ceph: clean PgPrivate2 on returning from readpages

In some cases the ceph readapages code code bails without filling all the pages
already marked by fscache. When we return back to readahead code this causes
a BUG.
Signed-off-by: Milosz Tanski <milosz@adfin.com>

fs/ceph/addr.c

@@ -398,6 +398,8 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
 		BUG_ON(rc == 0);
 	}
 out:
+	ceph_fscache_readpages_cancel(inode, page_list);
+
 	dout("readpages %p file %p ret %d\n", inode, file, rc);
 	return rc;
 }

fs/ceph/cache.h

@@ -58,6 +58,13 @@ static inline int ceph_release_fscache_page(struct page *page, gfp_t gfp)
 	return fscache_maybe_release_page(ci->fscache, page, gfp);
 }
 
+static inline void ceph_fscache_readpages_cancel(struct inode *inode,
+						 struct list_head *pages)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	return fscache_readpages_cancel(ci->fscache, pages);
+}
+
 #else
 
 static inline int ceph_fscache_register(void)