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fix: increase ext4 filesystem overhead from 20% to 50% #55

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Merged
hiroTamada merged 1 commit into from
Jan 12, 2026
Merged

fix: increase ext4 filesystem overhead from 20% to 50% #55

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6 changes: 4 additions & 2 deletions lib/images/disk.go
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Original file line number Diff line number Diff line change
Expand Up @@ -116,8 +116,10 @@ func convertToExt4(rootfsDir, diskPath string) (int64, error) {
return 0, fmt.Errorf("calculate dir size: %w", err)
}

// Add 20% overhead for filesystem metadata, minimum 10MB
diskSizeBytes := sizeBytes + (sizeBytes / 5)
// Add 50% overhead for filesystem metadata, minimum 10MB
// ext4 needs significant overhead for superblock, group descriptors, inode tables, etc.
// 20% was insufficient for small filesystems with many files (like tzdata)
diskSizeBytes := sizeBytes + (sizeBytes / 2)
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@tembo tembo bot Jan 9, 2026

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Nit: to keep the comment and math from drifting, consider pulling the ratio into a named constant.

Suggested change
diskSizeBytes := sizeBytes + (sizeBytes / 2)
const ext4MetadataOverheadPercent int64 = 50
diskSizeBytes := sizeBytes + (sizeBytes*ext4MetadataOverheadPercent)/100

const minSize = 10 * 1024 * 1024 // 10MB
if diskSizeBytes < minSize {
diskSizeBytes = minSize
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