[v2,7/9] memarea: support backup memory mechanism

diff --git a/doc/guides/prog_guide/memarea_lib.rst b/doc/guides/prog_guide/memarea_lib.rst
index 7686625c90..c52ab95aeb 100644
--- a/doc/guides/prog_guide/memarea_lib.rst
+++ b/doc/guides/prog_guide/memarea_lib.rst
@@ -26,6 +26,9 @@  The main features are as follows:
 
 * It supports MT-safe as long as it's specified at creation time.
 
+* It provides backup memory mechanism, the memory object could use another
+  memarea object as a backup.
+
 Library API Overview
 --------------------
 
diff --git a/lib/memarea/memarea_private.h b/lib/memarea/memarea_private.h
index 98406879b9..08735ca81f 100644
--- a/lib/memarea/memarea_private.h
+++ b/lib/memarea/memarea_private.h
@@ -23,11 +23,13 @@  struct rte_memarea {
 	struct rte_memarea_param init;
 	rte_spinlock_t           lock;
 	void                    *area_addr;
+	void                    *top_addr;
 	struct memarea_elem_list elem_list;
 	struct memarea_elem_list free_list;
 
 	uint64_t alloc_fails;
 	uint64_t refcnt_check_fails;
+	uint64_t bak_alloc_fails;
 } __rte_cache_aligned;
 
 #endif /* MEMAREA_PRIVATE_H */
diff --git a/lib/memarea/rte_memarea.c b/lib/memarea/rte_memarea.c
index e4d43e5907..6cad9d5b2f 100644
--- a/lib/memarea/rte_memarea.c
+++ b/lib/memarea/rte_memarea.c
@@ -121,6 +121,7 @@  rte_memarea_create(const struct rte_memarea_param *init)
 	TAILQ_INIT(&ma->elem_list);
 	TAILQ_INIT(&ma->free_list);
 	ma->area_addr = addr;
+	ma->top_addr = (void *)((uintptr_t)addr + init->total_sz - 1);
 	elem = addr;
 	elem->size = init->total_sz - sizeof(struct memarea_elem);
 	elem->cookie = MEMAREA_FREE_ELEM_COOKIE;
@@ -187,6 +188,15 @@  memarea_add_node(struct rte_memarea *ma, struct memarea_elem *elem, size_t need_
 	elem->size = align_size;
 }
 
+static inline void *
+memarea_alloc_backup(struct rte_memarea *ma, size_t size, uint32_t cookie)
+{
+	void *ptr = rte_memarea_alloc(ma->init.bak_memarea, size, cookie);
+	if (unlikely(ptr == NULL))
+		ma->bak_alloc_fails++;
+	return ptr;
+}
+
 void *
 rte_memarea_alloc(struct rte_memarea *ma, size_t size, uint32_t cookie)
 {
@@ -208,6 +218,8 @@  rte_memarea_alloc(struct rte_memarea *ma, size_t size, uint32_t cookie)
 		ptr = (void *)((uintptr_t)elem + sizeof(struct memarea_elem));
 		break;
 	}
+	if (ptr == NULL && ma->init.bak_memarea != NULL)
+		ptr = memarea_alloc_backup(ma, size, cookie);
 	if (unlikely(ptr == NULL))
 		ma->alloc_fails++;
 	memarea_unlock(ma);
@@ -268,6 +280,12 @@  rte_memarea_update_refcnt(struct rte_memarea *ma, void *ptr, int16_t value)
 		return;
 
 	memarea_lock(ma);
+	if (ptr < ma->area_addr || ptr > ma->top_addr) {
+		rte_memarea_update_refcnt(ma->init.bak_memarea, ptr, value);
+		memarea_unlock(ma);
+		return;
+	}
+
 	if (unlikely(elem->refcnt <= 0 || elem->refcnt + value < 0)) {
 		RTE_LOG(ERR, MEMAREA,
 			"memarea: %s cookie: %u curr refcnt: %d update refcnt: %d check fail!\n",
@@ -346,10 +364,13 @@  rte_memarea_dump(struct rte_memarea *ma, FILE *f, bool dump_all)
 		fprintf(f, "  source-user-memarea: %s\n", ma->init.user_memarea->init.name);
 	fprintf(f, "  total-size: 0x%zx\n", ma->init.total_sz);
 	fprintf(f, "  mt-safe: %s\n", ma->init.mt_safe ? "yes" : "no");
+	if (ma->init.bak_memarea)
+		fprintf(f, "  backup-memarea-name: %s\n", ma->init.bak_memarea->init.name);
 	fprintf(f, "  total-regions: %u\n", memarea_elem_list_num(ma));
 	fprintf(f, "  total-free-regions: %u\n", memarea_free_list_num(ma));
 	fprintf(f, "  alloc_fails: %" PRIu64 "\n", ma->alloc_fails);
 	fprintf(f, "  refcnt_check_fails: %" PRIu64 "\n", ma->refcnt_check_fails);
+	fprintf(f, "  backup_alloc_fails: %" PRIu64 "\n", ma->bak_alloc_fails);
 	if (dump_all)
 		memarea_dump_all(ma, f);
 	memarea_unlock(ma);
diff --git a/lib/memarea/rte_memarea.h b/lib/memarea/rte_memarea.h
index 2a92755b63..ed5e8c5db5 100644
--- a/lib/memarea/rte_memarea.h
+++ b/lib/memarea/rte_memarea.h
@@ -41,6 +41,8 @@ 
  *      specified, all the functions of the memarea API are lock-free, and
  *      assume to not be invoked in parallel on different logical cores to work
  *      on the same memarea object.
+ *   f) It provides backup memory mechanism, the memarea object could use
+ *      another memarea object as a backup.
  */
 
 #include <stdbool.h>
@@ -87,6 +89,10 @@  struct rte_memarea_param {
 		 */
 		struct rte_memarea *user_memarea;
 	};
+	/** Backup memarea, which is used to handle the scenario where the
+	 * current memarea object allocation failure.
+	 */
+	struct rte_memarea *bak_memarea;
 };
 
 /**