do_readahead() doesn't make sense if the file is opened with O_DIRECT, 
since only the page cache is stuffed but never used.

Signed-off-by: Jan Blunck <j.blunck@tu-harburg.de>

 mm/filemap.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

Index: experimental-um/mm/filemap.c
===================================================================
--- experimental-um.orig/mm/filemap.c
+++ experimental-um/mm/filemap.c
@@ -1110,7 +1110,8 @@ static ssize_t
 do_readahead(struct address_space *mapping, struct file *filp,
 	     unsigned long index, unsigned long nr)
 {
-	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage
+	    || mapping->a_ops->direct_IO)
 		return -EINVAL;
 
 	force_page_cache_readahead(mapping, filp, index,