[PATCH 4/4] NFS/SUNRPC: Remove other deadlock-avoidance mechanisms in nfs_release_page()
From: NeilBrown <hidden>
Date: 2014-09-16 05:31:35
Also in:
linux-fsdevel, linux-nfs, lkml
Subsystem:
filesystems (vfs and infrastructure), kernel nfsd, sunrpc, and lockd servers, networking [general], nfs, sunrpc, and lockd clients, the rest · Maintainers:
Alexander Viro, Christian Brauner, Chuck Lever, Jeff Layton, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Trond Myklebust, Anna Schumaker, Linus Torvalds
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 <redacted> --- fs/nfs/file.c | 16 +++++++--------- net/sunrpc/sched.c | 2 -- net/sunrpc/xprtrdma/transport.c | 2 -- net/sunrpc/xprtsock.c | 10 ---------- 4 files changed, 7 insertions(+), 23 deletions(-)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 8d74983417af..5949ca37cd18 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c@@ -469,18 +469,16 @@ 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. 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. + * wait for it if __GFP_WAIT is set. Even then, only wait 1 + * second. Waiting indefinitely can cause deadlocks when the + * NFS 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) { nfs_commit_inode(mapping->host, 0); - if ((gfp & __GFP_WAIT) && - !current_is_kswapd() && - !(current->flags & PF_FSTRANS)) + if ((gfp & __GFP_WAIT)) wait_on_page_bit_killable_timeout(page, PG_private, HZ); }
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 9358c79fd589..fe3441abdbe5 100644
--- 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 2faac4940563..6a4615dd0261 100644
--- 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 43cd89eacfab..4707c0c8568b 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c@@ -1927,8 +1927,6 @@ 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);
@@ -1968,7 +1966,6 @@ 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; }
@@ -2071,8 +2068,6 @@ 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,
@@ -2092,7 +2087,6 @@ 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; } /*
@@ -2229,8 +2223,6 @@ 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,
@@ -2276,7 +2268,6 @@ 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
@@ -2294,7 +2285,6 @@ out_eagain: out: xprt_clear_connecting(xprt); xprt_wake_pending_tasks(xprt, status); - current->flags &= ~PF_FSTRANS; } /** --
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