[Qemu-devel] [PATCH v3] qga: add mountpoint usage to GuestFilesystemInfo

[Qemu-devel] [PATCH v3] qga: add mountpoint usage to GuestFilesystemInfo

[Chen Hanxiao]

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.

Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: Eric Blake <eblake@redhat.com>

Signed-off-by: Chen Hanxiao <chenhanxiao@gmail.com>
---
v2:
   add description in qapi-schema and version numbers
v3:
   use float for usage to get more precision.

 qga/commands-posix.c | 16 ++++++++++++++++
 qga/qapi-schema.json |  3 ++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 0dc219dbcf..7601978a11 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -46,6 +46,7 @@ extern char **environ;
 #include <arpa/inet.h>
 #include <sys/socket.h>
 #include <net/if.h>
+#include <sys/statvfs.h>
 
 #ifdef FIFREEZE
 #define CONFIG_FSFREEZE
@@ -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 used, nonroot_total;
+    double usage;
     char *devpath = g_strdup_printf("/sys/dev/block/%u:%u",
                                     mount->devmajor, mount->devminor);
 
@@ -1079,7 +1083,19 @@ 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;
+    nonroot_total = used + buf.f_bavail;
+    usage = (double) used / nonroot_total;
+
+    fs->usage = usage;
+
     g_free(devpath);
+
     return fs;
 }
 
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 17884c7c70..68b9f60824 100644
--- a/qga/qapi-schema.json
+++ 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, fraction between 0 and 1 (since 3.0)
 # @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': 'number',
            'disk': ['GuestDiskAddress']} }
 
 ##
-- 
2.17.0

Re: [Qemu-devel] [PATCH v3] qga: add mountpoint usage to GuestFilesystemInfo

[Eric Blake]

On 05/30/2018 09:19 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.
> 
> Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
> Cc: Eric Blake <eblake@redhat.com>
> 
> Signed-off-by: Chen Hanxiao <chenhanxiao@gmail.com>
> ---

> @@ -1079,7 +1083,19 @@ 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;
> +    }

Failing where we used to succeed is not nice.  Perhaps it would be 
better to make usage a best-effort query; and ignore statvfs() failure,

> +
> +    used = buf.f_blocks - buf.f_bfree;
> +    nonroot_total = used + buf.f_bavail;
> +    usage = (double) used / nonroot_total;
> +
> +    fs->usage = usage;
> +
>       g_free(devpath);
> +
>       return fs;
>   }
>   
> diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
> index 17884c7c70..68b9f60824 100644
> --- a/qga/qapi-schema.json
> +++ 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, fraction between 0 and 1 (since 3.0)
>   # @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': 'number',

...by instead marking this optional, as in '*usage'; and only setting 
has_usage=true when statvfs() succeeds.

Also, hitting exactly 80 columns already feels long; and if you go with 
my suggestion, you'd be lengthening it even more, so wrap the new member 
to the next line to keep length under 80.

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