nfs: enable swap on NFS

Implement the new swapfile a_ops for NFS and hook up ->direct_IO.  This
will set the NFS socket to SOCK_MEMALLOC and run socket reconnect under
PF_MEMALLOC as well as reset SOCK_MEMALLOC 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_MEMALLOC should allow us to
receive the packets required for the TCP connection buildup.

[jlayton@redhat.com: Restore PF_MEMALLOC task flags in all cases]
[dfeng@redhat.com: Fix handling of multiple swap files]
[a.p.zijlstra@chello.nl: Original patch]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 4b6043c20f77..35994f975a7f 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -473,10 +473,10 @@ extern ssize_t nfs_direct_IO(int, struct kiocb *, const struct iovec *, loff_t,
                         unsigned long);
 extern ssize_t nfs_file_direct_read(struct kiocb *iocb,
                         const struct iovec *iov, unsigned long nr_segs,
-                        loff_t pos);
+                        loff_t pos, bool uio);
 extern ssize_t nfs_file_direct_write(struct kiocb *iocb,
                         const struct iovec *iov, unsigned long nr_segs,
-                        loff_t pos);
+                        loff_t pos, bool uio);
 
 /*
  * linux/fs/nfs/dir.c
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 77d278defa70..cff40aa7db62 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -174,6 +174,8 @@ struct rpc_xprt {
         unsigned long           state;          /* transport state */
         unsigned char           shutdown   : 1, /* being shut down */
                                 resvport   : 1; /* use a reserved port */
+        unsigned int            swapper;        /* we're swapping over this
+                                                   transport */
         unsigned int            bind_index;     /* bind function index */
 
         /*
@@ -316,6 +318,7 @@ void			xprt_release_rqst_cong(struct rpc_task *task);
 void                    xprt_disconnect_done(struct rpc_xprt *xprt);
 void                    xprt_force_disconnect(struct rpc_xprt *xprt);
 void                    xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie);
+int                     xs_swapper(struct rpc_xprt *xprt, int enable);
 
 /*
  * Reserved bit positions in xprt->state