diff --git a/include/jemalloc/internal/emap.h b/include/jemalloc/internal/emap.h
index 93fa472a..e8b422e7 100644
--- a/include/jemalloc/internal/emap.h
+++ b/include/jemalloc/internal/emap.h
@@ -43,4 +43,26 @@ void emap_rtree_write_acquired(tsdn_t *tsdn, emap_t *emap,
 bool emap_register_boundary(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
     edata_t *edata, szind_t szind, bool slab);
 
+/*
+ * Does the same thing, but with the interior of the range, for slab
+ * allocations.
+ *
+ * You might wonder why we don't just have a single emap_register function that
+ * does both depending on the value of 'slab'.  The answer is twofold:
+ * - As a practical matter, in places like the extract->split->commit pathway,
+ *   we defer the interior operation until we're sure that the commit won't fail
+ *   (but we have to register the split boundaries there).
+ * - In general, we're trying to move to a world where the page-specific
+ *   allocator doesn't know as much about how the pages it allocates will be
+ *   used, and passing a 'slab' parameter everywhere makes that more
+ *   complicated.
+ *
+ * Unlike the boundary version, this function can't fail; this is because slabs
+ * can't get big enough to touch a new page that neither of the boundaries
+ * touched, so no allocation is necessary to fill the interior once the boundary
+ * has been touched.
+ */
+void emap_register_interior(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
+    edata_t *edata, szind_t szind);
+
 #endif /* JEMALLOC_INTERNAL_EMAP_H */
diff --git a/src/emap.c b/src/emap.c
index 4371c4a2..0a37d17e 100644
--- a/src/emap.c
+++ b/src/emap.c
@@ -148,3 +148,16 @@ emap_register_boundary(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
 	emap_rtree_write_acquired(tsdn, emap, elm_a, elm_b, edata, szind, slab);
 	return false;
 }
+
+void
+emap_register_interior(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
+    edata_t *edata, szind_t szind) {
+	assert(edata_slab_get(edata));
+
+	/* Register interior. */
+	for (size_t i = 1; i < (edata_size_get(edata) >> LG_PAGE) - 1; i++) {
+		rtree_write(tsdn, &emap->rtree, rtree_ctx,
+		    (uintptr_t)edata_base_get(edata) + (uintptr_t)(i <<
+		    LG_PAGE), edata, szind, true);
+	}
+}
diff --git a/src/extent.c b/src/extent.c
index 4c4e16a2..9975dd25 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -270,19 +270,6 @@ extent_activate_locked(tsdn_t *tsdn, ecache_t *ecache, edata_t *edata) {
 	edata_state_set(edata, extent_state_active);
 }
 
-static void
-extent_interior_register(tsdn_t *tsdn, rtree_ctx_t *rtree_ctx, edata_t *edata,
-    szind_t szind) {
-	assert(edata_slab_get(edata));
-
-	/* Register interior. */
-	for (size_t i = 1; i < (edata_size_get(edata) >> LG_PAGE) - 1; i++) {
-		rtree_write(tsdn, &emap_global.rtree, rtree_ctx,
-		    (uintptr_t)edata_base_get(edata) + (uintptr_t)(i <<
-		    LG_PAGE), edata, szind, true);
-	}
-}
-
 static void
 extent_gdump_add(tsdn_t *tsdn, const edata_t *edata) {
 	cassert(config_prof);
@@ -341,7 +328,8 @@ extent_register_impl(tsdn_t *tsdn, edata_t *edata, bool gdump_add) {
 	}
 
 	if (slab) {
-		extent_interior_register(tsdn, rtree_ctx, edata, szind);
+		emap_register_interior(tsdn, &emap_global, rtree_ctx, edata,
+		    szind);
 	}
 
 	emap_unlock_edata(tsdn, &emap_global, edata);
@@ -704,7 +692,8 @@ extent_recycle(tsdn_t *tsdn, arena_t *arena, ehooks_t *ehooks, ecache_t *ecache,
 	assert(edata_state_get(edata) == extent_state_active);
 	if (slab) {
 		edata_slab_set(edata, slab);
-		extent_interior_register(tsdn, rtree_ctx, edata, szind);
+		emap_register_interior(tsdn, &emap_global, rtree_ctx, edata,
+		    szind);
 	}
 
 	if (*zero) {
@@ -867,7 +856,8 @@ extent_grow_retained(tsdn_t *tsdn, arena_t *arena, ehooks_t *ehooks,
 		    &rtree_ctx_fallback);
 
 		edata_slab_set(edata, true);
-		extent_interior_register(tsdn, rtree_ctx, edata, szind);
+		emap_register_interior(tsdn, &emap_global, rtree_ctx, edata,
+		    szind);
 	}
 	if (*zero && !edata_zeroed_get(edata)) {
 		void *addr = edata_base_get(edata);