Provide a proper a_ops->swapfile() implementation for NFS. This will
set the NFS socket to SOCK_VMIO and put the socket reconnection under
PF_MEMALLOC (I hope this is enough, otherwise more work needs to be done).

Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
---
 fs/nfs/file.c               |   21 ++++++++++++++++++++-
 include/linux/sunrpc/xprt.h |    4 +++-
 net/sunrpc/xprtsock.c       |   16 ++++++++++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)

Index: linux-2.6/fs/nfs/file.c
===================================================================
--- linux-2.6.orig/fs/nfs/file.c
+++ linux-2.6/fs/nfs/file.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/smp_lock.h>
+#include <net/sock.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -317,7 +318,25 @@ static int nfs_release_page(struct page 
 
 static int nfs_swapfile(struct address_space *mapping, int enable)
 {
-       return 0;
+       int err = -EINVAL;
+       struct rpc_clnt *client = NFS_CLIENT(mapping->host);
+       struct sock *sk = client->cl_xprt->inet;
+
+       if (enable) {
+               client->cl_xprt->swapper = 1;
+               /*
+                * keep one extra sock reference so the reserve won't dip
+                * when the socket gets reconnected.
+                */
+               sk_adjust_memalloc(1, 1);
+               err = sk_set_vmio(sk);
+       } else if (client->cl_xprt->swapper) {
+               client->cl_xprt->swapper = 0;
+               sk_adjust_memalloc(-1, -1);
+               err = sk_clear_vmio(sk);
+       }
+
+       return err;
 }
 
 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) {
@@ -1170,10 +1182,14 @@ static void xs_tcp_connect_worker(void *
                                break;
                }
        }
+
+       if (xprt->swapper)
+               sk_set_vmio(xprt->inet);
 out:
        xprt_wake_pending_tasks(xprt, status);
 out_clear:
        xprt_clear_connecting(xprt);
+       current->flags = pflags;
 }
 
 /**
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
-
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