feat(loop-device):实现Dragonos对loop的支持 #1261

Vitus213 · 2025-08-19T13:45:14Z

Note

Implements a full loop device stack (/dev/loop-control, /dev/loopX) with IOCTLs, lifecycle management, safe unregister, devfs integration, and unit tests.

Kernel Block Subsystem:
- Loop Device: New module driver/block/loop_device/* implementing LoopDevice, LoopControlDevice, LoopManager, LoopDeviceDriver, and IOCTLs (LOOP_SET/GET_STATUS(64), LOOP_SET_FD, LOOP_CLR_FD, LOOP_CHANGE_FD, LOOP_SET_CAPACITY).
- State & I/O Handling: State machine (Unbound/Bound/Rundown/Draining/Deleting), active I/O tracking with drain-on-delete, read-only enforcement, offset/size-limit handling with atomic updates.
- Integration: Exported via kernel/src/driver/block/mod.rs; new majors LOOP_MAJOR and LOOP_CONTROL_MAJOR.
DevFS & Device Registration:
- Register /dev/loop-control (char) at /dev; register /dev/loopN (block) at /dev with special-case unregister logic.
- gendisk: enable byte read_at/write_at, dynamic metadata sizing, and forward ioctl to LoopDevice.
- BlockDevManager: Two-phase unregister() with devfs rollback for consistency; uses vectors to stage/remove gendisks.
Utilities:
- ida: add alloc_specific(id) for fixed minor allocation used by loop manager.
- vfs/file.rs: add FilePrivateData::Loop variant.
Docs:
- Add docs/kernel/device/loop_device.md and index entry describing architecture and design.
User-space Tests:
- New user/apps/c_unitest/test_loop.c covering creation, binding, status change, capacity, concurrent I/O deletion, leak detection, and deletion behavior.

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= 添加loopdevice的四种状态

- 添加loop_add和loop_remove函数 - 添加loop_control_ioctl的loop文件私有信息，发现data可以代替 - 待完成loop_ctl的read 和write

- 修改gendisk中的默认行为，使得read和write能传递到loop_device中 - 完成loop_device的正确挂载和写入数据的行为

Copilot

Pull Request Overview

This PR upgrades the Rust toolchain from nightly-2024-11-05 to nightly-2025-08-10 and introduces a loop device driver implementation for DragonOS.

Key changes include:

Toolchain version update across all Makefiles and configuration files
New loop device driver with complete device management infrastructure
Integration of loop devices into the DevFS and block device management systems

Reviewed Changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
user/apps/*/Makefile	Updated Rust toolchain version from nightly-2024-11-05 to nightly-2025-08-10
tools/nix-dev-shell/flake.nix	Updated Rust toolchain version in Nix dev shell configuration
tools/Makefile	Updated cargo toolchain version for check command
build-scripts/Makefile	Updated cargo toolchain version for build and check commands
kernel/src/driver/base/block/loop_device.rs	New file implementing loop device driver with control device, manager, and device structures
kernel/src/driver/base/block/mod.rs	Added loop_device module and removed blank line
kernel/src/driver/base/block/manager.rs	Implemented unregister functionality for block devices
kernel/src/driver/base/block/gendisk/mod.rs	Added read/write support, dynamic metadata, and ioctl forwarding to underlying loop devices
kernel/src/driver/base/device/device_number.rs	Added LOOP_MAJOR constant (7) for loop devices
kernel/src/filesystem/vfs/file.rs	Added Loop variant to FilePrivateData enum with typo in comment
kernel/src/filesystem/devfs/mod.rs	Added special handling for loop-control and loop* devices in registration and removal
user/apps/c_unitest/test_loop.c	New test file for loop device functionality
config/app-blocklist.toml	Blocked NovaShell app with typo in toolchain version

Comments suppressed due to low confidence (1)

kernel/src/driver/base/block/loop_device.rs:1

Inconsistent indentation: line 47 has incorrect spacing (3 spaces instead of 4) compared to line 46.

use crate::{

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kernel/src/filesystem/vfs/file.rs

config/app-blocklist.toml

- feat: supplement test_loop

- add docs - delete some useless code - cargo fmt

- 在IdAllocator中新增alloc_specific方法，允许按用户指定的ID进行分配 - 重构LoopManager，移除next_free_minor字段，简化minor号管理逻辑 - 修改设备查找和创建逻辑，直接使用ID作为minor号，提高代码简洁性 Signed-off-by: longjin <longjin@DragonOS.org>

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kernel/src/driver/block/loop_device/loop_device.rs

…oop-device

kernel/src/driver/block/loop_device/loop_device.rs

kernel/src/driver/base/block/manager.rs

- Make LOOP_SET_STATUS64 update offset/limit and file_size atomically to avoid new offset with stale size during concurrent I/O. - Allow Draining -> Rundown rollback on drain timeout to prevent devices getting stuck in Draining and leaking resources. - Implement LoopDevice/LoopControlDevice IndexNode::fs() to avoid todo!() panics by returning DevFS (with /dev fallback). - Make BlockDevManager::unregister transactional: unregister from devfs first, rollback on partial failures, then clear manager/meta state. Signed-off-by: longjin <longjin@DragonOS.org>

kernel/src/driver/block/loop_device/manager.rs

- Introduced a new method `calc_effective_size` to centralize the logic for calculating the effective size based on total size, offset, and size limit. - Updated `set_file_locked` and `recalc_effective_size` methods to utilize the new calculation method, improving code clarity and reducing duplication. - Enhanced error handling during effective size recalculation to ensure stability under high concurrency scenarios. - Added comments to clarify the locking strategy and the importance of atomic updates to prevent inconsistent states. This refactor aims to improve maintainability and reliability of loop device operations. Signed-off-by: longjin <longjin@DragonOS.org>

…e and LoopDevice - Replaced `todo!()` with actual implementation for the `fs` method in both `LoopControlDevice` and `LoopDevice`. - The new implementation retrieves the filesystem from the device inode, ensuring it is properly set and upgraded. This change enhances the functionality of loop devices by providing a valid filesystem reference, improving overall stability and reliability. Signed-off-by: longjin <longjin@DragonOS.org>

…wo-phase rollback mechanism - Improved the `unregister` method in `BlockDevManager` to implement a two-phase approach for safely unregistering devices from the manager and devfs. - Added detailed comments to clarify the importance of maintaining atomicity and recoverability during the unregistration process. - Ensured that device metadata is only cleared after successful unregistration of all devfs nodes, preventing inconsistent states. This change enhances the reliability of device management by ensuring that failures during unregistration do not leave the system in an unrecoverable state. Signed-off-by: longjin <longjin@DragonOS.org>

- Introduced a new inline method `device_reusable` to determine if a loop device is in a reusable state, specifically checking for the `Unbound` state. - Updated device allocation logic to utilize the new method, ensuring that devices in `Rundown`, `Draining`, or `Deleting` states are not mistakenly considered available for reuse. - Enhanced comments for clarity on device state management during allocation and reuse processes. This refactor aims to improve the reliability of loop device management by preventing the allocation of devices that are in the process of being deleted.

… into zhanghuizhou-feat/loop-device

kernel/src/driver/block/loop_device/manager.rs

- Updated the LoopDevice implementation to ensure that the Deleting state returns Ok idempotently, preventing devices from getting stuck in a zombie state after a failed deletion attempt. - Enhanced comments to clarify the importance of maintaining device state consistency during the unregistration process from BlockDevManager, allowing for retries without resource leaks. This fix improves the reliability of loop device management by addressing potential deadlock scenarios during device removal.

kernel/src/driver/block/loop_device/loop_device.rs

- Updated the LoopDevice implementation to handle the transition to the Deleting state idempotently, preventing errors when multiple threads attempt to set the state concurrently. - Enhanced comments to clarify the rationale behind the idempotent handling, ensuring consistent device state management during deletion.

- Added a new `LoopStatus` structure to represent legacy loop device status information, including fields for name and encryption key sizes. - Implemented validation logic for `LoopStatus` parameters to ensure correct offset and flag values during state updates. - Updated `set_status` and `get_status` methods to handle `LoopStatus`, maintaining compatibility with legacy loop device operations. This enhancement improves the handling of legacy loop device states and ensures proper validation of input parameters, contributing to overall system stability.

kernel/src/driver/block/loop_device/constants.rs

- Introduced a new type `KernelOldDevT` for compatibility with legacy loop device structures. - Updated `LoopStatus` and `LoopStatus64` to use `KernelOldDevT` for device identifiers, ensuring consistency with Linux UAPI. - Enhanced the test suite for loop devices, improving readability and structure of test output. - Added comprehensive tests for loop device operations, including read/write, capacity changes, and deletion scenarios. These changes improve the robustness and maintainability of loop device management, ensuring better alignment with Linux standards and enhancing testing capabilities.

cursor · 2025-12-19T04:02:23Z

kernel/src/driver/block/loop_device/loop_device.rs

+        };
+        drop(inner);
+        self.recalc_effective_size()?;
+        Ok(())


Bug: State inconsistency if recalc_effective_size fails after binding

In bind_file, the lock is dropped and then recalc_effective_size() is called. If recalc_effective_size() fails (e.g., due to a transient metadata read failure), the function returns an error but the device state has already been set to Bound with file_inode set. The caller receives an error suggesting binding failed, but subsequent bind attempts would get EBUSY since the device is now Bound. This leaves the device in a usable but caller-confusing state where the error return doesn't match the actual device state.

Vitus213 added the enhancement New feature or request label Aug 19, 2025

sparkzky marked this pull request as draft August 19, 2025 13:48

Vitus213 force-pushed the feat/loop-device branch from da1ac6a to f7e4c02 Compare August 19, 2025 16:00

完成loop_device的注册，能在/dev下看见8个loopdevice

5cbe962

Vitus213 force-pushed the feat/loop-device branch from f7e4c02 to 5cbe962 Compare August 19, 2025 20:14

fmt & 删除loopdevice中的devid字段

be65aaa

Vitus213 force-pushed the feat/loop-device branch from e9ebe47 to be65aaa Compare August 20, 2025 06:59

Vitus213 added 14 commits August 20, 2025 11:01

添加了driver和control device和manager，将注册逻辑移动至driver中

c9157f8

- 将具体注册逻辑移动到loopdriver中，由loopmanager封装init函数，管理loopdevice信息

0867f83

= 添加loopdevice的四种状态

注册loop-control设备

d8eb2e7

复用linux中关于loop的ioctl魔数

521d819

- 往loop_control_device中加入loopmanager的arc实例

327d166

- 添加loop_add和loop_remove函数 - 添加loop_control_ioctl的loop文件私有信息，发现data可以代替 - 待完成loop_ctl的read 和write

添加不对回环路由代理

e7363e3

add test

a1f2a30

Merge remote-tracking branch 'upstream/master' into feat/loop-device

9f5ebdf

merge 主线，调整版本号和工具链

89c7fb1

fmt

9ef8d3c

fix : function loop_add()

786c435

- 增加read_async，write_async

29c7679

- 修改gendisk中的默认行为，使得read和write能传递到loop_device中 - 完成loop_device的正确挂载和写入数据的行为

feat:增添删除设备逻辑和测试

e87dcd8

fmt

0b43777

Vitus213 marked this pull request as ready for review November 2, 2025 16:41

Copilot AI review requested due to automatic review settings November 2, 2025 16:41

Copilot AI reviewed Nov 2, 2025

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kernel/src/filesystem/vfs/file.rs Outdated Show resolved Hide resolved

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Vitus213 added 4 commits November 3, 2025 08:01

- feat: add loop_set_status and loop_get_status

bd115d9

- feat: supplement test_loop

Merge remote-tracking branch 'upstream/master' into feat/loop-device

9f9f246

- add ioctl change_fd and set_capacity

293f529

- add docs - delete some useless code - cargo fmt

Merge remote-tracking branch 'origin/master' into feat/loop-device

e4bde6b

Vitus213 self-assigned this Nov 9, 2025

Vitus213 requested a review from fslongjin November 9, 2025 09:06

Vitus213 added 2 commits December 11, 2025 15:57

Merge remote-tracking branch 'upstream/master' into feat/loop-device

bdad11f

- fix ：增大超时时间

a1c83a4

Vitus213 requested a review from fslongjin December 11, 2025 15:20

github-actions bot added documentation Improvements or additions to documentation and removed enhancement New feature or request labels Dec 17, 2025

cursor bot reviewed Dec 17, 2025

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Merge remote-tracking branch 'origin/master' into zhanghuizhou-feat/l…

6151dbf

…oop-device

fslongjin force-pushed the feat/loop-device branch from e72bab9 to 6151dbf Compare December 17, 2025 12:08

1

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github-actions bot removed the documentation Improvements or additions to documentation label Dec 17, 2025

cursor bot reviewed Dec 17, 2025

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fslongjin added 5 commits December 18, 2025 17:11

Merge branch 'feat/loop-device' of https://github.com/Vitus213/DragonOS…

bf7c306

… into zhanghuizhou-feat/loop-device

cursor bot reviewed Dec 18, 2025

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fslongjin mentioned this pull request Dec 18, 2025

[BUG REPORT] Potential inconsistent state in devfs_setup if devfs_register fails #1499

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github-actions bot removed the documentation Improvements or additions to documentation label Dec 18, 2025

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Bug: State inconsistency if recalc_effective_size fails after binding

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