[libvirt] [PATCH 05/11] qemu: block: Use 'auto-read-only' instead of 'read-only' for backing chain

[Ján Tomko]

On Thu, Jul 04, 2019 at 04:26:29PM +0200, Peter Krempa wrote:
>To allow using -blockdev with blockjobs need to reopen files in
>read-write mode when modifying the backing chain.

-EPARSE

s/blockjobs need/blockjobs QEMU needs/


>To achieve this we
>need to use 'auto-read-only' for the backing files rather than the
>normal 'read-only' property. That way qemu knows that the files need to
>be reopened.
>
>Note that the format drivers (e.g. qcow2) are still opened with the
>read-only property enabled when being a member of the backing chain
>since they are supposed to be immutable unless a block job is started.
>
>QEMU v4.0 allows also dynamic behaviour for auto-read-only which allows
>us to use sVirt as we only grant write permissions to files when doing
>a blockjob.

commit 23dece19da41724349809873923e20a48b619cb7
    file-posix: Make auto-read-only dynamic

>
>Signed-off-by: Peter Krempa <pkrempa at redhat.com>
>---
> src/qemu/qemu_block.c                         | 26 ++++++++++++++++---
> src/qemu/qemu_block.h                         |  6 +++--

[...]

> .../qemu-ns.x86_64-latest.args                |  2 +-
> 39 files changed, 115 insertions(+), 92 deletions(-)
>
>diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
>index c9e6af49c9..9abdac5ca3 100644
>--- a/src/qemu/qemu_block.c
>+++ b/src/qemu/qemu_block.c
>@@ -1027,6 +1027,7 @@ qemuBlockStorageSourceGetBlockdevGetCacheProps(virStorageSourcePtr src,
>  * @src: disk source
>  * @legacy: use legacy formatting of attributes (for -drive / old qemus)
>  * @onlytarget: omit any data which does not identify the image itself
>+ * @autoreadonly: Use the new auto-readonly feature in qemu

I'd rather avoid use of the word 'new'. Just copy the other wording
which also spells the feature name correctly:

@autoreadonly: use 'auto-read-only' feature of qemu

>  *
>  * Creates a JSON object describing the underlying storage or protocol of a
>  * storage source. Returns NULL on error and reports an appropriate error message.

Reviewed-by: Ján Tomko <jtomko at redhat.com>

Jano
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