran 6 tests
+Ran 9 tests
 
 OK
-- 
2.11.1

[Qemu-devel] [PATCH v2 5/6] iotests: implement QemuIoInteractive class

[Vladimir Sementsov-Ogievskiy]

Implement QemuIoInteractive to test nbd-server-remove command when
there are active connections.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 tests/qemu-iotests/iotests.py | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 44477e9295..5a10b2d534 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -93,6 +93,44 @@ def qemu_io(*args):
         sys.stderr.write('qemu-io received signal %i: %s\n' % (-exitcode, ' '.join(args)))
     return subp.communicate()[0]
 
+
+class QemuIoInteractive:
+    def __init__(self, *args):
+        self.args = qemu_io_args + list(args)
+        self._p = subprocess.Popen(self.args, stdin=subprocess.PIPE,
+                                   stdout=subprocess.PIPE,
+                                   stderr=subprocess.STDOUT)
+        assert self._p.stdout.read(9) == 'qemu-io> '
+
+    def close(self):
+        self._p.communicate('q\n')
+
+    def _read_output(self):
+        pattern = 'qemu-io> '
+        n = len(pattern)
+        pos = 0
+        s = []
+        while pos != n:
+            c = self._p.stdout.read(1)
+            # check unexpected EOF
+            assert c != ''
+            s.append(c)
+            if c == pattern[pos]:
+                pos += 1
+            else:
+                pos = 0
+
+        return ''.join(s[:-n])
+
+    def cmd(self, cmd):
+        # quit command is in close(), '\n' is added automatically
+        assert '\n' not in cmd
+        cmd = cmd.strip()
+        assert cmd != 'q' and cmd != 'quit'
+        self._p.stdin.write(cmd + '\n')
+        return self._read_output()
+
+
 def qemu_nbd(*args):
     '''Run qemu-nbd in daemon mode and return the parent's exit code'''
     return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))
-- 
2.11.1

[Qemu-devel] [PATCH v2 6/6] iotest 201: new test for qmp nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 tests/qemu-iotests/201     | 159 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/201.out |   5 ++
 tests/qemu-iotests/group   |   1 +
 3 files changed, 165 insertions(+)
 create mode 100644 tests/qemu-iotests/201
 create mode 100644 tests/qemu-iotests/201.out

diff --git a/tests/qemu-iotests/201 b/tests/qemu-iotests/201
new file mode 100644
index 0000000000..1ac6d953c0
--- /dev/null
+++ b/tests/qemu-iotests/201
@@ -0,0 +1,159 @@
+#!/usr/bin/env python
+#
+# Tests for qmp command nbd-server-remove.
+#
+# Copyright (c) 2017 Virtuozzo International GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import sys
+import iotests
+import time
+from iotests import qemu_img, qemu_io, filter_qemu_io, QemuIoInteractive
+
+nbd_port = '10900'
+nbd_uri = 'nbd+tcp://localhost:' + nbd_port + '/exp'
+disk = os.path.join(iotests.test_dir, 'disk')
+
+
+class TestNbdServerRemove(iotests.QMPTestCase):
+    def setUp(self):
+        qemu_img('create', '-f', iotests.imgfmt, disk, '1M')
+
+        self.vm = iotests.VM().add_drive(disk)
+        self.vm.launch()
+
+        address = {
+            'type': 'inet',
+            'data': {
+                'host': 'localhost',
+                'port': nbd_port
+            }
+        }
+
+        result = self.vm.qmp('nbd-server-start', addr=address)
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp('nbd-server-add', device='drive0', name='exp')
+        self.assert_qmp(result, 'return', {})
+
+    def tearDown(self):
+        self.vm.shutdown()
+        os.remove(disk)
+
+    def remove_export(self, name, mode=None):
+        if mode is None:
+            return self.vm.qmp('nbd-server-remove', name=name)
+        else:
+            return self.vm.qmp('nbd-server-remove', name=name, mode=mode)
+
+    def assertExportNotFound(self, name):
+        result = self.vm.qmp('nbd-server-remove', name=name)
+        self.assert_qmp(result, 'error/desc', "Export 'exp' is not found")
+
+    def assertExistingClients(self, result):
+        self.assert_qmp(result, 'error/desc',
+                        "NBD export 'exp' has 1 active connection. To force "
+                        "remove it (and hard disconnect clients) use "
+                        "mode='hard'")
+
+    def assertReadOk(self, qemu_io_output):
+        self.assertEqual(
+                filter_qemu_io(qemu_io_output).strip(),
+                'read 512/512 bytes at offset 0\n' +
+                '512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)')
+
+    def assertReadFailed(self, qemu_io_output):
+        self.assertEqual(filter_qemu_io(qemu_io_output).strip(),
+                         'read failed: Input/output error')
+
+    def assertConnectFailed(self, qemu_io_output):
+        self.assertEqual(filter_qemu_io(qemu_io_output).strip(),
+                         "can't open device nbd+tcp://localhost:" + nbd_port +
+                         "/exp: Requested export not available\n"
+                         "server reported: export 'exp' not present")
+
+    def do_test_connect_after_remove(self, mode=None):
+        args = ('-r', '-f', 'raw', '-c', 'read 0 512', nbd_uri)
+        self.assertReadOk(qemu_io(*args))
+
+        result = self.remove_export('exp', mode)
+        self.assert_qmp(result, 'return', {})
+
+        self.assertExportNotFound('exp')
+        self.assertConnectFailed(qemu_io(*args))
+
+    def test_connect_after_remove_default(self):
+        self.do_test_connect_after_remove()
+
+    def test_connect_after_remove_safe(self):
+        self.do_test_connect_after_remove('safe')
+
+    def test_connect_after_remove_force(self):
+        self.do_test_connect_after_remove('hard')
+
+    def do_test_remove_during_connect_safe(self, mode=None):
+        qio = QemuIoInteractive('-r', '-f', 'raw', nbd_uri)
+        self.assertReadOk(qio.cmd('read 0 512'))
+
+        result = self.remove_export('exp', mode)
+        self.assertExistingClients(result)
+
+        self.assertReadOk(qio.cmd('read 0 512'))
+
+        qio.close()
+
+        result = self.remove_export('exp', mode)
+        self.assert_qmp(result, 'return', {})
+
+        self.assertExportNotFound('exp')
+
+    def test_remove_during_connect_default(self):
+        self.do_test_remove_during_connect_safe()
+
+    def test_remove_during_connect_safe(self):
+        self.do_test_remove_during_connect_safe('safe')
+
+    def test_remove_during_connect_hard(self):
+        qio = QemuIoInteractive('-r', '-f', 'raw', nbd_uri)
+        self.assertReadOk(qio.cmd('read 0 512'))
+
+        result = self.remove_export('exp', 'hard')
+        self.assert_qmp(result, 'return', {})
+
+        self.assertReadFailed(qio.cmd('read 0 512'))
+        self.assertExportNotFound('exp')
+
+        qio.close()
+
+    def test_remove_during_connect_safe_hard(self):
+        qio = QemuIoInteractive('-r', '-f', 'raw', nbd_uri)
+        self.assertReadOk(qio.cmd('read 0 512'))
+
+        result = self.remove_export('exp', 'safe')
+        self.assertExistingClients(result)
+
+        self.assertReadOk(qio.cmd('read 0 512'))
+
+        result = self.remove_export('exp', 'hard')
+        self.assert_qmp(result, 'return', {})
+
+        self.assertExportNotFound('exp')
+        self.assertReadFailed(qio.cmd('read 0 512'))
+        qio.close()
+
+
+if __name__ == '__main__':
+    iotests.main()
diff --git a/tests/qemu-iotests/201.out b/tests/qemu-iotests/201.out
new file mode 100644
index 0000000000..2f7d3902f2
--- /dev/null
+++ b/tests/qemu-iotests/201.out
@@ -0,0 +1,5 @@
+.......
+----------------------------------------------------------------------
+Ran 7 tests
+
+OK
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 93d96fb22f..f07d3e3df6 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -197,5 +197,6 @@
 197 rw auto quick
 198 rw auto
 200 rw auto
+201 rw auto quick
 202 rw auto quick
 203 rw auto
-- 
2.11.1

Re: [Qemu-devel] [PATCH v2 6/6] iotest 201: new test for qmp nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1233 bytes --]

On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  tests/qemu-iotests/201     | 159 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/201.out |   5 ++
>  tests/qemu-iotests/group   |   1 +
>  3 files changed, 165 insertions(+)
>  create mode 100644 tests/qemu-iotests/201
>  create mode 100644 tests/qemu-iotests/201.out
> 

> +
> +    def assertExistingClients(self, result):
> +        self.assert_qmp(result, 'error/desc',
> +                        "NBD export 'exp' has 1 active connection. To force "
> +                        "remove it (and hard disconnect clients) use "
> +                        "mode='hard'")

Needs tweaking if we massage the error message earlier in the series.

I'm still worried that this test may fail spuriously due to a hard-coded
port, but some testing is better than none, and if the CI engines don't
immediately reject it, whoever first encounters it will be nice and let
us know.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 6/6] iotest 201: new test for qmp nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

19.01.2018 01:43, Eric Blake wrote:
> On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   tests/qemu-iotests/201     | 159 +++++++++++++++++++++++++++++++++++++++++++++
>>   tests/qemu-iotests/201.out |   5 ++
>>   tests/qemu-iotests/group   |   1 +
>>   3 files changed, 165 insertions(+)
>>   create mode 100644 tests/qemu-iotests/201
>>   create mode 100644 tests/qemu-iotests/201.out
>>
>> +
>> +    def assertExistingClients(self, result):
>> +        self.assert_qmp(result, 'error/desc',
>> +                        "NBD export 'exp' has 1 active connection. To force "
>> +                        "remove it (and hard disconnect clients) use "
>> +                        "mode='hard'")
> Needs tweaking if we massage the error message earlier in the series.
>
> I'm still worried that this test may fail spuriously due to a hard-coded
> port, but some testing is better than none, and if the CI engines don't
> immediately reject it, whoever first encounters it will be nice and let
> us know.
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>

Looked through other tests, looks like same approach is only in 147, and 
other iotests uses unix sockets for nbd-server-start. May be, it is 
better to move to unix socket here.
I'll resend today with unix-socket.

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 0/6] nbd export qmp interface

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 1185 bytes --]

On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
> v2:
> 01: tweak comment
>     add Eric's r-b
> 02: new patch
> 03: rewritten, to move form 'bool force' flag to 'enum mode' parameter
> 04: add Eric's r-b
> 05: improve commit message
>     tweak comment
> 06: rebase on 03 changes
>     make PEP8 happy
>     some other tweaks
>     I've left nbd_port variable hard-set to 10900. I think all such things
>     should be fixed together, and it is simple to change in future
>     nbd_port = '10900'
>     to
>     nbd_port = iotests.get_free_port()
>     if needed.
> 
> [Unfortunately, qmp query-nbd-server is not finished yet, coming soon,
>  but may be after my vocation on the next week]

Enjoy your time off. I think the series is nearly ready to go; I had
some tweaks that I suggested, and will probably replace your 2/6 with my
counterproposal, but I don't mind doing that cleanup if you don't have
time to respin.  I'll give it a few more days in case anyone else has
comments, then add it to my NBD queue.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 0/6] nbd export qmp interface

[Kevin Wolf]

[-- Attachment #1: Type: text/plain, Size: 1251 bytes --]

Am 18.01.2018 um 23:45 hat Eric Blake geschrieben:
> On 01/18/2018 12:11 PM, Vladimir Sementsov-Ogievskiy wrote:
> > v2:
> > 01: tweak comment
> >     add Eric's r-b
> > 02: new patch
> > 03: rewritten, to move form 'bool force' flag to 'enum mode' parameter
> > 04: add Eric's r-b
> > 05: improve commit message
> >     tweak comment
> > 06: rebase on 03 changes
> >     make PEP8 happy
> >     some other tweaks
> >     I've left nbd_port variable hard-set to 10900. I think all such things
> >     should be fixed together, and it is simple to change in future
> >     nbd_port = '10900'
> >     to
> >     nbd_port = iotests.get_free_port()
> >     if needed.
> > 
> > [Unfortunately, qmp query-nbd-server is not finished yet, coming soon,
> >  but may be after my vocation on the next week]
> 
> Enjoy your time off. I think the series is nearly ready to go; I had
> some tweaks that I suggested, and will probably replace your 2/6 with my
> counterproposal, but I don't mind doing that cleanup if you don't have
> time to respin.  I'll give it a few more days in case anyone else has
> comments, then add it to my NBD queue.

I haven't reviewed the patches in detail, but the API changes look good
to me.

Kevin

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 801 bytes --]

[Qemu-devel] [PATCH v2 0/6] nbd export qmp interface

[Vladimir Sementsov-Ogievskiy]

Here:
    1. separate export name from device name
    1.1 several exports per device possible
    2. add nbd-server-remove

v2:
01: add r-bs by Max and Eric, add comment to code (hope you don't mind)
03: address export by its name, not by device name
    make it possible to force-remove export, which is already
    non-force-removed (thourh new "hidden" field)
other patches are new

v1:
Add command to remove nbd export, pair to nbd-server-add.
The whole thing and description are in patch 02.


Vladimir Sementsov-Ogievskiy (6):
  nbd/server: add additional assert to nbd_export_put
  qapi: add name parameter to nbd-server-add
  qapi: add nbd-server-remove
  iotest 147: add cases to test new @name parameter of nbd-server-add
  iotests: implement QemuIoInteractive class
  iotest 201: new test for qmp nbd-server-remove

 qapi/block.json               |  27 ++++++++-
 include/block/nbd.h           |   3 +-
 blockdev-nbd.c                |  41 +++++++++++--
 hmp.c                         |   5 +-
 nbd/server.c                  |  31 +++++++++-
 tests/qemu-iotests/147        |  68 +++++++++++++++++-----
 tests/qemu-iotests/147.out    |   4 +-
 tests/qemu-iotests/201        | 130 ++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/201.out    |   5 ++
 tests/qemu-iotests/group      |   1 +
 tests/qemu-iotests/iotests.py |  38 ++++++++++++
 11 files changed, 325 insertions(+), 28 deletions(-)
 create mode 100644 tests/qemu-iotests/201
 create mode 100644 tests/qemu-iotests/201.out

-- 
2.11.1

[Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

Add command for export removing. It is needed for cases when we
don't want to keep export after the operation on it was completed.
The other example is temporary node, created with blockdev-add.
If we want to delete it we should firstly remove corresponding
NBD export.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qapi/block.json     | 18 ++++++++++++++++++
 include/block/nbd.h |  3 ++-
 blockdev-nbd.c      | 29 ++++++++++++++++++++++++++++-
 nbd/server.c        | 25 ++++++++++++++++++++++---
 4 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/qapi/block.json b/qapi/block.json
index 503d4b287b..f83485c325 100644
--- a/qapi/block.json
+++ b/qapi/block.json
@@ -228,6 +228,24 @@
   'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
 
 ##
+# @nbd-server-remove:
+#
+# Remove NBD export by name.
+#
+# @name: Export name.
+#
+# @force: Whether active connections to the export should be closed. If this
+#         parameter is false the export only becomes hidden from clients (new
+#         connections are impossible), and would be automatically freed after
+#         all clients are disconnected (default false).
+#
+# Returns: error if the server is not running or export is not found.
+#
+# Since: 2.12
+##
+{ 'command': 'nbd-server-remove', 'data': {'name': 'str', '*force': 'bool'} }
+
+##
 # @nbd-server-stop:
 #
 # Stop QEMU's embedded NBD server, and unregister all devices previously
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 113c707a5e..b89d116597 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -261,12 +261,13 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
                           bool writethrough, BlockBackend *on_eject_blk,
                           Error **errp);
 void nbd_export_close(NBDExport *exp);
+void nbd_export_hide(NBDExport *exp);
 void nbd_export_get(NBDExport *exp);
 void nbd_export_put(NBDExport *exp);
 
 BlockBackend *nbd_export_get_blockdev(NBDExport *exp);
 
-NBDExport *nbd_export_find(const char *name);
+NBDExport *nbd_export_find(const char *name, bool include_hidden);
 void nbd_export_set_name(NBDExport *exp, const char *name);
 void nbd_export_set_description(NBDExport *exp, const char *description);
 void nbd_export_close_all(void);
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
index 46c885aa35..2495d38f2c 100644
--- a/blockdev-nbd.c
+++ b/blockdev-nbd.c
@@ -174,7 +174,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
         name = device;
     }
 
-    if (nbd_export_find(name)) {
+    if (nbd_export_find(name, true)) {
         error_setg(errp, "NBD server already has export named '%s'", name);
         return;
     }
@@ -207,6 +207,33 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
     nbd_export_put(exp);
 }
 
+void qmp_nbd_server_remove(const char *name, bool has_force, bool force,
+                           Error **errp)
+{
+    NBDExport *exp;
+
+    if (!nbd_server) {
+        error_setg(errp, "NBD server not running");
+        return;
+    }
+
+    exp = nbd_export_find(name, true);
+    if (exp == NULL) {
+        error_setg(errp, "Export '%s' is not found", name);
+        return;
+    }
+
+    if (!has_force) {
+        force = false;
+    }
+
+    if (force) {
+        nbd_export_close(exp);
+    } else {
+        nbd_export_hide(exp);
+    }
+}
+
 void qmp_nbd_server_stop(Error **errp)
 {
     nbd_export_close_all();
diff --git a/nbd/server.c b/nbd/server.c
index e817c48087..d85f2dc747 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -78,6 +78,10 @@ struct NBDExport {
 
     BlockBackend *eject_notifier_blk;
     Notifier eject_notifier;
+
+    /* hidden export is not available for new connections and should be removed
+     * after last client disconnect */
+    bool hidden;
 };
 
 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
@@ -300,7 +304,7 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length,
 
     trace_nbd_negotiate_handle_export_name_request(name);
 
-    client->exp = nbd_export_find(name);
+    client->exp = nbd_export_find(name, false);
     if (!client->exp) {
         error_setg(errp, "export not found");
         return -EINVAL;
@@ -429,7 +433,7 @@ static int nbd_negotiate_handle_info(NBDClient *client, uint32_t length,
     }
     assert(length == 0);
 
-    exp = nbd_export_find(name);
+    exp = nbd_export_find(name, false);
     if (!exp) {
         return nbd_negotiate_send_rep_err(client->ioc, NBD_REP_ERR_UNKNOWN,
                                           opt, errp, "export '%s' not present",
@@ -966,6 +970,9 @@ void nbd_client_put(NBDClient *client)
         if (client->exp) {
             QTAILQ_REMOVE(&client->exp->clients, client, next);
             nbd_export_put(client->exp);
+            if (client->exp->hidden && QTAILQ_EMPTY(&client->exp->clients)) {
+                nbd_export_close(client->exp);
+            }
         }
         g_free(client);
     }
@@ -1125,10 +1132,14 @@ fail:
     return NULL;
 }
 
-NBDExport *nbd_export_find(const char *name)
+NBDExport *nbd_export_find(const char *name, bool include_hidden)
 {
     NBDExport *exp;
     QTAILQ_FOREACH(exp, &exports, next) {
+        if (!include_hidden && exp->hidden) {
+            continue;
+        }
+
         if (strcmp(name, exp->name) == 0) {
             return exp;
         }
@@ -1177,6 +1188,14 @@ void nbd_export_close(NBDExport *exp)
     nbd_export_put(exp);
 }
 
+void nbd_export_hide(NBDExport *exp)
+{
+    exp->hidden = true;
+    if (QTAILQ_EMPTY(&exp->clients)) {
+        nbd_export_close(exp);
+    }
+}
+
 void nbd_export_get(NBDExport *exp)
 {
     assert(exp->refcount > 0);
-- 
2.11.1

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 2292 bytes --]

On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
> Add command for export removing. It is needed for cases when we
> don't want to keep export after the operation on it was completed.
> The other example is temporary node, created with blockdev-add.
> If we want to delete it we should firstly remove corresponding
> NBD export.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  qapi/block.json     | 18 ++++++++++++++++++
>  include/block/nbd.h |  3 ++-
>  blockdev-nbd.c      | 29 ++++++++++++++++++++++++++++-
>  nbd/server.c        | 25 ++++++++++++++++++++++---
>  4 files changed, 70 insertions(+), 5 deletions(-)
> 
> diff --git a/qapi/block.json b/qapi/block.json
> index 503d4b287b..f83485c325 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -228,6 +228,24 @@
>    'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
>  
>  ##
> +# @nbd-server-remove:
> +#
> +# Remove NBD export by name.
> +#
> +# @name: Export name.
> +#
> +# @force: Whether active connections to the export should be closed. If this
> +#         parameter is false the export only becomes hidden from clients (new
> +#         connections are impossible), and would be automatically freed after
> +#         all clients are disconnected (default false).

Unstated, but if the parameter is true, existing clients are forcefully
disconnected, possibly losing pending transactions.

Do we want a third mode in the middle, where the server starts replying
to all existing clients with ESHUTDOWN errors for all new requests
rather than abruptly disconnecting (no new I/O, but no forced disconnect
and pending in-flight transactions can still complete gracefully)?

> +#
> +# Returns: error if the server is not running or export is not found.
> +#
> +# Since: 2.12
> +##
> +{ 'command': 'nbd-server-remove', 'data': {'name': 'str', '*force': 'bool'} }
> +

If we're okay with just the bool parameter, then this patch looks good;
but if we want a third mode, then we want '*force' to be an enum type.
So tentative:

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

09.01.2018 22:52, Eric Blake wrote:
> On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>> Add command for export removing. It is needed for cases when we
>> don't want to keep export after the operation on it was completed.
>> The other example is temporary node, created with blockdev-add.
>> If we want to delete it we should firstly remove corresponding
>> NBD export.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   qapi/block.json     | 18 ++++++++++++++++++
>>   include/block/nbd.h |  3 ++-
>>   blockdev-nbd.c      | 29 ++++++++++++++++++++++++++++-
>>   nbd/server.c        | 25 ++++++++++++++++++++++---
>>   4 files changed, 70 insertions(+), 5 deletions(-)
>>
>> diff --git a/qapi/block.json b/qapi/block.json
>> index 503d4b287b..f83485c325 100644
>> --- a/qapi/block.json
>> +++ b/qapi/block.json
>> @@ -228,6 +228,24 @@
>>     'data': {'device': 'str', '*name': 'str', '*writable': 'bool'} }
>>   
>>   ##
>> +# @nbd-server-remove:
>> +#
>> +# Remove NBD export by name.
>> +#
>> +# @name: Export name.
>> +#
>> +# @force: Whether active connections to the export should be closed. If this
>> +#         parameter is false the export only becomes hidden from clients (new
>> +#         connections are impossible), and would be automatically freed after
>> +#         all clients are disconnected (default false).
> Unstated, but if the parameter is true, existing clients are forcefully
> disconnected, possibly losing pending transactions.
>
> Do we want a third mode in the middle, where the server starts replying
> to all existing clients with ESHUTDOWN errors for all new requests
> rather than abruptly disconnecting (no new I/O, but no forced disconnect
> and pending in-flight transactions can still complete gracefully)?

looks interesting. what about the following naming?

@mode: possible values:
               hide - just hide server from new clients, maintain 
existing connections,
                           remove after all clients disconnected
               soft - like hide, but answer with ESHUTDOWN for all 
further requests from
                           existing connections
               hard - hard disconnect all clients and remove server
               (default: soft)

new corresponding states of nbd export:
hidden, shutting_down

and we allow transitions:

normal_execution -> hidden
normal_execution -> shutting_down
normal_execution -> exit
hidden -> shutting_down
hidden -> exit
shutting_down -> exit


>
>> +#
>> +# Returns: error if the server is not running or export is not found.
>> +#
>> +# Since: 2.12
>> +##
>> +{ 'command': 'nbd-server-remove', 'data': {'name': 'str', '*force': 'bool'} }
>> +
> If we're okay with just the bool parameter, then this patch looks good;
> but if we want a third mode, then we want '*force' to be an enum type.
> So tentative:
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
>


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 2108 bytes --]

On 01/12/2018 03:47 AM, Vladimir Sementsov-Ogievskiy wrote:
> 09.01.2018 22:52, Eric Blake wrote:
>> On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Add command for export removing. It is needed for cases when we
>>> don't want to keep export after the operation on it was completed.
>>> The other example is temporary node, created with blockdev-add.
>>> If we want to delete it we should firstly remove corresponding
>>> NBD export.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>> ---

>> Do we want a third mode in the middle, where the server starts replying
>> to all existing clients with ESHUTDOWN errors for all new requests
>> rather than abruptly disconnecting (no new I/O, but no forced disconnect
>> and pending in-flight transactions can still complete gracefully)?
> 
> looks interesting. what about the following naming?
> 
> @mode: possible values:
>               hide - just hide server from new clients, maintain
> existing connections,
>                           remove after all clients disconnected
>               soft - like hide, but answer with ESHUTDOWN for all
> further requests from
>                           existing connections
>               hard - hard disconnect all clients and remove server
>               (default: soft)

Or even a fourth mode that causes an immediate error return without
state change if there are any connected clients, but otherwise removes
the server.

> 
> new corresponding states of nbd export:
> hidden, shutting_down
> 
> and we allow transitions:
> 
> normal_execution -> hidden
> normal_execution -> shutting_down
> normal_execution -> exit
> hidden -> shutting_down
> hidden -> exit
> shutting_down -> exit

Seems reasonable.  Are you planning on tackling a respin of this series
incorporating that idea?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

15.01.2018 18:09, Eric Blake wrote:
> On 01/12/2018 03:47 AM, Vladimir Sementsov-Ogievskiy wrote:
>> 09.01.2018 22:52, Eric Blake wrote:
>>> On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>> Add command for export removing. It is needed for cases when we
>>>> don't want to keep export after the operation on it was completed.
>>>> The other example is temporary node, created with blockdev-add.
>>>> If we want to delete it we should firstly remove corresponding
>>>> NBD export.
>>>>
>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>>> ---
>>> Do we want a third mode in the middle, where the server starts replying
>>> to all existing clients with ESHUTDOWN errors for all new requests
>>> rather than abruptly disconnecting (no new I/O, but no forced disconnect
>>> and pending in-flight transactions can still complete gracefully)?
>> looks interesting. what about the following naming?
>>
>> @mode: possible values:
>>                hide - just hide server from new clients, maintain
>> existing connections,
>>                            remove after all clients disconnected
>>                soft - like hide, but answer with ESHUTDOWN for all
>> further requests from
>>                            existing connections
>>                hard - hard disconnect all clients and remove server
>>                (default: soft)
> Or even a fourth mode that causes an immediate error return without
> state change if there are any connected clients, but otherwise removes
> the server.
>
>> new corresponding states of nbd export:
>> hidden, shutting_down
>>
>> and we allow transitions:
>>
>> normal_execution -> hidden
>> normal_execution -> shutting_down
>> normal_execution -> exit
>> hidden -> shutting_down
>> hidden -> exit
>> shutting_down -> exit
> Seems reasonable.  Are you planning on tackling a respin of this series
> incorporating that idea?
>

yes, will do.


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

15.01.2018 20:47, Vladimir Sementsov-Ogievskiy wrote:
> 15.01.2018 18:09, Eric Blake wrote:
>> On 01/12/2018 03:47 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> 09.01.2018 22:52, Eric Blake wrote:
>>>> On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>>> Add command for export removing. It is needed for cases when we
>>>>> don't want to keep export after the operation on it was completed.
>>>>> The other example is temporary node, created with blockdev-add.
>>>>> If we want to delete it we should firstly remove corresponding
>>>>> NBD export.
>>>>>
>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy 
>>>>> <vsementsov@virtuozzo.com>
>>>>> ---
>>>> Do we want a third mode in the middle, where the server starts 
>>>> replying
>>>> to all existing clients with ESHUTDOWN errors for all new requests
>>>> rather than abruptly disconnecting (no new I/O, but no forced 
>>>> disconnect
>>>> and pending in-flight transactions can still complete gracefully)?
>>> looks interesting. what about the following naming?
>>>
>>> @mode: possible values:
>>>                hide - just hide server from new clients, maintain
>>> existing connections,
>>>                            remove after all clients disconnected
>>>                soft - like hide, but answer with ESHUTDOWN for all
>>> further requests from
>>>                            existing connections
>>>                hard - hard disconnect all clients and remove server
>>>                (default: soft)
>> Or even a fourth mode that causes an immediate error return without
>> state change if there are any connected clients, but otherwise removes
>> the server.
>>
>>> new corresponding states of nbd export:
>>> hidden, shutting_down
>>>
>>> and we allow transitions:
>>>
>>> normal_execution -> hidden
>>> normal_execution -> shutting_down
>>> normal_execution -> exit
>>> hidden -> shutting_down
>>> hidden -> exit
>>> shutting_down -> exit
>> Seems reasonable.  Are you planning on tackling a respin of this series
>> incorporating that idea?
>>
>
> yes, will do.
>
>

Discussed with Nikolay.
For now we actually need only one mode: hard.
In near future we _may be_ will need your proposed fourth mode (what 
about "safe" name for it ?)

I was going to implement all 4 modes, but now I doubt, isn't it too 
hastily, to introduce 3 new modes to the
interface, which we (personally) do not need. May be it is better to 
start from one or two modes.

Finally what do you think, Eric? Which modes do you need?

ps: I've created hmp version for 2/6, it will be in v2.
  also, I'm going to add query-nbd-server, which should list all exports

also, about HMP: If I understand correctly, people use it because 
writing qmp command by hand is not very comfortable.
I have a script (for managing libvirt guest, but it can be adopted for 
qemu or even used for qemu monitor), which allows
me run qmp commands on vms as easy as:

|qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1 
mode hard or even |

|qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true 
direct true} aio native discard unmap file {driver file filename 
/tmp/somedisk} |||

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 3757 bytes --]

On 01/17/2018 07:36 AM, Vladimir Sementsov-Ogievskiy wrote:

>>>> looks interesting. what about the following naming?
>>>>
>>>> @mode: possible values:
>>>>                hide - just hide server from new clients, maintain
>>>> existing connections,
>>>>                            remove after all clients disconnected
>>>>                soft - like hide, but answer with ESHUTDOWN for all
>>>> further requests from
>>>>                            existing connections
>>>>                hard - hard disconnect all clients and remove server
>>>>                (default: soft)
>>> Or even a fourth mode that causes an immediate error return without
>>> state change if there are any connected clients, but otherwise removes
>>> the server.
>>>
>>>> new corresponding states of nbd export:
>>>> hidden, shutting_down
>>>>
>>>> and we allow transitions:
>>>>
>>>> normal_execution -> hidden
>>>> normal_execution -> shutting_down
>>>> normal_execution -> exit
>>>> hidden -> shutting_down
>>>> hidden -> exit
>>>> shutting_down -> exit
>>> Seems reasonable.  Are you planning on tackling a respin of this series
>>> incorporating that idea?
>>>
>>
>> yes, will do.
>>
>>
> 
> Discussed with Nikolay.
> For now we actually need only one mode: hard.
> In near future we _may be_ will need your proposed fourth mode (what
> about "safe" name for it ?)

'safe' sounds reasonable.

Of course, if we only have two modes at front ('safe' which returns an
error if a client is connected, and 'hard' which disconnects all clients
immediately; leaving 'hide' and 'soft' for the future), then we don't
have to worry about a state transition or any hidden exports.

A QAPI enum with only two values now is at least extensible in the
future if someone has a need for another mode, and introspectible to
learn which modes are currently supported.

> 
> I was going to implement all 4 modes, but now I doubt, isn't it too
> hastily, to introduce 3 new modes to the
> interface, which we (personally) do not need. May be it is better to
> start from one or two modes.

Starting with just two modes is fine as well.

> 
> Finally what do you think, Eric? Which modes do you need?

'hide' may be interesting for the purpose of connecting a single client,
then hiding the export so no other clients can connect, while waiting
for the first client to take its time.  But right now, I don't have
actual use cases in mind so much as making sure we aren't limiting
ourself from future expansion as needs are identified, so a conservative
choice of just 'safe' and 'hard' for now is reasonable.

> 
> ps: I've created hmp version for 2/6, it will be in v2.
>  also, I'm going to add query-nbd-server, which should list all exports

Sounds good.

> 
> also, about HMP: If I understand correctly, people use it because
> writing qmp command by hand is not very comfortable.
> I have a script (for managing libvirt guest, but it can be adopted for
> qemu or even used for qemu monitor), which allows
> me run qmp commands on vms as easy as:
> 
> |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
> mode hard or even |
> 
> |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
> direct true} aio native discard unmap file {driver file filename
> /tmp/somedisk} |||

Yeah, there are various scripting solutions around QMP that can make it
easier; but HMP is often still an easy front-line interface for experiments.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

17.01.2018 18:23, Eric Blake wrote:
> On 01/17/2018 07:36 AM, Vladimir Sementsov-Ogievskiy wrote:
>
>>>>> looks interesting. what about the following naming?
>>>>>
>>>>> @mode: possible values:
>>>>>                 hide - just hide server from new clients, maintain
>>>>> existing connections,
>>>>>                             remove after all clients disconnected
>>>>>                 soft - like hide, but answer with ESHUTDOWN for all
>>>>> further requests from
>>>>>                             existing connections
>>>>>                 hard - hard disconnect all clients and remove server
>>>>>                 (default: soft)
>>>> Or even a fourth mode that causes an immediate error return without
>>>> state change if there are any connected clients, but otherwise removes
>>>> the server.
>>>>
>>>>> new corresponding states of nbd export:
>>>>> hidden, shutting_down
>>>>>
>>>>> and we allow transitions:
>>>>>
>>>>> normal_execution -> hidden
>>>>> normal_execution -> shutting_down
>>>>> normal_execution -> exit
>>>>> hidden -> shutting_down
>>>>> hidden -> exit
>>>>> shutting_down -> exit
>>>> Seems reasonable.  Are you planning on tackling a respin of this series
>>>> incorporating that idea?
>>>>
>>> yes, will do.
>>>
>>>
>> Discussed with Nikolay.
>> For now we actually need only one mode: hard.
>> In near future we _may be_ will need your proposed fourth mode (what
>> about "safe" name for it ?)
> 'safe' sounds reasonable.
>
> Of course, if we only have two modes at front ('safe' which returns an
> error if a client is connected, and 'hard' which disconnects all clients
> immediately; leaving 'hide' and 'soft' for the future), then we don't
> have to worry about a state transition or any hidden exports.
>
> A QAPI enum with only two values now is at least extensible in the
> future if someone has a need for another mode, and introspectible to
> learn which modes are currently supported.
>
>> I was going to implement all 4 modes, but now I doubt, isn't it too
>> hastily, to introduce 3 new modes to the
>> interface, which we (personally) do not need. May be it is better to
>> start from one or two modes.
> Starting with just two modes is fine as well.
>
>> Finally what do you think, Eric? Which modes do you need?
> 'hide' may be interesting for the purpose of connecting a single client,
> then hiding the export so no other clients can connect, while waiting
> for the first client to take its time.  But right now, I don't have
> actual use cases in mind so much as making sure we aren't limiting
> ourself from future expansion as needs are identified, so a conservative
> choice of just 'safe' and 'hard' for now is reasonable.

ok, I agree. 'safe' looks like better option for default behavior. So 
I'll post these two options in v3.

>
>> ps: I've created hmp version for 2/6, it will be in v2.
>>   also, I'm going to add query-nbd-server, which should list all exports
> Sounds good.
>
>> also, about HMP: If I understand correctly, people use it because
>> writing qmp command by hand is not very comfortable.
>> I have a script (for managing libvirt guest, but it can be adopted for
>> qemu or even used for qemu monitor), which allows
>> me run qmp commands on vms as easy as:
>>
>> |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
>> mode hard or even |
>>
>> |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
>> direct true} aio native discard unmap file {driver file filename
>> /tmp/somedisk} |||
> Yeah, there are various scripting solutions around QMP that can make it
> easier; but HMP is often still an easy front-line interface for experiments.
>

isn't it because these solutions are not available directly in monitor, 
when HMP is?
may be, we need third type of monitor HQMP which is QMP with simplified 
syntax? Or
allow qmp commands in simplified syntax directly in HMP?

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 2090 bytes --]

On 01/17/2018 09:51 AM, Vladimir Sementsov-Ogievskiy wrote:

>>> I have a script (for managing libvirt guest, but it can be adopted for
>>> qemu or even used for qemu monitor), which allows
>>> me run qmp commands on vms as easy as:
>>>
>>> |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
>>> mode hard or even |
>>>
>>> |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
>>> direct true} aio native discard unmap file {driver file filename
>>> /tmp/somedisk} |||
>> Yeah, there are various scripting solutions around QMP that can make it
>> easier; but HMP is often still an easy front-line interface for
>> experiments.
>>
> 
> isn't it because these solutions are not available directly in monitor,
> when HMP is?

QMP can be directly accessed in a monitor; it just requires more typing.
 If you are developing QMP commands, it may be easier to use
./scripts/qmp/qmp-shell (couple it with a readline wrapper, and you can
even get tab-completion and history across sessions).  There's also
things like libvirt's 'virsh qmp-monitor-command' for shell-scripting
access to arbitrary QMP commands, provided your guest is run by libvirt.

> may be, we need third type of monitor HQMP which is QMP with simplified
> syntax? Or
> allow qmp commands in simplified syntax directly in HMP?

No, I don't think we need either thing.  Wrappers around existing
monitors is better than bloating qemu proper with a third flavor of
monitor.  And HMP is for humans, with no restrictions on back-compat
changes, so if it doesn't do something you want for quick-and-dirty
testing, you can either add a new HMP command, or just use QMP (or one
of its wrappers, like qmp-shell) in the first place.  Ultimately, our
long-term concern is only about the QMP interface; HMP is supposed to be
convenient.  So if it starts costing too much time to port a QMP
interface to HMP, then don't worry about it.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

17.01.2018 19:03, Eric Blake wrote:
> On 01/17/2018 09:51 AM, Vladimir Sementsov-Ogievskiy wrote:
>
>>>> I have a script (for managing libvirt guest, but it can be adopted for
>>>> qemu or even used for qemu monitor), which allows
>>>> me run qmp commands on vms as easy as:
>>>>
>>>> |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
>>>> mode hard or even |
>>>>
>>>> |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
>>>> direct true} aio native discard unmap file {driver file filename
>>>> /tmp/somedisk} |||
>>> Yeah, there are various scripting solutions around QMP that can make it
>>> easier; but HMP is often still an easy front-line interface for
>>> experiments.
>>>
>> isn't it because these solutions are not available directly in monitor,
>> when HMP is?
> QMP can be directly accessed in a monitor; it just requires more typing.
>   If you are developing QMP commands, it may be easier to use
> ./scripts/qmp/qmp-shell (couple it with a readline wrapper, and you can
> even get tab-completion and history across sessions).  There's also
> things like libvirt's 'virsh qmp-monitor-command' for shell-scripting
> access to arbitrary QMP commands, provided your guest is run by libvirt.
>
>> may be, we need third type of monitor HQMP which is QMP with simplified
>> syntax? Or
>> allow qmp commands in simplified syntax directly in HMP?
> No, I don't think we need either thing.  Wrappers around existing
> monitors is better than bloating qemu proper with a third flavor of
> monitor.  And HMP is for humans, with no restrictions on back-compat
> changes, so if it doesn't do something you want for quick-and-dirty
> testing, you can either add a new HMP command, or just use QMP (or one
> of its wrappers, like qmp-shell) in the first place.  Ultimately, our
> long-term concern is only about the QMP interface; HMP is supposed to be
> convenient.  So if it starts costing too much time to port a QMP
> interface to HMP, then don't worry about it.
>

most of commands, ported to hmp are done in same style: they just call 
corresponding qmp command.
Isn't it better to provide common interface for calling qmp commands 
through HMP monitor, to never
create hmp versions of new commands? they will be available automatically.

-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Dr. David Alan Gilbert]

* Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
> 17.01.2018 19:03, Eric Blake wrote:
> > On 01/17/2018 09:51 AM, Vladimir Sementsov-Ogievskiy wrote:
> > 
> > > > > I have a script (for managing libvirt guest, but it can be adopted for
> > > > > qemu or even used for qemu monitor), which allows
> > > > > me run qmp commands on vms as easy as:
> > > > > 
> > > > > |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
> > > > > mode hard or even |
> > > > > 
> > > > > |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
> > > > > direct true} aio native discard unmap file {driver file filename
> > > > > /tmp/somedisk} |||
> > > > Yeah, there are various scripting solutions around QMP that can make it
> > > > easier; but HMP is often still an easy front-line interface for
> > > > experiments.
> > > > 
> > > isn't it because these solutions are not available directly in monitor,
> > > when HMP is?
> > QMP can be directly accessed in a monitor; it just requires more typing.
> >   If you are developing QMP commands, it may be easier to use
> > ./scripts/qmp/qmp-shell (couple it with a readline wrapper, and you can
> > even get tab-completion and history across sessions).  There's also
> > things like libvirt's 'virsh qmp-monitor-command' for shell-scripting
> > access to arbitrary QMP commands, provided your guest is run by libvirt.
> > 
> > > may be, we need third type of monitor HQMP which is QMP with simplified
> > > syntax? Or
> > > allow qmp commands in simplified syntax directly in HMP?
> > No, I don't think we need either thing.  Wrappers around existing
> > monitors is better than bloating qemu proper with a third flavor of
> > monitor.  And HMP is for humans, with no restrictions on back-compat
> > changes, so if it doesn't do something you want for quick-and-dirty
> > testing, you can either add a new HMP command, or just use QMP (or one
> > of its wrappers, like qmp-shell) in the first place.  Ultimately, our
> > long-term concern is only about the QMP interface; HMP is supposed to be
> > convenient.  So if it starts costing too much time to port a QMP
> > interface to HMP, then don't worry about it.
> > 
> 
> most of commands, ported to hmp are done in same style: they just call
> corresponding qmp command.
> Isn't it better to provide common interface for calling qmp commands through
> HMP monitor, to never
> create hmp versions of new commands? they will be available automatically.

It would be nice to do that, but they're not that consistent in how they
convert parameters and options, but I occasionally wonder if we could
automate more of it.

Dave

> -- 
> Best regards,
> Vladimir
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

26.01.2018 18:05, Dr. David Alan Gilbert wrote:
> * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
>> 17.01.2018 19:03, Eric Blake wrote:
>>> On 01/17/2018 09:51 AM, Vladimir Sementsov-Ogievskiy wrote:
>>>
>>>>>> I have a script (for managing libvirt guest, but it can be adopted for
>>>>>> qemu or even used for qemu monitor), which allows
>>>>>> me run qmp commands on vms as easy as:
>>>>>>
>>>>>> |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
>>>>>> mode hard or even |
>>>>>>
>>>>>> |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
>>>>>> direct true} aio native discard unmap file {driver file filename
>>>>>> /tmp/somedisk} |||
>>>>> Yeah, there are various scripting solutions around QMP that can make it
>>>>> easier; but HMP is often still an easy front-line interface for
>>>>> experiments.
>>>>>
>>>> isn't it because these solutions are not available directly in monitor,
>>>> when HMP is?
>>> QMP can be directly accessed in a monitor; it just requires more typing.
>>>    If you are developing QMP commands, it may be easier to use
>>> ./scripts/qmp/qmp-shell (couple it with a readline wrapper, and you can
>>> even get tab-completion and history across sessions).  There's also
>>> things like libvirt's 'virsh qmp-monitor-command' for shell-scripting
>>> access to arbitrary QMP commands, provided your guest is run by libvirt.
>>>
>>>> may be, we need third type of monitor HQMP which is QMP with simplified
>>>> syntax? Or
>>>> allow qmp commands in simplified syntax directly in HMP?
>>> No, I don't think we need either thing.  Wrappers around existing
>>> monitors is better than bloating qemu proper with a third flavor of
>>> monitor.  And HMP is for humans, with no restrictions on back-compat
>>> changes, so if it doesn't do something you want for quick-and-dirty
>>> testing, you can either add a new HMP command, or just use QMP (or one
>>> of its wrappers, like qmp-shell) in the first place.  Ultimately, our
>>> long-term concern is only about the QMP interface; HMP is supposed to be
>>> convenient.  So if it starts costing too much time to port a QMP
>>> interface to HMP, then don't worry about it.
>>>
>> most of commands, ported to hmp are done in same style: they just call
>> corresponding qmp command.
>> Isn't it better to provide common interface for calling qmp commands through
>> HMP monitor, to never
>> create hmp versions of new commands? they will be available automatically.
> It would be nice to do that, but they're not that consistent in how they
> convert parameters and options, but I occasionally wonder if we could
> automate more of it.


What about allowing some new syntax in hmp, directly mapped to qmp?

something like

 >>> blockdev-add id disk driver qcow2 cache {writeback true direct 
true} aio native discard unmap file {driver file filename /tmp/somedisk}

?

Or it may be realized as a separate hmp command "qmp" (looks more safe 
as a first step, however, I think previous variant (direct call) is better):

 >>> qmp blockdev-add id disk driver qcow2 cache {writeback true direct 
true} aio native discard unmap file {driver file filename /tmp/somedisk}

what do think? This looks simple to implement and should be useful.

>
> Dave
>
>> -- 
>> Best regards,
>> Vladimir
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

On 02/06/2018 09:29 AM, Vladimir Sementsov-Ogievskiy wrote:

>>> most of commands, ported to hmp are done in same style: they just call
>>> corresponding qmp command.
>>> Isn't it better to provide common interface for calling qmp commands 
>>> through
>>> HMP monitor, to never
>>> create hmp versions of new commands? they will be available 
>>> automatically.
>> It would be nice to do that, but they're not that consistent in how they
>> convert parameters and options, but I occasionally wonder if we could
>> automate more of it.
> 
> 
> What about allowing some new syntax in hmp, directly mapped to qmp?
> 
> something like
> 
>  >>> blockdev-add id disk driver qcow2 cache {writeback true direct 
> true} aio native discard unmap file {driver file filename /tmp/somedisk}
> 

Personally, if I'm testing blockdev-add, I'll use QMP directly (or even 
scripts/qmp/qmp-shell or virsh qemu-monitor-command), not an HMP wrapper 
where I have to learn a new syntax of how to write something that will 
convert to QMP.  We already have enough different ways to write things 
that I don't need to learn yet another syntax wrapper.  Or maybe what 
I'm saying is that instead of inventing a new syntax, that if you DO add 
an HMP command that forwards to QMP, please reuse an existing syntax 
(whether direct JSON as used by QMP, or the syntax used by qmp-shell).

If you think writing a new HMP command is worth it, I won't stop you 
from writing it.  But at this point, our current approach of writing a 
manual wrapper per command as we have interest, rather than a generic 
wrap-anything, has worked for the cases that HMP users have cared about. 
  Remember, QMP is the interface that MUST work, while HMP is only for 
convenience, and if it is not trivial to make HMP do everything that QMP 
can do, it is no real loss.

> ?
> 
> Or it may be realized as a separate hmp command "qmp" (looks more safe 
> as a first step, however, I think previous variant (direct call) is 
> better):
> 
>  >>> qmp blockdev-add id disk driver qcow2 cache {writeback true direct 
> true} aio native discard unmap file {driver file filename /tmp/somedisk}
> 
> what do think? This looks simple to implement and should be useful.

Up to you if you want to tackle anything like that, but it would be a 
new thread (a generic way to invoke QMP from HMP is independent of 
nbd-server-remove).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Vladimir Sementsov-Ogievskiy]

06.02.2018 19:06, Eric Blake wrote:
> On 02/06/2018 09:29 AM, Vladimir Sementsov-Ogievskiy wrote:
>
>>>> most of commands, ported to hmp are done in same style: they just call
>>>> corresponding qmp command.
>>>> Isn't it better to provide common interface for calling qmp 
>>>> commands through
>>>> HMP monitor, to never
>>>> create hmp versions of new commands? they will be available 
>>>> automatically.
>>> It would be nice to do that, but they're not that consistent in how 
>>> they
>>> convert parameters and options, but I occasionally wonder if we could
>>> automate more of it.
>>
>>
>> What about allowing some new syntax in hmp, directly mapped to qmp?
>>
>> something like
>>
>>  >>> blockdev-add id disk driver qcow2 cache {writeback true direct 
>> true} aio native discard unmap file {driver file filename /tmp/somedisk}
>>
>
> Personally, if I'm testing blockdev-add, I'll use QMP directly (or 
> even scripts/qmp/qmp-shell or virsh qemu-monitor-command), not an HMP 
> wrapper where I have to learn a new syntax of how to write something 
> that will convert to QMP.  We already have enough different ways to 
> write things that I don't need to learn yet another syntax wrapper.  
> Or maybe what I'm saying is that instead of inventing a new syntax, 
> that if you DO add an HMP command that forwards to QMP, please reuse 
> an existing syntax (whether direct JSON as used by QMP, or the syntax 
> used by qmp-shell).

I'm afraid, that JSON is too hard to use in human monitor. And this will 
make the whole feature useless.

>
> If you think writing a new HMP command is worth it, I won't stop you 
> from writing it.  But at this point, our current approach of writing a 
> manual wrapper per command as we have interest, rather than a generic 
> wrap-anything, has worked for the cases that HMP users have cared 
> about.  Remember, QMP is the interface that MUST work, while HMP is 
> only for convenience, and if it is not trivial to make HMP do 
> everything that QMP can do, it is no real loss.
>

But we create hmp wrappers on demand, and for each case, we actually 
invent new syntax. I just search for the way to avoid creating new and 
new hmp wrappers, by introducing new syntax only once.
And, here is almost nothing to learn:

command := command-name parameters
parameters = [key value ]...
value = simple-value | array | map
map = '{' parameters '}'
array = '[' [value ]... ']'

another variant is to use yaml - like json, but we do not need put all 
keys into quotes.

On the other hand, implementing new parser in qemu is not trivial task 
(hmm, I don't want do it=), it should be simpler to create direct JSON 
wrapper in HMP monitor, and use some python wrapper around the monitor. 
And this looks useless, as with same result I can use wrapper around QMP 
monitor. So, may be the most interesting solution would be to make some 
easy-to-use python-based wrapper, which will give a simple way to use 
both qmp and hmp commands.. I'll think about it. However it doesn't 
solve initial problem of creating new and new hmp wrappers by hand.

>> ?
>>
>> Or it may be realized as a separate hmp command "qmp" (looks more 
>> safe as a first step, however, I think previous variant (direct call) 
>> is better):
>>
>>  >>> qmp blockdev-add id disk driver qcow2 cache {writeback true 
>> direct true} aio native discard unmap file {driver file filename 
>> /tmp/somedisk}
>>
>> what do think? This looks simple to implement and should be useful.
>
> Up to you if you want to tackle anything like that, but it would be a 
> new thread (a generic way to invoke QMP from HMP is independent of 
> nbd-server-remove).
>


-- 
Best regards,
Vladimir

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Dr. David Alan Gilbert]

* Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
> 26.01.2018 18:05, Dr. David Alan Gilbert wrote:
> > * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
> > > 17.01.2018 19:03, Eric Blake wrote:
> > > > On 01/17/2018 09:51 AM, Vladimir Sementsov-Ogievskiy wrote:
> > > > 
> > > > > > > I have a script (for managing libvirt guest, but it can be adopted for
> > > > > > > qemu or even used for qemu monitor), which allows
> > > > > > > me run qmp commands on vms as easy as:
> > > > > > > 
> > > > > > > |qmp VMNAME query-block-jobs or qmp VMNAME nbd-server-remove name exp1
> > > > > > > mode hard or even |
> > > > > > > 
> > > > > > > |qmp VMNAME blockdev-add id disk driver qcow2 cache {writeback true
> > > > > > > direct true} aio native discard unmap file {driver file filename
> > > > > > > /tmp/somedisk} |||
> > > > > > Yeah, there are various scripting solutions around QMP that can make it
> > > > > > easier; but HMP is often still an easy front-line interface for
> > > > > > experiments.
> > > > > > 
> > > > > isn't it because these solutions are not available directly in monitor,
> > > > > when HMP is?
> > > > QMP can be directly accessed in a monitor; it just requires more typing.
> > > >    If you are developing QMP commands, it may be easier to use
> > > > ./scripts/qmp/qmp-shell (couple it with a readline wrapper, and you can
> > > > even get tab-completion and history across sessions).  There's also
> > > > things like libvirt's 'virsh qmp-monitor-command' for shell-scripting
> > > > access to arbitrary QMP commands, provided your guest is run by libvirt.
> > > > 
> > > > > may be, we need third type of monitor HQMP which is QMP with simplified
> > > > > syntax? Or
> > > > > allow qmp commands in simplified syntax directly in HMP?
> > > > No, I don't think we need either thing.  Wrappers around existing
> > > > monitors is better than bloating qemu proper with a third flavor of
> > > > monitor.  And HMP is for humans, with no restrictions on back-compat
> > > > changes, so if it doesn't do something you want for quick-and-dirty
> > > > testing, you can either add a new HMP command, or just use QMP (or one
> > > > of its wrappers, like qmp-shell) in the first place.  Ultimately, our
> > > > long-term concern is only about the QMP interface; HMP is supposed to be
> > > > convenient.  So if it starts costing too much time to port a QMP
> > > > interface to HMP, then don't worry about it.
> > > > 
> > > most of commands, ported to hmp are done in same style: they just call
> > > corresponding qmp command.
> > > Isn't it better to provide common interface for calling qmp commands through
> > > HMP monitor, to never
> > > create hmp versions of new commands? they will be available automatically.
> > It would be nice to do that, but they're not that consistent in how they
> > convert parameters and options, but I occasionally wonder if we could
> > automate more of it.
> 
> 
> What about allowing some new syntax in hmp, directly mapped to qmp?
> 
> something like
> 
> >>> blockdev-add id disk driver qcow2 cache {writeback true direct true} aio
> native discard unmap file {driver file filename /tmp/somedisk}
> 
> ?

Hmm, I don't particularly find that easy to read either; however the
actual block device specification for HMP should be the same as what we
pass on the command line, so we only have to worry about any extra
things that are part of blockdev_add.
(I'm sure we can find a way of making the one we pass on the commandline
more readable as well, there's so much duplication).

Dave

> Or it may be realized as a separate hmp command "qmp" (looks more safe as a
> first step, however, I think previous variant (direct call) is better):
> 
> >>> qmp blockdev-add id disk driver qcow2 cache {writeback true direct true}
> aio native discard unmap file {driver file filename /tmp/somedisk}
> 
> what do think? This looks simple to implement and should be useful.
> 
> > 
> > Dave
> > 
> > > -- 
> > > Best regards,
> > > Vladimir
> > > 
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> 
> 
> -- 
> Best regards,
> Vladimir
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Markus Armbruster]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:

> * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
>> 26.01.2018 18:05, Dr. David Alan Gilbert wrote:
>> > * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote:
[...]
>> > > most of commands, ported to hmp are done in same style: they just call
>> > > corresponding qmp command.

HMP commands *should* call the QMP command to do the actual work.  That
way, we *know* all the functionality is available in QMP, and HMP is
consistent with it.

Sometimes, calling helpers shared with QMP is more convenient, and
that's okay, but then you have to think about QMP completeness and
HMP/QMP consistency.

The only exception are HMP commands that don't make sense in QMP, such
as @cpu.

>> > > Isn't it better to provide common interface for calling qmp commands through
>> > > HMP monitor, to never
>> > > create hmp versions of new commands? they will be available automatically.
>> > It would be nice to do that, but they're not that consistent in how they
>> > convert parameters and options, but I occasionally wonder if we could
>> > automate more of it.
>> 
>> 
>> What about allowing some new syntax in hmp, directly mapped to qmp?
>> 
>> something like
>> 
>> >>> blockdev-add id disk driver qcow2 cache {writeback true direct true} aio
>> native discard unmap file {driver file filename /tmp/somedisk}
>> 
>> ?
>
> Hmm, I don't particularly find that easy to read either; however the
> actual block device specification for HMP should be the same as what we
> pass on the command line, so we only have to worry about any extra
> things that are part of blockdev_add.
> (I'm sure we can find a way of making the one we pass on the commandline
> more readable as well, there's so much duplication).

Good points.

QMP syntax is different for a good reason: it serves machines rather
than humans.

Both HMP and command line serve the same humans, yet the syntax they
wrap around common functionality is different.  Sad waste of developer
time, sad waste of user brain power.  The former could perhaps be
reduced with better tooling, say having QAPI generate the details.

If you have QAPI generate HMP and command line from the exact same
definitions as QMP, you get what Vladimir wants: different interfaces to
the exact same functionality, without additional coding.

Note that the needs of humans and machines differ in more ways than just
syntax.  For instance, humans appreciate convenience features to save
typing.  In a machine interface, they'd add unnecessary and
inappropriate complexity.  Adding convenience is a good reason for
actually designing the HMP interface, rather than copying the QMP one
blindly.