Storage source format backing a shared device (e.g. running a cluster
filesystem) needs to support the sharing so that metadata are not
corrupted. Add a central function for checking this.
Extract the part formatting the basic URI part so that it can be reused
to format JSON backing definitions. Parts specific to the command line
format will remain in qemuBuildNetworkDriveURI. The new function is
called qemuBlockStorageSourceGetURI.
Remove the complex and unreliable code which inferred the node name
hierarchy only from data returned by 'query-named-block-nodes'. It turns
out that query-blockstats contain the full hierarchy of nodes as
perceived by qemu so the inference code is not necessary.
In query blockstats, the 'parent' object corresponds to the storage
behind a storage volume and 'backing' corresponds to the lower level of
backing chain. Since all have node names this data can be really easily
used to detect node names.
In addition to the code refactoring the one remaining test case needed
to be fixed along.
Reviewed-by: Eric Blake <eblake@redhat.com>
Rename it to qemuBlockStorageSourceGetBackendProps and refactor it to
return the JSON object instead of filling a pointer since now it's
always expected to return data.
To allow updating stats based on the node name, add a helper function
that will fetch the required data from 'query-named-block-nodes' and
return it in hash table for easy lookup.
Detect the node names when setting block threshold and when reconnecting
or when they are cleared when a block job finishes. This operation will
become a no-op once we fully support node names.
qemu for some time already sets node names automatically for the block
nodes. This patch adds code that attempts a best-effort detection of the
node names for the backing chain from the output of
'query-named-block-nodes'. The only drawback is that the data provided
by qemu needs to be matched by the filename as seen by qemu and thus
if two disks share a single backing store file the detection won't work.
This will allow us to use qemu commands such as
'block-set-write-threshold' which only accepts node names.
In this patch only the detection code is added, it will be used later.
