Improved disk usage entry in statistics

Now will calculate usage as (total - avail).
In Linux, ext filesystems by default reserves 5% of the space to be
usable by root, making them essentially already "used" space.
Originally we didn't take that into account.

Disk usage percentage will now round down: Math.round() -> Math.floor().
The general behavior in other tools such as "df".

controllers/utilsController.js

@@ -746,7 +746,7 @@ self.stats = async (req, res, next) => {
         await new Promise((resolve, reject) => {
           const proc = spawn('df', [
             '--block-size=1',
-            '--output=used,size',
+            '--output=size,avail',
             paths.uploads
           ])
 
@@ -764,9 +764,11 @@ self.stats = async (req, res, next) => {
               // Skip lines that have non-number chars
               if (columns.some(w => !/^\d+$/.test(w))) continue
 
+              const total = parseInt(columns[0])
+              const avail = parseInt(columns[1])
               stats.disk.drive = {
-                used: parseInt(columns[0]),
-                total: parseInt(columns[1])
+                total,
+                used: total - avail
               }
             }
           })

src/js/dashboard.js

@@ -2860,7 +2860,7 @@ page.getStatistics = (params = {}) => {
             if ((types.byte || []).includes(valKeys[j]))
               parsed = page.getPrettyBytes(value)
             if ((types.byteUsage || []).includes(valKeys[j]))
-              parsed = `${page.getPrettyBytes(value.used)} / ${page.getPrettyBytes(value.total)} (${Math.round(value.used / value.total * 100)}%)`
+              parsed = `${page.getPrettyBytes(value.used)} / ${page.getPrettyBytes(value.total)} (${Math.floor(value.used / value.total * 100)}%)`
             if ((types.uptime || []).includes(valKeys[j]))
               parsed = page.getPrettyUptime(value)