Broken stuff in new dtrace probes

I notice that we have in md.c

TRACE_POSTGRESQL_SMGR_MD_READ_DONE(forknum, blocknum, reln->smgr_rnode.spcNode, reln->smgr_rnode.dbNode, reln->smgr_rnode.relNode, relpath(reln->smgr_rnode, forknum), nbytes, BLCKSZ);

TRACE_POSTGRESQL_SMGR_MD_WRITE_DONE(forknum, blocknum, reln->smgr_rnode.spcNode, reln->smgr_rnode.dbNode, reln->smgr_rnode.relNode, relpath(reln->smgr_rnode, forknum), nbytes, BLCKSZ);

relpath() returns a palloc'd string, which will not get freed, which
means that any serious use of these probe points will shortly blow out
the backend's memory. So far as I can see the path argument is
redundant with the other probe arguments and we might as well just
remove it --- objections?

There's another problem in tuplesort.c:

TRACE_POSTGRESQL_SORT_DONE(state->tapeset,
(state->tapeset ? LogicalTapeSetBlocks(state->tapeset) :
(state->allowedMem - state->availMem + 1023) / 1024));

This is called after state->tapeset has been freed, which means that the
LogicalTapeSetBlocks call will very likely give a wrong answer,
especially in assert-enabled builds but maybe even in a regular one.

Seems that we need to have been quality-checking the dtrace patches
a bit more carefully.

regards, tom lane