fix(vfs): 当以相对路径 + dirfd 调用 openat/unlinkat 时，父目录被错误解析为 root 的问题。

[kaleidoscope416]

-修复 VFS 中相对路径与 dirfd 的解析逻辑，确保 parent inode 选取正确
-增强路径名检查，处理空路径/特殊名等异常情况
-添加针对 unlink 的测试用例

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Note

Fixes parent inode resolution for dirfd-relative paths in openat/unlinkat, adds stricter path/dir checks and unlink behavior, and enables unlink tests.

• VFS:
  • Parent resolution: Add vcore::resolve_parent_inode and use it in open.rs::do_sys_openat2 (on O_CREAT) and vcore.rs::{do_remove_dir, do_unlink_at} to correctly resolve parents for dirfd-relative paths.
  • Unlink / Rmdir validation:
    • do_remove_dir: reject / (EBUSY), empty path (ENOENT); ensure parent and target are dirs.
    • do_unlink_at: reject empty path (ENOENT), trailing / (ENOTDIR); check parent is dir; do not follow final symlink; return EISDIR for directories; truncate page cache before unlink.
• Tests:
  • Enable unlink_test in gvisor/whitelist.txt and add blocklisted cases in blocklists/unlink_test (pending fchmod).

^{Written by Cursor Bugbot for commit 6592e11. This will update automatically on new commits. Configure here.}

[Copilot]

Pull Request Overview

This PR adds support for the unlink_test from the gvisor test suite and fixes several path handling issues in filesystem operations. The changes improve edge case handling for empty paths, trailing slashes, and parent directory lookups.

Key changes:

• Added unlink_test to the gvisor test whitelist with a corresponding blocklist for unsupported test cases
• Fixed parent directory lookup logic in do_remove_dir, do_unlink_at, and do_sys_openat2 to handle cases where parent_path is None
• Added validation for empty paths and trailing slashes in do_unlink_at
• Added validation for empty paths and root directory in do_remove_dir
• Removed unused variable and unnecessary blank lines

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
user/apps/tests/syscall/gvisor/whitelist.txt	Adds unlink_test to the test whitelist
user/apps/tests/syscall/gvisor/blocklists/unlink_test	Creates blocklist for unsupported unlink_test cases requiring fchmod
kernel/src/syscall/user_access.rs	Removes unnecessary blank line
kernel/src/filesystem/vfs/vcore.rs	Fixes parent directory lookup logic and adds path validation for do_remove_dir and do_unlink_at
kernel/src/filesystem/vfs/open.rs	Fixes parent directory lookup logic in do_sys_openat2 and removes unused variable

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[Copilot]

The unwrap_or(\"/\") fallback on line 249 is unreachable since the else branch is only taken when parent_path.is_some(). Consider using unwrap() instead to make the code's intent clearer, or restructure the logic to avoid the unnecessary fallback.

Suggested change

	.lookup_follow_symlink(parent_path.unwrap_or("/"), VFS_MAX_FOLLOW_SYMLINK_TIMES)?
	.lookup_follow_symlink(parent_path.unwrap(), VFS_MAX_FOLLOW_SYMLINK_TIMES)?

[Copilot]

The unwrap_or(\"/\") fallback on line 286 is unreachable since the else branch is only taken when parent_path.is_some(). Consider using unwrap() instead to make the code's intent clearer, or restructure the logic to avoid the unnecessary fallback.

Suggested change

	.lookup_follow_symlink(parent_path.unwrap_or("/"), VFS_MAX_FOLLOW_SYMLINK_TIMES)?
	.lookup_follow_symlink(parent_path.unwrap(), VFS_MAX_FOLLOW_SYMLINK_TIMES)?

[Copilot]

The unwrap_or(\"/\") fallback on line 190 is unreachable since the else branch is only taken when parent_path.is_some(). Consider using unwrap() instead to make the code's intent clearer, or restructure the logic to avoid the unnecessary fallback.

Suggested change

	parent_path.unwrap_or("/"),
	parent_path.unwrap(),