Add "nonseekable_open()" helper functions for nonseekable

file descriptors.

fs/open.c

@@ -1070,3 +1070,15 @@ int generic_file_open(struct inode * inode, struct file * filp)
 }
 
 EXPORT_SYMBOL(generic_file_open);
+
+/*
+ * This is used by subsystems that don't want seekable
+ * file descriptors
+ */
+int nonseekable_open(struct inode *inode, struct file *filp)
+{
+	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+	return 0;
+}
+
+EXPORT_SYMBOL(nonseekable_open);

include/linux/fs.h

@@ -1435,6 +1435,7 @@ extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t remote_llseek(struct file *file, loff_t offset, int origin);
 extern int generic_file_open(struct inode * inode, struct file * filp);
+extern int nonseekable_open(struct inode * inode, struct file * filp);
 
 static inline void do_generic_file_read(struct file * filp, loff_t *ppos,
 					read_descriptor_t * desc,