fs: add a new user_write_streams() callback

so that filesystem can control number of write streams for user space.

Signed-off-by: Kanchan Joshi <[email protected]>

Author: Kanchan Joshi

include/linux/fs.h

@@ -2377,6 +2377,11 @@ struct super_operations {
 	 */
 	int (*remove_bdev)(struct super_block *sb, struct block_device *bdev);
 	void (*shutdown)(struct super_block *sb);
+	/*
+	 * Implement this callback if filesystem wants to control the
+	 * number of streams that are available to user space.
+	 */
+	u8 (*user_write_streams)(struct super_block *sb);
 };
 
 /*