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