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#define PIPE_BUF_FLAG_CAN_MERGE 0x10 /* can merge buffers */
12#define PIPE_BUF_FLAG_WHOLE 0x20 /* read() must return entire buffer or error */
13#ifdef CONFIG_WATCH_QUEUE
14#define PIPE_BUF_FLAG_LOSS 0x40 /* Message loss happened after this buffer */
15#endif
16
17/**
18 * struct pipe_buffer - a linux kernel pipe buffer
19 * @page: the page containing the data for the pipe buffer
20 * @offset: offset of data inside the @page
21 * @len: length of data inside the @page
22 * @ops: operations associated with this buffer. See @pipe_buf_operations.
23 * @flags: pipe buffer flags. See above.
24 * @private: private data owned by the ops.
25 **/
26struct pipe_buffer {
27 struct page *page;
28 unsigned int offset, len;
29 const struct pipe_buf_operations *ops;
30 unsigned int flags;
31 unsigned long private;
32};
33
34/**
35 * struct pipe_inode_info - a linux kernel pipe
36 * @mutex: mutex protecting the whole thing
37 * @rd_wait: reader wait point in case of empty pipe
38 * @wr_wait: writer wait point in case of full pipe
39 * @head: The point of buffer production
40 * @tail: The point of buffer consumption
41 * @note_loss: The next read() should insert a data-lost message
42 * @max_usage: The maximum number of slots that may be used in the ring
43 * @ring_size: total number of buffers (should be a power of 2)
44 * @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
45 * @tmp_page: cached released page
46 * @readers: number of current readers of this pipe
47 * @writers: number of current writers of this pipe
48 * @files: number of struct file referring this pipe (protected by ->i_lock)
49 * @r_counter: reader counter
50 * @w_counter: writer counter
51 * @poll_usage: is this pipe used for epoll, which has crazy wakeups?
52 * @fasync_readers: reader side fasync
53 * @fasync_writers: writer side fasync
54 * @bufs: the circular array of pipe buffers
55 * @user: the user who created this pipe
56 * @watch_queue: If this pipe is a watch_queue, this is the stuff for that
57 **/
58struct pipe_inode_info {
59 struct mutex mutex;
60 wait_queue_head_t rd_wait, wr_wait;
61 unsigned int head;
62 unsigned int tail;
63 unsigned int max_usage;
64 unsigned int ring_size;
65#ifdef CONFIG_WATCH_QUEUE
66 bool note_loss;
67#endif
68 unsigned int nr_accounted;
69 unsigned int readers;
70 unsigned int writers;
71 unsigned int files;
72 unsigned int r_counter;
73 unsigned int w_counter;
74 bool poll_usage;
75 struct page *tmp_page;
76 struct fasync_struct *fasync_readers;
77 struct fasync_struct *fasync_writers;
78 struct pipe_buffer *bufs;
79 struct user_struct *user;
80#ifdef CONFIG_WATCH_QUEUE
81 struct watch_queue *watch_queue;
82#endif
83};
84
85/*
86 * Note on the nesting of these functions:
87 *
88 * ->confirm()
89 * ->try_steal()
90 *
91 * That is, ->try_steal() must be called on a confirmed buffer. See below for
92 * the meaning of each operation. Also see the kerneldoc in fs/pipe.c for the
93 * pipe and generic variants of these hooks.
94 */
95struct pipe_buf_operations {
96 /*
97 * ->confirm() verifies that the data in the pipe buffer is there
98 * and that the contents are good. If the pages in the pipe belong
99 * to a file system, we may need to wait for IO completion in this
100 * hook. Returns 0 for good, or a negative error value in case of
101 * error. If not present all pages are considered good.
102 */
103 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
104
105 /*
106 * When the contents of this pipe buffer has been completely
107 * consumed by a reader, ->release() is called.
108 */
109 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
110
111 /*
112 * Attempt to take ownership of the pipe buffer and its contents.
113 * ->try_steal() returns %true for success, in which case the contents
114 * of the pipe (the buf->page) is locked and now completely owned by the
115 * caller. The page may then be transferred to a different mapping, the
116 * most often used case is insertion into different file address space
117 * cache.
118 */
119 bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
120
121 /*
122 * Get a reference to the pipe buffer.
123 */
124 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
125};
126
127/**
128 * pipe_empty - Return true if the pipe is empty
129 * @head: The pipe ring head pointer
130 * @tail: The pipe ring tail pointer
131 */
132static inline bool pipe_empty(unsigned int head, unsigned int tail)
133{
134 return head == tail;
135}
136
137/**
138 * pipe_occupancy - Return number of slots used in the pipe
139 * @head: The pipe ring head pointer
140 * @tail: The pipe ring tail pointer
141 */
142static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
143{
144 return head - tail;
145}
146
147/**
148 * pipe_full - Return true if the pipe is full
149 * @head: The pipe ring head pointer
150 * @tail: The pipe ring tail pointer
151 * @limit: The maximum amount of slots available.
152 */
153static inline bool pipe_full(unsigned int head, unsigned int tail,
154 unsigned int limit)
155{
156 return pipe_occupancy(head, tail) >= limit;
157}
158
159/**
160 * pipe_buf_get - get a reference to a pipe_buffer
161 * @pipe: the pipe that the buffer belongs to
162 * @buf: the buffer to get a reference to
163 *
164 * Return: %true if the reference was successfully obtained.
165 */
166static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
167 struct pipe_buffer *buf)
168{
169 return buf->ops->get(pipe, buf);
170}
171
172/**
173 * pipe_buf_release - put a reference to a pipe_buffer
174 * @pipe: the pipe that the buffer belongs to
175 * @buf: the buffer to put a reference to
176 */
177static inline void pipe_buf_release(struct pipe_inode_info *pipe,
178 struct pipe_buffer *buf)
179{
180 const struct pipe_buf_operations *ops = buf->ops;
181
182 buf->ops = NULL;
183 ops->release(pipe, buf);
184}
185
186/**
187 * pipe_buf_confirm - verify contents of the pipe buffer
188 * @pipe: the pipe that the buffer belongs to
189 * @buf: the buffer to confirm
190 */
191static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
192 struct pipe_buffer *buf)
193{
194 if (!buf->ops->confirm)
195 return 0;
196 return buf->ops->confirm(pipe, buf);
197}
198
199/**
200 * pipe_buf_try_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 bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
205 struct pipe_buffer *buf)
206{
207 if (!buf->ops->try_steal)
208 return false;
209 return buf->ops->try_steal(pipe, buf);
210}
211
212static inline void pipe_discard_from(struct pipe_inode_info *pipe,
213 unsigned int old_head)
214{
215 unsigned int mask = pipe->ring_size - 1;
216
217 while (pipe->head > old_head)
218 pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
219}
220
221/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
222 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
223#define PIPE_SIZE PAGE_SIZE
224
225/* Pipe lock and unlock operations */
226void pipe_lock(struct pipe_inode_info *);
227void pipe_unlock(struct pipe_inode_info *);
228void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
229
230/* Wait for a pipe to be readable/writable while dropping the pipe lock */
231void pipe_wait_readable(struct pipe_inode_info *);
232void pipe_wait_writable(struct pipe_inode_info *);
233
234struct pipe_inode_info *alloc_pipe_info(void);
235void free_pipe_info(struct pipe_inode_info *);
236
237/* Generic pipe buffer ops functions */
238bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
239bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
240void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
241
242extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
243
244#ifdef CONFIG_WATCH_QUEUE
245unsigned long account_pipe_buffers(struct user_struct *user,
246 unsigned long old, unsigned long new);
247bool too_many_pipe_buffers_soft(unsigned long user_bufs);
248bool too_many_pipe_buffers_hard(unsigned long user_bufs);
249bool pipe_is_unprivileged_user(void);
250#endif
251
252/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
253#ifdef CONFIG_WATCH_QUEUE
254int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
255#endif
256long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
257struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
258
259int create_pipe_files(struct file **, int);
260unsigned int round_pipe_size(unsigned long size);
261
262#endif
263

source code of linux/include/linux/pipe_fs_i.h