Kaben123 opened a new pull request, #19949:
URL: https://github.com/apache/nuttx/pull/19949
## Summary
This PR adds the core hardlink and mountpoint link infrastructure to the
NuttX filesystem layer. It is the foundation of a larger PSE52/POSIX
filesystem-enhancement stack (path resolution, FS backends, and bug fixes
will follow in separate PRs).
Changes (one upstream commit each):
1. **fs/vfs: add hardlink function of pseudofs** — `link()` now creates a
real hard link within the pseudo-filesystem (instead of silently
degrading to a symlink). A hard-link inode type
(`FSNODEFLAG_TYPE_HARDLINK`)
is added, and the target link count is tracked in the high bits of
`i_crefs` (`INODE_NLINK_INC`), enforcing `_POSIX_LINK_MAX`.
2. **fs: rename PSEUDOFS_SOFTLINKS to FS_LINKS** — the config now covers both
soft and hard links, so the option is renamed. All references
(syscall.csv, syscall_lookup.h, lib_realpath, link/at wrappers, board
defconfigs) are updated accordingly.
3. **fs/vfs: add link/symlink/readlink support for mountpt** — adds `link`,
`symlink`, `readlink` methods to `mountpt_operations` so mounted
filesystems can implement links; the VFS wrappers are updated to route to
them.
4. **fs/vfs/rename: rename a directory to an empty directory** — implements
POSIX rename semantics for directories (empty target dir is removed;
non-empty yields `ENOTEMPTY`).
5. **fs/vfs: add lstat interface to mountpt_operations** — adds `lstat` so
rename does not dereference symbolic links.
## Impact
- **Breaking config change:** `CONFIG_PSEUDOFS_SOFTLINKS` is renamed to
`CONFIG_FS_LINKS`. Out-of-tree configs referencing the old name must be
updated. In-tree defconfigs are migrated in this PR.
- New `mountpt_operations` methods (`link`/`symlink`/`readlink`/`lstat`) are
appended at the end of the struct (guarded by `CONFIG_FS_LINKS`), so
existing filesystems' positional initializers are unaffected.
- `link()` behavior changes for pseudofs: it now creates a true hard link
rather than a symlink.
## Testing
- Built `sim:nsh` with `CONFIG_FS_LINKS` enabled — zero errors/warnings.
- `tools/checkpatch.sh` passes on all changed lines.
---
This is part of a filesystem enhancement stack. Follow-up PRs:
- inode path-resolution infrastructure (independent, based on master)
- hostfs/rpmsgfs link/lstat backends (**depends on this PR**)
- target FS bug fixes (**depends on this PR + the other two**)
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