1 files changed, 65 insertions, 20 deletions

diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 8ff23bf5a819..7f6a92ac9704 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -31,13 +31,39 @@ struct pipe_buffer {
 	unsigned long private;
 };
 
+/*
+ * Really only alpha needs 32-bit fields, but
+ * might as well do it for 64-bit architectures
+ * since that's what we've historically done,
+ * and it makes 'head_tail' always be a simple
+ * 'unsigned long'.
+ */
+#ifdef CONFIG_64BIT
+typedef unsigned int pipe_index_t;
+#else
+typedef unsigned short pipe_index_t;
+#endif
+
+/**
+ *	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;
+	struct {
+		pipe_index_t head;
+		pipe_index_t tail;
+	};
+};
+
 /**
  *	struct pipe_inode_info - a linux kernel pipe
  *	@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
+ *	@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)
@@ -58,8 +84,9 @@ struct pipe_buffer {
 struct pipe_inode_info {
 	struct mutex mutex;
 	wait_queue_head_t rd_wait, wr_wait;
-	unsigned int head;
-	unsigned int tail;
+
+	union pipe_index;
+
 	unsigned int max_usage;
 	unsigned int ring_size;
 	unsigned int nr_accounted;
@@ -72,7 +99,7 @@ struct pipe_inode_info {
 #ifdef CONFIG_WATCH_QUEUE
 	bool note_loss;
 #endif
-	struct page *tmp_page;
+	struct page *tmp_page[2];
 	struct fasync_struct *fasync_readers;
 	struct fasync_struct *fasync_writers;
 	struct pipe_buffer *bufs;
@@ -141,23 +168,23 @@ static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
 }
 
 /**
- * pipe_empty - Return true if the pipe is empty
+ * pipe_occupancy - Return number of slots used in the pipe
  * @head: The pipe ring head pointer
  * @tail: The pipe ring tail pointer
  */
-static inline bool pipe_empty(unsigned int head, unsigned int tail)
+static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
 {
-	return head == tail;
+	return (pipe_index_t)(head - tail);
 }
 
 /**
- * pipe_occupancy - Return number of slots used in the pipe
+ * pipe_empty - Return true if the pipe is empty
  * @head: The pipe ring head pointer
  * @tail: The pipe ring tail pointer
  */
-static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
+static inline bool pipe_empty(unsigned int head, unsigned int tail)
 {
-	return head - tail;
+	return !pipe_occupancy(head, tail);
 }
 
 /**
@@ -173,6 +200,33 @@ static inline bool pipe_full(unsigned int head, unsigned int tail,
 }
 
 /**
+ * pipe_is_full - Return true if the pipe is full
+ * @pipe: the pipe
+ */
+static inline bool pipe_is_full(const struct pipe_inode_info *pipe)
+{
+	return pipe_full(pipe->head, pipe->tail, pipe->max_usage);
+}
+
+/**
+ * pipe_is_empty - Return true if the pipe is empty
+ * @pipe: the pipe
+ */
+static inline bool pipe_is_empty(const struct pipe_inode_info *pipe)
+{
+	return pipe_empty(pipe->head, pipe->tail);
+}
+
+/**
+ * pipe_buf_usage - Return how many pipe buffers are in use
+ * @pipe: the pipe
+ */
+static inline unsigned int pipe_buf_usage(const struct pipe_inode_info *pipe)
+{
+	return pipe_occupancy(pipe->head, pipe->tail);
+}
+
+/**
  * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
  * @pipe: The pipe to access
  * @slot: The slot of interest
@@ -245,15 +299,6 @@ static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
 	return buf->ops->try_steal(pipe, buf);
 }
 
-static inline void pipe_discard_from(struct pipe_inode_info *pipe,
-		unsigned int old_head)
-{
-	unsigned int mask = pipe->ring_size - 1;
-
-	while (pipe->head > old_head)
-		pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
-}
-
 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 #define PIPE_SIZE		PAGE_SIZE