On Sat, 30 May 2015 13:55:44 -0400 Chuck Lever <[email protected]> wrote:
> Hi Jeff- > > On May 30, 2015, at 8:03 AM, Jeff Layton <[email protected]> wrote: > > > 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 <[email protected]> > > Signed-off-by: Jeff Layton <[email protected]> > > --- > > 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 8b93ef53df3c..26b1624128ec 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 */ > > > > @@ -345,7 +345,8 @@ 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 383cb778179f..804a75e71e84 100644 > > --- a/net/sunrpc/clnt.c > > +++ b/net/sunrpc/clnt.c > > @@ -2492,7 +2492,7 @@ retry: > > goto retry; > > } > > > > - ret = xs_swapper(xprt, 1); > > + ret = xs_swapper_enable(xprt); > > xprt_put(xprt); > > } > > return ret; > > @@ -2519,7 +2519,7 @@ retry: > > goto retry; > > } > > > > - xs_swapper(xprt, 0); > > + xs_swapper_disable(xprt); > > xprt_put(xprt); > > } > > } > > Seems like xs_swapper() is specific to socket-based transports. > > There’s no struct sock * to use as an argument with RDMA, so xs_swapper() > would probably dereference garbage if “swapon” was invoked on a > proto=rdma mount point. > > Should these new functions be made members of the rpc_xprt_ops? The > RDMA version of the methods can be made no-ops for now. > Oh, right -- rdma uses rpcrdma_xprt instead. Yeah, adding a new ops to handle this sounds like the right thing to do. I'll roll that into the v2 set. Thanks! Jeff > > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > > index b29703996028..a2861bbfd319 100644 > > --- a/net/sunrpc/xprtsock.c > > +++ b/net/sunrpc/xprtsock.c > > @@ -1966,31 +1966,43 @@ 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) > > -- > > 2.4.1 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe > > linux-nfs" in the body of a message to [email protected] > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > Chuck Lever > chuck[dot]lever[at]oracle[dot]com > > > -- 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/
