builder: use proper percentage calculations for default gc policy

jsternberg · jsternberg · commit 1a7d7cc0158a · 2025-10-07T10:18:17.000-05:00
The default gc policy calculations based on percentage were calculated
improperly. These were calculated correctly in buildkit, but the
calculation method was not copied over correctly when updating the
values.

Signed-off-by: Jonathan A. Sternberg &lt;jonathan.sternberg@docker.com&gt;
diff --git a/daemon/internal/builder-next/worker/gc.go b/daemon/internal/builder-next/worker/gc.go
@@ -72,6 +72,6 @@ func DefaultGCPolicy(p string, reservedSpace, maxUsedSpace, minFreeSpace int64)
 }
 
 func diskPercentage(dstat disk.DiskStat, percentage int64) int64 {
-	avail := dstat.Total / percentage
+	avail := dstat.Total * percentage / 100
 	return (avail/(1<<30) + 1) * 1e9 // round up
 }

Original file line number	Diff line number	Diff line change
`@@ -72,6 +72,6 @@ func DefaultGCPolicy(p string, reservedSpace, maxUsedSpace, minFreeSpace int64)`
`72`	`72`	`}`
`73`	`73`
`74`	`74`	`func diskPercentage(dstat disk.DiskStat, percentage int64) int64 {`
`75`		`- avail := dstat.Total / percentage`
	`75`	`+ avail := dstat.Total * percentage / 100`
`76`	`76`	`return (avail/(1<<30) + 1) * 1e9 // round up`
`77`	`77`	`}`