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SUNRPC: change locking for xs_swap_enable/disable

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It is not in general safe to wait for XPRT_LOCKED to clear.
A wakeup is only sent when
 - connection completes
 - sock close completes
so during normal operations, this can wait indefinitely.

The event we need to protect against is ->inet being set to NULL, and
that happens under the recv_mutex lock.

So drop the handlign of XPRT_LOCKED and use recv_mutex instead.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
NeilBrown 2022-03-07 10:41:45 +11:00 committed by Trond Myklebust
parent c265de257f
commit 693486d5f8
1 changed files with 11 additions and 15 deletions
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26
net/sunrpc/xprtsock.c
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@ -1936,9 +1936,9 @@ static void xs_local_connect(struct rpc_xprt *xprt, struct rpc_task *task)
#if IS_ENABLED(CONFIG_SUNRPC_SWAP)
/*
* Note that this should be called with XPRT_LOCKED held (or when we otherwise
* know that we have exclusive access to the socket), to guard against
* races with xs_reset_transport.
* Note that this should be called with XPRT_LOCKED held, or recv_mutex
* held, or when we otherwise know that we have exclusive access to the
* socket, to guard against races with xs_reset_transport.
*/
static void xs_set_memalloc(struct rpc_xprt *xprt)
{
@ -1967,13 +1967,11 @@ xs_enable_swap(struct rpc_xprt *xprt)
{
struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);
if (atomic_inc_return(&xprt->swapper) != 1)
return 0;
if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE))
return -ERESTARTSYS;
if (xs->inet)
mutex_lock(&xs->recv_mutex);
if (atomic_inc_return(&xprt->swapper) == 1 &&
xs->inet)
sk_set_memalloc(xs->inet);
xprt_release_xprt(xprt, NULL);
mutex_unlock(&xs->recv_mutex);
return 0;
}
@ -1989,13 +1987,11 @@ xs_disable_swap(struct rpc_xprt *xprt)
{
struct sock_xprt *xs = container_of(xprt, struct sock_xprt, xprt);
if (!atomic_dec_and_test(&xprt->swapper))
return;
if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE))
return;
if (xs->inet)
mutex_lock(&xs->recv_mutex);
if (atomic_dec_and_test(&xprt->swapper) &&
xs->inet)
sk_clear_memalloc(xs->inet);
xprt_release_xprt(xprt, NULL);
mutex_unlock(&xs->recv_mutex);
}
#else
static void xs_set_memalloc(struct rpc_xprt *xprt)