afs: Wait for outstanding async calls before closing rxrpc socket

The afs filesystem needs to wait for any outstanding asynchronous calls
(such as FS.GiveUpCallBacks cleaning up the callbacks lodged with a server)
to complete before closing the AF_RXRPC socket when unloading the module.

This may occur if the module is removed too quickly after unmounting all
filesystems.  This will produce an error report that looks like:

	AFS: Assertion failed
	1 == 0 is false
	0x1 == 0x0 is false
	------------[ cut here ]------------
	kernel BUG at ../fs/afs/rxrpc.c:135!
	...
	RIP: 0010:[<ffffffffa004111c>] afs_close_socket+0xec/0x107 [kafs]
	...
	Call Trace:
	 [<ffffffffa004a160>] afs_exit+0x1f/0x57 [kafs]
	 [<ffffffff810c30a0>] SyS_delete_module+0xec/0x17d
	 [<ffffffff81610417>] entry_SYSCALL_64_fastpath+0x12/0x6b

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index b506428..b4d337a 100644 (file)
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -65,6 +65,12 @@ static void afs_async_workfn(struct work_struct *work)
        call->async_workfn(call);
 }
 
+static int afs_wait_atomic_t(atomic_t *p)
+{
+       schedule();
+       return 0;
+}
+
 /*
  * open an RxRPC socket and bind it to be a server for callback notifications
  * - the socket is left in blocking mode and non-blocking ops use MSG_DONTWAIT
@@ -126,13 +132,16 @@ void afs_close_socket(void)
 {
        _enter("");
 
+       wait_on_atomic_t(&afs_outstanding_calls, afs_wait_atomic_t,
+                        TASK_UNINTERRUPTIBLE);
+       _debug("no outstanding calls");
+
        sock_release(afs_socket);
 
        _debug("dework");
        destroy_workqueue(afs_async_calls);
 
        ASSERTCMP(atomic_read(&afs_outstanding_skbs), ==, 0);
-       ASSERTCMP(atomic_read(&afs_outstanding_calls), ==, 0);
        _leave("");
 }
 
@@ -178,8 +187,6 @@ static void afs_free_call(struct afs_call *call)
 {
        _debug("DONE %p{%s} [%d]",
               call, call->type->name, atomic_read(&afs_outstanding_calls));
-       if (atomic_dec_return(&afs_outstanding_calls) == -1)
-               BUG();
 
        ASSERTCMP(call->rxcall, ==, NULL);
        ASSERT(!work_pending(&call->async_work));
@@ -188,6 +195,9 @@ static void afs_free_call(struct afs_call *call)
 
        kfree(call->request);
        kfree(call);
+
+       if (atomic_dec_and_test(&afs_outstanding_calls))
+               wake_up_atomic_t(&afs_outstanding_calls);
 }
 
 /*