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Message-ID: <20140916053135.22257.46476.stgit@notabene.brown>
Date: Tue, 16 Sep 2014 15:31:35 +1000
From: NeilBrown <neilb@...e.de>
To: Peter Zijlstra <peterz@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Trond Myklebust <trond.myklebust@...marydata.com>,
Ingo Molnar <mingo@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
Jeff Layton <jeff.layton@...marydata.com>
Subject: [PATCH 4/4] 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@...e.de>
---
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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