Re: [PATCH v3 1/7] qga: guest-get-fsinfo: add optional 'total-bytes-root' field

[Daniel P . Berrangé]

On Fri, Mar 15, 2024 at 02:29:40PM +0200, Andrey Drobyshev wrote:
> Since the commit 25b5ff1a86 ("qga: add mountpoint usage info to
> GuestFilesystemInfo") we have 2 values reported in guest-get-fsinfo:
> used = (f_blocks - f_bfree), total = (f_blocks - f_bfree + f_bavail) as
> returned by statvfs(3).  While on Windows guests that's all we can get
> with GetDiskFreeSpaceExA(), on POSIX guests we might also be interested in
> total file system size, as it's visible for root user.  Let's add an
> optional field 'total-bytes-root' to GuestFilesystemInfo struct, which'd
> only be reported on POSIX and represent f_blocks value as returned by
> statvfs(3).
> 
> While here, let's document better where those values come from in both
> POSIX and Windows.
> 
> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> ---
>  qga/commands-posix.c |  2 ++
>  qga/commands-win32.c |  1 +
>  qga/qapi-schema.json | 12 +++++++++++-
>  3 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 26008db497..8207c4c47e 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -1569,8 +1569,10 @@ static GuestFilesystemInfo *build_guest_fsinfo(struct 
> FsMount *mount,
>          nonroot_total = used + buf.f_bavail;
>          fs->used_bytes = used * fr_size;
>          fs->total_bytes = nonroot_total * fr_size;
> +        fs->total_bytes_root = buf.f_blocks * fr_size;
>  
>          fs->has_total_bytes = true;
> +        fs->has_total_bytes_root = true;
>          fs->has_used_bytes = true;
>      }
>  
> diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> index a1015757d8..9e820aad8d 100644
> --- a/qga/commands-win32.c
> +++ b/qga/commands-win32.c
> @@ -1143,6 +1143,7 @@ static GuestFilesystemInfo *build_guest_fsinfo(char 
> *guid, Error **errp)
>      fs = g_malloc(sizeof(*fs));
>      fs->name = g_strdup(guid);
>      fs->has_total_bytes = false;
> +    fs->has_total_bytes_root = false;

Can we use GetDiskSpaceInformationA to return this information
on Windows ? In contrast to GetDiskFreeSpaceExA(), the
DISK_SPACE_INFORMATION struct details both the real sizes
and the current user available sizes.

>      fs->has_used_bytes = false;
>      if (len == 0) {
>          fs->mountpoint = g_strdup("System Reserved");
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index b8efe31897..093a5ab602 100644
> --- a/qga/qapi-schema.json
> +++ b/qga/qapi-schema.json
> @@ -1031,8 +1031,18 @@
>  # @type: file system type string
>  #
>  # @used-bytes: file system used bytes (since 3.0)
> +#     * POSIX: (f_blocks - f_bfree) * f_frsize, as returned by statvfs(3)
> +#     * Windows: (TotalNumberOfBytes - TotalNumberOfFreeBytes), as returned
> +#       by GetDiskFreeSpaceEx()
>  #
>  # @total-bytes: non-root file system total bytes (since 3.0)
> +#     * POSIX: (f_blocks - f_bfree + f_bavail) * f_frsize, as returned by
> +#       statvfs(3)
> +#     * Windows: TotalNumberOfBytes, as returned by GetDiskFreeSpaceEx()
> +#
> +# @total-bytes-root: total file system size in bytes (as visible for a
> +#     priviledged user) (since 8.3)
> +#     * POSIX only: (f_blocks * f_frsize), returned by statvfs(3)

I tend to wonder whether it is really a good idea to document
our specific implementation details in the public API

I might suggest

  @total-bytes: filesystem capacity in bytes for unprivileged users
  @total-bytes-root: filesystem capacity in bytes for privileged users

also should we call it 'total-bytes-privilegd', to avoid UNIX specific
terminology.

>  #
>  # @disk: an array of disk hardware information that the volume lies
>  #     on, which may be empty if the disk type is not supported
> @@ -1042,7 +1052,7 @@
>  { 'struct': 'GuestFilesystemInfo',
>    'data': {'name': 'str', 'mountpoint': 'str', 'type': 'str',
>             '*used-bytes': 'uint64', '*total-bytes': 'uint64',
> -           'disk': ['GuestDiskAddress']} }
> +           '*total-bytes-root': 'uint64', 'disk': ['GuestDiskAddress']} }
>  
>  ##
>  # @guest-get-fsinfo:
> -- 
> 2.39.3
> 

With regards,
Daniel
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