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authorChuck Lever <chuck.lever@oracle.com>2016-09-06 11:22:58 -0400
committerTrond Myklebust <trond.myklebust@primarydata.com>2016-09-06 15:59:35 -0400
commit05c974669ecec510a85d8534099bb75404e82c41 (patch)
tree8f35a5f3dfa7f9b98781c1026e17b26c5e716097 /net
parent78d506e1b7071b24850fd5ac22b896c459b0a04c (diff)
downloadlinux-stericsson-05c974669ecec510a85d8534099bb75404e82c41.tar.gz
xprtrdma: Fix receive buffer accounting
An RPC can terminate before its reply arrives, if a credential problem or a soft timeout occurs. After this happens, xprtrdma reports it is out of Receive buffers. A Receive buffer is posted before each RPC is sent, and returned to the buffer pool when a reply is received. If no reply is received for an RPC, that Receive buffer remains posted. But xprtrdma tries to post another when the next RPC is sent. If this happens a few dozen times, there are no receive buffers left to be posted at send time. I don't see a way for a transport connection to recover at that point, and it will spit warnings and unnecessarily delay RPCs on occasion for its remaining lifetime. Commit 1e465fd4ff47 ("xprtrdma: Replace send and receive arrays") removed a little bit of logic to detect this case and not provide a Receive buffer so no more buffers are posted, and then transport operation continues correctly. We didn't understand what that logic did, and it wasn't commented, so it was removed as part of the overhaul to support backchannel requests. Restore it, but be wary of the need to keep extra Receives posted to deal with backchannel requests. Fixes: 1e465fd4ff47 ("xprtrdma: Replace send and receive arrays") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'net')
-rw-r--r--net/sunrpc/xprtrdma/verbs.c41
-rw-r--r--net/sunrpc/xprtrdma/xprt_rdma.h1
2 files changed, 30 insertions, 12 deletions
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index fefcba982415..799cce6cbe45 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -51,6 +51,7 @@
#include <linux/slab.h>
#include <linux/prefetch.h>
#include <linux/sunrpc/addr.h>
+#include <linux/sunrpc/svc_rdma.h>
#include <asm/bitops.h>
#include <linux/module.h> /* try_module_get()/module_put() */
@@ -923,7 +924,7 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
}
INIT_LIST_HEAD(&buf->rb_recv_bufs);
- for (i = 0; i < buf->rb_max_requests + 2; i++) {
+ for (i = 0; i < buf->rb_max_requests + RPCRDMA_MAX_BC_REQUESTS; i++) {
struct rpcrdma_rep *rep;
rep = rpcrdma_create_rep(r_xprt);
@@ -1018,6 +1019,7 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
rep = rpcrdma_buffer_get_rep_locked(buf);
rpcrdma_destroy_rep(ia, rep);
}
+ buf->rb_send_count = 0;
spin_lock(&buf->rb_reqslock);
while (!list_empty(&buf->rb_allreqs)) {
@@ -1032,6 +1034,7 @@ rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
spin_lock(&buf->rb_reqslock);
}
spin_unlock(&buf->rb_reqslock);
+ buf->rb_recv_count = 0;
rpcrdma_destroy_mrs(buf);
}
@@ -1074,6 +1077,23 @@ rpcrdma_put_mw(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mw *mw)
spin_unlock(&buf->rb_mwlock);
}
+static struct rpcrdma_rep *
+rpcrdma_buffer_get_rep(struct rpcrdma_buffer *buffers)
+{
+ /* If an RPC previously completed without a reply (say, a
+ * credential problem or a soft timeout occurs) then hold off
+ * on supplying more Receive buffers until the number of new
+ * pending RPCs catches up to the number of posted Receives.
+ */
+ if (unlikely(buffers->rb_send_count < buffers->rb_recv_count))
+ return NULL;
+
+ if (unlikely(list_empty(&buffers->rb_recv_bufs)))
+ return NULL;
+ buffers->rb_recv_count++;
+ return rpcrdma_buffer_get_rep_locked(buffers);
+}
+
/*
* Get a set of request/reply buffers.
*
@@ -1087,10 +1107,9 @@ rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
spin_lock(&buffers->rb_lock);
if (list_empty(&buffers->rb_send_bufs))
goto out_reqbuf;
+ buffers->rb_send_count++;
req = rpcrdma_buffer_get_req_locked(buffers);
- if (list_empty(&buffers->rb_recv_bufs))
- goto out_repbuf;
- req->rl_reply = rpcrdma_buffer_get_rep_locked(buffers);
+ req->rl_reply = rpcrdma_buffer_get_rep(buffers);
spin_unlock(&buffers->rb_lock);
return req;
@@ -1098,11 +1117,6 @@ out_reqbuf:
spin_unlock(&buffers->rb_lock);
pr_warn("RPC: %s: out of request buffers\n", __func__);
return NULL;
-out_repbuf:
- spin_unlock(&buffers->rb_lock);
- pr_warn("RPC: %s: out of reply buffers\n", __func__);
- req->rl_reply = NULL;
- return req;
}
/*
@@ -1119,9 +1133,12 @@ rpcrdma_buffer_put(struct rpcrdma_req *req)
req->rl_reply = NULL;
spin_lock(&buffers->rb_lock);
+ buffers->rb_send_count--;
list_add_tail(&req->rl_free, &buffers->rb_send_bufs);
- if (rep)
+ if (rep) {
+ buffers->rb_recv_count--;
list_add_tail(&rep->rr_list, &buffers->rb_recv_bufs);
+ }
spin_unlock(&buffers->rb_lock);
}
@@ -1135,8 +1152,7 @@ rpcrdma_recv_buffer_get(struct rpcrdma_req *req)
struct rpcrdma_buffer *buffers = req->rl_buffer;
spin_lock(&buffers->rb_lock);
- if (!list_empty(&buffers->rb_recv_bufs))
- req->rl_reply = rpcrdma_buffer_get_rep_locked(buffers);
+ req->rl_reply = rpcrdma_buffer_get_rep(buffers);
spin_unlock(&buffers->rb_lock);
}
@@ -1150,6 +1166,7 @@ rpcrdma_recv_buffer_put(struct rpcrdma_rep *rep)
struct rpcrdma_buffer *buffers = &rep->rr_rxprt->rx_buf;
spin_lock(&buffers->rb_lock);
+ buffers->rb_recv_count--;
list_add_tail(&rep->rr_list, &buffers->rb_recv_bufs);
spin_unlock(&buffers->rb_lock);
}
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 670fad57153a..a71b0f5897d8 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -321,6 +321,7 @@ struct rpcrdma_buffer {
char *rb_pool;
spinlock_t rb_lock; /* protect buf lists */
+ int rb_send_count, rb_recv_count;
struct list_head rb_send_bufs;
struct list_head rb_recv_bufs;
u32 rb_max_requests;