| Message ID | 20231201211549.126941-4-anna@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | SUNRPC: Various RCU fixes | expand |
On Fri, 2023-12-01 at 16:15 -0500, Anna Schumaker wrote: > From: Anna Schumaker <Anna.Schumaker@Netapp.com> > > This function takes the necessary rcu read lock to dereference the > client's rpc_xprt_switch and bump the reference count so it doesn't > disappear underneath us before returning. This does mean that callers > are responsible for calling xprt_switch_put() on the returned object > when they are done with it. > > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> > --- > net/sunrpc/clnt.c | 34 +++++++++++++++++++++------------- > 1 file changed, 21 insertions(+), 13 deletions(-) > > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index 8df944444e9b..0b2c4b5484f5 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -797,15 +797,24 @@ int rpc_switch_client_transport(struct rpc_clnt *clnt, > } > EXPORT_SYMBOL_GPL(rpc_switch_client_transport); > > +static struct rpc_xprt_switch *rpc_clnt_xprt_switch_get(struct rpc_clnt *clnt) > +{ > + struct rpc_xprt_switch *xps; > + > + rcu_read_lock(); > + xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); > + rcu_read_unlock(); > + > + return xps; > +} > + > static > int _rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi, > void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps)) > { > struct rpc_xprt_switch *xps; > > - rcu_read_lock(); > - xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); > - rcu_read_unlock(); > + xps = rpc_clnt_xprt_switch_get(clnt); > if (xps == NULL) > return -EAGAIN; > func(xpi, xps); > @@ -2206,9 +2215,7 @@ call_connect_status(struct rpc_task *task) > struct rpc_xprt *saved = task->tk_xprt; > struct rpc_xprt_switch *xps; > > - rcu_read_lock(); > - xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); > - rcu_read_unlock(); > + xps = rpc_clnt_xprt_switch_get(clnt); > if (xps->xps_nxprts > 1) { > long value; > > @@ -3251,22 +3258,23 @@ void rpc_clnt_xprt_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt) > { > struct rpc_xprt_switch *xps; > > - rcu_read_lock(); > - xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch); > - rcu_read_unlock(); > + xps = rpc_clnt_xprt_switch_get(clnt); > xprt_set_online_locked(xprt, xps); > + xprt_switch_put(xps); > } FWIW, it looks like the above fixes a real bug. It's almost certainly not safe to dereference xps once you drop the rcu_read_lock there. > > void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt) > { > + struct rpc_xprt_switch *xps; > + > if (rpc_clnt_xprt_switch_has_addr(clnt, > (const struct sockaddr *)&xprt->addr)) { > return rpc_clnt_xprt_set_online(clnt, xprt); > } > - rcu_read_lock(); > - rpc_xprt_switch_add_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch), > - xprt); > - rcu_read_unlock(); > + > + xps = rpc_clnt_xprt_switch_get(clnt); > + rpc_xprt_switch_add_xprt(xps, xprt); > + xprt_switch_put(xps); > } > EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_add_xprt); > Reviewed-by: Jeff Layton <jlayton@kernel.org>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 8df944444e9b..0b2c4b5484f5 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -797,15 +797,24 @@ int rpc_switch_client_transport(struct rpc_clnt *clnt, } EXPORT_SYMBOL_GPL(rpc_switch_client_transport); +static struct rpc_xprt_switch *rpc_clnt_xprt_switch_get(struct rpc_clnt *clnt) +{ + struct rpc_xprt_switch *xps; + + rcu_read_lock(); + xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); + rcu_read_unlock(); + + return xps; +} + static int _rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi, void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps)) { struct rpc_xprt_switch *xps; - rcu_read_lock(); - xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); - rcu_read_unlock(); + xps = rpc_clnt_xprt_switch_get(clnt); if (xps == NULL) return -EAGAIN; func(xpi, xps); @@ -2206,9 +2215,7 @@ call_connect_status(struct rpc_task *task) struct rpc_xprt *saved = task->tk_xprt; struct rpc_xprt_switch *xps; - rcu_read_lock(); - xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch)); - rcu_read_unlock(); + xps = rpc_clnt_xprt_switch_get(clnt); if (xps->xps_nxprts > 1) { long value; @@ -3251,22 +3258,23 @@ void rpc_clnt_xprt_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt) { struct rpc_xprt_switch *xps; - rcu_read_lock(); - xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch); - rcu_read_unlock(); + xps = rpc_clnt_xprt_switch_get(clnt); xprt_set_online_locked(xprt, xps); + xprt_switch_put(xps); } void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt) { + struct rpc_xprt_switch *xps; + if (rpc_clnt_xprt_switch_has_addr(clnt, (const struct sockaddr *)&xprt->addr)) { return rpc_clnt_xprt_set_online(clnt, xprt); } - rcu_read_lock(); - rpc_xprt_switch_add_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch), - xprt); - rcu_read_unlock(); + + xps = rpc_clnt_xprt_switch_get(clnt); + rpc_xprt_switch_add_xprt(xps, xprt); + xprt_switch_put(xps); } EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_add_xprt);