From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:38765 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756686Ab2JITfL (ORCPT ); Tue, 9 Oct 2012 15:35:11 -0400 Date: Tue, 9 Oct 2012 15:35:06 -0400 From: "J. Bruce Fields" To: Stanislav Kinsbursky Cc: Trond.Myklebust@netapp.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, devel@openvz.org, "Eric W. Biederman" Subject: Re: [PATCH v3] SUNRPC: set desired file system root before connecting local transports Message-ID: <20121009193506.GA19680@fieldses.org> References: <20121008105437.18668.99905.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20121008105437.18668.99905.stgit@localhost.localdomain> Sender: linux-nfs-owner@vger.kernel.org List-ID: Cc'ing Eric since I seem to recall he suggested doing it this way? Seems OK to me, but maybe that swap_root should be in common code? (Or maybe we could use set_fs_root()?) I'm assuming it's up to Trond to take this.--b. On Mon, Oct 08, 2012 at 02:56:32PM +0400, Stanislav Kinsbursky wrote: > Today, there is a problem in connecting of local SUNRPC thansports. These > transports uses UNIX sockets and connection itself is done by rpciod > workqueue. > But all local transports are connecting in rpciod context. I.e. UNIX sockets > lookup is done in context of process file system root. > This works nice until we will try to mount NFS from process with other root - > for example in container. This container can have it's own (nested) root and > rcpbind process, listening on it's own unix sockets. But NFS mount attempt in > this container will register new service (Lockd for example) in global rpcbind > - not containers's one. > This patch solves the problem by switching rpciod kernel thread's file system > root to the right one (stored on transport) while connecting of local > transports. > > Signed-off-by: Stanislav Kinsbursky > --- > net/sunrpc/xprtsock.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++-- > 1 files changed, 50 insertions(+), 2 deletions(-) > > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > index aaaadfb..ecbced1 100644 > --- a/net/sunrpc/xprtsock.c > +++ b/net/sunrpc/xprtsock.c > @@ -37,6 +37,7 @@ > #include > #include > #include > +#include > #ifdef CONFIG_SUNRPC_BACKCHANNEL > #include > #endif > @@ -255,6 +256,11 @@ struct sock_xprt { > void (*old_state_change)(struct sock *); > void (*old_write_space)(struct sock *); > void (*old_error_report)(struct sock *); > + > + /* > + * Saved transport creator root. Required for local transports only. > + */ > + struct path root; > }; > > /* > @@ -1876,6 +1882,30 @@ static int xs_local_finish_connecting(struct rpc_xprt *xprt, > return kernel_connect(sock, xs_addr(xprt), xprt->addrlen, 0); > } > > +/* > + * __xs_local_swap_root - swap current root to tranport's root helper. > + * @new_root - path to set to current fs->root. > + * @old_root - optinal paoinet to save current root to > + * > + * This routine is requieed to connecting unix sockets to absolute path in > + * proper root environment. > + * Note: no path_get() will be called. I.e. caller have to hold reference to > + * new_root. > + */ > +static void __xs_local_swap_root(struct path *new_root, struct path *old_root) > +{ > + struct fs_struct *fs = current->fs; > + > + spin_lock(&fs->lock); > + write_seqcount_begin(&fs->seq); > + if (old_root) > + *old_root = fs->root; > + fs->root = *new_root; > + write_seqcount_end(&fs->seq); > + spin_unlock(&fs->lock); > +} > + > + > /** > * xs_local_setup_socket - create AF_LOCAL socket, connect to a local endpoint > * @xprt: RPC transport to connect > @@ -1891,6 +1921,7 @@ static void xs_local_setup_socket(struct work_struct *work) > struct rpc_xprt *xprt = &transport->xprt; > struct socket *sock; > int status = -EIO; > + struct path root; > > current->flags |= PF_FSTRANS; > > @@ -1907,7 +1938,10 @@ static void xs_local_setup_socket(struct work_struct *work) > dprintk("RPC: worker connecting xprt %p via AF_LOCAL to %s\n", > xprt, xprt->address_strings[RPC_DISPLAY_ADDR]); > > + __xs_local_swap_root(&transport->root, &root); > status = xs_local_finish_connecting(xprt, sock); > + __xs_local_swap_root(&root, NULL); > + > switch (status) { > case 0: > dprintk("RPC: xprt %p connected to %s\n", > @@ -2256,6 +2290,18 @@ static void xs_connect(struct rpc_task *task) > } > } > > +static void xs_local_destroy(struct rpc_xprt *xprt) > +{ > + struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt); > + struct path root = transport->root; > + > + dprintk("RPC: xs_local_destroy xprt %p\n", xprt); > + > + xs_destroy(xprt); > + > + path_put(&root); > +} > + > /** > * xs_local_print_stats - display AF_LOCAL socket-specifc stats > * @xprt: rpc_xprt struct containing statistics > @@ -2475,7 +2521,7 @@ static struct rpc_xprt_ops xs_local_ops = { > .send_request = xs_local_send_request, > .set_retrans_timeout = xprt_set_retrans_timeout_def, > .close = xs_close, > - .destroy = xs_destroy, > + .destroy = xs_local_destroy, > .print_stats = xs_local_print_stats, > }; > > @@ -2654,8 +2700,10 @@ static struct rpc_xprt *xs_setup_local(struct xprt_create *args) > dprintk("RPC: set up xprt to %s via AF_LOCAL\n", > xprt->address_strings[RPC_DISPLAY_ADDR]); > > - if (try_module_get(THIS_MODULE)) > + if (try_module_get(THIS_MODULE)) { > + get_fs_root(current->fs, &transport->root); > return xprt; > + } > ret = ERR_PTR(-EINVAL); > out_err: > xprt_free(xprt); >