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nfsd41: Fix a crash when a callback is retried 

If a callback is retried at nfsd4_cb_recall_done() due to
some error, the returned rpc reply crashes here:

@@ -514,6 +514,7 @@ decode_cb_sequence(struct xdr_stream *xdr, struct nfsd4_cb_sequence *res,
 	u32 dummy;
 	__be32 *p;

 +	BUG_ON(!res);
 	if (res->cbs_minorversion == 0)
 		return 0;

[BUG_ON added for demonstration]

This is because the nfsd4_cb_done_sequence() has NULLed out
the task->tk_msg.rpc_resp pointer.

Also eventually the rpc would use the new slot without making
sure it is free by calling nfsd41_cb_setup_sequence().

This problem was introduced by a 4.1 protocol addition patch:
	[0421b5c5] nfsd41: Backchannel: Implement cb_recall over NFSv4.1

Which was overlooking the possibility of an RPC callback retries.
For not-4.1 case redoing the _prepare is harmless.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Boaz Harrosh 2010-06-29 14:33:55 +03:00 committed by J. Bruce Fields
parent 774f8bbd9e
commit c18c821fd4
1 changed files with 1 additions and 1 deletions
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2
fs/nfsd/nfs4callback.c
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@ -697,7 +697,7 @@ static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
if (dp->dl_retries--) {
rpc_delay(task, 2*HZ);
task->tk_status = 0;
rpc_restart_call(task);
rpc_restart_call_prepare(task);
return;
} else {
atomic_set(&clp->cl_cb_set, 0);