rxrpc: Impose a maximum number of client calls
Impose a maximum on the number of client rxrpc calls that are allowed
simultaneously. This will be in lieu of a maximum number of client
connections as this is easier to administed as, unlike connections, calls
aren't reusable (to be changed in a subsequent patch)..
This doesn't affect the limits on service calls and connections.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index a40fae0..c8015c7 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -41,6 +41,11 @@ const char *const rxrpc_call_completions[NR__RXRPC_CALL_COMPLETIONS] = {
struct kmem_cache *rxrpc_call_jar;
+static struct semaphore rxrpc_call_limiter =
+ __SEMAPHORE_INITIALIZER(rxrpc_call_limiter, 1000);
+static struct semaphore rxrpc_kernel_call_limiter =
+ __SEMAPHORE_INITIALIZER(rxrpc_kernel_call_limiter, 1000);
+
static void rxrpc_call_timer_expired(struct timer_list *t)
{
struct rxrpc_call *call = from_timer(call, t, timer);
@@ -210,6 +215,34 @@ static void rxrpc_start_call_timer(struct rxrpc_call *call)
}
/*
+ * Wait for a call slot to become available.
+ */
+static struct semaphore *rxrpc_get_call_slot(struct rxrpc_call_params *p, gfp_t gfp)
+{
+ struct semaphore *limiter = &rxrpc_call_limiter;
+
+ if (p->kernel)
+ limiter = &rxrpc_kernel_call_limiter;
+ if (p->interruptibility == RXRPC_UNINTERRUPTIBLE) {
+ down(limiter);
+ return limiter;
+ }
+ return down_interruptible(limiter) < 0 ? NULL : limiter;
+}
+
+/*
+ * Release a call slot.
+ */
+static void rxrpc_put_call_slot(struct rxrpc_call *call)
+{
+ struct semaphore *limiter = &rxrpc_call_limiter;
+
+ if (test_bit(RXRPC_CALL_KERNEL, &call->flags))
+ limiter = &rxrpc_kernel_call_limiter;
+ up(limiter);
+}
+
+/*
* Set up a call for the given parameters.
* - Called with the socket lock held, which it must release.
* - If it returns a call, the call's lock will need releasing by the caller.
@@ -225,15 +258,21 @@ struct rxrpc_call *rxrpc_new_client_call(struct rxrpc_sock *rx,
{
struct rxrpc_call *call, *xcall;
struct rxrpc_net *rxnet;
+ struct semaphore *limiter;
struct rb_node *parent, **pp;
const void *here = __builtin_return_address(0);
int ret;
_enter("%p,%lx", rx, p->user_call_ID);
+ limiter = rxrpc_get_call_slot(p, gfp);
+ if (!limiter)
+ return ERR_PTR(-ERESTARTSYS);
+
call = rxrpc_alloc_client_call(rx, srx, gfp, debug_id);
if (IS_ERR(call)) {
release_sock(&rx->sk);
+ up(limiter);
_leave(" = %ld", PTR_ERR(call));
return call;
}
@@ -243,6 +282,8 @@ struct rxrpc_call *rxrpc_new_client_call(struct rxrpc_sock *rx,
trace_rxrpc_call(call->debug_id, rxrpc_call_new_client,
atomic_read(&call->usage),
here, (const void *)p->user_call_ID);
+ if (p->kernel)
+ __set_bit(RXRPC_CALL_KERNEL, &call->flags);
/* We need to protect a partially set up call against the user as we
* will be acting outside the socket lock.
@@ -471,6 +512,8 @@ void rxrpc_release_call(struct rxrpc_sock *rx, struct rxrpc_call *call)
BUG();
spin_unlock_bh(&call->lock);
+ rxrpc_put_call_slot(call);
+
del_timer_sync(&call->timer);
/* Make sure we don't get any more notifications */