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authorChuck Lever <chuck.lever@oracle.com>2019-06-19 10:32:48 -0400
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2019-07-09 10:30:16 -0400
commit05eb06d86685e7d9dac60e6bbb46d7f4c30b056e (patch)
tree8f04bce3b88e16afd6912e44681b80752721c171 /net/sunrpc
parent1310051c720a83c5717658bcbff710b260f2bff9 (diff)
downloadlinux-05eb06d86685e7d9dac60e6bbb46d7f4c30b056e.tar.bz2
xprtrdma: Fix occasional transport deadlock
Under high I/O workloads, I've noticed that an RPC/RDMA transport occasionally deadlocks (IOPS goes to zero, and doesn't recover). Diagnosis shows that the sendctx queue is empty, but when sendctxs are returned to the queue, the xprt_write_space wake-up never occurs. The wake-up logic in rpcrdma_sendctx_put_locked is racy. I noticed that both EMPTY_SCQ and XPRT_WRITE_SPACE are implemented via an atomic bit. Just one of those is sufficient. Removing EMPTY_SCQ in favor of the generic bit mechanism makes the deadlock un-reproducible. Without EMPTY_SCQ, rpcrdma_buffer::rb_flags is no longer used and is therefore removed. Unfortunately this patch does not apply cleanly to stable. If needed, someone will have to port it and test it. Fixes: 2fad659209d5 ("xprtrdma: Wait on empty sendctx queue") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc')
-rw-r--r--net/sunrpc/xprtrdma/frwr_ops.c6
-rw-r--r--net/sunrpc/xprtrdma/rpc_rdma.c26
-rw-r--r--net/sunrpc/xprtrdma/verbs.c11
-rw-r--r--net/sunrpc/xprtrdma/xprt_rdma.h6
4 files changed, 20 insertions, 29 deletions
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 794ba4ca0994..ac47314fb751 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -391,7 +391,7 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
rpcrdma_mr_recycle(mr);
mr = rpcrdma_mr_get(r_xprt);
if (!mr)
- return ERR_PTR(-EAGAIN);
+ goto out_getmr_err;
} while (mr->frwr.fr_state != FRWR_IS_INVALID);
frwr = &mr->frwr;
frwr->fr_state = FRWR_IS_VALID;
@@ -448,6 +448,10 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
*out = mr;
return seg;
+out_getmr_err:
+ xprt_wait_for_buffer_space(&r_xprt->rx_xprt);
+ return ERR_PTR(-EAGAIN);
+
out_dmamap_err:
mr->mr_dir = DMA_NONE;
trace_xprtrdma_frwr_sgerr(mr, i);
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 97bfb804b6c6..59b214ba8813 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -699,22 +699,28 @@ rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_req *req, u32 hdrlen,
struct xdr_buf *xdr, enum rpcrdma_chunktype rtype)
{
+ int ret;
+
+ ret = -EAGAIN;
req->rl_sendctx = rpcrdma_sendctx_get_locked(r_xprt);
if (!req->rl_sendctx)
- return -EAGAIN;
+ goto err;
req->rl_sendctx->sc_wr.num_sge = 0;
req->rl_sendctx->sc_unmap_count = 0;
req->rl_sendctx->sc_req = req;
__clear_bit(RPCRDMA_REQ_F_TX_RESOURCES, &req->rl_flags);
+ ret = -EIO;
if (!rpcrdma_prepare_hdr_sge(r_xprt, req, hdrlen))
- return -EIO;
-
+ goto err;
if (rtype != rpcrdma_areadch)
if (!rpcrdma_prepare_msg_sges(r_xprt, req, xdr, rtype))
- return -EIO;
-
+ goto err;
return 0;
+
+err:
+ trace_xprtrdma_prepsend_failed(&req->rl_slot, ret);
+ return ret;
}
/**
@@ -877,15 +883,7 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
out_err:
trace_xprtrdma_marshal_failed(rqst, ret);
- switch (ret) {
- case -EAGAIN:
- xprt_wait_for_buffer_space(rqst->rq_xprt);
- break;
- case -ENOBUFS:
- break;
- default:
- r_xprt->rx_stats.failed_marshal_count++;
- }
+ r_xprt->rx_stats.failed_marshal_count++;
return ret;
}
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index e71315e9dca2..0be5a36cacb6 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -901,7 +901,7 @@ out_emptyq:
* completions recently. This is a sign the Send Queue is
* backing up. Cause the caller to pause and try again.
*/
- set_bit(RPCRDMA_BUF_F_EMPTY_SCQ, &buf->rb_flags);
+ xprt_wait_for_buffer_space(&r_xprt->rx_xprt);
r_xprt->rx_stats.empty_sendctx_q++;
return NULL;
}
@@ -936,10 +936,7 @@ rpcrdma_sendctx_put_locked(struct rpcrdma_sendctx *sc)
/* Paired with READ_ONCE */
smp_store_release(&buf->rb_sc_tail, next_tail);
- if (test_and_clear_bit(RPCRDMA_BUF_F_EMPTY_SCQ, &buf->rb_flags)) {
- smp_mb__after_atomic();
- xprt_write_space(&sc->sc_xprt->rx_xprt);
- }
+ xprt_write_space(&sc->sc_xprt->rx_xprt);
}
static void
@@ -977,8 +974,6 @@ rpcrdma_mrs_create(struct rpcrdma_xprt *r_xprt)
r_xprt->rx_stats.mrs_allocated += count;
spin_unlock(&buf->rb_mrlock);
trace_xprtrdma_createmrs(r_xprt, count);
-
- xprt_write_space(&r_xprt->rx_xprt);
}
static void
@@ -990,6 +985,7 @@ rpcrdma_mr_refresh_worker(struct work_struct *work)
rx_buf);
rpcrdma_mrs_create(r_xprt);
+ xprt_write_space(&r_xprt->rx_xprt);
}
/**
@@ -1089,7 +1085,6 @@ int rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
int i, rc;
- buf->rb_flags = 0;
buf->rb_max_requests = r_xprt->rx_ep.rep_max_requests;
buf->rb_bc_srv_max_requests = 0;
spin_lock_init(&buf->rb_mrlock);
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index d1e0749bcbc4..2c6c5d8c3de1 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -391,7 +391,6 @@ struct rpcrdma_buffer {
struct list_head rb_recv_bufs;
struct list_head rb_allreqs;
- unsigned long rb_flags;
u32 rb_max_requests;
u32 rb_credits; /* most recent credit grant */
@@ -402,11 +401,6 @@ struct rpcrdma_buffer {
struct delayed_work rb_refresh_worker;
};
-/* rb_flags */
-enum {
- RPCRDMA_BUF_F_EMPTY_SCQ = 0,
-};
-
/*
* Statistics for RPCRDMA
*/