xprtrdma: Acquire MRs in rpcrdma_register_external()

Acquiring 64 MRs in rpcrdma_buffer_get() while holding the buffer
pool lock is expensive, and unnecessary because most modern adapters
can transfer 100s of KBs of payload using just a single MR.

Instead, acquire MRs one-at-a-time as chunks are registered, and
return them to rb_mws immediately during deregistration.

Note: commit 539431a437d2 ("xprtrdma: Don't invalidate FRMRs if
registration fails") is reverted: There is now a valid case where
registration can fail (with -ENOMEM) but the QP is still in RTS.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Reviewed-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index a06d9a3..133edf6 100644 (file)
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -11,6 +11,62 @@
  * 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)
@@ -250,9 +306,9 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
        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;
@@ -261,12 +317,25 @@ 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;
@@ -285,8 +354,6 @@ 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;
@@ -298,6 +365,7 @@ 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;
@@ -307,6 +375,7 @@ 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;
@@ -315,10 +384,9 @@ 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;
 }
 
@@ -330,15 +398,19 @@ 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;
 
-       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);
 
        while (seg1->mr_nsegs--)
@@ -348,12 +420,13 @@ frwr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
        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;
 }
 
@@ -400,6 +473,9 @@ 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);

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 3f422ca..84ea37d 100644 (file)
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -284,9 +284,6 @@ rpcrdma_create_chunks(struct rpc_rqst *rqst, struct xdr_buf *target,
        return (unsigned char *)iptr - (unsigned char *)headerp;
 
 out:
-       if (r_xprt->rx_ia.ri_memreg_strategy == RPCRDMA_FRMR)
-               return n;
-
        for (pos = 0; nchunks--;)
                pos += r_xprt->rx_ia.ri_ops->ro_unmap(r_xprt,
                                                      &req->rl_segments[pos]);

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 3188e36..768bb77 100644 (file)
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1336,12 +1336,11 @@ rpcrdma_buffer_get_frmrs(struct rpcrdma_req *req, struct rpcrdma_buffer *buf,
 struct rpcrdma_req *
 rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
 {
-       struct rpcrdma_ia *ia = rdmab_to_ia(buffers);
-       struct list_head stale;
        struct rpcrdma_req *req;
        unsigned long flags;
 
        spin_lock_irqsave(&buffers->rb_lock, flags);
+
        if (buffers->rb_send_index == buffers->rb_max_requests) {
                spin_unlock_irqrestore(&buffers->rb_lock, flags);
                dprintk("RPC:       %s: out of request buffers\n", __func__);
@@ -1360,17 +1359,7 @@ rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
        }
        buffers->rb_send_bufs[buffers->rb_send_index++] = NULL;
 
-       INIT_LIST_HEAD(&stale);
-       switch (ia->ri_memreg_strategy) {
-       case RPCRDMA_FRMR:
-               req = rpcrdma_buffer_get_frmrs(req, buffers, &stale);
-               break;
-       default:
-               break;
-       }
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
-       if (!list_empty(&stale))
-               rpcrdma_retry_flushed_linv(&stale, buffers);
        return req;
 }
 
@@ -1382,18 +1371,10 @@ void
 rpcrdma_buffer_put(struct rpcrdma_req *req)
 {
        struct rpcrdma_buffer *buffers = req->rl_buffer;
-       struct rpcrdma_ia *ia = rdmab_to_ia(buffers);
        unsigned long flags;
 
        spin_lock_irqsave(&buffers->rb_lock, flags);
        rpcrdma_buffer_put_sendbuf(req, buffers);
-       switch (ia->ri_memreg_strategy) {
-       case RPCRDMA_FRMR:
-               rpcrdma_buffer_put_mrs(req, buffers);
-               break;
-       default:
-               break;
-       }
        spin_unlock_irqrestore(&buffers->rb_lock, flags);
 }