From 8e2281330f9930bccf77cf04027ec60b6cc0fb34 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 3 Jun 2015 16:14:26 -0400 Subject: [PATCH] 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 Signed-off-by: Jeff Layton Reviewed-by: Chuck Lever Signed-off-by: Trond Myklebust --- include/linux/sunrpc/xprt.h | 5 +++-- net/sunrpc/clnt.c | 4 ++-- net/sunrpc/xprtsock.c | 38 ++++++++++++++++++++++++------------- 3 files changed, 30 insertions(+), 17 deletions(-) diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h index bc9c39d6d30d..9a3308703c15 100644 --- a/include/linux/sunrpc/xprt.h +++ b/include/linux/sunrpc/xprt.h @@ -180,7 +180,7 @@ struct rpc_xprt { atomic_t num_reqs; /* total slots */ unsigned long state; /* transport state */ unsigned char resvport : 1; /* use a reserved port */ - unsigned int swapper; /* we're swapping over this + atomic_t swapper; /* we're swapping over this transport */ unsigned int bind_index; /* bind function index */ @@ -346,7 +346,8 @@ void xprt_release_rqst_cong(struct rpc_task *task); void xprt_disconnect_done(struct rpc_xprt *xprt); void xprt_force_disconnect(struct rpc_xprt *xprt); void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie); -int xs_swapper(struct rpc_xprt *xprt, int enable); +int xs_swapper_enable(struct rpc_xprt *xprt); +void xs_swapper_disable(struct rpc_xprt *xprt); bool xprt_lock_connect(struct rpc_xprt *, struct rpc_task *, void *); void xprt_unlock_connect(struct rpc_xprt *, void *); diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 0ba65156a62b..801044aeeedd 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -2495,7 +2495,7 @@ retry: goto retry; } - ret = xs_swapper(xprt, 1); + ret = xs_swapper_enable(xprt); xprt_put(xprt); } return ret; @@ -2522,7 +2522,7 @@ retry: goto retry; } - xs_swapper(xprt, 0); + xs_swapper_disable(xprt); xprt_put(xprt); } } diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index f344c0f8974c..6538e6fbb7ba 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -1961,31 +1961,43 @@ static void xs_set_memalloc(struct rpc_xprt *xprt) 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--; - sk_clear_memalloc(transport->inet); - } + if (atomic_inc_return(&xprt->swapper) == 1) + sk_set_memalloc(transport->inet); + return 0; +} - return err; +/** + * 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); } #else static void xs_set_memalloc(struct rpc_xprt *xprt) -- 2.39.2