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: NeilBrown <neilb@suse.de>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 24832d040eb89d8117eeffcf5c2ed00a2e678ab6..6920127c5eb7eebce51958422dfbfaf38cbd4b29 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -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);

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 9358c79fd5893eacc94e3ba3969d72b6c11b0845..fe3441abdbe5a7a95825c93454ed6a7def75f55e 100644 (file)
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -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;
 }
 
 /**

diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index 2faac49405633000f7aa528085a7ecf7994015fd..6a4615dd02618318ce145b95367011150fd35a68 100644 (file)
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -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;
 }
 
 /*

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 02603ec2460a8f801935ac53f56dafd1c0424304..3b305ab17afe932c6b96aeff24061e6db85fc516 100644 (file)
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -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;
 }
 
 /**