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xprtrdma: Release in-flight MRs on disconnect

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Dan Aloni reports that when a server disconnects abruptly, a few
memory regions are left DMA mapped. Over time this leak could pin
enough I/O resources to slow or even deadlock an NFS/RDMA client.

I found that if a transport disconnects before pending Send and
FastReg WRs can be posted, the to-be-registered MRs are stranded on
the req's rl_registered list and never released -- since they
weren't posted, there's no Send completion to DMA unmap them.

Reported-by: Dan Aloni <dan@kernelim.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2020-08-17 11:19:26 -04:00 committed by Anna Schumaker
parent d012a7190f
commit 5de55ce951
1 changed files with 2 additions and 0 deletions
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2
net/sunrpc/xprtrdma/verbs.c
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@ -933,6 +933,8 @@ static void rpcrdma_req_reset(struct rpcrdma_req *req)
rpcrdma_regbuf_dma_unmap(req->rl_sendbuf);
rpcrdma_regbuf_dma_unmap(req->rl_recvbuf);
frwr_reset(req);
}
/* ASSUMPTION: the rb_allreqs list is stable for the duration,