1 files changed, 68 insertions, 0 deletions
diff --git a/libdiskfs/io-prenotify.c b/libdiskfs/io-prenotify.c
new file mode 100644
index 00000000..fc6048ec
--- /dev/null
+++ b/libdiskfs/io-prenotify.c
@@ -0,0 +1,68 @@
+/* 
+   Copyright (C) 1994 Free Software Foundation
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "priv.h"
+
+/* Implement io_prenotify as described in <hurd/io.defs>. 
+
+   We set the prenotify size to be the allocated size of the file;
+   then users are forced to call this routine before writing past
+   that, and we can do allocation (orreturn ENOSPC if necessary. */
+error_t
+diskfs_S_io_prenotify (struct protid *cred,
+		       int start,
+		       int end)
+{
+  struct node *np;
+  int err = 0;
+  
+  if (!cred)
+    return EOPNOTSUPP;
+  
+  np = cred->po->np;
+
+  /* Clamp it down */
+  mutex_lock (&np->lock);
+
+  if (!cred->mapped)
+    {
+      err = EINVAL;
+      goto out;
+    }
+
+  err = ioserver_verify_user_conch (&np->conch, cred);
+  if (err)
+    goto out;
+  
+  ioserver_fetch_shared_data (cred);
+  
+  if (end < np->allocsize)
+    {
+      /* The user is either foolin' with us, or has the wrong
+	 prenotify size, hence the diagnostic. */
+      printf ("io_prenotify: unnecessary call\n");
+      spin_lock (&cred->mapped->lock);
+      err = ioserver_put_shared_data (cred);
+      spin_unlock (&cred->mapped->lock);
+      goto out;
+    }
+  
+  err =  file_extend (np, end, cred);
+ out:
+  mutex_unlock (&np->i_toplock);
+  return err;
+}