xfs: rearrange xrep_reap_block to make future code flow easier

Rearrange the logic inside xrep_reap_block to make it more obvious that
crosslinked metadata blocks are handled differently.  Add a couple of
tracepoints so that we can tell what's going on at the end of a btree
rebuild operation.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/agheader_repair.c

@@ -646,13 +646,13 @@ xrep_agfl_fill(
 	xfs_fsblock_t		fsbno = start;
 	int			error;
 
+	trace_xrep_agfl_insert(sc->sa.pag, XFS_FSB_TO_AGBNO(sc->mp, start),
+			len);
+
 	while (fsbno < start + len && af->fl_off < af->flcount)
 		af->agfl_bno[af->fl_off++] =
 				cpu_to_be32(XFS_FSB_TO_AGBNO(sc->mp, fsbno++));
 
-	trace_xrep_agfl_insert(sc->mp, sc->sa.pag->pag_agno,
-			XFS_FSB_TO_AGBNO(sc->mp, start), len);
-
 	error = xbitmap_set(&af->used_extents, start, fsbno - 1);
 	if (error)
 		return error;

fs/xfs/scrub/reap.c

@@ -175,8 +175,6 @@ xrep_reap_block(
 	agno = XFS_FSB_TO_AGNO(sc->mp, fsbno);
 	agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno);
 
-	trace_xrep_dispose_btree_extent(sc->mp, agno, agbno, 1);
-
 	/* We don't support reaping file extents yet. */
 	if (sc->ip != NULL || sc->sa.pag->pag_agno != agno) {
 		ASSERT(0);
@@ -206,10 +204,21 @@ xrep_reap_block(
 	 * to run xfs_repair.
 	 */
 	if (has_other_rmap) {
+		trace_xrep_dispose_unmap_extent(sc->sa.pag, agbno, 1);
+
 		error = xfs_rmap_free(sc->tp, sc->sa.agf_bp, sc->sa.pag, agbno,
 				1, rs->oinfo);
-	} else if (rs->resv == XFS_AG_RESV_AGFL) {
+		if (error)
+			return error;
+
+		goto roll_out;
+	}
+
+	trace_xrep_dispose_free_extent(sc->sa.pag, agbno, 1);
+
 	xrep_block_reap_binval(sc, fsbno);
+
+	if (rs->resv == XFS_AG_RESV_AGFL) {
 		error = xrep_put_freelist(sc, agbno);
 	} else {
 		/*
@@ -219,7 +228,6 @@ xrep_reap_block(
 		 * every 100 or so EFIs so that we don't exceed the log
 		 * reservation.
 		 */
-		xrep_block_reap_binval(sc, fsbno);
 		error = __xfs_free_extent_later(sc->tp, fsbno, 1, rs->oinfo,
 				rs->resv, true);
 		if (error)
@@ -230,6 +238,7 @@ xrep_reap_block(
 	if (error || !need_roll)
 		return error;
 
+roll_out:
 	rs->deferred = 0;
 	return xrep_roll_ag_trans(sc);
 }

fs/xfs/scrub/trace.h

@@ -729,9 +729,8 @@ TRACE_EVENT(xchk_refcount_incorrect,
 #if IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR)
 
 DECLARE_EVENT_CLASS(xrep_extent_class,
-	TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
-		 xfs_agblock_t agbno, xfs_extlen_t len),
-	TP_ARGS(mp, agno, agbno, len),
+	TP_PROTO(struct xfs_perag *pag, xfs_agblock_t agbno, xfs_extlen_t len),
+	TP_ARGS(pag, agbno, len),
 	TP_STRUCT__entry(
 		__field(dev_t, dev)
 		__field(xfs_agnumber_t, agno)
@@ -739,8 +738,8 @@ DECLARE_EVENT_CLASS(xrep_extent_class,
 		__field(xfs_extlen_t, len)
 	),
 	TP_fast_assign(
-		__entry->dev = mp->m_super->s_dev;
-		__entry->agno = agno;
+		__entry->dev = pag->pag_mount->m_super->s_dev;
+		__entry->agno = pag->pag_agno;
 		__entry->agbno = agbno;
 		__entry->len = len;
 	),
@@ -752,10 +751,10 @@ DECLARE_EVENT_CLASS(xrep_extent_class,
 );
 #define DEFINE_REPAIR_EXTENT_EVENT(name) \
 DEFINE_EVENT(xrep_extent_class, name, \
-	TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno, \
-		 xfs_agblock_t agbno, xfs_extlen_t len), \
-	TP_ARGS(mp, agno, agbno, len))
-DEFINE_REPAIR_EXTENT_EVENT(xrep_dispose_btree_extent);
+	TP_PROTO(struct xfs_perag *pag, xfs_agblock_t agbno, xfs_extlen_t len), \
+	TP_ARGS(pag, agbno, len))
+DEFINE_REPAIR_EXTENT_EVENT(xrep_dispose_unmap_extent);
+DEFINE_REPAIR_EXTENT_EVENT(xrep_dispose_free_extent);
 DEFINE_REPAIR_EXTENT_EVENT(xrep_agfl_insert);
 
 DECLARE_EVENT_CLASS(xrep_rmap_class,