NFS: make direct write path generate write requests concurrently

Duplicate infrastructure from direct read path that will allow write
path to generate multiple write requests concurrently.  This will
enable us to add support for aio in this path.

Temporarily we will lose the ability to do UNSTABLE writes followed by
a COMMIT in the direct write path.  However, all applications I am
aware of that use NFS O_DIRECT currently write in relatively small
chunks, so this should not be inconvenient in any way.

Test plan:
Millions of fsx-odirect ops. OraSim.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 5912274ff1a1..875f5b060533 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -77,7 +77,6 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context*,
                                             struct inode *,
                                             struct page *,
                                             unsigned int, unsigned int);
-static int nfs_writeback_done(struct rpc_task *, struct nfs_write_data *);
 static int nfs_wait_on_write_congestion(struct address_space *, int);
 static int nfs_wait_on_requests(struct inode *, unsigned long, unsigned int);
 static int nfs_flush_inode(struct inode *inode, unsigned long idx_start,
@@ -1183,7 +1182,7 @@ static const struct rpc_call_ops nfs_write_full_ops = {
 /*
  * This function is called when the WRITE call is complete.
  */
-static int nfs_writeback_done(struct rpc_task *task, struct nfs_write_data *data)
+int nfs_writeback_done(struct rpc_task *task, struct nfs_write_data *data)
 {
         struct nfs_writeargs    *argp = &data->args;
         struct nfs_writeres     *resp = &data->res;