[PATCH 5.4 109/155] afs: Fix handling of an abort from a service handler

Greg Kroah-Hartman
2020-03-31T09:18:37Z

From: David Howells <dhowells@redhat.com>

commit dde9f095583b3f375ba23979045ee10dfcebec2f upstream.

When an AFS service handler function aborts a call, AF_RXRPC marks the call
as complete - which means that it's not going to get any more packets from
the receiver. This is a problem because reception of the final ACK is what
triggers afs_deliver_to_call() to drop the final ref on the afs_call
object.

Instead, aborted AFS service calls may then just sit around waiting for
ever or until they're displaced by a new call on the same connection
channel or a connection-level abort.

Fix this by calling afs_set_call_complete() to finalise the afs_call struct
representing the call.

However, we then need to drop the ref that stops the call from being
deallocated. We can do this in afs_set_call_complete(), as the work queue
is holding a separate ref of its own, but then we shouldn't do it in
afs_process_async_call() and afs_delete_async_call().

call->drop_ref is set to indicate that a ref needs dropping for a call and
this is dealt with when we transition a call to AFS_CALL_COMPLETE.

But then we also need to get rid of the ref that pins an asynchronous
client call. We can do this by the same mechanism, setting call->drop_ref
for an async client call too.

We can also get rid of call->incoming since nothing ever sets it and only
one thing ever checks it (futilely).

A trace of the rxrpc_call and afs_call struct ref counting looks like:

<idle>-0 [001] ..s5 164.764892: rxrpc_call: c=00000002 SEE u=3 sp=rxrpc_new_incoming_call+0x473/0xb34 a=00000000442095b5
<idle>-0 [001] .Ns5 164.766001: rxrpc_call: c=00000002 QUE u=4 sp=rxrpc_propose_ACK+0xbe/0x551 a=00000000442095b5
<idle>-0 [001] .Ns4 164.766005: rxrpc_call: c=00000002 PUT u=3 sp=rxrpc_new_incoming_call+0xa3f/0xb34 a=00000000442095b5
<idle>-0 [001] .Ns7 164.766433: afs_call: c=00000002 WAKE u=2 o=11 sp=rxrpc_notify_socket+0x196/0x33c
kworker/1:2-1810 [001] ...1 164.768409: rxrpc_call: c=00000002 SEE u=3 sp=rxrpc_process_call+0x25/0x7ae a=00000000442095b5
kworker/1:2-1810 [001] ...1 164.769439: rxrpc_tx_packet: c=00000002 e9f1a7a8:95786a88:00000008:09c5 00000001 00000000 02 22 ACK CallAck
kworker/1:2-1810 [001] ...1 164.769459: rxrpc_call: c=00000002 PUT u=2 sp=rxrpc_process_call+0x74f/0x7ae a=00000000442095b5
kworker/1:2-1810 [001] ...1 164.770794: afs_call: c=00000002 QUEUE u=3 o=12 sp=afs_deliver_to_call+0x449/0x72c
kworker/1:2-1810 [001] ...1 164.770829: afs_call: c=00000002 PUT u=2 o=12 sp=afs_process_async_call+0xdb/0x11e
kworker/1:2-1810 [001] ...2 164.771084: rxrpc_abort: c=00000002 95786a88:00000008 s=0 a=1 e=1 K-1
kworker/1:2-1810 [001] ...1 164.771461: rxrpc_tx_packet: c=00000002 e9f1a7a8:95786a88:00000008:09c5 00000002 00000000 04 00 ABORT CallAbort
kworker/1:2-1810 [001] ...1 164.771466: afs_call: c=00000002 PUT u=1 o=12 sp=SRXAFSCB_ProbeUuid+0xc1/0x106

The abort generated in SRXAFSCB_ProbeUuid(), labelled "K-1", indicates that
the local filesystem/cache manager didn't recognise the UUID as its own.

Fixes: 2067b2b3f484 ("afs: Fix the CB.ProbeUuid service handler to reply correctly")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/afs/cmservice.c | 14 ++++++++++++--
fs/afs/internal.h | 12 ++++++++++--
fs/afs/rxrpc.c | 33 ++++-----------------------------
3 files changed, 26 insertions(+), 33 deletions(-)

--- a/fs/afs/cmservice.c
+++ b/fs/afs/cmservice.c
@@ -244,6 +244,17 @@ static void afs_cm_destructor(struct afs
}

/*
+ * Abort a service call from within an action function.
+ */
+static void afs_abort_service_call(struct afs_call *call, u32 abort_code, int error,
+ const char *why)
+{
+ rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
+ abort_code, error, why);
+ afs_set_call_complete(call, error, 0);
+}
+
+/*
* The server supplied a list of callbacks that it wanted to break.
*/
static void SRXAFSCB_CallBack(struct work_struct *work)
@@ -510,8 +521,7 @@ static void SRXAFSCB_ProbeUuid(struct wo
if (memcmp(r, &call->net->uuid, sizeof(call->net->uuid)) == 0)
afs_send_empty_reply(call);
else
- rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
- 1, 1, "K-1");
+ afs_abort_service_call(call, 1, 1, "K-1");

afs_put_call(call);
_leave("");
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -154,7 +154,7 @@ struct afs_call {
};
unsigned char unmarshall; /* unmarshalling phase */
unsigned char addr_ix; /* Address in ->alist */
- bool incoming; /* T if incoming call */
+ bool drop_ref; /* T if need to drop ref for incoming call */
bool send_pages; /* T if data from mapping should be sent */
bool need_attention; /* T if RxRPC poked us */
bool async; /* T if asynchronous */
@@ -1203,8 +1203,16 @@ static inline void afs_set_call_complete
ok = true;
}
spin_unlock_bh(&call->state_lock);
- if (ok)
+ if (ok) {
trace_afs_call_done(call);
+
+ /* Asynchronous calls have two refs to release - one from the alloc and
+ * one queued with the work item - and we can't just deallocate the
+ * call because the work item may be queued again.
+ */
+ if (call->drop_ref)
+ afs_put_call(call);
+ }
}

/*
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -18,7 +18,6 @@ struct workqueue_struct *afs_async_calls

static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_wake_up_async_call(struct sock *, struct rxrpc_call *, unsigned long);
-static void afs_delete_async_call(struct work_struct *);
static void afs_process_async_call(struct work_struct *);
static void afs_rx_new_call(struct sock *, struct rxrpc_call *, unsigned long);
static void afs_rx_discard_new_call(struct rxrpc_call *, unsigned long);
@@ -402,8 +401,10 @@ void afs_make_call(struct afs_addr_curso
/* If the call is going to be asynchronous, we need an extra ref for
* the call to hold itself so the caller need not hang on to its ref.
*/
- if (call->async)
+ if (call->async) {
afs_get_call(call, afs_call_trace_get);
+ call->drop_ref = true;
+ }

/* create a call */
rxcall = rxrpc_kernel_begin_call(call->net->socket, srx, call->key,
@@ -584,8 +585,6 @@ static void afs_deliver_to_call(struct a
done:
if (call->type->done)
call->type->done(call);
- if (state == AFS_CALL_COMPLETE && call->incoming)
- afs_put_call(call);
out:
_leave("");
return;
@@ -745,21 +744,6 @@ static void afs_wake_up_async_call(struc
}

/*
- * Delete an asynchronous call. The work item carries a ref to the call struct
- * that we need to release.
- */
-static void afs_delete_async_call(struct work_struct *work)
-{
- struct afs_call *call = container_of(work, struct afs_call, async_work);
-
- _enter("");
-
- afs_put_call(call);
-
- _leave("");
-}
-
-/*
* Perform I/O processing on an asynchronous call. The work item carries a ref
* to the call struct that we either need to release or to pass on.
*/
@@ -774,16 +758,6 @@ static void afs_process_async_call(struc
afs_deliver_to_call(call);
}

- if (call->state == AFS_CALL_COMPLETE) {
- /* We have two refs to release - one from the alloc and one
- * queued with the work item - and we can't just deallocate the
- * call because the work item may be queued again.
- */
- call->async_work.func = afs_delete_async_call;
- if (!queue_work(afs_async_calls, &call->async_work))
- afs_put_call(call);
- }
-
afs_put_call(call);
_leave("");
}
@@ -810,6 +784,7 @@ void afs_charge_preallocation(struct wor
if (!call)
break;

+ call->drop_ref = true;
call->async = true;
call->state = AFS_CALL_SV_AWAIT_OP_ID;
init_waitqueue_head(&call->waitq);