fellow_logcache: for prefetch, do not wait for allocations

src/fellow_log.c

@@ -1234,9 +1234,6 @@ fellow_logcache_init(struct fellow_logcache *flc, struct fellow_fd *ffd,
 		VTAILQ_INSERT_TAIL(&flc->free, fle, list);
 	}
 
-	//XXX
-	(void) flc_mempool_avail(flc->mempool);
-
 	fellow_fd_ioctx_get(ffd, &flc->fdil);
 }
 
@@ -1309,9 +1306,13 @@ fellow_logcache_steal(struct fellow_logcache *flc, int direction)
 	return (fle);
 }
 
-/* get an element from the free list, if any */
+/*
+ * get an element from the free list, if any
+ *
+ * prefetch uses it with need == 0 to not wait for allocations
+ */
 static struct fellow_logcache_entry *
-fellow_logcache_take(struct fellow_logcache *flc, int direction)
+fellow_logcache_take(struct fellow_logcache *flc, int direction, int need)
 {
 	struct fellow_logcache_entry *fle;
 
@@ -1320,6 +1321,9 @@ fellow_logcache_take(struct fellow_logcache *flc, int direction)
 	if (fle == NULL)
 		return (fellow_logcache_steal(flc, direction));
 
+	if (need == 0 && ! flc_mempool_avail(flc->mempool))
+		return (NULL);
+
 	VTAILQ_REMOVE(&flc->free, fle, list);
 	AZ(fle->alloc.ptr);
 
@@ -1489,7 +1493,7 @@ fellow_logcache_prefetch(struct fellow_logcache *flc,
 		}
 		if (noff == 0)
 			break;
-		next = fellow_logcache_take(flc, direction);
+		next = fellow_logcache_take(flc, direction, 0);
 		if (next == NULL)
 			break;
 		//DBG("%zu %s", noff, direction < 0 ? "<-" : "->");
@@ -1528,7 +1532,7 @@ fellow_logcache_get(struct fellow_logcache *flc, off_t off, int direction,
 
 	if (flc->current == NULL) {
 		DBG("1st  %zu %s", off, direction < 0 ? "<-" : "->");
-		fle = fellow_logcache_take(flc, direction);
+		fle = fellow_logcache_take(flc, direction, 1);
 		AN(fle);
 		flc->current = fle;
 		assert(VTAILQ_EMPTY(&flc->used));
@@ -1546,7 +1550,7 @@ fellow_logcache_get(struct fellow_logcache *flc, off_t off, int direction,
 		CHECK_OBJ_ORNULL(fle, FELLOW_LOGCACHE_ENTRY_MAGIC);
 		if (fle == NULL) {
 			DBG("miss %zu %s", off, direction < 0 ? "<-" : "->");
-			fle = fellow_logcache_take(flc, direction);
+			fle = fellow_logcache_take(flc, direction, 1);
 			AN(fle);
 			fellow_logcache_insert(flc, flc->current,
 			    fle, direction);