xprtrdma: Refactor MR recovery work queues

I found that commit ead3f26e359e ("xprtrdma: Add ro_unmap_safe
memreg method"), which introduces ro_unmap_safe, never wired up the
FMR recovery worker.

The FMR and FRWR recovery work queues both do the same thing.
Instead of setting up separate individual work queues for this,
schedule a delayed worker to deal with them, since recovering MRs is
not performance-critical.

Fixes: ead3f26e359e ("xprtrdma: Add ro_unmap_safe memreg method")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/fmr_ops.c

@@ -19,13 +19,6 @@
  * verb (fmr_op_unmap).
  */
 
-/* Transport recovery
- *
- * After a transport reconnect, fmr_op_map re-uses the MR already
- * allocated for the RPC, but generates a fresh rkey then maps the
- * MR again. This process is synchronous.
- */
-
 #include "xprt_rdma.h"
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
@@ -41,30 +34,6 @@ enum {
 					  IB_ACCESS_REMOTE_READ,
 };
 
-static struct workqueue_struct *fmr_recovery_wq;
-
-#define FMR_RECOVERY_WQ_FLAGS		(WQ_UNBOUND)
-
-int
-fmr_alloc_recovery_wq(void)
-{
-	fmr_recovery_wq = alloc_workqueue("fmr_recovery", WQ_UNBOUND, 0);
-	return !fmr_recovery_wq ? -ENOMEM : 0;
-}
-
-void
-fmr_destroy_recovery_wq(void)
-{
-	struct workqueue_struct *wq;
-
-	if (!fmr_recovery_wq)
-		return;
-
-	wq = fmr_recovery_wq;
-	fmr_recovery_wq = NULL;
-	destroy_workqueue(wq);
-}
-
 static int
 __fmr_init(struct rpcrdma_mw *mw, struct ib_pd *pd)
 {
@@ -115,66 +84,56 @@ __fmr_unmap(struct rpcrdma_mw *mw)
 	return rc;
 }
 
-static void
-__fmr_dma_unmap(struct rpcrdma_mw *mw)
-{
-	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
-
-	ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,
-			mw->mw_sg, mw->mw_nents, mw->mw_dir);
-	rpcrdma_put_mw(r_xprt, mw);
-}
-
-static void
-__fmr_reset_and_unmap(struct rpcrdma_mw *mw)
-{
-	int rc;
-
-	/* ORDER */
-	rc = __fmr_unmap(mw);
-	if (rc) {
-		pr_warn("rpcrdma: ib_unmap_fmr status %d, fmr %p orphaned\n",
-			rc, mw);
-		return;
-	}
-	__fmr_dma_unmap(mw);
-}
-
 static void
 __fmr_release(struct rpcrdma_mw *r)
 {
+	LIST_HEAD(unmap_list);
 	int rc;
 
 	kfree(r->fmr.fm_physaddrs);
 	kfree(r->mw_sg);
 
+	/* In case this one was left mapped, try to unmap it
+	 * to prevent dealloc_fmr from failing with EBUSY
+	 */
+	rc = __fmr_unmap(r);
+	if (rc)
+		pr_err("rpcrdma: final ib_unmap_fmr for %p failed %i\n",
+		       r, rc);
+
 	rc = ib_dealloc_fmr(r->fmr.fm_mr);
 	if (rc)
 		pr_err("rpcrdma: final ib_dealloc_fmr for %p returned %i\n",
 		       r, rc);
 }
 
-/* Deferred reset of a single FMR. Generate a fresh rkey by
- * replacing the MR. There's no recovery if this fails.
+/* Reset of a single FMR.
+ *
+ * There's no recovery if this fails. The FMR is abandoned, but
+ * remains in rb_all. It will be cleaned up when the transport is
+ * destroyed.
  */
 static void
-__fmr_recovery_worker(struct work_struct *work)
+fmr_op_recover_mr(struct rpcrdma_mw *mw)
 {
-	struct rpcrdma_mw *mw = container_of(work, struct rpcrdma_mw,
-					     mw_work);
+	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
+	int rc;
 
-	__fmr_reset_and_unmap(mw);
-	return;
-}
+	/* ORDER: invalidate first */
+	rc = __fmr_unmap(mw);
 
-/* A broken MR was discovered in a context that can't sleep.
- * Defer recovery to the recovery worker.
- */
-static void
-__fmr_queue_recovery(struct rpcrdma_mw *mw)
-{
-	INIT_WORK(&mw->mw_work, __fmr_recovery_worker);
-	queue_work(fmr_recovery_wq, &mw->mw_work);
+	/* ORDER: then DMA unmap */
+	ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,
+			mw->mw_sg, mw->mw_nents, mw->mw_dir);
+	if (rc) {
+		pr_err("rpcrdma: FMR reset status %d, %p orphaned\n",
+		       rc, mw);
+		r_xprt->rx_stats.mrs_orphaned++;
+		return;
+	}
+
+	rpcrdma_put_mw(r_xprt, mw);
+	r_xprt->rx_stats.mrs_recovered++;
 }
 
 static int
@@ -245,16 +204,11 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 
 	mw = seg1->rl_mw;
 	seg1->rl_mw = NULL;
-	if (!mw) {
-		mw = rpcrdma_get_mw(r_xprt);
-		if (!mw)
-			return -ENOMEM;
-	} else {
-		/* this is a retransmit; generate a fresh rkey */
-		rc = __fmr_unmap(mw);
-		if (rc)
-			return rc;
-	}
+	if (mw)
+		rpcrdma_defer_mr_recovery(mw);
+	mw = rpcrdma_get_mw(r_xprt);
+	if (!mw)
+		return -ENOMEM;
 
 	pageoff = offset_in_page(seg1->mr_offset);
 	seg1->mr_offset -= pageoff;	/* start of page */
@@ -309,7 +263,7 @@ out_maperr:
 	pr_err("rpcrdma: ib_map_phys_fmr %u@0x%llx+%i (%d) status %i\n",
 	       len, (unsigned long long)dma_pages[0],
 	       pageoff, mw->mw_nents, rc);
-	__fmr_dma_unmap(mw);
+	rpcrdma_defer_mr_recovery(mw);
 	return rc;
 }
 
@@ -332,7 +286,7 @@ fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	/* ORDER: Invalidate all of the req's MRs first
 	 *
 	 * ib_unmap_fmr() is slow, so use a single call instead
-	 * of one call per mapped MR.
+	 * of one call per mapped FMR.
 	 */
 	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
 		seg = &req->rl_segments[i];
@@ -344,7 +298,7 @@ fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	}
 	rc = ib_unmap_fmr(&unmap_list);
 	if (rc)
-		pr_warn("%s: ib_unmap_fmr failed (%i)\n", __func__, rc);
+		goto out_reset;
 
 	/* ORDER: Now DMA unmap all of the req's MRs, and return
 	 * them to the free MW list.
@@ -354,7 +308,9 @@ fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 		mw = seg->rl_mw;
 
 		list_del_init(&mw->fmr.fm_mr->list);
-		__fmr_dma_unmap(mw);
+		ib_dma_unmap_sg(r_xprt->rx_ia.ri_device,
+				mw->mw_sg, mw->mw_nents, mw->mw_dir);
+		rpcrdma_put_mw(r_xprt, mw);
 
 		i += seg->mr_nsegs;
 		seg->mr_nsegs = 0;
@@ -362,6 +318,20 @@ fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	}
 
 	req->rl_nchunks = 0;
+	return;
+
+out_reset:
+	pr_err("rpcrdma: ib_unmap_fmr failed (%i)\n", rc);
+
+	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
+		seg = &req->rl_segments[i];
+		mw = seg->rl_mw;
+
+		list_del_init(&mw->fmr.fm_mr->list);
+		fmr_op_recover_mr(mw);
+
+		i += seg->mr_nsegs;
+	}
 }
 
 /* Use a slow, safe mechanism to invalidate all memory regions
@@ -380,9 +350,9 @@ fmr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		mw = seg->rl_mw;
 
 		if (sync)
-			__fmr_reset_and_unmap(mw);
+			fmr_op_recover_mr(mw);
 		else
-			__fmr_queue_recovery(mw);
+			rpcrdma_defer_mr_recovery(mw);
 
 		i += seg->mr_nsegs;
 		seg->mr_nsegs = 0;
@@ -407,6 +377,7 @@ const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
 	.ro_map				= fmr_op_map,
 	.ro_unmap_sync			= fmr_op_unmap_sync,
 	.ro_unmap_safe			= fmr_op_unmap_safe,
+	.ro_recover_mr			= fmr_op_recover_mr,
 	.ro_open			= fmr_op_open,
 	.ro_maxpages			= fmr_op_maxpages,
 	.ro_init			= fmr_op_init,

net/sunrpc/xprtrdma/frwr_ops.c

@@ -73,31 +73,6 @@
 # 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);
-}
-
 static int
 __frwr_init(struct rpcrdma_mw *r, struct ib_pd *pd, unsigned int depth)
 {
@@ -168,8 +143,14 @@ __frwr_reset_mr(struct rpcrdma_ia *ia, struct rpcrdma_mw *r)
 	return 0;
 }
 
+/* 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_reset_and_unmap(struct rpcrdma_mw *mw)
+frwr_op_recover_mr(struct rpcrdma_mw *mw)
 {
 	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
@@ -177,35 +158,15 @@ __frwr_reset_and_unmap(struct rpcrdma_mw *mw)
 
 	rc = __frwr_reset_mr(ia, mw);
 	ib_dma_unmap_sg(ia->ri_device, mw->mw_sg, mw->mw_nents, mw->mw_dir);
-	if (rc)
+	if (rc) {
+		pr_err("rpcrdma: FRMR reset status %d, %p orphaned\n",
+		       rc, mw);
+		r_xprt->rx_stats.mrs_orphaned++;
 		return;
-	rpcrdma_put_mw(r_xprt, mw);
-}
-
-/* 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,
-					    mw_work);
-
-	__frwr_reset_and_unmap(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->mw_work, __frwr_recovery_worker);
-	queue_work(frwr_recovery_wq, &r->mw_work);
+	rpcrdma_put_mw(r_xprt, mw);
+	r_xprt->rx_stats.mrs_recovered++;
 }
 
 static int
@@ -401,7 +362,7 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	seg1->rl_mw = NULL;
 	do {
 		if (mw)
-			__frwr_queue_recovery(mw);
+			rpcrdma_defer_mr_recovery(mw);
 		mw = rpcrdma_get_mw(r_xprt);
 		if (!mw)
 			return -ENOMEM;
@@ -483,12 +444,11 @@ out_mapmr_err:
 	pr_err("rpcrdma: failed to map mr %p (%u/%u)\n",
 	       frmr->fr_mr, n, mw->mw_nents);
 	rc = n < 0 ? n : -EIO;
-	__frwr_queue_recovery(mw);
+	rpcrdma_defer_mr_recovery(mw);
 	return rc;
 
 out_senderr:
-	pr_err("rpcrdma: ib_post_send status %i\n", rc);
-	__frwr_queue_recovery(mw);
+	rpcrdma_defer_mr_recovery(mw);
 	return rc;
 }
 
@@ -627,9 +587,9 @@ frwr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		mw = seg->rl_mw;
 
 		if (sync)
-			__frwr_reset_and_unmap(mw);
+			frwr_op_recover_mr(mw);
 		else
-			__frwr_queue_recovery(mw);
+			rpcrdma_defer_mr_recovery(mw);
 
 		i += seg->mr_nsegs;
 		seg->mr_nsegs = 0;
@@ -642,9 +602,6 @@ 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);
@@ -657,6 +614,7 @@ const struct rpcrdma_memreg_ops rpcrdma_frwr_memreg_ops = {
 	.ro_map				= frwr_op_map,
 	.ro_unmap_sync			= frwr_op_unmap_sync,
 	.ro_unmap_safe			= frwr_op_unmap_safe,
+	.ro_recover_mr			= frwr_op_recover_mr,
 	.ro_open			= frwr_op_open,
 	.ro_maxpages			= frwr_op_maxpages,
 	.ro_init			= frwr_op_init,

net/sunrpc/xprtrdma/transport.c

@@ -660,7 +660,7 @@ void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
 		   xprt->stat.bad_xids,
 		   xprt->stat.req_u,
 		   xprt->stat.bklog_u);
-	seq_printf(seq, "%lu %lu %lu %llu %llu %llu %llu %lu %lu %lu %lu\n",
+	seq_printf(seq, "%lu %lu %lu %llu %llu %llu %llu %lu %lu %lu %lu ",
 		   r_xprt->rx_stats.read_chunk_count,
 		   r_xprt->rx_stats.write_chunk_count,
 		   r_xprt->rx_stats.reply_chunk_count,
@@ -672,6 +672,9 @@ void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
 		   r_xprt->rx_stats.failed_marshal_count,
 		   r_xprt->rx_stats.bad_reply_count,
 		   r_xprt->rx_stats.nomsg_call_count);
+	seq_printf(seq, "%lu %lu\n",
+		   r_xprt->rx_stats.mrs_recovered,
+		   r_xprt->rx_stats.mrs_orphaned);
 }
 
 static int
@@ -741,7 +744,6 @@ void xprt_rdma_cleanup(void)
 			__func__, rc);
 
 	rpcrdma_destroy_wq();
-	frwr_destroy_recovery_wq();
 
 	rc = xprt_unregister_transport(&xprt_rdma_bc);
 	if (rc)
@@ -753,20 +755,13 @@ int xprt_rdma_init(void)
 {
 	int rc;
 
-	rc = frwr_alloc_recovery_wq();
-	if (rc)
-		return rc;
-
 	rc = rpcrdma_alloc_wq();
-	if (rc) {
-		frwr_destroy_recovery_wq();
+	if (rc)
 		return rc;
-	}
 
 	rc = xprt_register_transport(&xprt_rdma);
 	if (rc) {
 		rpcrdma_destroy_wq();
-		frwr_destroy_recovery_wq();
 		return rc;
 	}
 
@@ -774,7 +769,6 @@ int xprt_rdma_init(void)
 	if (rc) {
 		xprt_unregister_transport(&xprt_rdma);
 		rpcrdma_destroy_wq();
-		frwr_destroy_recovery_wq();
 		return rc;
 	}
 

net/sunrpc/xprtrdma/verbs.c

@@ -777,6 +777,41 @@ rpcrdma_ep_disconnect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
 	ib_drain_qp(ia->ri_id->qp);
 }
 
+static void
+rpcrdma_mr_recovery_worker(struct work_struct *work)
+{
+	struct rpcrdma_buffer *buf = container_of(work, struct rpcrdma_buffer,
+						  rb_recovery_worker.work);
+	struct rpcrdma_mw *mw;
+
+	spin_lock(&buf->rb_recovery_lock);
+	while (!list_empty(&buf->rb_stale_mrs)) {
+		mw = list_first_entry(&buf->rb_stale_mrs,
+				      struct rpcrdma_mw, mw_list);
+		list_del_init(&mw->mw_list);
+		spin_unlock(&buf->rb_recovery_lock);
+
+		dprintk("RPC:       %s: recovering MR %p\n", __func__, mw);
+		mw->mw_xprt->rx_ia.ri_ops->ro_recover_mr(mw);
+
+		spin_lock(&buf->rb_recovery_lock);
+	};
+	spin_unlock(&buf->rb_recovery_lock);
+}
+
+void
+rpcrdma_defer_mr_recovery(struct rpcrdma_mw *mw)
+{
+	struct rpcrdma_xprt *r_xprt = mw->mw_xprt;
+	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
+
+	spin_lock(&buf->rb_recovery_lock);
+	list_add(&mw->mw_list, &buf->rb_stale_mrs);
+	spin_unlock(&buf->rb_recovery_lock);
+
+	schedule_delayed_work(&buf->rb_recovery_worker, 0);
+}
+
 struct rpcrdma_req *
 rpcrdma_create_req(struct rpcrdma_xprt *r_xprt)
 {
@@ -837,8 +872,12 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
 
 	buf->rb_max_requests = r_xprt->rx_data.max_requests;
 	buf->rb_bc_srv_max_requests = 0;
-	spin_lock_init(&buf->rb_lock);
 	atomic_set(&buf->rb_credits, 1);
+	spin_lock_init(&buf->rb_lock);
+	spin_lock_init(&buf->rb_recovery_lock);
+	INIT_LIST_HEAD(&buf->rb_stale_mrs);
+	INIT_DELAYED_WORK(&buf->rb_recovery_worker,
+			  rpcrdma_mr_recovery_worker);
 
 	rc = ia->ri_ops->ro_init(r_xprt);
 	if (rc)
@@ -923,6 +962,8 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
 {
 	struct rpcrdma_ia *ia = rdmab_to_ia(buf);
 
+	cancel_delayed_work_sync(&buf->rb_recovery_worker);
+
 	while (!list_empty(&buf->rb_recv_bufs)) {
 		struct rpcrdma_rep *rep;
 

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -245,7 +245,6 @@ struct rpcrdma_mw {
 		struct rpcrdma_fmr	fmr;
 		struct rpcrdma_frmr	frmr;
 	};
-	struct work_struct	mw_work;
 	struct rpcrdma_xprt	*mw_xprt;
 	struct list_head	mw_all;
 };
@@ -341,6 +340,10 @@ struct rpcrdma_buffer {
 	struct list_head	rb_allreqs;
 
 	u32			rb_bc_max_requests;
+
+	spinlock_t		rb_recovery_lock; /* protect rb_stale_mrs */
+	struct list_head	rb_stale_mrs;
+	struct delayed_work	rb_recovery_worker;
 };
 #define rdmab_to_ia(b) (&container_of((b), struct rpcrdma_xprt, rx_buf)->rx_ia)
 
@@ -387,6 +390,8 @@ struct rpcrdma_stats {
 	unsigned long		bad_reply_count;
 	unsigned long		nomsg_call_count;
 	unsigned long		bcall_count;
+	unsigned long		mrs_recovered;
+	unsigned long		mrs_orphaned;
 };
 
 /*
@@ -400,6 +405,7 @@ struct rpcrdma_memreg_ops {
 					 struct rpcrdma_req *);
 	void		(*ro_unmap_safe)(struct rpcrdma_xprt *,
 					 struct rpcrdma_req *, bool);
+	void		(*ro_recover_mr)(struct rpcrdma_mw *);
 	int		(*ro_open)(struct rpcrdma_ia *,
 				   struct rpcrdma_ep *,
 				   struct rpcrdma_create_data_internal *);
@@ -477,6 +483,8 @@ void rpcrdma_buffer_put(struct rpcrdma_req *);
 void rpcrdma_recv_buffer_get(struct rpcrdma_req *);
 void rpcrdma_recv_buffer_put(struct rpcrdma_rep *);
 
+void rpcrdma_defer_mr_recovery(struct rpcrdma_mw *);
+
 struct rpcrdma_regbuf *rpcrdma_alloc_regbuf(struct rpcrdma_ia *,
 					    size_t, gfp_t);
 void rpcrdma_free_regbuf(struct rpcrdma_ia *,
@@ -484,9 +492,6 @@ void rpcrdma_free_regbuf(struct rpcrdma_ia *,
 
 int rpcrdma_ep_post_extra_recv(struct rpcrdma_xprt *, unsigned int);
 
-int frwr_alloc_recovery_wq(void);
-void frwr_destroy_recovery_wq(void);
-
 int rpcrdma_alloc_wq(void);
 void rpcrdma_destroy_wq(void);