apple/containerization

[Bug]: Support a partial last block group to avoid expanding the EXT4 filesystem size

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#647 建立於 2026年4月3日

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 (2 留言) (0 反應) (1 負責人)Swift (8,542 star) (278 fork)batch import
help wanted

描述

I have done the following

  • I have searched the existing issues
  • If possible, I've reproduced the issue using the 'main' branch of this project

Steps to reproduce

Create an EXT4 filesystem with 160 MiB:

container volume create -s 160M size-test
stat -f%z ~/Library/Application\ Support/com.apple.container/volumes/size-test/volume.img

Current behavior

When creating an EXT4 filesystem, the requested size is expanded to the nearest block group boundary. A filesystem whose requested size falls between two block group boundaries ends up larger than requested - 256 MiB:

268435456

Expected behavior

The fix is to support a partial last block group so the filesystem uses exactly the requested size - 160 MiB:

167772160

Environment

N/A

Relevant log output

N/A

Code of Conduct

  • I agree to follow this project's Code of Conduct

Related to https://github.com/apple/containerization/pull/640.

貢獻者指南

技術棧
swift
領域
backendinfrastructure
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
half day
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
blocked
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
EXT4 filesystem knowledgeSwift programming
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
40
研究方向
The issue states that creating an EXT4 filesystem expands the size to the nearest block group boundary. The fix is to support a partial last block group. The related PR at https://github.com/apple/containerization/pull/640 may contain initial work or discussion. Examine the Swift code that creates EXT4 filesystems, likely in a file related to volume creation. Focus on the logic that calculates block group boundaries and ensure the final block group can be partial to match the exact requested size.