fellow_busy: Use dowry

src/fellow_cache.c

@@ -2519,20 +2519,29 @@ fellow_busy_body_seg_alloc(struct fellow_busy *fbo,
 		memset(fbr, 0, sizeof *fbr);
 
 		reqs = &fbo->bbrr.reqs;
-		reg = buddy_off_extent_nil;
+		reg = fbo->segdskdowry;
+		fbo->segdskdowry = buddy_off_extent_nil;
 
 	  wait_dskalloc:
-		if (buddy_alloc_wait(reqs)) {
+		if (reg.off < 0 && buddy_alloc_async_wait(reqs)) {
 			reg = buddy_get_next_off_extent(reqs);
-			buddy_alloc_wait_done(reqs);
 			assert(reg.off >= 0);
 		}
 
-		if (reg.off < 0) {
-			szc = fellow_busy_body_size_strategy(fbo);
-			// must return a size, or sz_estimate is wrong
-			AN(szc.sz);
+		buddy_alloc_wait_done(reqs);
+
+		// must return a size, or sz_estimate is wrong
+		szc = fellow_busy_body_size_strategy(fbo);
+		AN(szc.sz);
+
+		// return and realloc if one power of two too big
+		if (reg.off < 0 ||
+		    (log2up(reg.size) > MIN_FELLOW_BITS &&
+		     log2up(reg.size) > log2up(szc.sz))) {
 			AN(buddy_req_extent(reqs, szc.sz, szc.cram));
+			(void) buddy_alloc_async(reqs);
+			if (reg.off >= 0)
+				buddy_return1_off_extent(reqs->buddy, &reg);
 			goto wait_dskalloc;
 		}
 
@@ -2546,8 +2555,10 @@ fellow_busy_body_seg_alloc(struct fellow_busy *fbo,
 
 		// async allocation for remaining known size
 		szc = fellow_busy_body_size_strategy(fbo);
-		if (szc.sz)
+		if (szc.sz) {
 			AN(buddy_req_extent(reqs, szc.sz, szc.cram));
+			(void) buddy_alloc_async(reqs);
+		}
 	}
 
 	assert(fbr->len < fdr->size);