SUNRPC: Fix backchannel RPC soft lockups

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Currently, after the forward channel connection goes away,
backchannel operations are causing soft lockups on the server
because call_transmit_status's SOFTCONN logic ignores ENOTCONN.
Such backchannel Calls are aggressively retried until the client
reconnects.

Backchannel Calls should use RPC_TASK_NOCONNECT rather than
RPC_TASK_SOFTCONN. If there is no forward connection, the server is
not capable of establishing a connection back to the client, thus
that backchannel request should fail before the server attempts to
send it. Commit 58255a4e3c ("NFSD: NFSv4 callback client should
use RPC_TASK_SOFTCONN") was merged several years before
RPC_TASK_NOCONNECT was available.

Because setup_callback_client() explicitly sets NOPING, the NFSv4.0
callback connection depends on the first callback RPC to initiate
a connection to the client. Thus NFSv4.0 needs to continue to use
RPC_TASK_SOFTCONN.

Suggested-by: Trond Myklebust <trondmy@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org> # v4.20+

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This commit is contained in:

Chuck Lever 2020-04-17 12:40:31 -04:00

parent 43e33924c3

commit 6221f1d9b6

4 changed files with 8 additions and 1 deletions

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4

fs/nfsd/nfs4callback.c

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2

net/sunrpc/svc_xprt.c

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2

net/sunrpc/xprtrdma/svc_rdma_backchannel.c

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1

net/sunrpc/xprtsock.c

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