Re: [RFC PATCH v1 02/25] hw/xen: Add basic XenStore tree walk and write/read/directory support

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 02/03/2023 15:34, David Woodhouse wrote:
> From: David Woodhouse <dwmw@xxxxxxxxxxxx>
>
> This is a fairly simple implementation of a copy-on-write tree.
>
> The node walk function starts off at the root, with 'inplace == true'.
> If it ever encounters a node with a refcount greater than one (including
> the root node), then that node is shared with other trees, and cannot
> be modified in place, so the inplace flag is cleared and we copy on
> write from there on down.
>
> Xenstore write has 'mkdir -p' semantics and will create the intermediate
> nodes if they don't already exist, so in that case we flip the inplace
> flag back to true as as populated the newly-created nodes.
Something has gone wrong with the comment there... 'as we populate' perhaps?

> We put a copy of the absolute path into the buffer in the struct walk_op,
> with *two* NUL terminators at the end. As xs_node_walk() goes down the
> tree, it replaces the next '/' separator with a NUL so that it can use
> the 'child name' in place. The next recursion down then puts the '/'
> back and repeats the exercise for the next path element... if it doesn't
> hit that *second* NUL termination which indicates the true end of the
> path.
>
> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
> ---
>   hw/i386/kvm/xenstore_impl.c | 527 +++++++++++++++++++++++++++++++++++-
>   tests/unit/meson.build      |   1 +
>   tests/unit/test-xs-node.c   | 197 ++++++++++++++
>   3 files changed, 718 insertions(+), 7 deletions(-)
>   create mode 100644 tests/unit/test-xs-node.c
With the comment fixed...

Reviewed-by: Paul Durrant <paul@xxxxxxx>