staging: lustre: lnet: lock improvement for ko2iblnd

kiblnd_check_sends() takes conn::ibc_lock at the begin and release
this lock at the end, this is inefficient because most use-case
needs to explicitly release ibc_lock before caling this function.

This patches changes it to kiblnd_check_sends_locked() and avoid
unnecessary lock dances.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Signed-off-by: Doug Oucharek <doug.s.oucharek@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7099
Reviewed-on: http://review.whamcloud.com/20322
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index 6cd78ea279a7d7dd06a2a55cdbb6d15d40abaa45..6d1b14a79ac93e3ffb8016bb25f0f9db92f8ad3e 100644 (file)
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -38,7 +38,6 @@
 
 static void kiblnd_peer_alive(struct kib_peer *peer);
 static void kiblnd_peer_connect_failed(struct kib_peer *peer, int active, int error);
-static void kiblnd_check_sends(struct kib_conn *conn);
 static void kiblnd_init_tx_msg(lnet_ni_t *ni, struct kib_tx *tx,
                                int type, int body_nob);
 static int kiblnd_init_rdma(struct kib_conn *conn, struct kib_tx *tx, int type,
@@ -46,6 +45,7 @@ static int kiblnd_init_rdma(struct kib_conn *conn, struct kib_tx *tx, int type,
 static void kiblnd_queue_tx_locked(struct kib_tx *tx, struct kib_conn *conn);
 static void kiblnd_queue_tx(struct kib_tx *tx, struct kib_conn *conn);
 static void kiblnd_unmap_tx(lnet_ni_t *ni, struct kib_tx *tx);
+static void kiblnd_check_sends_locked(struct kib_conn *conn);
 
 static void
 kiblnd_tx_done(lnet_ni_t *ni, struct kib_tx *tx)
@@ -211,9 +211,9 @@ kiblnd_post_rx(struct kib_rx *rx, int credit)
                conn->ibc_outstanding_credits++;
        else
                conn->ibc_reserved_credits++;
+       kiblnd_check_sends_locked(conn);
        spin_unlock(&conn->ibc_lock);
 
-       kiblnd_check_sends(conn);
 out:
        kiblnd_conn_decref(conn);
        return rc;
@@ -344,8 +344,8 @@ kiblnd_handle_rx(struct kib_rx *rx)
                    !IBLND_OOB_CAPABLE(conn->ibc_version)) /* v1 only */
                        conn->ibc_outstanding_credits++;
 
+               kiblnd_check_sends_locked(conn);
                spin_unlock(&conn->ibc_lock);
-               kiblnd_check_sends(conn);
        }
 
        switch (msg->ibm_type) {
@@ -800,7 +800,7 @@ kiblnd_post_tx_locked(struct kib_conn *conn, struct kib_tx *tx, int credit)
              conn->ibc_noops_posted == IBLND_OOB_MSGS(ver)))) {
                /*
                 * OK to drop when posted enough NOOPs, since
-                * kiblnd_check_sends will queue NOOP again when
+                * kiblnd_check_sends_locked will queue NOOP again when
                 * posted NOOPs complete
                 */
                spin_unlock(&conn->ibc_lock);
@@ -905,7 +905,7 @@ kiblnd_post_tx_locked(struct kib_conn *conn, struct kib_tx *tx, int credit)
 }
 
 static void
-kiblnd_check_sends(struct kib_conn *conn)
+kiblnd_check_sends_locked(struct kib_conn *conn)
 {
        int ver = conn->ibc_version;
        lnet_ni_t *ni = conn->ibc_peer->ibp_ni;
@@ -918,8 +918,6 @@ kiblnd_check_sends(struct kib_conn *conn)
                return;
        }
 
-       spin_lock(&conn->ibc_lock);
-
        LASSERT(conn->ibc_nsends_posted <= kiblnd_concurrent_sends(ver, ni));
        LASSERT(!IBLND_OOB_CAPABLE(ver) ||
                conn->ibc_noops_posted <= IBLND_OOB_MSGS(ver));
@@ -969,8 +967,6 @@ kiblnd_check_sends(struct kib_conn *conn)
                if (kiblnd_post_tx_locked(conn, tx, credit))
                        break;
        }
-
-       spin_unlock(&conn->ibc_lock);
 }
 
 static void
@@ -1016,16 +1012,11 @@ kiblnd_tx_complete(struct kib_tx *tx, int status)
        if (idle)
                list_del(&tx->tx_list);
 
-       kiblnd_conn_addref(conn);              /* 1 ref for me.... */
-
+       kiblnd_check_sends_locked(conn);
        spin_unlock(&conn->ibc_lock);
 
        if (idle)
                kiblnd_tx_done(conn->ibc_peer->ibp_ni, tx);
-
-       kiblnd_check_sends(conn);
-
-       kiblnd_conn_decref(conn);              /* ...until here */
 }
 
 static void
@@ -1204,9 +1195,8 @@ kiblnd_queue_tx(struct kib_tx *tx, struct kib_conn *conn)
 {
        spin_lock(&conn->ibc_lock);
        kiblnd_queue_tx_locked(tx, conn);
+       kiblnd_check_sends_locked(conn);
        spin_unlock(&conn->ibc_lock);
-
-       kiblnd_check_sends(conn);
 }
 
 static int kiblnd_resolve_addr(struct rdma_cm_id *cmid,
@@ -2183,14 +2173,11 @@ kiblnd_connreq_done(struct kib_conn *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.
+       /*
+        * +1 ref for myself, this connection is visible to other threads
+        * now, refcount of peer:ibp_conns can be released by connection
+        * close from either a different thread, or the calling of
+        * kiblnd_check_sends_locked() below. See bz21911 for details.
         */
        kiblnd_conn_addref(conn);
        write_unlock_irqrestore(&kiblnd_data.kib_global_lock, flags);
@@ -2202,10 +2189,9 @@ kiblnd_connreq_done(struct kib_conn *conn, int status)
 
                kiblnd_queue_tx_locked(tx, conn);
        }
+       kiblnd_check_sends_locked(conn);
        spin_unlock(&conn->ibc_lock);
 
-       kiblnd_check_sends(conn);
-
        /* schedule blocked rxs */
        kiblnd_handle_early_rxs(conn);
 
@@ -3233,7 +3219,11 @@ kiblnd_check_conns(int idx)
         */
        list_for_each_entry_safe(conn, temp, &checksends, ibc_connd_list) {
                list_del(&conn->ibc_connd_list);
-               kiblnd_check_sends(conn);
+
+               spin_lock(&conn->ibc_lock);
+               kiblnd_check_sends_locked(conn);
+               spin_unlock(&conn->ibc_lock);
+
                kiblnd_conn_decref(conn);
        }
 }