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SUNRPC: fix race to sk_err after xs_error_report 

Since commit 4f8943f808 ("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: 4f8943f808 ("SUNRPC: Replace direct task wakeups from softirq context")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Benjamin Coddington 2019-10-02 10:40:55 -04:00 committed by Anna Schumaker
parent 1047ec8683
commit af84537dbd
2 changed files with 9 additions and 9 deletions
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1
include/linux/sunrpc/xprtsock.h
View File

@ -61,6 +61,7 @@ struct sock_xprt {
struct mutex recv_mutex; struct mutex recv_mutex;
struct sockaddr_storage srcaddr; struct sockaddr_storage srcaddr;
unsigned short srcport; unsigned short srcport;
int xprt_err;
/* /*
* UDP socket buffer size parameters * UDP socket buffer size parameters

17
net/sunrpc/xprtsock.c
View File

@ -1249,19 +1249,21 @@ static void xs_error_report(struct sock *sk)
{ {
struct sock_xprt *transport; struct sock_xprt *transport;
struct rpc_xprt *xprt; struct rpc_xprt *xprt;
int err;
read_lock_bh(&sk->sk_callback_lock); read_lock_bh(&sk->sk_callback_lock);
if (!(xprt = xprt_from_sock(sk))) if (!(xprt = xprt_from_sock(sk)))
goto out; goto out;
transport = container_of(xprt, struct sock_xprt, xprt); transport = container_of(xprt, struct sock_xprt, xprt);
err = -sk->sk_err; transport->xprt_err = -sk->sk_err;
if (err == 0) if (transport->xprt_err == 0)
goto out; goto out;
dprintk("RPC: xs_error_report client %p, error=%d...\n", dprintk("RPC: xs_error_report client %p, error=%d...\n",
xprt, -err); xprt, -transport->xprt_err);
trace_rpc_socket_error(xprt, sk->sk_socket, err); trace_rpc_socket_error(xprt, sk->sk_socket, transport->xprt_err);
/* barrier ensures xprt_err is set before XPRT_SOCK_WAKE_ERROR */
smp_mb__before_atomic();
xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR); xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR);
out: out:
read_unlock_bh(&sk->sk_callback_lock); read_unlock_bh(&sk->sk_callback_lock);
@ -2476,7 +2478,6 @@ static void xs_wake_write(struct sock_xprt *transport)
static void xs_wake_error(struct sock_xprt *transport) static void xs_wake_error(struct sock_xprt *transport)
{ {
int sockerr; int sockerr;
int sockerr_len = sizeof(sockerr);
if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state)) if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
return; return;
@ -2485,9 +2486,7 @@ static void xs_wake_error(struct sock_xprt *transport)
goto out; goto out;
if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state)) if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
goto out; goto out;
if (kernel_getsockopt(transport->sock, SOL_SOCKET, SO_ERROR, sockerr = xchg(&transport->xprt_err, 0);
(char *)&sockerr, &sockerr_len) != 0)
goto out;
if (sockerr < 0) if (sockerr < 0)
xprt_wake_pending_tasks(&transport->xprt, sockerr); xprt_wake_pending_tasks(&transport->xprt, sockerr);
out: out: