On Sat, 30 May 2015 08:03:13 -0400 Jeff Layton <[email protected]> wrote:
> It's possible that we could race with a call to xs_reset_transport, in > which case the xprt->inet pointer could be zeroed out while we're > accessing it. Lock the xprt before we try to set memalloc on it. > > Cc: Mel Gorman <[email protected]> > Signed-off-by: Jeff Layton <[email protected]> > --- > net/sunrpc/xprtsock.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > index 359446442112..91770ccab608 100644 > --- a/net/sunrpc/xprtsock.c > +++ b/net/sunrpc/xprtsock.c > @@ -1964,11 +1964,22 @@ static void xs_local_connect(struct rpc_xprt *xprt, > struct rpc_task *task) > } > > #ifdef CONFIG_SUNRPC_SWAP > +/* > + * Note that this should be called with XPRT_LOCKED held (or when we > otherwise > + * know that we have exclusive access to the socket), to guard against > + * races with xs_reset_transport. > + */ > static void xs_set_memalloc(struct rpc_xprt *xprt) > { > struct sock_xprt *transport = container_of(xprt, struct sock_xprt, > xprt); > > + /* > + * If there's no sock, then we have nothing to set. The > + * reconnecting process will get it for us. > + */ > + if (!transport->inet) > + return; > if (atomic_read(&xprt->swapper)) > sk_set_memalloc(transport->inet); > } > @@ -1986,8 +1997,11 @@ xs_swapper_enable(struct rpc_xprt *xprt) > struct sock_xprt *transport = container_of(xprt, struct sock_xprt, > xprt); > > + if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE)) > + return -ERESTARTSYS; > if (atomic_inc_return(&xprt->swapper) == 1) > sk_set_memalloc(transport->inet); Oh, we need to check that transport->inet is not NULL before we call sk_set/clear_memalloc on it. I'll respin with that fix once I give everyone a chance to comment on the rest... > + xprt_release_xprt(xprt, NULL); > return 0; > } > > @@ -2004,8 +2018,11 @@ xs_swapper_disable(struct rpc_xprt *xprt) > struct sock_xprt *transport = container_of(xprt, struct sock_xprt, > xprt); > > + if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE)) > + return; > if (atomic_dec_and_test(&xprt->swapper)) > sk_clear_memalloc(transport->inet); > + xprt_release_xprt(xprt, NULL); > } > #else > static void xs_set_memalloc(struct rpc_xprt *xprt) -- Jeff Layton <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
