mdtruncate leaking fd.c handles?

Hi,

Am I missing something or is md.c:mdtruncate() leaking open files?
The relevant piece of code is:
    if (priorblocks > nblocks)    {        /*         * This segment is no longer active (and has already been unlinked
       * from the mdfd_chain). We truncate the file, but do not delete         * it, for reasons explained in the
headercomments.         */        if (FileTruncate(v->mdfd_vfd, 0) < 0)            ereport(ERROR,
(errcode_for_file_access(),                    errmsg("could not truncate file \"%s\": %m",
FilePathName(v->mdfd_vfd))));
        if (!SmgrIsTemp(reln))            register_dirty_segment(reln, forknum, v);        v = v->mdfd_chain;
Assert(ov!= reln->md_fd[forknum]); /* we never drop the 1st                                             * segment */
   pfree(ov);    }
 

note that we're freeing the chain entry, which contains the mdfd_vfd,
without previously calling FileClose().

This only really matters for VACUUM truncate and ON COMMIT TRUNCATE temp
table truncation afaics.  But it seems like we should fix it everywhere
nonetheless.

Greetings,

Andres Freund