podman system df: fix percent calculation

The calculate the percentage we need floating point numbers. The current
code however casted the result of reclaimable/size to an int first.
Casting to an int in go will just discard the decimal points, thus the
result was either 0 or 1 so if multiplied by 100 it would show up as 0%
or 100%.

To fix this we have to multiply by 100 first before casting the result
to an int. Also add a check for div by zero which results in NaN and use
math.Round() to correctly round a number.

Ref #13516

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/cmd/podman/system/df.go b/cmd/podman/system/df.go
index b2325507a..49918487a 100644
--- a/cmd/podman/system/df.go
+++ b/cmd/podman/system/df.go
@@ -2,6 +2,7 @@ package system
 
 import (
 	"fmt"
+	"math"
 	"os"
 	"strings"
 	"time"
@@ -288,6 +289,10 @@ func (d *dfSummary) Size() string {
 }
 
 func (d *dfSummary) Reclaimable() string {
-	percent := int(float64(d.reclaimable)/float64(d.size)) * 100
+	percent := 0
+	// make sure to check this to prevent div by zero problems
+	if d.size > 0 {
+		percent = int(math.Round(float64(d.reclaimable) / float64(d.size) * float64(100)))
+	}
 	return fmt.Sprintf("%s (%d%%)", units.HumanSize(float64(d.reclaimable)), percent)
 }