[PATCH 23/27] staging: lustre: take extra refcount in kiblnd_connreq_done

James Simmons
2016-03-02T22:04:00Z

From: Liang Zhen <liang.zhen@intel.com>

refcount taken by cmid is not reliable after kiblnd_connreq_done
released the glock because this connection is visible to other
threads, another thread can find and close this connection right
after kiblnd_connreq_done released the glock, if kiblnd_cm_callback
for RDMA_CM_EVENT_DISCONNECTED is called, it can release the
connection refcount taken by cmid. It means the connection could be
destroyed before kiblnd_connreq_done() finish operations on it.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
ntel-bug-id: https://jira.hpdd.intel.com/browse/LU-7210
Reviewed-on: http://review.whamcloud.com/17527
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---
.../staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index fb3873a..11e12ae 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -939,8 +939,6 @@ kiblnd_check_sends(kib_conn_t *conn)
kiblnd_queue_tx_locked(tx, conn);
}

- kiblnd_conn_addref(conn); /* 1 ref for me.... (see b21911) */
-
for (;;) {
int credit;

@@ -966,8 +964,6 @@ kiblnd_check_sends(kib_conn_t *conn)
}

spin_unlock(&conn->ibc_lock);
-
- kiblnd_conn_decref(conn); /* ...until here */
}

static void
@@ -2132,6 +2128,16 @@ kiblnd_connreq_done(kib_conn_t *conn, int status)
return;
}

+ /**
+ * refcount taken by cmid is not reliable after I released the glock
+ * because this connection is visible to other threads now, another
+ * thread can find and close this connection right after I released
+ * the glock, if kiblnd_cm_callback for RDMA_CM_EVENT_DISCONNECTED is
+ * called, it can release the connection refcount taken by cmid.
+ * It means the connection could be destroyed before I finish my
+ * operations on it.
+ */
+ kiblnd_conn_addref(conn);
write_unlock_irqrestore(&kiblnd_data.kib_global_lock, flags);

/* Schedule blocked txs */
@@ -2147,6 +2153,8 @@ kiblnd_connreq_done(kib_conn_t *conn, int status)

/* schedule blocked rxs */
kiblnd_handle_early_rxs(conn);
+
+ kiblnd_conn_decref(conn);
}

static void
--
1.7.1