xprtrdma: Fix cwnd update ordering

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After a reconnect, the reply handler is opening the cwnd (and thus
enabling more RPC Calls to be sent) /before/ rpcrdma_post_recvs()
can post enough Receive WRs to receive their replies. This causes an
RNR and the new connection is lost immediately.

The race is most clearly exposed when KASAN and disconnect injection
are enabled. This slows down rpcrdma_rep_create() enough to allow
the send side to post a bunch of RPC Calls before the Receive
completion handler can invoke ib_post_recv().

Fixes: 2ae50ad68c ("xprtrdma: Close window between waking RPC senders and posting Receives")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

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Chuck Lever 2021-04-19 14:02:41 -04:00 • committed by Trond Myklebust

parent 9e3ca33b62

commit 35d8b10a25

3 changed files with 8 additions and 7 deletions

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3

net/sunrpc/xprtrdma/rpc_rdma.c

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10

net/sunrpc/xprtrdma/verbs.c

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2

net/sunrpc/xprtrdma/xprt_rdma.h

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