mm/readahead.c:do_readhead(): don't check for ->readpage

The callee force_page_cache_readahead() already does this and unlike
do_readahead(), force_page_cache_readahead() remembers to check for
->readpages() as well.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/readahead.c b/mm/readahead.c
index e4ed041..5024183 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -569,7 +569,7 @@
 do_readahead(struct address_space *mapping, struct file *filp,
 	     pgoff_t index, unsigned long nr)
 {
-	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
+	if (!mapping || !mapping->a_ops)
 		return -EINVAL;
 
 	force_page_cache_readahead(mapping, filp, index, nr);