Re: [Qemu-block] [PATCH v6 23/42] blockdev: Use CAF in external_snapshot_prepare()

[Max Reitz]

On 10.09.19 17:02, Kevin Wolf wrote:
> Am 09.08.2019 um 18:13 hat Max Reitz geschrieben:
>> This allows us to differentiate between filters and nodes with COW
>> backing files: Filters cannot be used as overlays at all (for this
>> function).
>>
>> Signed-off-by: Max Reitz 
>> Reviewed-by: Vladimir Sementsov-Ogievskiy 
> 
> Didn't we occasionally advertise blockdev-snapshot as the way to insert
> filters on top at runtime?

I can only remember advertising for it as the only graph manipulation
tool we had, and maybe saying “We’d want something like
blockdev-snapshot for filters, too”.

Max

> Though it seems it has always only worked for
> filters that use bs->backing, among which I think there aren't any
> user-creatable ones. So we're probably good.
> 
> Kevin
> 
>>  blockdev.c | 7 ++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/blockdev.c b/blockdev.c
>> index 29c6c6044a..c540802127 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -1664,7 +1664,12 @@ static void external_snapshot_prepare(BlkActionState 
>> *common,
>>  goto out;
>>  }
>>  
>> -if (state->new_bs->backing != NULL) {
>> +if (state->new_bs->drv->is_filter) {
>> +error_setg(errp, "Filters cannot be used as overlays");
>> +goto out;
>> +}
>> +
>> +if (bdrv_filtered_cow_child(state->new_bs)) {
>>  error_setg(errp, "The overlay already has a backing image");
>>  goto out;
>>  }
>> -- 
>> 2.21.0
>>




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Re: [Qemu-block] [PATCH v6 23/42] blockdev: Use CAF in external_snapshot_prepare()

[Kevin Wolf]

Am 09.08.2019 um 18:13 hat Max Reitz geschrieben:
> This allows us to differentiate between filters and nodes with COW
> backing files: Filters cannot be used as overlays at all (for this
> function).
> 
> Signed-off-by: Max Reitz 
> Reviewed-by: Vladimir Sementsov-Ogievskiy 

Didn't we occasionally advertise blockdev-snapshot as the way to insert
filters on top at runtime? Though it seems it has always only worked for
filters that use bs->backing, among which I think there aren't any
user-creatable ones. So we're probably good.

Kevin

>  blockdev.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 29c6c6044a..c540802127 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1664,7 +1664,12 @@ static void external_snapshot_prepare(BlkActionState 
> *common,
>  goto out;
>  }
>  
> -if (state->new_bs->backing != NULL) {
> +if (state->new_bs->drv->is_filter) {
> +error_setg(errp, "Filters cannot be used as overlays");
> +goto out;
> +}
> +
> +if (bdrv_filtered_cow_child(state->new_bs)) {
>  error_setg(errp, "The overlay already has a backing image");
>  goto out;
>  }
> -- 
> 2.21.0
> 

[Qemu-block] [PATCH v6 23/42] blockdev: Use CAF in external_snapshot_prepare()

[Max Reitz]

This allows us to differentiate between filters and nodes with COW
backing files: Filters cannot be used as overlays at all (for this
function).

Signed-off-by: Max Reitz 
Reviewed-by: Vladimir Sementsov-Ogievskiy 
---
 blockdev.c | 7 ++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index 29c6c6044a..c540802127 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1664,7 +1664,12 @@ static void external_snapshot_prepare(BlkActionState 
*common,
 goto out;
 }
 
-if (state->new_bs->backing != NULL) {
+if (state->new_bs->drv->is_filter) {
+error_setg(errp, "Filters cannot be used as overlays");
+goto out;
+}
+
+if (bdrv_filtered_cow_child(state->new_bs)) {
 error_setg(errp, "The overlay already has a backing image");
 goto out;
 }
-- 
2.21.0