relay revamp v8

@@ -0,0 +1,176 @@
+/*
+ * linux/include/linux/relay.h
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected])
+ * Copyright (C) 2008 - Tom Zanussi ([email protected])
+ *
+ * CONFIG_RELAY definitions and declarations
+ */
+
+#ifndef _LINUX_RELAY_H
+#define _LINUX_RELAY_H
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/wait.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/kref.h>
+#include <linux/pagevec.h>
+
+/*
+ * relay channel flags
+ */
+#define RCHAN_GLOBAL_BUFFER		0x00000001	/* not using per-cpu */
+
+/*
+ * For page lists
+ */
+struct relay_page {
+	struct page *page;
+	size_t len;
+	struct list_head list;
+	struct relay_page_callbacks *cb;
+	void *private_data;
+};
+
+/*
+ * Per-cpu relay channel buffer
+ */
+struct rchan_buf {
+	struct rchan *chan;		/* associated channel */
+	wait_queue_head_t read_wait;	/* reader wait queue */
+	struct timer_list timer; 	/* reader wake-up timer */
+	struct dentry *dentry;		/* channel file dentry */
+	struct kref kref;		/* channel buffer refcount */
+	struct list_head pages;		/* current set of unconsumed pages */
+	size_t nr_pages;		/* number of unconsumed pages */
+	spinlock_t lock;		/* protect pages list */
+	size_t consumed_offset;		/* bytes consumed in cur page */
+	unsigned int finalized;		/* buffer has been finalized */
+	unsigned int cpu;		/* this buf's cpu */
+} ____cacheline_aligned;
+
+/*
+ * Relay channel data structure
+ */
+struct rchan
+{
+	size_t n_pages_wakeup;		/* wake up readers after filling n */
+	struct rchan_callbacks *cb;	/* client callbacks */
+	struct kref kref;		/* channel refcount */
+	void *private_data;		/* for user-defined data */
+	struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+	struct list_head list;		/* for channel list */
+	struct dentry *parent;		/* parent dentry passed to open */
+	char base_filename[NAME_MAX];	/* saved base filename */
+	unsigned long flags;		/* relay flags for this channel */
+};
+
+/*
+ * Relay channel client callbacks
+ */
+struct rchan_callbacks
+{
+	/*
+	 * create_buf_file - create file to represent a relay channel buffer
+	 * @filename: the name of the file to create
+	 * @parent: the parent of the file to create
+	 * @mode: the mode of the file to create
+	 * @buf: the channel buffer
+	 *
+	 * Called during relay_open(), once for each per-cpu buffer,
+	 * to allow the client to create a file to be used to
+	 * represent the corresponding channel buffer.  If the file is
+	 * created outside of relay, the parent must also exist in
+	 * that filesystem.
+	 *
+	 * The callback should return the dentry of the file created
+	 * to represent the relay buffer.
+	 *
+	 * See Documentation/filesystems/relayfs.txt for more info.
+	 */
+	struct dentry *(*create_buf_file)(const char *filename,
+					  struct dentry *parent,
+					  int mode,
+					  struct rchan_buf *buf);
+
+	/*
+	 * remove_buf_file - remove file representing a relay channel buffer
+	 * @dentry: the dentry of the file to remove
+	 *
+	 * Called during relay_close(), once for each per-cpu buffer,
+	 * to allow the client to remove a file used to represent a
+	 * channel buffer.
+	 *
+	 * The callback should return 0 if successful, negative if not.
+	 */
+	int (*remove_buf_file)(struct dentry *dentry);
+};
+
+/*
+ * Relay page callbacks
+ */
+struct relay_page_callbacks
+{
+	/*
+	 * page_released - notification that a page is ready for re-use
+	 * @page: the released page
+	 * @private_data: user-defined data associated with the page
+	 *
+	 * This callback is a notification that a given page has been
+	 * read by userspace and can be re-used.  Always called in
+	 * user context.
+	 */
+	void (*page_released) (struct page *page, void *private_data);
+
+	/*
+	 * page_released - notification that a page has been stolen
+	 * @page: the stolen page
+	 * @private_data: user-defined data associated with the page
+	 *
+	 * This callback is a notification that a given page has been
+	 * stolen by userspace.  The owner may wish to replace it;
+	 * this gives it the opportunity to do so.  Always called in
+	 * user context.
+	 */
+	void (*page_stolen) (struct page *page, void *private_data);
+};
+
+/*
+ * CONFIG_RELAY kernel API, kernel/relay.c
+ */
+
+extern struct rchan *relay_open(const char *base_filename,
+				struct dentry *parent,
+				size_t n_pages_wakeup,
+				struct rchan_callbacks *cb,
+				void *private_data,
+				unsigned long rchan_flags);
+extern void relay_add_partial_page(struct rchan *chan,
+				   struct page *page,
+				   size_t len,
+				   struct relay_page_callbacks *cb,
+				   void *private_data);
+extern void relay_add_page(struct rchan *chan,
+			   struct page *page,
+			   struct relay_page_callbacks *cb,
+			   void *private_data);
+extern void relay_add_pages(struct rchan *chan,
+			    struct pagevec *pages,
+			    struct relay_page_callbacks *cb,
+			    void *private_data);
+extern void relay_flush(struct rchan *chan);
+extern void relay_close(struct rchan *chan);
+extern void relay_reset(struct rchan *chan);
+
+/*
+ * exported relay file operations, kernel/relay.c
+ */
+extern const struct file_operations relay_file_operations;
+
+#endif /* _LINUX_RELAY_H */
+

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