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

[Chen Hanxiao]

At 2018-05-30 11:19:27, "Eric Blake" <address@hidden> wrote:
>On 05/29/2018 10:01 PM, Chen Hanxiao wrote:
>> From: Chen Hanxiao <address@hidden>
>> 
>> 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 <address@hidden>
>> Signed-off-by: Chen Hanxiao <address@hidden>
>> ---
>
>> @@ -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?

I followed the style of df from coreutils.
As the percentage already multiplied by 100,
I think it has enough precision.

>
>> +++ 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.

Will be updated in the following patch.

Regards,
- Chen

>
>>   # @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