Fix littlefs dir lseek to keep file->pos in user-space offset

[wdfk-prog]

[

为什么提交这份PR (why to submit this PR)

Fix littlefs dir lseek to keep file->pos in user-space offset

• Convert seek offset to littlefs entry index (skip dot entries) and back to user byte offset after lfs_dir_seek
• Align telldir/seekdir with getdents behavior

#29

你的解决方案是什么 (what is your solution)

Adjust directory lseek to skip the first two dot entries by converting the byte offset into a dirent index and adding 2 before calling lfs_dir_seek.

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

• BSP: N/A (logic-only change, no board-specific validation yet)

• .config: N/A

• action: N/A

• 测试代码

#define SEEKDIR_FIXTURE "/flash/seekdir_bug"
static void lfs_seekdir_bug(void)
{
    struct stat st;
    rt_bool_t exists = RT_FALSE;
    if (stat(SEEKDIR_FIXTURE, &st) == 0 && S_ISDIR(st.st_mode))
    {
        rt_kprintf("seekdir fixture already exists: %s\n", SEEKDIR_FIXTURE);
        exists = RT_TRUE;
    }

    if (!exists && mkdir(SEEKDIR_FIXTURE, 0) < 0 && errno != EEXIST)
    {
        rt_kprintf("create %s failed, errno=%d\n", SEEKDIR_FIXTURE, errno);
        return;
    }

    /* 准备 3 个文件，确保条目数足够 */
    const char *names[] = {"a", "b", "c"};
    for (int i = 0; i < 3; i++)
    {
        char path[64];
        rt_snprintf(path, sizeof(path), "%s/%s", SEEKDIR_FIXTURE, names[i]);
        int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0);
        if (fd >= 0) { write(fd, "1", 1); close(fd); }
    }

    DIR *dir = opendir(SEEKDIR_FIXTURE);
    if (dir == RT_NULL)
    {
        rt_kprintf("open %s failed, errno=%d\n", SEEKDIR_FIXTURE, errno);
        return;
    }

    char n1[DFS_PATH_MAX] = {0};
    char n2[DFS_PATH_MAX] = {0};
    char n3[DFS_PATH_MAX] = {0};
    struct dirent *de;
    long p1 = -1, p2 = -1;

    seekdir(dir, 0); /* 显式回到起点 */

    de = readdir(dir);
    if (de) rt_strncpy(n1, de->d_name, sizeof(n1));
    p1 = telldir(dir);

    de = readdir(dir);
    if (de) rt_strncpy(n2, de->d_name, sizeof(n2));
    p2 = telldir(dir);

    seekdir(dir, p2);
    de = readdir(dir);
    if (de) rt_strncpy(n3, de->d_name, sizeof(n3));

    rt_kprintf("readdir1=%s, telldir_after1=%ld (expect 0), readdir2=%s, telldir_after2=%ld (expect %d), after_seek=%s, errno=%d\n",
               n1[0] ? n1 : "(null)",
               p1,
               n2[0] ? n2 : "(null)",
               p2, (int)sizeof(struct dirent),
               n3[0] ? n3 : "(null)",
               errno);

    if (p1 == 0 &&
        p2 == sizeof(struct dirent) &&
        n2[0] && n3[0] && rt_strcmp(n2, n3) == 0)
        rt_kprintf("PASS: seekdir/telldir 一致\n");
    else
        rt_kprintf("FAIL: mismatch\n");

    closedir(dir);
}
MSH_CMD_EXPORT(lfs_seekdir_bug, reproduce seekdir / telldir mismatch);

• 修复前

msh />lfs_seekdir_bug
seekdir fixture already exists: /flash/seekdir_bug
readdir1=a, telldir_after1=2 (expect 0), readdir2=b, telldir_after2=262 (expect 260), after_seek=b, errno=0
FAIL: mismatch

• 修复后

msh />lfs_seekdir_bug
seekdir fixture already exists: /flash/seekdir_bug
readdir1=a, telldir_after1=0 (expect 0), readdir2=b, telldir_after2=260 (expect 260), after_seek=b, errno=0
PASS: seekdir/telldir 一致

]

当前拉取/合并请求的状态 Intent for your PR

• 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：

• 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/ALL_BSP_COMPILE.json（如适用）

Summary by CodeRabbit

• Bug Fixes
  • Corrected directory seek behavior so user-visible directory positions skip the implicit "." and ".." entries, ensuring directory listings and offsets align with expected entry indexing.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

The _dfs_lfs_lseek function in dfs_lfs.c was changed to convert user-space byte offsets to directory-entry indices before seeking. For directories the code now computes off = offset / sizeof(struct dirent) + 2, calls lfs_dir_seek(off), and maps the internal position back to user-space excluding "." and "..".

Changes

Cohort / File(s)	Summary
Directory seek offset conversion dfs_lfs.c	_dfs_lfs_lseek now translates byte offsets for directory targets into directory-entry indices by dividing by sizeof(struct dirent) and adding 2 before calling lfs_dir_seek; post-seek, the file position is converted back to user-space by subtracting the two leading entries.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Specific areas requiring attention:
  • Verify offset / sizeof(struct dirent) + 2 correctly maps user-space offsets to littlefs directory-entry indices.
  • Confirm post-seek conversion of internal dir.pos back to user-space (subtracting 2) is consistent and safe for edge cases.

Possibly related issues

• 对目录执行lseek结果不正确 #29: Matches the same bug description—converting telldir-style offsets to directory-entry indices before calling lfs_dir_seek.

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: fixing littlefs directory lseek to maintain file->pos as a user-space offset, which is the core purpose of the changeset.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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Reviewing files that changed from the base of the PR and between 644344b and cef0433.

📒 Files selected for processing (1)

• dfs_lfs.c (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• dfs_lfs.c

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Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3a8be27 and 644344b.

📒 Files selected for processing (1)

• dfs_lfs.c (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

dfs_lfs.c (1)

lfs.c (1)

• lfs_dir_seek (6385-6398)

🪛 GitHub Actions: test

dfs_lfs.c

[error] 1-1: Compilation failed: fatal error: rtdevice.h: No such file or directory (included by dfs_lfs.c)

[wdfk-prog]

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