Re: [Qemu-devel] [PATCH] qga: add mountpoint usage to GuestFilesystemInfo

[Eric Blake <eblake@redhat.com>]

On 05/29/2018 10:01 PM, Chen Hanxiao wrote:
> From: Chen Hanxiao <chenhanxiao@gmail.com>
> 
> This patch adds support for getting the usage of mounted
> filesystem.
> It's very useful when we try to monitor guest's filesystem.
> Use df of coreutils for reference.
> 
> Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
> Signed-off-by: Chen Hanxiao <chenhanxiao@gmail.com>
> ---

> @@ -1072,6 +1073,9 @@ static GuestFilesystemInfo *build_guest_fsinfo(struct FsMount *mount,
>                                                  Error **errp)
>   {
>       GuestFilesystemInfo *fs = g_malloc0(sizeof(*fs));
> +    struct statvfs buf;
> +    unsigned long u100, used, nonroot_total;
> +    int usage;
>       char *devpath = g_strdup_printf("/sys/dev/block/%u:%u",
>                                       mount->devmajor, mount->devminor);
>   
> @@ -1079,7 +1083,20 @@ static GuestFilesystemInfo *build_guest_fsinfo(struct FsMount *mount,
>       fs->type = g_strdup(mount->devtype);
>       build_guest_fsinfo_for_device(devpath, fs, errp);
>   
> +    if (statvfs(fs->mountpoint, &buf)) {
> +        error_setg_errno(errp, errno, "Failed to get statvfs");
> +        return NULL;
> +    }
> +
> +    used = buf.f_blocks - buf.f_bfree;
> +    u100 = 100 * used;
> +    nonroot_total = used + buf.f_bavail;
> +    usage = u100 / nonroot_total + (u100 % nonroot_total != 0);

Why integral instead of floating point?

> +++ b/qga/qapi-schema.json
> @@ -846,13 +846,14 @@
>   # @name: disk name
>   # @mountpoint: mount point path
>   # @type: file system type string
> +# @usage: file system usage

Needs more details.  As written, it is an integer between 0 and 100; but 
if you use floating point, a better description would be a fraction 
between 0 and 1.

>   # @disk: an array of disk hardware information that the volume lies on,
>   #        which may be empty if the disk type is not supported
>   #
>   # Since: 2.2
>   ##
>   { 'struct': 'GuestFilesystemInfo',
> -  'data': {'name': 'str', 'mountpoint': 'str', 'type': 'str',
> +  'data': {'name': 'str', 'mountpoint': 'str', 'type': 'str', 'usage': 'int',
>              'disk': ['GuestDiskAddress']} }
>   
>   ##
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org