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Commit 8e228133 authored by Jeff Layton's avatar Jeff Layton Committed by Trond Myklebust
Browse files

sunrpc: make xprt->swapper an atomic_t 



Split xs_swapper into enable/disable functions and eliminate the
"enable" flag.

Currently, it's racy if you have multiple swapon/swapoff operations
running in parallel over the same xprt. Also fix it so that we only
set it to a memalloc socket on a 0->1 transition and only clear it
on a 1->0 transition.

Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: default avatarJeff Layton <jeff.layton@primarydata.com>
Reviewed-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 3c87ef6e

include/linux/sunrpc/xprt.h

+3 −2
Original line number Diff line number Diff line
@@ -180,7 +180,7 @@ struct rpc_xprt { 
	atomic_t		num_reqs;	/* total slots */

	unsigned long		state;		/* transport state */

	unsigned char		resvport   : 1; /* use a reserved port */

	unsigned int		swapper;	/* we're swapping over this

	atomic_t		swapper;	/* we're swapping over this

						   transport */

	unsigned int		bind_index;	/* bind function index */
@@ -346,7 +346,8 @@ void xprt_release_rqst_cong(struct rpc_task *task); 
void			xprt_disconnect_done(struct rpc_xprt *xprt);

void			xprt_force_disconnect(struct rpc_xprt *xprt);

void			xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie);

int			xs_swapper(struct rpc_xprt *xprt, int enable);

int			xs_swapper_enable(struct rpc_xprt *xprt);

void			xs_swapper_disable(struct rpc_xprt *xprt);



bool			xprt_lock_connect(struct rpc_xprt *, struct rpc_task *, void *);

void			xprt_unlock_connect(struct rpc_xprt *, void *);

net/sunrpc/clnt.c

+2 −2
Original line number Diff line number Diff line
@@ -2495,7 +2495,7 @@ rpc_clnt_swap_activate(struct rpc_clnt *clnt) 
			goto retry;

		}



		ret = xs_swapper(xprt, 1);

		ret = xs_swapper_enable(xprt);

		xprt_put(xprt);

	}

	return ret;
@@ -2522,7 +2522,7 @@ rpc_clnt_swap_deactivate(struct rpc_clnt *clnt) 
			goto retry;

		}



		xs_swapper(xprt, 0);

		xs_swapper_disable(xprt);

		xprt_put(xprt);

	}

}

net/sunrpc/xprtsock.c

+25 −13
Original line number Diff line number Diff line
@@ -1961,31 +1961,43 @@ static void xs_set_memalloc(struct rpc_xprt *xprt) 
	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,

			xprt);



	if (xprt->swapper)

	if (atomic_read(&xprt->swapper))

		sk_set_memalloc(transport->inet);

}



/**

 * xs_swapper - Tag this transport as being used for swap.

 * xs_swapper_enable - Tag this transport as being used for swap.

 * @xprt: transport to tag

 * @enable: enable/disable

 *

 * Take a reference to this transport on behalf of the rpc_clnt, and

 * optionally mark it for swapping if it wasn't already.

 */

int xs_swapper(struct rpc_xprt *xprt, int enable)

int

xs_swapper_enable(struct rpc_xprt *xprt)

{

	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,

			xprt);

	int err = 0;



	if (enable) {

		xprt->swapper++;

		xs_set_memalloc(xprt);

	} else if (xprt->swapper) {

		xprt->swapper--;

		sk_clear_memalloc(transport->inet);

	if (atomic_inc_return(&xprt->swapper) == 1)

		sk_set_memalloc(transport->inet);

	return 0;

}



	return err;

/**

 * xs_swapper_disable - Untag this transport as being used for swap.

 * @xprt: transport to tag

 *

 * Drop a "swapper" reference to this xprt on behalf of the rpc_clnt. If the

 * swapper refcount goes to 0, untag the socket as a memalloc socket.

 */

void

xs_swapper_disable(struct rpc_xprt *xprt)

{

	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,

			xprt);



	if (atomic_dec_and_test(&xprt->swapper))

		sk_clear_memalloc(transport->inet);

}

#else

static void xs_set_memalloc(struct rpc_xprt *xprt)