feat(ext4): 添加move_to函数 #1758

xboHodx · 2026-02-02T13:01:23Z

2026/2/5

Summary

实现 ext4 文件系统完整的 POSIX rename 语义，包括原子替换和目录循环检测
新增 RENAME_EXCHANGE 支持，实现原子交换两个目录项
VFS 层集成 move_to 接口，包含缓存一致性管理
添加全面的用户态测试程序，覆盖各种边界情况

详细变更

1. ext4 底层 rename 实现 (`another_ext4/src/ext4/low_level.rs`)

原子替换语义：当目标已存在时，不再返回 EEXIST，而是按 POSIX 标准原子替换：

同一 inode → 无操作返回成功
文件替换文件 → 直接替换目录项，递减被替换文件的 link_count
目录替换目录 → 仅允许空目录，正确处理 .. 的 link_count 变更

循环检测：新增 check_ancestor_cycle() 辅助函数，防止把目录移动到自己的子目录下（返回
EINVAL）

新增 rename_exchange()：实现 RENAME_EXCHANGE 标志功能，原子交换两个目录项的 inode 引用

2. 目录操作扩展 (`another_ext4/src/ext4/dir.rs`, `ext4_defs/dir.rs`)

dir_replace_entry(): 原地替换目录项的 inode（原子操作核心）
dir_is_empty(): 检查目录是否为空（仅含 . 和 ..）
DirEntry::set_inode(): 修改目录项 inode 号

3. VFS 层集成 (`kernel/src/filesystem/ext4/inode.rs`)

实现 IndexNode::move_to() trait 方法：

处理 RENAME_NOREPLACE 和 RENAME_EXCHANGE 标志
替换时清理目标文件的 page cache（调用 truncate_inode_pages）
缓存一致性：update_rename_cache() 和 update_exchange_cache() 正确更新 children 映射和 parent
引用

4. VFS syscall 层 (`rename_utils.rs`)

添加标志互斥性检查：EXCHANGE 与 NOREPLACE/WHITEOUT 互斥
RENAME_EXCHANGE 前置检查：目标必须存在

5. 测试 (`user/apps/c_unitest/test_rename.c`)

约 1000 行全面测试，覆盖：

基本文件/目录重命名
跨目录移动
原子替换（文件覆盖文件、目录覆盖空目录）
类型不兼容错误（文件 vs 目录）
循环检测
RENAME_NOREPLACE / RENAME_EXCHANGE 标志
边界情况（同名重命名、./.. 处理等）

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

fslongjin · 2026-02-02T13:45:41Z

@codex review

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chatgpt-codex-connector · 2026-02-02T13:48:23Z

kernel/src/filesystem/ext4/inode.rs

+        // 目标必须是 LockedExt4Inode（同一文件系统）
+        let target_locked = target
+            .clone()
+            .downcast_arc::<LockedExt4Inode>()
+            .ok_or(SystemError::EXDEV)?;


Reject cross-mount renames before using ext4 fs

The downcast only proves target is a LockedExt4Inode, not that it belongs to the same Ext4FileSystem. If target is from another ext4 mount, the code will pass that inode number into the source filesystem (ext4_fs.fs), which can corrupt or misaddress inodes instead of returning EXDEV. Please compare concret_fs() (or an fs id) between self and target_locked and return EXDEV when they differ.

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这个在另一个pr里面解决了

chatgpt-codex-connector · 2026-02-02T13:48:23Z

kernel/src/filesystem/ext4/inode.rs

+                    }
+                }
+                ext4.unlink(target_inode_num, new_name)?;


Avoid deleting destination before a failing rename

When the destination exists you remove it (unlink/rmdir) before calling ext4.rename. The underlying ext4 rename can still fail (e.g., ENOSPC or I/O), so this sequence can lose the original destination entry even though the rename didn’t happen. Linux rename is atomic w.r.t. replacement; the destination should remain unchanged if the rename fails. Consider performing the replacement inside a single ext4 operation or ensure rollback when ext4.rename fails.

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Signed-off-by: xboHodx <xbohodx2024@gmail.com>

…ove_to

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

xboHodx · 2026-02-03T12:51:05Z

想要真正实现原子性还是得日志系统。

fslongjin · 2026-02-04T07:16:02Z

ext4的更改需要补充充分的测试用例。那个库可以单独cargo test的。

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

- 新增rename_exchange方法实现原子交换两个目录项 - 添加辅助函数read_rename_dirs和check_ancestor_cycle - 在VFS层添加EXCHANGE标志处理和缓存更新逻辑 - 遵循POSIX语义实现目录循环检测和跨目录处理 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

…ove_to

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

- 新增rename_exchange_test函数测试文件/目录交换功能 - 修改BlockFile实现使用Box包装buffer - 在Cargo.toml中添加workspace配置 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

…ove_to

fslongjin · 2026-02-05T18:02:32Z

kernel/crates/another_ext4/ext4_test/src/block_file.rs

        let _r = file.read_exact(&mut buffer);
-        Block::new(block_id, buffer)
+        Block::new(block_id, Box::new(buffer))
    }


这里为什么要多一次动态内存分配？性能损失

fslongjin · 2026-02-05T18:03:11Z

kernel/crates/another_ext4/ext4_test/src/main.rs

    assert_eq!(names, vec!["user.testtwo"]);
 }

+fn rename_exchange_test(ext4: &mut Ext4) {


测试写单独文件里面去，这个main太长了。

fslongjin · 2026-02-05T18:03:25Z

kernel/crates/another_ext4/ext4_test/Cargo.toml

+[workspace]
+


fslongjin · 2026-02-05T18:04:37Z

@codex review，尤其是看看正确性、并发安全、有没有TOCTOU问题、有没有性能可优化的地方

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chatgpt-codex-connector · 2026-02-05T18:08:02Z

kernel/src/filesystem/ext4/inode.rs

+        // NOREPLACE check (VFS layer responsibility - ext4 lib doesn't know about flags)
+        if flags.contains(RenameFlags::NOREPLACE) && ext4.lookup(target_inode_num, new_name).is_ok()
+        {
+            return Err(SystemError::EEXIST);
+        }


Avoid TOCTOU in RENAME_NOREPLACE handling

The NOREPLACE path checks ext4.lookup() and then later calls ext4.rename() without holding a filesystem lock or passing the flag down, so a concurrent creator can race between the check and the rename. In that case renameat2(..., RENAME_NOREPLACE) will incorrectly overwrite an existing target, which violates Linux semantics. This is a true TOCTOU introduced by moving atomic-replace behavior into ext4 and keeping NOREPLACE only as a VFS pre-check; the filesystem needs to enforce NOREPLACE atomically or provide a locked rename-with-flags path.

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chatgpt-codex-connector · 2026-02-05T18:08:02Z

kernel/crates/another_ext4/src/ext4/low_level.rs

+                if existing_is_dir {
+                    self.dir_remove_entry(&existing_inode, "..")?;
+                    target_dir


Do not delete .. in replaced directory

When replacing an existing empty directory, the implementation removes the .. entry from the replaced directory before dropping its link count. If that directory is still reachable via an open fd or is the process’s cwd, Linux keeps .. valid even after unlink/rmdir; removing it makes .. lookups fail or behave inconsistently. The correct behavior is to adjust link counts and remove the parent’s entry, but leave the directory’s .. entry intact until the inode is fully freed.

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Signed-off-by: xboHodx <xbohodx2024@gmail.com>

- 移除link.rs中冗余的目录".."删除操作 - 重构low_level.rs中的rename逻辑，使其更接近Linux ext4实现 - 优化目录移动时的link count处理流程 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

- 取消注释所有被注释的测试代码段 - 确保所有测试用例都能正常执行 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

feat(ext4): 添加move_to函数

fa307d6

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

chatgpt-codex-connector bot reviewed Feb 2, 2026

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xboHodx added 5 commits February 2, 2026 23:37

feat(ext4): 优化move_to函数以支持临时备份重命名

87471b1

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

Merge branch 'master' of github.com:xboHodx/DragonOS into feat/ext4_m…

b744e44

…ove_to

feat(ext4): 优化rename操作，增加预检查和缓存更新逻辑

e9054bd

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

feat(ext4): 实现原子重命名操作，支持目录项替换和空目录检查

4463fb8

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

注释+fmt

bdd3593

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

xboHodx added 7 commits February 4, 2026 22:23

feat(tests): 添加重命名系统调用全面测试程序，涵盖各种边界情况

ca278a9

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

Merge branch 'master' of github.com:xboHodx/DragonOS into feat/ext4_m…

334d56d

…ove_to

feat(tests): 添加rename/move系统调用全面测试程序，涵盖各种边界情况

1d22ea0

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

feat(ext4_test): 添加rename_exchange功能测试

0dce3b9

- 新增rename_exchange_test函数测试文件/目录交换功能 - 修改BlockFile实现使用Box包装buffer - 在Cargo.toml中添加workspace配置 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

fmt

153058a

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

Merge branch 'master' of github.com:xboHodx/DragonOS into feat/ext4_m…

4e7572a

…ove_to

fslongjin reviewed Feb 5, 2026

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chatgpt-codex-connector bot reviewed Feb 5, 2026

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xboHodx added 5 commits February 7, 2026 22:10

refactor(ext4_test): 将rename_exchange_test函数提取到单独模块

24ace95

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

fix(ext4): 移除不必要的目录项删除操作以优化跨目录移动逻辑

4621b91

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

test: 恢复c_unitest中test_rename.c的全部测试用例

6e2df08

- 取消注释所有被注释的测试代码段 - 确保所有测试用例都能正常执行 Signed-off-by: xboHodx <xbohodx2024@gmail.com>

fmt

3f68c48

Signed-off-by: xboHodx <xbohodx2024@gmail.com>

		[workspace]

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feat(ext4): 添加move_to函数 #1758

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xboHodx commented Feb 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

详细变更

1. ext4 底层 rename 实现 (another_ext4/src/ext4/low_level.rs)

2. 目录操作扩展 (another_ext4/src/ext4/dir.rs, ext4_defs/dir.rs)

3. VFS 层集成 (kernel/src/filesystem/ext4/inode.rs)

4. VFS syscall 层 (rename_utils.rs)

5. 测试 (user/apps/c_unitest/test_rename.c)

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xboHodx commented Feb 2, 2026 •

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1. ext4 底层 rename 实现 (`another_ext4/src/ext4/low_level.rs`)

2. 目录操作扩展 (`another_ext4/src/ext4/dir.rs`, `ext4_defs/dir.rs`)

3. VFS 层集成 (`kernel/src/filesystem/ext4/inode.rs`)

4. VFS syscall 层 (`rename_utils.rs`)

5. 测试 (`user/apps/c_unitest/test_rename.c`)

fslongjin commented Feb 4, 2026 •

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