From: Chuck Lever <chuck.le...@oracle.com>

[ Upstream commit d698c4a02ee02053bbebe051322ff427a2dad56a ]

The backchannel code uses rpcrdma_recv_buffer_put to add new reps
to the free rep list. This also decrements rb_recv_count, which
spoofs the receive overrun logic in rpcrdma_buffer_get_rep.

Commit 9b06688bc3b9 ("xprtrdma: Fix additional uses of
spin_lock_irqsave(rb_lock)") replaced the original open-coded
list_add with a call to rpcrdma_recv_buffer_put(), but then a year
later, commit 05c974669ece ("xprtrdma: Fix receive buffer
accounting") added rep accounting to rpcrdma_recv_buffer_put.
It was an oversight to let the backchannel continue to use this
function.

The fix this, let's combine the "add to free list" logic with
rpcrdma_create_rep.

Also, do not allocate RPCRDMA_MAX_BC_REQUESTS rpcrdma_reps in
rpcrdma_buffer_create and then allocate additional rpcrdma_reps in
rpcrdma_bc_setup_reps. Allocating the extra reps during backchannel
set-up is sufficient.

Fixes: 05c974669ece ("xprtrdma: Fix receive buffer accounting")
Signed-off-by: Chuck Lever <chuck.le...@oracle.com>
Signed-off-by: Anna Schumaker <anna.schuma...@netapp.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 net/sunrpc/xprtrdma/backchannel.c | 12 ++----------
 net/sunrpc/xprtrdma/verbs.c       | 32 +++++++++++++++++++-------------
 net/sunrpc/xprtrdma/xprt_rdma.h   |  2 +-
 3 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/net/sunrpc/xprtrdma/backchannel.c 
b/net/sunrpc/xprtrdma/backchannel.c
index 8b818bb3518a..256c67b433c1 100644
--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -74,21 +74,13 @@ out_fail:
 static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
                                 unsigned int count)
 {
-       struct rpcrdma_rep *rep;
        int rc = 0;
 
        while (count--) {
-               rep = rpcrdma_create_rep(r_xprt);
-               if (IS_ERR(rep)) {
-                       pr_err("RPC:       %s: reply buffer alloc failed\n",
-                              __func__);
-                       rc = PTR_ERR(rep);
+               rc = rpcrdma_create_rep(r_xprt);
+               if (rc)
                        break;
-               }
-
-               rpcrdma_recv_buffer_put(rep);
        }
-
        return rc;
 }
 
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 8cd7ee4fa0cd..371fbd9b55bb 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1093,10 +1093,17 @@ rpcrdma_create_req(struct rpcrdma_xprt *r_xprt)
        return req;
 }
 
-struct rpcrdma_rep *
+/**
+ * rpcrdma_create_rep - Allocate an rpcrdma_rep object
+ * @r_xprt: controlling transport
+ *
+ * Returns 0 on success or a negative errno on failure.
+ */
+int
 rpcrdma_create_rep(struct rpcrdma_xprt *r_xprt)
 {
        struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
+       struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
        struct rpcrdma_rep *rep;
        int rc;
 
@@ -1121,12 +1128,18 @@ rpcrdma_create_rep(struct rpcrdma_xprt *r_xprt)
        rep->rr_recv_wr.wr_cqe = &rep->rr_cqe;
        rep->rr_recv_wr.sg_list = &rep->rr_rdmabuf->rg_iov;
        rep->rr_recv_wr.num_sge = 1;
-       return rep;
+
+       spin_lock(&buf->rb_lock);
+       list_add(&rep->rr_list, &buf->rb_recv_bufs);
+       spin_unlock(&buf->rb_lock);
+       return 0;
 
 out_free:
        kfree(rep);
 out:
-       return ERR_PTR(rc);
+       dprintk("RPC:       %s: reply buffer %d alloc failed\n",
+               __func__, rc);
+       return rc;
 }
 
 int
@@ -1167,17 +1180,10 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
        }
 
        INIT_LIST_HEAD(&buf->rb_recv_bufs);
-       for (i = 0; i < buf->rb_max_requests + RPCRDMA_MAX_BC_REQUESTS; i++) {
-               struct rpcrdma_rep *rep;
-
-               rep = rpcrdma_create_rep(r_xprt);
-               if (IS_ERR(rep)) {
-                       dprintk("RPC:       %s: reply buffer %d alloc failed\n",
-                               __func__, i);
-                       rc = PTR_ERR(rep);
+       for (i = 0; i <= buf->rb_max_requests; i++) {
+               rc = rpcrdma_create_rep(r_xprt);
+               if (rc)
                        goto out;
-               }
-               list_add(&rep->rr_list, &buf->rb_recv_bufs);
        }
 
        rc = rpcrdma_sendctxs_create(r_xprt);
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 1342f743f1c4..3b63e61feae2 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -564,8 +564,8 @@ int rpcrdma_ep_post_recv(struct rpcrdma_ia *, struct 
rpcrdma_rep *);
  * Buffer calls - xprtrdma/verbs.c
  */
 struct rpcrdma_req *rpcrdma_create_req(struct rpcrdma_xprt *);
-struct rpcrdma_rep *rpcrdma_create_rep(struct rpcrdma_xprt *);
 void rpcrdma_destroy_req(struct rpcrdma_req *);
+int rpcrdma_create_rep(struct rpcrdma_xprt *r_xprt);
 int rpcrdma_buffer_create(struct rpcrdma_xprt *);
 void rpcrdma_buffer_destroy(struct rpcrdma_buffer *);
 struct rpcrdma_sendctx *rpcrdma_sendctx_get_locked(struct rpcrdma_buffer *buf);
-- 
2.15.1

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