sunrpc: make xprt->swapper an atomic_t
Split xs_swapper into enable/disable functions and eliminate the
"enable" flag.
Currently, it's racy if you have multiple swapon/swapoff operations
running in parallel over the same xprt. Also fix it so that we only
set it to a memalloc socket on a 0->1 transition and only clear it
on a 1->0 transition.
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index f344c0f..6538e6f 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1961,31 +1961,43 @@
struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
xprt);
- if (xprt->swapper)
+ if (atomic_read(&xprt->swapper))
sk_set_memalloc(transport->inet);
}
/**
- * xs_swapper - Tag this transport as being used for swap.
+ * xs_swapper_enable - Tag this transport as being used for swap.
* @xprt: transport to tag
- * @enable: enable/disable
*
+ * Take a reference to this transport on behalf of the rpc_clnt, and
+ * optionally mark it for swapping if it wasn't already.
*/
-int xs_swapper(struct rpc_xprt *xprt, int enable)
+int
+xs_swapper_enable(struct rpc_xprt *xprt)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
xprt);
- int err = 0;
- if (enable) {
- xprt->swapper++;
- xs_set_memalloc(xprt);
- } else if (xprt->swapper) {
- xprt->swapper--;
+ if (atomic_inc_return(&xprt->swapper) == 1)
+ sk_set_memalloc(transport->inet);
+ return 0;
+}
+
+/**
+ * xs_swapper_disable - Untag this transport as being used for swap.
+ * @xprt: transport to tag
+ *
+ * Drop a "swapper" reference to this xprt on behalf of the rpc_clnt. If the
+ * swapper refcount goes to 0, untag the socket as a memalloc socket.
+ */
+void
+xs_swapper_disable(struct rpc_xprt *xprt)
+{
+ struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
+ xprt);
+
+ if (atomic_dec_and_test(&xprt->swapper))
sk_clear_memalloc(transport->inet);
- }
-
- return err;
}
#else
static void xs_set_memalloc(struct rpc_xprt *xprt)