Re: [Qemu-block] [PATCH v4 07/11] block: Accept node-name for change-backing-file

[Alberto Garcia]

On Thu 14 Jul 2016 03:28:10 PM CEST, Kevin Wolf wrote:
> In order to remove the necessity to use BlockBackend names in the
> external API, we want to allow node-names everywhere. This converts
> change-backing-file to accept a node-name without lifting the
> restriction that we're operating at a root node.
>
> In case of an invalid device name, the command returns the GenericError
> error class now instead of DeviceNotFound, because this is what
> qmp_get_root_bs() returns.
>
> Signed-off-by: Kevin Wolf 

Reviewed-by: Alberto Garcia 

Berto

Re: [Qemu-block] [PATCH v4 07/11] block: Accept node-name for change-backing-file

[Max Reitz]

On 14.07.2016 22:44, Eric Blake wrote:
> On 07/14/2016 07:28 AM, Kevin Wolf wrote:
>> In order to remove the necessity to use BlockBackend names in the
>> external API, we want to allow node-names everywhere. This converts
>> change-backing-file to accept a node-name without lifting the
>> restriction that we're operating at a root node.
>>
>> In case of an invalid device name, the command returns the GenericError
>> error class now instead of DeviceNotFound, because this is what
>> qmp_get_root_bs() returns.
>>
>> Signed-off-by: Kevin Wolf 
>> ---
>>  blockdev.c   | 15 +++
>>  qapi/block-core.json |  3 ++-
>>  qmp-commands.hx  |  3 ++-
>>  3 files changed, 7 insertions(+), 14 deletions(-)
>>
> 
> Reviewed-by: Eric Blake 
> 
> Sometimes I wonder why this command is limited to only the root node -
> it seems like tweaking the backing file text of an intermediate node in
> a chain would be useful to someone.  But that's not the problem for this
> series.

Is it? The main argument of change-backing-file is not @device but
@image-node-name. @device is just used for a sanity check.

Max



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Re: [Qemu-block] [PATCH v4 07/11] block: Accept node-name for change-backing-file

[Eric Blake]

On 07/14/2016 07:28 AM, Kevin Wolf wrote:
> In order to remove the necessity to use BlockBackend names in the
> external API, we want to allow node-names everywhere. This converts
> change-backing-file to accept a node-name without lifting the
> restriction that we're operating at a root node.
> 
> In case of an invalid device name, the command returns the GenericError
> error class now instead of DeviceNotFound, because this is what
> qmp_get_root_bs() returns.
> 
> Signed-off-by: Kevin Wolf 
> ---
>  blockdev.c   | 15 +++
>  qapi/block-core.json |  3 ++-
>  qmp-commands.hx  |  3 ++-
>  3 files changed, 7 insertions(+), 14 deletions(-)
> 

Reviewed-by: Eric Blake 

Sometimes I wonder why this command is limited to only the root node -
it seems like tweaking the backing file text of an intermediate node in
a chain would be useful to someone.  But that's not the problem for this
series.

-- 
Eric Blake   eblake redhat com+1-919-301-3266
Libvirt virtualization library http://libvirt.org



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[Qemu-block] [PATCH v4 07/11] block: Accept node-name for change-backing-file

[Kevin Wolf]

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This converts
change-backing-file to accept a node-name without lifting the
restriction that we're operating at a root node.

In case of an invalid device name, the command returns the GenericError
error class now instead of DeviceNotFound, because this is what
qmp_get_root_bs() returns.

Signed-off-by: Kevin Wolf 
---
 blockdev.c   | 15 +++
 qapi/block-core.json |  3 ++-
 qmp-commands.hx  |  3 ++-
 3 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 05f7ad0..6b1f2f0 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3791,7 +3791,6 @@ void qmp_change_backing_file(const char *device,
  const char *backing_file,
  Error **errp)
 {
-BlockBackend *blk;
 BlockDriverState *bs = NULL;
 AioContext *aio_context;
 BlockDriverState *image_bs = NULL;
@@ -3800,22 +3799,14 @@ void qmp_change_backing_file(const char *device,
 int open_flags;
 int ret;
 
-blk = blk_by_name(device);
-if (!blk) {
-error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
-  "Device '%s' not found", device);
+bs = qmp_get_root_bs(device, errp);
+if (!bs) {
 return;
 }
 
-aio_context = blk_get_aio_context(blk);
+aio_context = bdrv_get_aio_context(bs);
 aio_context_acquire(aio_context);
 
-if (!blk_is_available(blk)) {
-error_setg(errp, "Device '%s' has no medium", device);
-goto out;
-}
-bs = blk_bs(blk);
-
 image_bs = bdrv_lookup_bs(NULL, image_node_name, _err);
 if (local_err) {
 error_propagate(errp, local_err);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 6266748..a73cd0d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -994,7 +994,8 @@
 # @image-node-name: The name of the block driver state node of the
 #   image to modify.
 #
-# @device:  The name of the device that owns image-node-name.
+# @device:  The device name or node-name of the root node that owns
+#   image-node-name.
 #
 # @backing-file:The string to write as the backing file.  This
 #   string is not validated, so care should be taken
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 0283387..7e643f3 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1806,7 +1806,8 @@ Arguments:
 "device".
 (json-string, optional)
 
-- "device": The name of the device.
+- "device": The device name or node-name of the root node that owns
+image-node-name.
 (json-string)
 
 - "backing-file":   The string to write as the backing file.  This string 
is
-- 
1.8.3.1