Re: [PATCH 6/9] kernel/api: add API specification for sys_close

+ * notes: This syscall has subtle non-POSIX semantics: the fd is ALWAYS closed
+ *   regardless of the return value. POSIX specifies that on EINTR, the state
+ *   of the fd is unspecified, but Linux always closes it. HP-UX requires
+ *   retrying close() on EINTR, but doing so on Linux may close an unrelated
+ *   fd that was reassigned by another thread. For portable code, the safest
+ *   approach is to check for errors but never retry close().

+ *   Error codes from the flush callback (EIO, ENOSPC, EDQUOT) indicate that
+ *   previously written data may have been lost. These errors are particularly
+ *   common on NFS where write errors are often deferred to close time.

+ *
+ *   The driver's release() callback errors are explicitly ignored by the
+ *   kernel, so device driver cleanup errors are not propagated to userspace.