logbuffer: When we need a regionlist under the logmtx, check the pool for memory

src/fellow_log.c

@@ -2598,6 +2598,26 @@ logbuffer_flush_finish(struct fellow_fd *ffd,
 static void
 logbuffer_flush_finish_work(struct worker *wrk, void *priv);
 
+/*
+ * for use under the lock. Uses the mempool if possible
+ */
+static void
+logbuffer_need_regions_to_free(struct fellow_logbuffer *lbuf)
+{
+
+	if (lbuf->regions_to_free != NULL)
+		return;
+
+	if (lbuf_mempool_avail(lbuf->mempool)) {
+		lbuf->regions_to_free = regionlist_init(
+		    buddy_get_next_ptr_page(
+			lbuf_mempool_get(lbuf->mempool, lbuf)),
+		    lbuf->membuddy);
+	}
+	else
+		lbuf->regions_to_free = regionlist_alloc(lbuf->membuddy);
+}
+
 static void
 logbuffer_flush(struct fellow_fd *ffd,
     struct fellow_logbuffer *lbuf, unsigned doclose, unsigned can)
@@ -2654,9 +2674,7 @@ logbuffer_flush(struct fellow_fd *ffd,
 		return;
 	}
 
-	if (lbuf->regions_to_free == NULL) {
-		lbuf->regions_to_free = regionlist_alloc(ffd->membuddy);
-	}
+	logbuffer_need_regions_to_free(lbuf);
 
 	if (lbuf->head.block == NULL) {
 		if (! cap(can, LBUF_CAN_REF) || lbuf->ff != NULL)
@@ -4349,9 +4367,7 @@ fellow_log_entries_add(struct fellow_fd *ffd,
 	AN(entry);
 
 	if (prep->tofree.n) {
-		if (lbuf->regions_to_free == NULL)
-			lbuf->regions_to_free = regionlist_alloc(ffd->membuddy);
-
+		logbuffer_need_regions_to_free(lbuf);
 		prep->tofree.regionlist = lbuf->regions_to_free;
 		regionlist_stk_flush(prep->tofree);
 	}

src/fellow_regionlist.h

@@ -182,17 +182,12 @@ regl_init(const struct buddy_ptr_page alloc, size_t off)
 }
 
 static struct regionlist *
-regionlist_alloc(buddy_t *membuddy)
+regionlist_init(struct buddy_ptr_page alloc, buddy_t *membuddy)
 {
-	struct buddy_ptr_page alloc;
 	struct regionlist *rl;
 	struct regl *r;
 	size_t sz;
 
-	alloc = buddy_alloc1_ptr_page_wait(membuddy, FEP_MEM_FREE,
-	    regl_bits, regl_bits_cram);
-	AN(alloc.ptr);
-
 	sz = (size_t)1 << alloc.bits;
 	assert(sz >= (2 * sizeof *r + sizeof *rl));
 
@@ -209,6 +204,18 @@ regionlist_alloc(buddy_t *membuddy)
 	return (rl);
 }
 
+static struct regionlist *
+regionlist_alloc(buddy_t *membuddy)
+{
+	struct buddy_ptr_page alloc;
+
+	alloc = buddy_alloc1_ptr_page_wait(membuddy, FEP_MEM_FREE,
+	    regl_bits, regl_bits_cram);
+	AN(alloc.ptr);
+
+	return (regionlist_init(alloc, membuddy));
+}
+
 static unsigned
 regionlist_used(const struct regionlist *rl)
 {