NFS: Add functionality to allow waiting on all outstanding reads to complete

This will later allow NFS locking code to wait for readahead to complete
before releasing byte range locks.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 55b840f..c1c7a9d 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -561,6 +561,7 @@
 	l_ctx->lockowner.l_owner = current->files;
 	l_ctx->lockowner.l_pid = current->tgid;
 	INIT_LIST_HEAD(&l_ctx->list);
+	nfs_iocounter_init(&l_ctx->io_count);
 }
 
 static struct nfs_lock_context *__nfs_find_lock_context(struct nfs_open_context *ctx)