SUNRPC: Set alloc_slot for backchannel tcp ops

commit 84e28a307e376f271505af65a7b7e212dd6f61f4 upstream.

f39c1bfb5a03e2d255451bff05be0d7255298fa4 (SUNRPC: Fix a UDP transport
regression) introduced the "alloc_slot" function for xprt operations,
but never created one for the backchannel operations.  This patch fixes
a null pointer dereference when mounting NFS over v4.1.

Call Trace:
 [<ffffffffa0207957>] ? xprt_reserve+0x47/0x50 [sunrpc]
 [<ffffffffa02023a4>] call_reserve+0x34/0x60 [sunrpc]
 [<ffffffffa020e280>] __rpc_execute+0x90/0x400 [sunrpc]
 [<ffffffffa020e61a>] rpc_async_schedule+0x2a/0x40 [sunrpc]
 [<ffffffff81073589>] process_one_work+0x139/0x500
 [<ffffffff81070e70>] ? alloc_worker+0x70/0x70
 [<ffffffffa020e5f0>] ? __rpc_execute+0x400/0x400 [sunrpc]
 [<ffffffff81073d1e>] worker_thread+0x15e/0x460
 [<ffffffff8145c839>] ? preempt_schedule+0x49/0x70
 [<ffffffff81073bc0>] ? rescuer_thread+0x230/0x230
 [<ffffffff81079603>] kthread+0x93/0xa0
 [<ffffffff81465d04>] kernel_thread_helper+0x4/0x10
 [<ffffffff81079570>] ? kthread_freezable_should_stop+0x70/0x70
 [<ffffffff81465d00>] ? gs_change+0x13/0x13

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 10a385b4181a437c1926e165a9dbbdb3e02391da..d68b653af7bf59065935eb79755e76a9c84236d0 100644 (file)
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -2488,6 +2488,7 @@ static struct rpc_xprt_ops xs_tcp_ops = {
 static struct rpc_xprt_ops bc_tcp_ops = {
        .reserve_xprt           = xprt_reserve_xprt,
        .release_xprt           = xprt_release_xprt,
+       .alloc_slot             = xprt_alloc_slot,
        .buf_alloc              = bc_malloc,
        .buf_free               = bc_free,
        .send_request           = bc_send_request,