Re: Should VOP_RENAME fail if tdvp has an IMMUTABLE flag set?

On Wed, Oct 16, 2024 at 04:11:28PM -0600, Alan Somers wrote:
> ufs_rename and ext2_rename will both fail with EPERM if the
> destination directory has an APPEND file flag set.  So will
> tmpfs_rename.  However, tmpfs_rename will also fail if the destination
> directory has an IMMUTABLE flag set.  That's inconsistent.  It seems
> to me that tmpfs's behavior is more reasonable.  Does anybody know why
> ufs and ext2 have always allowed rename even if the destination
> directory is IMMUTABLE?  For that matter, does anybody know the
> rationale for preventing it if the destination is APPEND?
> Intuitively, I would think that an APPEND-only directory would allow
> new entries.  And I don't see any checks for APPEND in ufs_mkdir,
> ufs_link, or ufs_create.

For UFS, IMMUTABLE is checked on lookup.  Search for 'RENAME' in ufs_lookup.c
and following call to VOP_ACCESSX().

APPEND for UFS directories is a strange idea, for instance, does the directory
compaction breaks append-only?