[PATCH 09/21] nfs: make swap on NFS robust

Peter Zijlstra
2006-09-06T13:43:05Z

[-- Attachment #1: nfs_vmio.patch --]
[-- Type: text/plain, Size: 5265 bytes --]

Provide a proper a_ops->swapfile() implementation for NFS. This will set the
NFS socket to SOCK_VMIO and run socket reconnect under PF_MEMALLOC as well
as reset SOCK_VMIO before engaging the protocol ->connect() method.

PF_MEMALLOC should allow the allocation of struct socket and related objects
and the early (re)setting of SOCK_VMIO should allow us to receive the packets
required for the TCP connection buildup.

(swapping continues over a server reset during a large (4k) ping flood)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Trond Myklebust <trond.myklebust@fys.uio.no>
---
fs/nfs/file.c | 2 +-
include/linux/sunrpc/xprt.h | 5 ++++-
net/sunrpc/sched.c | 4 ++--
net/sunrpc/xprtsock.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 51 insertions(+), 4 deletions(-)

Index: linux-2.6/fs/nfs/file.c
===================================================================
--- linux-2.6.orig/fs/nfs/file.c
+++ linux-2.6/fs/nfs/file.c
@@ -323,7 +323,7 @@ static int nfs_release_page(struct page

static int nfs_swapfile(struct address_space *mapping, int enable)
{
- return 0;
+ return xs_swapper(NFS_CLIENT(mapping->host)->cl_xprt, enable);
}

const struct address_space_operations nfs_file_aops = {
Index: linux-2.6/net/sunrpc/xprtsock.c
===================================================================
--- linux-2.6.orig/net/sunrpc/xprtsock.c
+++ linux-2.6/net/sunrpc/xprtsock.c
@@ -1014,6 +1014,7 @@ static void xs_udp_connect_worker(void *
{
struct rpc_xprt *xprt = (struct rpc_xprt *) args;
struct socket *sock = xprt->sock;
+ unsigned long pflags = current->flags;
int err, status = -EIO;

if (xprt->shutdown || xprt->addr.sin_port == 0)
@@ -1021,6 +1022,9 @@ static void xs_udp_connect_worker(void *

dprintk("RPC: xs_udp_connect_worker for xprt %p\n", xprt);

+ if (xprt->swapper)
+ current->flags |= PF_MEMALLOC;
+
/* Start by resetting any existing state */
xs_close(xprt);

@@ -1054,6 +1058,9 @@ static void xs_udp_connect_worker(void *
xprt->sock = sock;
xprt->inet = sk;

+ if (xprt->swapper)
+ sk_set_vmio(sk);
+
write_unlock_bh(&sk->sk_callback_lock);
}
xs_udp_do_set_buffer_size(xprt);
@@ -1061,6 +1068,7 @@ static void xs_udp_connect_worker(void *
out:
xprt_wake_pending_tasks(xprt, status);
xprt_clear_connecting(xprt);
+ current->flags = pflags;
}

/*
@@ -1097,11 +1105,15 @@ static void xs_tcp_connect_worker(void *
{
struct rpc_xprt *xprt = (struct rpc_xprt *)args;
struct socket *sock = xprt->sock;
+ unsigned long pflags = current->flags;
int err, status = -EIO;

if (xprt->shutdown || xprt->addr.sin_port == 0)
goto out;

+ if (xprt->swapper)
+ current->flags |= PF_MEMALLOC;
+
dprintk("RPC: xs_tcp_connect_worker for xprt %p\n", xprt);

if (!xprt->sock) {
@@ -1148,6 +1160,10 @@ static void xs_tcp_connect_worker(void *
write_unlock_bh(&sk->sk_callback_lock);
}

+
+ if (xprt->swapper)
+ sk_set_vmio(xprt->inet);
+
/* Tell the socket layer to start connecting... */
xprt->stat.connect_count++;
xprt->stat.connect_start = jiffies;
@@ -1174,6 +1190,7 @@ out:
xprt_wake_pending_tasks(xprt, status);
out_clear:
xprt_clear_connecting(xprt);
+ current->flags = pflags;
}

/**
@@ -1369,3 +1386,30 @@ int xs_setup_tcp(struct rpc_xprt *xprt,

return 0;
}
+
+/**
+ * xs_swapper - Tag this transport as being used for swap.
+ * @xprt: transport to tag
+ * @enable: enable/disable
+ *
+ */
+int xs_swapper(struct rpc_xprt *xprt, int enable)
+{
+ int err = 0;
+
+ if (enable) {
+ /*
+ * keep one extra sock reference so the reserve won't dip
+ * when the socket gets reconnected.
+ */
+ sk_adjust_memalloc(1, TX_RESERVE_PAGES);
+ sk_set_vmio(xprt->inet);
+ xprt->swapper = 1;
+ } else if (xprt->swapper) {
+ xprt->swapper = 0;
+ sk_clear_vmio(xprt->inet);
+ sk_adjust_memalloc(-1, -TX_RESERVE_PAGES);
+ }
+
+ return err;
+}
Index: linux-2.6/include/linux/sunrpc/xprt.h
===================================================================
--- linux-2.6.orig/include/linux/sunrpc/xprt.h
+++ linux-2.6/include/linux/sunrpc/xprt.h
@@ -147,7 +147,9 @@ struct rpc_xprt {
unsigned int max_reqs; /* total slots */
unsigned long state; /* transport state */
unsigned char shutdown : 1, /* being shut down */
- resvport : 1; /* use a reserved port */
+ resvport : 1, /* use a reserved port */
+ swapper : 1; /* we're swapping over this
+ transport */

/*
* XID
@@ -261,6 +263,7 @@ void xprt_disconnect(struct rpc_xprt *
*/
int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to);
int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to);
+int xs_swapper(struct rpc_xprt *xprt, int enable);

/*
* Reserved bit positions in xprt->state
Index: linux-2.6/net/sunrpc/sched.c
===================================================================
--- linux-2.6.orig/net/sunrpc/sched.c
+++ linux-2.6/net/sunrpc/sched.c
@@ -736,8 +736,8 @@ void * rpc_malloc(struct rpc_task *task,
struct rpc_rqst *req = task->tk_rqstp;
gfp_t gfp;

- if (task->tk_flags & RPC_TASK_SWAPPER)
- gfp = GFP_ATOMIC;
+ if (RPC_IS_SWAPPER(task))
+ gfp = GFP_ATOMIC | __GFP_EMERGENCY;
else
gfp = GFP_NOFS;

--