Commit 1aff5256 authored by NeilBrown's avatar NeilBrown Committed by Trond Myklebust
Browse files

NFS/SUNRPC: Remove other deadlock-avoidance mechanisms in nfs_release_page() 



Now that nfs_release_page() doesn't block indefinitely, other deadlock
avoidance mechanisms aren't needed.
 - it doesn't hurt for kswapd to block occasionally.  If it doesn't
   want to block it would clear __GFP_WAIT.  The current_is_kswapd()
   was only added to avoid deadlocks and we have a new approach for
   that.
 - memory allocation in the SUNRPC layer can very rarely try to
   ->releasepage() a page it is trying to handle.  The deadlock
   is removed as nfs_release_page() doesn't block indefinitely.

So we don't need to set PF_FSTRANS for sunrpc network operations any
more.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Acked-by: default avatarJeff Layton <jlayton@primarydata.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent 353db796

fs/nfs/file.c

+6 −8
Original line number Diff line number Diff line
@@ -476,20 +476,18 @@ static int nfs_release_page(struct page *page, gfp_t gfp) 
	dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);



	/* Always try to initiate a 'commit' if relevant, but only

	 * wait for it if __GFP_WAIT is set and the calling process is

	 * allowed to block.  Even then, only wait 1 second and only

	 * if the 'bdi' is not congested.

	 * wait for it if __GFP_WAIT is set.  Even then, only wait 1

	 * second and only if the 'bdi' is not congested.

	 * Waiting indefinitely can cause deadlocks when the NFS

	 * server is on this machine, and there is no particular need

	 * to wait extensively here.  A short wait has the benefit

	 * that someone else can worry about the freezer.

	 * server is on this machine, when a new TCP connection is

	 * needed and in other rare cases.  There is no particular

	 * need to wait extensively here.  A short wait has the

	 * benefit that someone else can worry about the freezer.

	 */

	if (mapping) {

		struct nfs_server *nfss = NFS_SERVER(mapping->host);

		nfs_commit_inode(mapping->host, 0);

		if ((gfp & __GFP_WAIT) &&

		    !current_is_kswapd() &&

		    !(current->flags & PF_FSTRANS) &&

		    !bdi_write_congested(&nfss->backing_dev_info)) {

			wait_on_page_bit_killable_timeout(page, PG_private,

							  HZ);

net/sunrpc/sched.c

+0 −2
Original line number Diff line number Diff line
@@ -821,9 +821,7 @@ void rpc_execute(struct rpc_task *task) 


static void rpc_async_schedule(struct work_struct *work)

{

	current->flags |= PF_FSTRANS;

	__rpc_execute(container_of(work, struct rpc_task, u.tk_work));

	current->flags &= ~PF_FSTRANS;

}



/**

net/sunrpc/xprtrdma/transport.c

+0 −2
Original line number Diff line number Diff line
@@ -205,7 +205,6 @@ xprt_rdma_connect_worker(struct work_struct *work) 
	struct rpc_xprt *xprt = &r_xprt->xprt;

	int rc = 0;



	current->flags |= PF_FSTRANS;

	xprt_clear_connected(xprt);



	dprintk("RPC:       %s: %sconnect\n", __func__,
@@ -216,7 +215,6 @@ xprt_rdma_connect_worker(struct work_struct *work) 


	dprintk("RPC:       %s: exit\n", __func__);

	xprt_clear_connecting(xprt);

	current->flags &= ~PF_FSTRANS;

}



/*

net/sunrpc/xprtsock.c

+0 −10
Original line number Diff line number Diff line
@@ -1954,8 +1954,6 @@ static int xs_local_setup_socket(struct sock_xprt *transport) 
	struct socket *sock;

	int status = -EIO;



	current->flags |= PF_FSTRANS;



	clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);

	status = __sock_create(xprt->xprt_net, AF_LOCAL,

					SOCK_STREAM, 0, &sock, 1);
@@ -1995,7 +1993,6 @@ static int xs_local_setup_socket(struct sock_xprt *transport) 
out:

	xprt_clear_connecting(xprt);

	xprt_wake_pending_tasks(xprt, status);

	current->flags &= ~PF_FSTRANS;

	return status;

}
@@ -2098,8 +2095,6 @@ static void xs_udp_setup_socket(struct work_struct *work) 
	struct socket *sock = transport->sock;

	int status = -EIO;



	current->flags |= PF_FSTRANS;



	/* Start by resetting any existing state */

	xs_reset_transport(transport);

	sock = xs_create_sock(xprt, transport,
@@ -2119,7 +2114,6 @@ static void xs_udp_setup_socket(struct work_struct *work) 
out:

	xprt_clear_connecting(xprt);

	xprt_wake_pending_tasks(xprt, status);

	current->flags &= ~PF_FSTRANS;

}



/*
@@ -2256,8 +2250,6 @@ static void xs_tcp_setup_socket(struct work_struct *work) 
	struct rpc_xprt *xprt = &transport->xprt;

	int status = -EIO;



	current->flags |= PF_FSTRANS;



	if (!sock) {

		clear_bit(XPRT_CONNECTION_ABORT, &xprt->state);

		sock = xs_create_sock(xprt, transport,
@@ -2305,7 +2297,6 @@ static void xs_tcp_setup_socket(struct work_struct *work) 
	case -EINPROGRESS:

	case -EALREADY:

		xprt_clear_connecting(xprt);

		current->flags &= ~PF_FSTRANS;

		return;

	case -EINVAL:

		/* Happens, for instance, if the user specified a link
@@ -2323,7 +2314,6 @@ out_eagain: 
out:

	xprt_clear_connecting(xprt);

	xprt_wake_pending_tasks(xprt, status);

	current->flags &= ~PF_FSTRANS;

}



/**

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