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#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 * @fasync_readers: reader side fasync
52 * @fasync_writers: writer side fasync
53 * @bufs: the circular array of pipe buffers
54 * @user: the user who created this pipe
55 * @watch_queue: If this pipe is a watch_queue, this is the stuff for that
56 **/
57struct pipe_inode_info {
58 struct mutex mutex;
59 wait_queue_head_t rd_wait, wr_wait;
60 unsigned int head;
61 unsigned int tail;
62 unsigned int max_usage;
63 unsigned int ring_size;
64#ifdef CONFIG_WATCH_QUEUE
65 bool note_loss;
66#endif
67 unsigned int nr_accounted;
68 unsigned int readers;
69 unsigned int writers;
70 unsigned int files;
71 unsigned int r_counter;
72 unsigned int w_counter;
73 struct page *tmp_page;
74 struct fasync_struct *fasync_readers;
75 struct fasync_struct *fasync_writers;
76 struct pipe_buffer *bufs;
77 struct user_struct *user;
78#ifdef CONFIG_WATCH_QUEUE
79 struct watch_queue *watch_queue;
80#endif
81};
82
83/*
84 * Note on the nesting of these functions:
85 *
86 * ->confirm()
87 * ->try_steal()
88 *
89 * That is, ->try_steal() must be called on a confirmed buffer. See below for
90 * the meaning of each operation. Also see the kerneldoc in fs/pipe.c for the
91 * pipe and generic variants of these hooks.
92 */
93struct pipe_buf_operations {
94 /*
95 * ->confirm() verifies that the data in the pipe buffer is there
96 * and that the contents are good. If the pages in the pipe belong
97 * to a file system, we may need to wait for IO completion in this
98 * hook. Returns 0 for good, or a negative error value in case of
99 * error. If not present all pages are considered good.
100 */
101 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
102
103 /*
104 * When the contents of this pipe buffer has been completely
105 * consumed by a reader, ->release() is called.
106 */
107 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
108
109 /*
110 * Attempt to take ownership of the pipe buffer and its contents.
111 * ->try_steal() returns %true for success, in which case the contents
112 * of the pipe (the buf->page) is locked and now completely owned by the
113 * caller. The page may then be transferred to a different mapping, the
114 * most often used case is insertion into different file address space
115 * cache.
116 */
117 bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
118
119 /*
120 * Get a reference to the pipe buffer.
121 */
122 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
123};
124
125/**
126 * pipe_empty - Return true if the pipe is empty
127 * @head: The pipe ring head pointer
128 * @tail: The pipe ring tail pointer
129 */
130static inline bool pipe_empty(unsigned int head, unsigned int tail)
131{
132 return head == tail;
133}
134
135/**
136 * pipe_occupancy - Return number of slots used in the pipe
137 * @head: The pipe ring head pointer
138 * @tail: The pipe ring tail pointer
139 */
140static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
141{
142 return head - tail;
143}
144
145/**
146 * pipe_full - Return true if the pipe is full
147 * @head: The pipe ring head pointer
148 * @tail: The pipe ring tail pointer
149 * @limit: The maximum amount of slots available.
150 */
151static inline bool pipe_full(unsigned int head, unsigned int tail,
152 unsigned int limit)
153{
154 return pipe_occupancy(head, tail) >= limit;
155}
156
157/**
158 * pipe_space_for_user - Return number of slots available to userspace
159 * @head: The pipe ring head pointer
160 * @tail: The pipe ring tail pointer
161 * @pipe: The pipe info structure
162 */
163static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
164 struct pipe_inode_info *pipe)
165{
166 unsigned int p_occupancy, p_space;
167
168 p_occupancy = pipe_occupancy(head, tail);
169 if (p_occupancy >= pipe->max_usage)
170 return 0;
171 p_space = pipe->ring_size - p_occupancy;
172 if (p_space > pipe->max_usage)
173 p_space = pipe->max_usage;
174 return p_space;
175}
176
177/**
178 * pipe_buf_get - get a reference to a pipe_buffer
179 * @pipe: the pipe that the buffer belongs to
180 * @buf: the buffer to get a reference to
181 *
182 * Return: %true if the reference was successfully obtained.
183 */
184static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
185 struct pipe_buffer *buf)
186{
187 return buf->ops->get(pipe, buf);
188}
189
190/**
191 * pipe_buf_release - put a reference to a pipe_buffer
192 * @pipe: the pipe that the buffer belongs to
193 * @buf: the buffer to put a reference to
194 */
195static inline void pipe_buf_release(struct pipe_inode_info *pipe,
196 struct pipe_buffer *buf)
197{
198 const struct pipe_buf_operations *ops = buf->ops;
199
200 buf->ops = NULL;
201 ops->release(pipe, buf);
202}
203
204/**
205 * pipe_buf_confirm - verify contents of the pipe buffer
206 * @pipe: the pipe that the buffer belongs to
207 * @buf: the buffer to confirm
208 */
209static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
210 struct pipe_buffer *buf)
211{
212 if (!buf->ops->confirm)
213 return 0;
214 return buf->ops->confirm(pipe, buf);
215}
216
217/**
218 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
219 * @pipe: the pipe that the buffer belongs to
220 * @buf: the buffer to attempt to steal
221 */
222static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
223 struct pipe_buffer *buf)
224{
225 if (!buf->ops->try_steal)
226 return false;
227 return buf->ops->try_steal(pipe, buf);
228}
229
230/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
231 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
232#define PIPE_SIZE PAGE_SIZE
233
234/* Pipe lock and unlock operations */
235void pipe_lock(struct pipe_inode_info *);
236void pipe_unlock(struct pipe_inode_info *);
237void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
238
239extern unsigned int pipe_max_size;
240extern unsigned long pipe_user_pages_hard;
241extern unsigned long pipe_user_pages_soft;
242
243/* Wait for a pipe to be readable/writable while dropping the pipe lock */
244void pipe_wait_readable(struct pipe_inode_info *);
245void pipe_wait_writable(struct pipe_inode_info *);
246
247struct pipe_inode_info *alloc_pipe_info(void);
248void free_pipe_info(struct pipe_inode_info *);
249
250/* Generic pipe buffer ops functions */
251bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
252bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
253void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
254
255extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
256
257#ifdef CONFIG_WATCH_QUEUE
258unsigned long account_pipe_buffers(struct user_struct *user,
259 unsigned long old, unsigned long new);
260bool too_many_pipe_buffers_soft(unsigned long user_bufs);
261bool too_many_pipe_buffers_hard(unsigned long user_bufs);
262bool pipe_is_unprivileged_user(void);
263#endif
264
265/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
266#ifdef CONFIG_WATCH_QUEUE
267int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
268#endif
269long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
270struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
271
272int create_pipe_files(struct file **, int);
273unsigned int round_pipe_size(unsigned long size);
274
275#endif