[bugfix][component/dfs] fix bugs for function _get_parent_path().

[GorrayLi]

… Scenario that parent path is root is not considered.

拉取/合并请求描述：(PR description)

[

为什么提交这份PR (why to submit this PR)

dfs_file.c中的_get_parent_path函数存在如下问题：

1. 如果输入fullpath路径末尾是“/”，函数本意是忽略这个“/”，如输入路径/home/a/b/，计算其父路径时，应先丢弃末尾的“/”，预期父路径结果应该是/home/a，但实际结果是/home/a/b；
2. 如果输入fullpath路径是类似“/home”，其输出父路径应该为根目录“/”。但函数未考虑这种场景，实际输出结果父路径为空，路径长度为0；

你的解决方案是什么 (what is your solution)

修复上述问题，并自测正常。

请提供验证的bsp和config (provide the config and bsp)

• BSP:

• .config:

• action:

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/workflows/bsp_buildings.yml 详细请参考链接BSP自查

[github-actions]

📌 Code Review Assignment

🏷️ Tag: components

Reviewers: Maihuanyi

Changed Files (Click to expand)

• components/dfs/dfs_v2/src/dfs_file.c

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📊 Current Review Status (Last Updated: 2025-07-29 10:15 CST)

• ✅ Maihuanyi Reviewed On 2025-07-25 15:53 CST

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   Comment LGTM/lgtm after confirming approval

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[GorrayLi]

CI错误与本次PR无关。

[Maihuanyi]

strdup()函数要手动释放内存的，没看到有释放的操作呀

[GorrayLi]

strdup()函数要手动释放内存的，没看到有释放的操作呀

已修复。

[Maihuanyi]

LGTM