1 files changed, 167 insertions, 60 deletions

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index dff0481..661fbc1 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -11,12 +11,136 @@
  * but most complex memory registration mode.
  */
 
+/* Normal operation
+ *
+ * A Memory Region is prepared for RDMA READ or WRITE using a FAST_REG
+ * Work Request (frmr_op_map). When the RDMA operation is finished, this
+ * Memory Region is invalidated using a LOCAL_INV Work Request
+ * (frmr_op_unmap).
+ *
+ * Typically these Work Requests are not signaled, and neither are RDMA
+ * SEND Work Requests (with the exception of signaling occasionally to
+ * prevent provider work queue overflows). This greatly reduces HCA
+ * interrupt workload.
+ *
+ * As an optimization, frwr_op_unmap marks MRs INVALID before the
+ * LOCAL_INV WR is posted. If posting succeeds, the MR is placed on
+ * rb_mws immediately so that no work (like managing a linked list
+ * under a spinlock) is needed in the completion upcall.
+ *
+ * But this means that frwr_op_map() can occasionally encounter an MR
+ * that is INVALID but the LOCAL_INV WR has not completed. Work Queue
+ * ordering prevents a subsequent FAST_REG WR from executing against
+ * that MR while it is still being invalidated.
+ */
+
+/* Transport recovery
+ *
+ * ->op_map and the transport connect worker cannot run at the same
+ * time, but ->op_unmap can fire while the transport connect worker
+ * is running. Thus MR recovery is handled in ->op_map, to guarantee
+ * that recovered MRs are owned by a sending RPC, and not one where
+ * ->op_unmap could fire at the same time transport reconnect is
+ * being done.
+ *
+ * When the underlying transport disconnects, MRs are left in one of
+ * three states:
+ *
+ * INVALID:	The MR was not in use before the QP entered ERROR state.
+ *		(Or, the LOCAL_INV WR has not completed or flushed yet).
+ *
+ * STALE:	The MR was being registered or unregistered when the QP
+ *		entered ERROR state, and the pending WR was flushed.
+ *
+ * VALID:	The MR was registered before the QP entered ERROR state.
+ *
+ * When frwr_op_map encounters STALE and VALID MRs, they are recovered
+ * with ib_dereg_mr and then are re-initialized. Beause MR recovery
+ * allocates fresh resources, it is deferred to a workqueue, and the
+ * recovered MRs are placed back on the rb_mws list when recovery is
+ * complete. frwr_op_map allocates another MR for the current RPC while
+ * the broken MR is reset.
+ *
+ * To ensure that frwr_op_map doesn't encounter an MR that is marked
+ * INVALID but that is about to be flushed due to a previous transport
+ * disconnect, the transport connect worker attempts to drain all
+ * pending send queue WRs before the transport is reconnected.
+ */
+
 #include "xprt_rdma.h"
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 # define RPCDBG_FACILITY	RPCDBG_TRANS
 #endif
 
+static struct workqueue_struct *frwr_recovery_wq;
+
+#define FRWR_RECOVERY_WQ_FLAGS		(WQ_UNBOUND | WQ_MEM_RECLAIM)
+
+int
+frwr_alloc_recovery_wq(void)
+{
+	frwr_recovery_wq = alloc_workqueue("frwr_recovery",
+					   FRWR_RECOVERY_WQ_FLAGS, 0);
+	return !frwr_recovery_wq ? -ENOMEM : 0;
+}
+
+void
+frwr_destroy_recovery_wq(void)
+{
+	struct workqueue_struct *wq;
+
+	if (!frwr_recovery_wq)
+		return;
+
+	wq = frwr_recovery_wq;
+	frwr_recovery_wq = NULL;
+	destroy_workqueue(wq);
+}
+
+/* Deferred reset of a single FRMR. Generate a fresh rkey by
+ * replacing the MR.
+ *
+ * There's no recovery if this fails. The FRMR is abandoned, but
+ * remains in rb_all. It will be cleaned up when the transport is
+ * destroyed.
+ */
+static void
+__frwr_recovery_worker(struct work_struct *work)
+{
+	struct rpcrdma_mw *r = container_of(work, struct rpcrdma_mw,
+					    r.frmr.fr_work);
+	struct rpcrdma_xprt *r_xprt = r->r.frmr.fr_xprt;
+	unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
+	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
+
+	if (ib_dereg_mr(r->r.frmr.fr_mr))
+		goto out_fail;
+
+	r->r.frmr.fr_mr = ib_alloc_fast_reg_mr(pd, depth);
+	if (IS_ERR(r->r.frmr.fr_mr))
+		goto out_fail;
+
+	dprintk("RPC:       %s: recovered FRMR %p\n", __func__, r);
+	r->r.frmr.fr_state = FRMR_IS_INVALID;
+	rpcrdma_put_mw(r_xprt, r);
+	return;
+
+out_fail:
+	pr_warn("RPC:       %s: FRMR %p unrecovered\n",
+		__func__, r);
+}
+
+/* A broken MR was discovered in a context that can't sleep.
+ * Defer recovery to the recovery worker.
+ */
+static void
+__frwr_queue_recovery(struct rpcrdma_mw *r)
+{
+	INIT_WORK(&r->r.frmr.fr_work, __frwr_recovery_worker);
+	queue_work(frwr_recovery_wq, &r->r.frmr.fr_work);
+}
+
 static int
 __frwr_init(struct rpcrdma_mw *r, struct ib_pd *pd, struct ib_device *device,
 	    unsigned int depth)
@@ -128,7 +252,7 @@ frwr_sendcompletion(struct ib_wc *wc)
 
 	/* WARNING: Only wr_id and status are reliable at this point */
 	r = (struct rpcrdma_mw *)(unsigned long)wc->wr_id;
-	dprintk("RPC:       %s: frmr %p (stale), status %d\n",
+	pr_warn("RPC:       %s: frmr %p flushed, status %d\n",
 		__func__, r, wc->status);
 	r->r.frmr.fr_state = FRMR_IS_STALE;
 }
@@ -137,16 +261,19 @@ static int
 frwr_op_init(struct rpcrdma_xprt *r_xprt)
 {
 	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
-	struct ib_device *device = r_xprt->rx_ia.ri_id->device;
+	struct ib_device *device = r_xprt->rx_ia.ri_device;
 	unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
 	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
 	int i;
 
+	spin_lock_init(&buf->rb_mwlock);
 	INIT_LIST_HEAD(&buf->rb_mws);
 	INIT_LIST_HEAD(&buf->rb_all);
 
-	i = (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS;
-	dprintk("RPC:       %s: initializing %d FRMRs\n", __func__, i);
+	i = max_t(int, RPCRDMA_MAX_DATA_SEGS / depth, 1);
+	i += 2;				/* head + tail */
+	i *= buf->rb_max_requests;	/* one set for each RPC slot */
+	dprintk("RPC:       %s: initalizing %d FRMRs\n", __func__, i);
 
 	while (i--) {
 		struct rpcrdma_mw *r;
@@ -165,6 +292,7 @@ frwr_op_init(struct rpcrdma_xprt *r_xprt)
 		list_add(&r->mw_list, &buf->rb_mws);
 		list_add(&r->mw_all, &buf->rb_all);
 		r->mw_sendcompletion = frwr_sendcompletion;
+		r->r.frmr.fr_xprt = r_xprt;
 	}
 
 	return 0;
@@ -178,12 +306,12 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	    int nsegs, bool writing)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
-	struct ib_device *device = ia->ri_id->device;
+	struct ib_device *device = ia->ri_device;
 	enum dma_data_direction direction = rpcrdma_data_dir(writing);
 	struct rpcrdma_mr_seg *seg1 = seg;
-	struct rpcrdma_mw *mw = seg1->rl_mw;
-	struct rpcrdma_frmr *frmr = &mw->r.frmr;
-	struct ib_mr *mr = frmr->fr_mr;
+	struct rpcrdma_mw *mw;
+	struct rpcrdma_frmr *frmr;
+	struct ib_mr *mr;
 	struct ib_send_wr fastreg_wr, *bad_wr;
 	u8 key;
 	int len, pageoff;
@@ -192,12 +320,25 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	u64 pa;
 	int page_no;
 
+	mw = seg1->rl_mw;
+	seg1->rl_mw = NULL;
+	do {
+		if (mw)
+			__frwr_queue_recovery(mw);
+		mw = rpcrdma_get_mw(r_xprt);
+		if (!mw)
+			return -ENOMEM;
+	} while (mw->r.frmr.fr_state != FRMR_IS_INVALID);
+	frmr = &mw->r.frmr;
+	frmr->fr_state = FRMR_IS_VALID;
+
 	pageoff = offset_in_page(seg1->mr_offset);
 	seg1->mr_offset -= pageoff;	/* start of page */
 	seg1->mr_len += pageoff;
 	len = -pageoff;
 	if (nsegs > ia->ri_max_frmr_depth)
 		nsegs = ia->ri_max_frmr_depth;
+
 	for (page_no = i = 0; i < nsegs;) {
 		rpcrdma_map_one(device, seg, direction);
 		pa = seg->mr_dma;
@@ -216,8 +357,6 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	dprintk("RPC:       %s: Using frmr %p to map %d segments (%d bytes)\n",
 		__func__, mw, i, len);
 
-	frmr->fr_state = FRMR_IS_VALID;
-
 	memset(&fastreg_wr, 0, sizeof(fastreg_wr));
 	fastreg_wr.wr_id = (unsigned long)(void *)mw;
 	fastreg_wr.opcode = IB_WR_FAST_REG_MR;
@@ -229,6 +368,7 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	fastreg_wr.wr.fast_reg.access_flags = writing ?
 				IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
 				IB_ACCESS_REMOTE_READ;
+	mr = frmr->fr_mr;
 	key = (u8)(mr->rkey & 0x000000FF);
 	ib_update_fast_reg_key(mr, ++key);
 	fastreg_wr.wr.fast_reg.rkey = mr->rkey;
@@ -238,6 +378,7 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	if (rc)
 		goto out_senderr;
 
+	seg1->rl_mw = mw;
 	seg1->mr_rkey = mr->rkey;
 	seg1->mr_base = seg1->mr_dma + pageoff;
 	seg1->mr_nsegs = i;
@@ -246,10 +387,9 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 
 out_senderr:
 	dprintk("RPC:       %s: ib_post_send status %i\n", __func__, rc);
-	ib_update_fast_reg_key(mr, --key);
-	frmr->fr_state = FRMR_IS_INVALID;
 	while (i--)
 		rpcrdma_unmap_one(device, --seg);
+	__frwr_queue_recovery(mw);
 	return rc;
 }
 
@@ -261,78 +401,46 @@ frwr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
 {
 	struct rpcrdma_mr_seg *seg1 = seg;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+	struct rpcrdma_mw *mw = seg1->rl_mw;
 	struct ib_send_wr invalidate_wr, *bad_wr;
 	int rc, nsegs = seg->mr_nsegs;
-	struct ib_device *device;
 
-	seg1->rl_mw->r.frmr.fr_state = FRMR_IS_INVALID;
+	dprintk("RPC:       %s: FRMR %p\n", __func__, mw);
+
+	seg1->rl_mw = NULL;
+	mw->r.frmr.fr_state = FRMR_IS_INVALID;
 
 	memset(&invalidate_wr, 0, sizeof(invalidate_wr));
-	invalidate_wr.wr_id = (unsigned long)(void *)seg1->rl_mw;
+	invalidate_wr.wr_id = (unsigned long)(void *)mw;
 	invalidate_wr.opcode = IB_WR_LOCAL_INV;
-	invalidate_wr.ex.invalidate_rkey = seg1->rl_mw->r.frmr.fr_mr->rkey;
+	invalidate_wr.ex.invalidate_rkey = mw->r.frmr.fr_mr->rkey;
 	DECR_CQCOUNT(&r_xprt->rx_ep);
 
-	read_lock(&ia->ri_qplock);
-	device = ia->ri_id->device;
 	while (seg1->mr_nsegs--)
-		rpcrdma_unmap_one(device, seg++);
+		rpcrdma_unmap_one(ia->ri_device, seg++);
+	read_lock(&ia->ri_qplock);
 	rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
 	read_unlock(&ia->ri_qplock);
 	if (rc)
 		goto out_err;
+
+	rpcrdma_put_mw(r_xprt, mw);
 	return nsegs;
 
 out_err:
-	/* Force rpcrdma_buffer_get() to retry */
-	seg1->rl_mw->r.frmr.fr_state = FRMR_IS_STALE;
 	dprintk("RPC:       %s: ib_post_send status %i\n", __func__, rc);
+	__frwr_queue_recovery(mw);
 	return nsegs;
 }
 
-/* After a disconnect, a flushed FAST_REG_MR can leave an FRMR in
- * an unusable state. Find FRMRs in this state and dereg / reg
- * each.  FRMRs that are VALID and attached to an rpcrdma_req are
- * also torn down.
- *
- * This gives all in-use FRMRs a fresh rkey and leaves them INVALID.
- *
- * This is invoked only in the transport connect worker in order
- * to serialize with rpcrdma_register_frmr_external().
- */
-static void
-frwr_op_reset(struct rpcrdma_xprt *r_xprt)
-{
-	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
-	struct ib_device *device = r_xprt->rx_ia.ri_id->device;
-	unsigned int depth = r_xprt->rx_ia.ri_max_frmr_depth;
-	struct ib_pd *pd = r_xprt->rx_ia.ri_pd;
-	struct rpcrdma_mw *r;
-	int rc;
-
-	list_for_each_entry(r, &buf->rb_all, mw_all) {
-		if (r->r.frmr.fr_state == FRMR_IS_INVALID)
-			continue;
-
-		__frwr_release(r);
-		rc = __frwr_init(r, pd, device, depth);
-		if (rc) {
-			dprintk("RPC:       %s: mw %p left %s\n",
-				__func__, r,
-				(r->r.frmr.fr_state == FRMR_IS_STALE ?
-					"stale" : "valid"));
-			continue;
-		}
-
-		r->r.frmr.fr_state = FRMR_IS_INVALID;
-	}
-}
-
 static void
 frwr_op_destroy(struct rpcrdma_buffer *buf)
 {
 	struct rpcrdma_mw *r;
 
+	/* Ensure stale MWs for "buf" are no longer in flight */
+	flush_workqueue(frwr_recovery_wq);
+
 	while (!list_empty(&buf->rb_all)) {
 		r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
 		list_del(&r->mw_all);
@@ -347,7 +455,6 @@ const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
 	.ro_open			= frwr_op_open,
 	.ro_maxpages			= frwr_op_maxpages,
 	.ro_init			= frwr_op_init,
-	.ro_reset			= frwr_op_reset,
 	.ro_destroy			= frwr_op_destroy,
 	.ro_displayname			= "frwr",
 };