mbuf: decrease reference counter when detaching

The rte_pktmbuf_detach() function should decrease refcnt on a direct
buffer as stated in doc/guides/prog_guide/mbuf_lib.rst:
"whenever the indirect buffer is detached, the reference counter on the
direct buffer is decremented."

Signed-off-by: Hiroyuki Mikita <h.mikita89@gmail.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>

diff --git a/app/test/test_mbuf.c b/app/test/test_mbuf.c
index 98ff93a..8460db7 100644 (file)
--- a/app/test/test_mbuf.c
+++ b/app/test/test_mbuf.c
@@ -511,10 +511,14 @@ test_attach_from_different_pool(void)
        rte_pktmbuf_detach(clone);
        if (c_data != rte_pktmbuf_mtod(clone, char *))
                GOTO_FAIL("clone was not detached properly\n");
+       if (rte_mbuf_refcnt_read(m) != 2)
+               GOTO_FAIL("invalid refcnt in m\n");
 
        rte_pktmbuf_detach(clone2);
        if (c_data2 != rte_pktmbuf_mtod(clone2, char *))
                GOTO_FAIL("clone2 was not detached properly\n");
+       if (rte_mbuf_refcnt_read(m) != 1)
+               GOTO_FAIL("invalid refcnt in m\n");
 
        /* free the clones and the initial mbuf */
        rte_pktmbuf_free(clone2);

diff --git a/doc/guides/rel_notes/release_16_07.rst b/doc/guides/rel_notes/release_16_07.rst
index 58c8ef9..a8c50c8 100644 (file)
--- a/doc/guides/rel_notes/release_16_07.rst
+++ b/doc/guides/rel_notes/release_16_07.rst
@@ -69,6 +69,12 @@ Drivers
 Libraries
 ~~~~~~~~~
 
+* **mbuf: Fixed refcnt update when detaching.**
+
+  Fix the ``rte_pktmbuf_detach()`` function to decrement the direct
+  mbuf's reference counter. The previous behavior was not to affect
+  the reference counter. It lead a memory leak of the direct mbuf.
+
 
 Examples
 ~~~~~~~~

diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index 7b92b88..48911a6 100644 (file)
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -1412,6 +1412,8 @@ static inline int rte_pktmbuf_alloc_bulk(struct rte_mempool *pool,
  *
  * After attachment we refer the mbuf we attached as 'indirect',
  * while mbuf we attached to as 'direct'.
+ * The direct mbuf's reference counter is incremented.
+ *
  * Right now, not supported:
  *  - attachment for already indirect mbuf (e.g. - mi has to be direct).
  *  - mbuf we trying to attach (mi) is used by someone else
@@ -1465,13 +1467,17 @@ static inline void rte_pktmbuf_attach(struct rte_mbuf *mi, struct rte_mbuf *m)
  *
  *  - restore original mbuf address and length values.
  *  - reset pktmbuf data and data_len to their default values.
- *  All other fields of the given packet mbuf will be left intact.
+ *  - decrement the direct mbuf's reference counter. When the
+ *  reference counter becomes 0, the direct mbuf is freed.
+ *
+ * All other fields of the given packet mbuf will be left intact.
  *
  * @param m
  *   The indirect attached packet mbuf.
  */
 static inline void rte_pktmbuf_detach(struct rte_mbuf *m)
 {
+       struct rte_mbuf *md = rte_mbuf_from_indirect(m);
        struct rte_mempool *mp = m->pool;
        uint32_t mbuf_size, buf_len, priv_size;
 
@@ -1486,6 +1492,9 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf *m)
        m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);
        m->data_len = 0;
        m->ol_flags = 0;
+
+       if (rte_mbuf_refcnt_update(md, -1) == 0)
+               __rte_mbuf_raw_free(md);
 }
 
 static inline struct rte_mbuf* __attribute__((always_inline))
@@ -1494,17 +1503,9 @@ __rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
        __rte_mbuf_sanity_check(m, 0);
 
        if (likely(rte_mbuf_refcnt_update(m, -1) == 0)) {
-
-               /* if this is an indirect mbuf, then
-                *  - detach mbuf
-                *  - free attached mbuf segment
-                */
-               if (RTE_MBUF_INDIRECT(m)) {
-                       struct rte_mbuf *md = rte_mbuf_from_indirect(m);
+               /* if this is an indirect mbuf, it is detached. */
+               if (RTE_MBUF_INDIRECT(m))
                        rte_pktmbuf_detach(m);
-                       if (rte_mbuf_refcnt_update(md, -1) == 0)
-                               __rte_mbuf_raw_free(md);
-               }
                return m;
        }
        return NULL;