Message ID | 9796ba15d926f65923965c2aedf777aaa59861e8.1569954618.git.bcodding@redhat.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | SUNRPC: fix race to sk_err after xs_error_report | expand |
On Tue, 2019-10-01 at 14:30 -0400, Benjamin Coddington wrote: > Since commit 4f8943f80883 ("SUNRPC: Replace direct task wakeups from > softirq context") there has been a race to the value of the sk_err if > both > XPRT_SOCK_WAKE_ERROR and XPRT_SOCK_WAKE_DISCONNECT are set. In that > case, > we may end up losing the sk_err value that existed when > xs_error_report was > called. > > Fix this by reverting to the previous behavior: instead of using > SO_ERROR > to retrieve the value at a later time (which might also return > sk_err_soft), > copy the sk_err value onto struct sock_xprt, and use that value to > wake > pending tasks. > > Signed-off-by: Benjamin Coddington <bcodding@redhat.com> > Fixes: 4f8943f80883 ("SUNRPC: Replace direct task wakeups from > softirq context") > --- > include/linux/sunrpc/xprtsock.h | 1 + > net/sunrpc/xprtsock.c | 13 +++++-------- > 2 files changed, 6 insertions(+), 8 deletions(-) > > diff --git a/include/linux/sunrpc/xprtsock.h > b/include/linux/sunrpc/xprtsock.h > index 7638dbe7bc50..8ffae73dea6c 100644 > --- a/include/linux/sunrpc/xprtsock.h > +++ b/include/linux/sunrpc/xprtsock.h > @@ -56,6 +56,7 @@ struct sock_xprt { > */ > unsigned long sock_state; > struct delayed_work connect_worker; > + int xprt_err; Perhaps move this down just after srcport so we don't create an unnecessary hole in the structure? > struct work_struct error_worker; > struct work_struct recv_worker; > struct mutex recv_mutex; > diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c > index e2176c167a57..7fe77eef7080 100644 > --- a/net/sunrpc/xprtsock.c > +++ b/net/sunrpc/xprtsock.c > @@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk) > goto out; > > transport = container_of(xprt, struct sock_xprt, xprt); > - err = -sk->sk_err; > - if (err == 0) > + transport->xprt_err = -sk->sk_err; Doesn't this need a smp write barrier to ensure it isn't reordered with the set_bit() in xs_run_error_worker()? > + if (transport->xprt_err == 0) > goto out; > dprintk("RPC: xs_error_report client %p, error=%d...\n", > - xprt, -err); > - trace_rpc_socket_error(xprt, sk->sk_socket, err); > + xprt, -transport->xprt_err); > + trace_rpc_socket_error(xprt, sk->sk_socket, transport- > >xprt_err); > xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR); > out: > read_unlock_bh(&sk->sk_callback_lock); > @@ -2470,7 +2470,6 @@ static void xs_wake_write(struct sock_xprt > *transport) > static void xs_wake_error(struct sock_xprt *transport) > { > int sockerr; > - int sockerr_len = sizeof(sockerr); > > if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state)) > return; > @@ -2479,9 +2478,7 @@ static void xs_wake_error(struct sock_xprt > *transport) > goto out; > if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport- > >sock_state)) > goto out; > - if (kernel_getsockopt(transport->sock, SOL_SOCKET, SO_ERROR, > - (char *)&sockerr, &sockerr_len) != 0) > - goto out; > + sockerr = xchg(&transport->xprt_err, 0); > if (sockerr < 0) > xprt_wake_pending_tasks(&transport->xprt, sockerr); > out:
On 1 Oct 2019, at 15:38, Trond Myklebust wrote: > On Tue, 2019-10-01 at 14:30 -0400, Benjamin Coddington wrote: >> ... >> diff --git a/include/linux/sunrpc/xprtsock.h >> b/include/linux/sunrpc/xprtsock.h >> index 7638dbe7bc50..8ffae73dea6c 100644 >> --- a/include/linux/sunrpc/xprtsock.h >> +++ b/include/linux/sunrpc/xprtsock.h >> @@ -56,6 +56,7 @@ struct sock_xprt { >> */ >> unsigned long sock_state; >> struct delayed_work connect_worker; >> + int xprt_err; > > Perhaps move this down just after srcport so we don't create an > unnecessary hole in the structure? Ok! >> struct work_struct error_worker; >> struct work_struct recv_worker; >> struct mutex recv_mutex; >> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c >> index e2176c167a57..7fe77eef7080 100644 >> --- a/net/sunrpc/xprtsock.c >> +++ b/net/sunrpc/xprtsock.c >> @@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk) >> goto out; >> >> transport = container_of(xprt, struct sock_xprt, xprt); >> - err = -sk->sk_err; >> - if (err == 0) >> + transport->xprt_err = -sk->sk_err; > > Doesn't this need a smp write barrier to ensure it isn't reordered with > the set_bit() in xs_run_error_worker()? Yes, it does need that or the error_worker may clear the bit without seeing the error. Ben
diff --git a/include/linux/sunrpc/xprtsock.h b/include/linux/sunrpc/xprtsock.h index 7638dbe7bc50..8ffae73dea6c 100644 --- a/include/linux/sunrpc/xprtsock.h +++ b/include/linux/sunrpc/xprtsock.h @@ -56,6 +56,7 @@ struct sock_xprt { */ unsigned long sock_state; struct delayed_work connect_worker; + int xprt_err; struct work_struct error_worker; struct work_struct recv_worker; struct mutex recv_mutex; diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index e2176c167a57..7fe77eef7080 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk) goto out; transport = container_of(xprt, struct sock_xprt, xprt); - err = -sk->sk_err; - if (err == 0) + transport->xprt_err = -sk->sk_err; + if (transport->xprt_err == 0) goto out; dprintk("RPC: xs_error_report client %p, error=%d...\n", - xprt, -err); - trace_rpc_socket_error(xprt, sk->sk_socket, err); + xprt, -transport->xprt_err); + trace_rpc_socket_error(xprt, sk->sk_socket, transport->xprt_err); xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR); out: read_unlock_bh(&sk->sk_callback_lock); @@ -2470,7 +2470,6 @@ static void xs_wake_write(struct sock_xprt *transport) static void xs_wake_error(struct sock_xprt *transport) { int sockerr; - int sockerr_len = sizeof(sockerr); if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state)) return; @@ -2479,9 +2478,7 @@ static void xs_wake_error(struct sock_xprt *transport) goto out; if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state)) goto out; - if (kernel_getsockopt(transport->sock, SOL_SOCKET, SO_ERROR, - (char *)&sockerr, &sockerr_len) != 0) - goto out; + sockerr = xchg(&transport->xprt_err, 0); if (sockerr < 0) xprt_wake_pending_tasks(&transport->xprt, sockerr); out:
Since commit 4f8943f80883 ("SUNRPC: Replace direct task wakeups from softirq context") there has been a race to the value of the sk_err if both XPRT_SOCK_WAKE_ERROR and XPRT_SOCK_WAKE_DISCONNECT are set. In that case, we may end up losing the sk_err value that existed when xs_error_report was called. Fix this by reverting to the previous behavior: instead of using SO_ERROR to retrieve the value at a later time (which might also return sk_err_soft), copy the sk_err value onto struct sock_xprt, and use that value to wake pending tasks. Signed-off-by: Benjamin Coddington <bcodding@redhat.com> Fixes: 4f8943f80883 ("SUNRPC: Replace direct task wakeups from softirq context") --- include/linux/sunrpc/xprtsock.h | 1 + net/sunrpc/xprtsock.c | 13 +++++-------- 2 files changed, 6 insertions(+), 8 deletions(-)