Linux kernel mirror (for testing)
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linux
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 **/
20struct 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 * @user: the user who created this pipe
46 **/
47struct pipe_inode_info {
48 struct mutex mutex;
49 wait_queue_head_t wait;
50 unsigned int nrbufs, curbuf, buffers;
51 unsigned int readers;
52 unsigned int writers;
53 unsigned int files;
54 unsigned int waiting_writers;
55 unsigned int r_counter;
56 unsigned int w_counter;
57 struct page *tmp_page;
58 struct fasync_struct *fasync_readers;
59 struct fasync_struct *fasync_writers;
60 struct pipe_buffer *bufs;
61 struct user_struct *user;
62};
63
64/*
65 * Note on the nesting of these functions:
66 *
67 * ->confirm()
68 * ->steal()
69 *
70 * That is, ->steal() must be called on a confirmed buffer.
71 * See below for the meaning of each operation. Also see kerneldoc
72 * in fs/pipe.c for the pipe and generic variants of these hooks.
73 */
74struct pipe_buf_operations {
75 /*
76 * This is set to 1, if the generic pipe read/write may coalesce
77 * data into an existing buffer. If this is set to 0, a new pipe
78 * page segment is always used for new data.
79 */
80 int can_merge;
81
82 /*
83 * ->confirm() verifies that the data in the pipe buffer is there
84 * and that the contents are good. If the pages in the pipe belong
85 * to a file system, we may need to wait for IO completion in this
86 * hook. Returns 0 for good, or a negative error value in case of
87 * error.
88 */
89 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
90
91 /*
92 * When the contents of this pipe buffer has been completely
93 * consumed by a reader, ->release() is called.
94 */
95 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
96
97 /*
98 * Attempt to take ownership of the pipe buffer and its contents.
99 * ->steal() returns 0 for success, in which case the contents
100 * of the pipe (the buf->page) is locked and now completely owned
101 * by the caller. The page may then be transferred to a different
102 * mapping, the most often used case is insertion into different
103 * file address space cache.
104 */
105 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
106
107 /*
108 * Get a reference to the pipe buffer.
109 */
110 void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
111};
112
113/**
114 * pipe_buf_get - get a reference to a pipe_buffer
115 * @pipe: the pipe that the buffer belongs to
116 * @buf: the buffer to get a reference to
117 */
118static inline void pipe_buf_get(struct pipe_inode_info *pipe,
119 struct pipe_buffer *buf)
120{
121 buf->ops->get(pipe, buf);
122}
123
124/**
125 * pipe_buf_release - put a reference to a pipe_buffer
126 * @pipe: the pipe that the buffer belongs to
127 * @buf: the buffer to put a reference to
128 */
129static inline void pipe_buf_release(struct pipe_inode_info *pipe,
130 struct pipe_buffer *buf)
131{
132 const struct pipe_buf_operations *ops = buf->ops;
133
134 buf->ops = NULL;
135 ops->release(pipe, buf);
136}
137
138/**
139 * pipe_buf_confirm - verify contents of the pipe buffer
140 * @pipe: the pipe that the buffer belongs to
141 * @buf: the buffer to confirm
142 */
143static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
144 struct pipe_buffer *buf)
145{
146 return buf->ops->confirm(pipe, buf);
147}
148
149/**
150 * pipe_buf_steal - attempt to take ownership of a pipe_buffer
151 * @pipe: the pipe that the buffer belongs to
152 * @buf: the buffer to attempt to steal
153 */
154static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
155 struct pipe_buffer *buf)
156{
157 return buf->ops->steal(pipe, buf);
158}
159
160/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
161 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
162#define PIPE_SIZE PAGE_SIZE
163
164/* Pipe lock and unlock operations */
165void pipe_lock(struct pipe_inode_info *);
166void pipe_unlock(struct pipe_inode_info *);
167void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
168
169extern unsigned int pipe_max_size, pipe_min_size;
170extern unsigned long pipe_user_pages_hard;
171extern unsigned long pipe_user_pages_soft;
172int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
173
174/* Drop the inode semaphore and wait for a pipe event, atomically */
175void pipe_wait(struct pipe_inode_info *pipe);
176
177struct pipe_inode_info *alloc_pipe_info(void);
178void free_pipe_info(struct pipe_inode_info *);
179
180/* Generic pipe buffer ops functions */
181void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
182int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
183int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
184void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
185
186extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
187
188/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
189long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
190struct pipe_inode_info *get_pipe_info(struct file *file);
191
192int create_pipe_files(struct file **, int);
193
194#endif