use atomic to protect f_refs

[hujun260]

Summary

use atomic to protect f_refs
fix regresion from #14801

Impact

fs refs

Testing

ci ostest

[nuttxpr]

[Experimental Bot, please feedback here]

No, this PR does not fully meet the NuttX requirements. While it provides a summary and mentions testing, it lacks crucial details.

Here's what's missing:

• Summary: Needs more detail. How does the small lock protect f_refs? What exactly was the regression from the linked PR? What functional part of the code changed (e.g., VFS, a specific filesystem)?
• Impact: The current description is insufficient. Address all impact points with "YES" or "NO" and provide descriptions for any "YES" responses. Consider:
  • User Impact: Will applications using the affected filesystem notice any changes?
  • Build Impact: Are any new build dependencies introduced?
  • Hardware Impact: Does this affect any specific architectures or boards?
  • Documentation Impact: Does this change require documentation updates?
  • Security Impact: Does using a smaller lock introduce or mitigate any security vulnerabilities?
  • Compatibility Impact: Does this break compatibility with any existing code or applications?
• Testing: "ci ostest" is not enough. Provide specific details about the build host (OS, CPU, compiler) and the target(s) (architecture, board, configuration). Include actual test logs before and after the change, demonstrating the issue and the fix. Just stating that it passed CI isn't sufficient for review; the reviewer needs to see the evidence.

The PR needs to be significantly expanded to meet the requirements and be properly reviewed.