1 #ifndef _LINUX_PIPE_FS_I_H
2 #define _LINUX_PIPE_FS_I_H
3 
4 #define PIPE_DEF_BUFFERS	16
5 
6 #define PIPE_BUF_FLAG_LRU	0x01	/* page is on the LRU */
7 #define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
8 #define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
9 #define PIPE_BUF_FLAG_PACKET	0x08	/* read() as a packet */
10 
11 /**
12  *	struct pipe_buffer - a linux kernel pipe buffer
13  *	@page: the page containing the data for the pipe buffer
14  *	@offset: offset of data inside the @page
15  *	@len: length of data inside the @page
16  *	@ops: operations associated with this buffer. See @pipe_buf_operations.
17  *	@flags: pipe buffer flags. See above.
18  *	@private: private data owned by the ops.
19  **/
20 struct pipe_buffer {
21 	struct page *page;
22 	unsigned int offset, len;
23 	const struct pipe_buf_operations *ops;
24 	unsigned int flags;
25 	unsigned long private;
26 };
27 
28 /**
29  *	struct pipe_inode_info - a linux kernel pipe
30  *	@mutex: mutex protecting the whole thing
31  *	@wait: reader/writer wait point in case of empty/full pipe
32  *	@nrbufs: the number of non-empty pipe buffers in this pipe
33  *	@buffers: total number of buffers (should be a power of 2)
34  *	@curbuf: the current pipe buffer entry
35  *	@tmp_page: cached released page
36  *	@readers: number of current readers of this pipe
37  *	@writers: number of current writers of this pipe
38  *	@files: number of struct file referring this pipe (protected by ->i_lock)
39  *	@waiting_writers: number of writers blocked waiting for room
40  *	@r_counter: reader counter
41  *	@w_counter: writer counter
42  *	@fasync_readers: reader side fasync
43  *	@fasync_writers: writer side fasync
44  *	@bufs: the circular array of pipe buffers
45  **/
46 struct pipe_inode_info {
47 	struct mutex mutex;
48 	wait_queue_head_t wait;
49 	unsigned int nrbufs, curbuf, buffers;
50 	unsigned int readers;
51 	unsigned int writers;
52 	unsigned int files;
53 	unsigned int waiting_writers;
54 	unsigned int r_counter;
55 	unsigned int w_counter;
56 	struct page *tmp_page;
57 	struct fasync_struct *fasync_readers;
58 	struct fasync_struct *fasync_writers;
59 	struct pipe_buffer *bufs;
60 };
61 
62 /*
63  * Note on the nesting of these functions:
64  *
65  * ->confirm()
66  *	->steal()
67  *	...
68  *	->map()
69  *	...
70  *	->unmap()
71  *
72  * That is, ->map() must be called on a confirmed buffer,
73  * same goes for ->steal(). See below for the meaning of each
74  * operation. Also see kerneldoc in fs/pipe.c for the pipe
75  * and generic variants of these hooks.
76  */
77 struct pipe_buf_operations {
78 	/*
79 	 * This is set to 1, if the generic pipe read/write may coalesce
80 	 * data into an existing buffer. If this is set to 0, a new pipe
81 	 * page segment is always used for new data.
82 	 */
83 	int can_merge;
84 
85 	/*
86 	 * ->confirm() verifies that the data in the pipe buffer is there
87 	 * and that the contents are good. If the pages in the pipe belong
88 	 * to a file system, we may need to wait for IO completion in this
89 	 * hook. Returns 0 for good, or a negative error value in case of
90 	 * error.
91 	 */
92 	int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
93 
94 	/*
95 	 * When the contents of this pipe buffer has been completely
96 	 * consumed by a reader, ->release() is called.
97 	 */
98 	void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
99 
100 	/*
101 	 * Attempt to take ownership of the pipe buffer and its contents.
102 	 * ->steal() returns 0 for success, in which case the contents
103 	 * of the pipe (the buf->page) is locked and now completely owned
104 	 * by the caller. The page may then be transferred to a different
105 	 * mapping, the most often used case is insertion into different
106 	 * file address space cache.
107 	 */
108 	int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
109 
110 	/*
111 	 * Get a reference to the pipe buffer.
112 	 */
113 	void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
114 };
115 
116 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
117    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
118 #define PIPE_SIZE		PAGE_SIZE
119 
120 /* Pipe lock and unlock operations */
121 void pipe_lock(struct pipe_inode_info *);
122 void pipe_unlock(struct pipe_inode_info *);
123 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
124 
125 extern unsigned int pipe_max_size, pipe_min_size;
126 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
127 
128 
129 /* Drop the inode semaphore and wait for a pipe event, atomically */
130 void pipe_wait(struct pipe_inode_info *pipe);
131 
132 struct pipe_inode_info *alloc_pipe_info(void);
133 void free_pipe_info(struct pipe_inode_info *);
134 
135 /* Generic pipe buffer ops functions */
136 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
137 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
138 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
139 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
140 
141 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
142 
143 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
144 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
145 struct pipe_inode_info *get_pipe_info(struct file *file);
146 
147 int create_pipe_files(struct file **, int);
148 
149 #endif
150