fs/pipe: stop duplicating union pipe_index declaration

Now that we build with -fms-extensions, union pipe_index can be
included as an anonymous member in struct pipe_inode_info, avoiding
the duplication.

Signed-off-by: Rasmus Villemoes <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>

include/linux/pipe_fs_i.h

···
 typedef unsigned short pipe_index_t;
 #endif
 
-/*
- * We have to declare this outside 'struct pipe_inode_info',
- * but then we can't use 'union pipe_index' for an anonymous
- * union, so we end up having to duplicate this declaration
- * below. Annoying.
+/**
+ *	struct pipe_index - pipe indeces
+ *	@head: The point of buffer production
+ *	@tail: The point of buffer consumption
+ *	@head_tail: unsigned long union of @head and @tail
  */
 union pipe_index {
 	unsigned long head_tail;
···
  *	@mutex: mutex protecting the whole thing
  *	@rd_wait: reader wait point in case of empty pipe
  *	@wr_wait: writer wait point in case of full pipe
- *	@head: The point of buffer production
- *	@tail: The point of buffer consumption
- *	@head_tail: unsigned long union of @head and @tail
+ *	@pipe_index: the pipe indeces
  *	@note_loss: The next read() should insert a data-lost message
  *	@max_usage: The maximum number of slots that may be used in the ring
  *	@ring_size: total number of buffers (should be a power of 2)
···
 	struct mutex mutex;
 	wait_queue_head_t rd_wait, wr_wait;
 
-	/* This has to match the 'union pipe_index' above */
-	union {
-		unsigned long head_tail;
-		struct {
-			pipe_index_t head;
-			pipe_index_t tail;
-		};
-	};
+	union pipe_index;
 
 	unsigned int max_usage;
 	unsigned int ring_size;