Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_PIPE_FS_I_H
3#define _LINUX_PIPE_FS_I_H
4
5#define PIPE_DEF_BUFFERS 16
6
7#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
8#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
9#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
10#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
11
12/**
13 * struct pipe_buffer - a linux kernel pipe buffer
14 * @page: the page containing the data for the pipe buffer
15 * @offset: offset of data inside the @page
16 * @len: length of data inside the @page
17 * @ops: operations associated with this buffer. See @pipe_buf_operations.
18 * @flags: pipe buffer flags. See above.
19 * @private: private data owned by the ops.
20 **/
21struct pipe_buffer {
22 struct page *page;
23 unsigned int offset, len;
24 const struct pipe_buf_operations *ops;
25 unsigned int flags;
26 unsigned long private;
27};
28
29/**
30 * struct pipe_inode_info - a linux kernel pipe
31 * @mutex: mutex protecting the whole thing
32 * @rd_wait: reader wait point in case of empty pipe
33 * @wr_wait: writer wait point in case of full pipe
34 * @head: The point of buffer production
35 * @tail: The point of buffer consumption
36 * @max_usage: The maximum number of slots that may be used in the ring
37 * @ring_size: total number of buffers (should be a power of 2)
38 * @tmp_page: cached released page
39 * @readers: number of current readers of this pipe
40 * @writers: number of current writers of this pipe
41 * @files: number of struct file referring this pipe (protected by ->i_lock)
42 * @r_counter: reader counter
43 * @w_counter: writer counter
44 * @fasync_readers: reader side fasync
45 * @fasync_writers: writer side fasync
46 * @bufs: the circular array of pipe buffers
47 * @user: the user who created this pipe
48 **/
49struct pipe_inode_info {
50 struct mutex mutex;
51 wait_queue_head_t rd_wait, wr_wait;
52 unsigned int head;
53 unsigned int tail;
54 unsigned int max_usage;
55 unsigned int ring_size;
56 unsigned int readers;
57 unsigned int writers;
58 unsigned int files;
59 unsigned int r_counter;
60 unsigned int w_counter;
61 struct page *tmp_page;
62 struct fasync_struct *fasync_readers;
63 struct fasync_struct *fasync_writers;
64 struct pipe_buffer *bufs;
65 struct user_struct *user;
66};
67
68/*
69 * Note on the nesting of these functions:
70 *
71 * ->confirm()
72 * ->steal()
73 *
74 * That is, ->steal() must be called on a confirmed buffer.
75 * See below for the meaning of each operation. Also see kerneldoc
76 * in fs/pipe.c for the pipe and generic variants of these hooks.
77 */
78struct pipe_buf_operations {
79 /*
80 * ->confirm() verifies that the data in the pipe buffer is there
81 * and that the contents are good. If the pages in the pipe belong
82 * to a file system, we may need to wait for IO completion in this
83 * hook. Returns 0 for good, or a negative error value in case of
84 * error.
85 */
86 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
87
88 /*
89 * When the contents of this pipe buffer has been completely
90 * consumed by a reader, ->release() is called.
91 */
92 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
93
94 /*
95 * Attempt to take ownership of the pipe buffer and its contents.
96 * ->steal() returns 0 for success, in which case the contents
97 * of the pipe (the buf->page) is locked and now completely owned
98 * by the caller. The page may then be transferred to a different
99 * mapping, the most often used case is insertion into different
100 * file address space cache.
101 */
102 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
103
104 /*
105 * Get a reference to the pipe buffer.
106 */
107 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
108};
109
110/**
111 * pipe_empty - Return true if the pipe is empty
112 * @head: The pipe ring head pointer
113 * @tail: The pipe ring tail pointer
114 */
115static inline bool pipe_empty(unsigned int head, unsigned int tail)
116{
117 return head == tail;
118}
119
120/**
121 * pipe_occupancy - Return number of slots used in the pipe
122 * @head: The pipe ring head pointer
123 * @tail: The pipe ring tail pointer
124 */
125static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
126{
127 return head - tail;
128}
129
130/**
131 * pipe_full - Return true if the pipe is full
132 * @head: The pipe ring head pointer
133 * @tail: The pipe ring tail pointer
134 * @limit: The maximum amount of slots available.
135 */
136static inline bool pipe_full(unsigned int head, unsigned int tail,
137 unsigned int limit)
138{
139 return pipe_occupancy(head, tail) >= limit;
140}
141
142/**
143 * pipe_space_for_user - Return number of slots available to userspace
144 * @head: The pipe ring head pointer
145 * @tail: The pipe ring tail pointer
146 * @pipe: The pipe info structure
147 */
148static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
149 struct pipe_inode_info *pipe)
150{
151 unsigned int p_occupancy, p_space;
152
153 p_occupancy = pipe_occupancy(head, tail);
154 if (p_occupancy >= pipe->max_usage)
155 return 0;
156 p_space = pipe->ring_size - p_occupancy;
157 if (p_space > pipe->max_usage)
158 p_space = pipe->max_usage;
159 return p_space;
160}
161
162/**
163 * pipe_buf_get - get a reference to a pipe_buffer
164 * @pipe: the pipe that the buffer belongs to
165 * @buf: the buffer to get a reference to
166 *
167 * Return: %true if the reference was successfully obtained.
168 */
169static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
170 struct pipe_buffer *buf)
171{
172 return buf->ops->get(pipe, buf);
173}
174
175/**
176 * pipe_buf_release - put a reference to a pipe_buffer
177 * @pipe: the pipe that the buffer belongs to
178 * @buf: the buffer to put a reference to
179 */
180static inline void pipe_buf_release(struct pipe_inode_info *pipe,
181 struct pipe_buffer *buf)
182{
183 const struct pipe_buf_operations *ops = buf->ops;
184
185 buf->ops = NULL;
186 ops->release(pipe, buf);
187}
188
189/**
190 * pipe_buf_confirm - verify contents of the pipe buffer
191 * @pipe: the pipe that the buffer belongs to
192 * @buf: the buffer to confirm
193 */
194static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
195 struct pipe_buffer *buf)
196{
197 return buf->ops->confirm(pipe, buf);
198}
199
200/**
201 * pipe_buf_steal - attempt to take ownership of a pipe_buffer
202 * @pipe: the pipe that the buffer belongs to
203 * @buf: the buffer to attempt to steal
204 */
205static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
206 struct pipe_buffer *buf)
207{
208 return buf->ops->steal(pipe, buf);
209}
210
211/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
212 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
213#define PIPE_SIZE PAGE_SIZE
214
215/* Pipe lock and unlock operations */
216void pipe_lock(struct pipe_inode_info *);
217void pipe_unlock(struct pipe_inode_info *);
218void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
219
220extern unsigned int pipe_max_size;
221extern unsigned long pipe_user_pages_hard;
222extern unsigned long pipe_user_pages_soft;
223
224/* Drop the inode semaphore and wait for a pipe event, atomically */
225void pipe_wait(struct pipe_inode_info *pipe);
226
227struct pipe_inode_info *alloc_pipe_info(void);
228void free_pipe_info(struct pipe_inode_info *);
229
230/* Generic pipe buffer ops functions */
231bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
232int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
233int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
234int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
235void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
236void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
237
238extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
239
240/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
241long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
242struct pipe_inode_info *get_pipe_info(struct file *file);
243
244int create_pipe_files(struct file **, int);
245unsigned int round_pipe_size(unsigned long size);
246
247#endif