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 **/
26 struct 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 **/
58 struct 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 unsigned int nr_accounted;
66 unsigned int readers;
67 unsigned int writers;
68 unsigned int files;
69 unsigned int r_counter;
70 unsigned int w_counter;
71 bool poll_usage;
72 #ifdef CONFIG_WATCH_QUEUE
73 bool note_loss;
74 #endif
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 */
95 struct 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_has_watch_queue - Check whether the pipe is a watch_queue,
129 * i.e. it was created with O_NOTIFICATION_PIPE
130 * @pipe: The pipe to check
131 *
132 * Return: true if pipe is a watch queue, false otherwise.
133 */
134 static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
135 {
136 #ifdef CONFIG_WATCH_QUEUE
137 return pipe->watch_queue != NULL;
138 #else
139 return false;
140 #endif
141 }
142
143 /**
144 * pipe_empty - Return true if the pipe is empty
145 * @head: The pipe ring head pointer
146 * @tail: The pipe ring tail pointer
147 */
148 static inline bool pipe_empty(unsigned int head, unsigned int tail)
149 {
150 return head == tail;
151 }
152
153 /**
154 * pipe_occupancy - Return number of slots used in the pipe
155 * @head: The pipe ring head pointer
156 * @tail: The pipe ring tail pointer
157 */
158 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
159 {
160 return head - tail;
161 }
162
163 /**
164 * pipe_full - Return true if the pipe is full
165 * @head: The pipe ring head pointer
166 * @tail: The pipe ring tail pointer
167 * @limit: The maximum amount of slots available.
168 */
169 static inline bool pipe_full(unsigned int head, unsigned int tail,
170 unsigned int limit)
171 {
172 return pipe_occupancy(head, tail) >= limit;
173 }
174
175 /**
176 * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
177 * @pipe: The pipe to access
178 * @slot: The slot of interest
179 */
180 static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
181 unsigned int slot)
182 {
183 return &pipe->bufs[slot & (pipe->ring_size - 1)];
184 }
185
186 /**
187 * pipe_head_buf - Return the pipe buffer at the head of the pipe ring
188 * @pipe: The pipe to access
189 */
190 static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe)
191 {
192 return pipe_buf(pipe, pipe->head);
193 }
194
195 /**
196 * pipe_buf_get - get a reference to a pipe_buffer
197 * @pipe: the pipe that the buffer belongs to
198 * @buf: the buffer to get a reference to
199 *
200 * Return: %true if the reference was successfully obtained.
201 */
202 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
203 struct pipe_buffer *buf)
204 {
205 return buf->ops->get(pipe, buf);
206 }
207
208 /**
209 * pipe_buf_release - put a reference to a pipe_buffer
210 * @pipe: the pipe that the buffer belongs to
211 * @buf: the buffer to put a reference to
212 */
213 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
214 struct pipe_buffer *buf)
215 {
216 const struct pipe_buf_operations *ops = buf->ops;
217
218 buf->ops = NULL;
219 ops->release(pipe, buf);
220 }
221
222 /**
223 * pipe_buf_confirm - verify contents of the pipe buffer
224 * @pipe: the pipe that the buffer belongs to
225 * @buf: the buffer to confirm
226 */
227 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
228 struct pipe_buffer *buf)
229 {
230 if (!buf->ops->confirm)
231 return 0;
232 return buf->ops->confirm(pipe, buf);
233 }
234
235 /**
236 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
237 * @pipe: the pipe that the buffer belongs to
238 * @buf: the buffer to attempt to steal
239 */
240 static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
241 struct pipe_buffer *buf)
242 {
243 if (!buf->ops->try_steal)
244 return false;
245 return buf->ops->try_steal(pipe, buf);
246 }
247
248 static inline void pipe_discard_from(struct pipe_inode_info *pipe,
249 unsigned int old_head)
250 {
251 unsigned int mask = pipe->ring_size - 1;
252
253 while (pipe->head > old_head)
254 pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
255 }
256
257 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
258 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
259 #define PIPE_SIZE PAGE_SIZE
260
261 /* Pipe lock and unlock operations */
262 void pipe_lock(struct pipe_inode_info *);
263 void pipe_unlock(struct pipe_inode_info *);
264 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
265
266 /* Wait for a pipe to be readable/writable while dropping the pipe lock */
267 void pipe_wait_readable(struct pipe_inode_info *);
268 void pipe_wait_writable(struct pipe_inode_info *);
269
270 struct pipe_inode_info *alloc_pipe_info(void);
271 void free_pipe_info(struct pipe_inode_info *);
272
273 /* Generic pipe buffer ops functions */
274 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
275 bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
276 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
277
278 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
279
280 unsigned long account_pipe_buffers(struct user_struct *user,
281 unsigned long old, unsigned long new);
282 bool too_many_pipe_buffers_soft(unsigned long user_bufs);
283 bool too_many_pipe_buffers_hard(unsigned long user_bufs);
284 bool pipe_is_unprivileged_user(void);
285
286 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
287 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
288 long pipe_fcntl(struct file *, unsigned int, unsigned int arg);
289 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
290
291 int create_pipe_files(struct file **, int);
292 unsigned int round_pipe_size(unsigned int size);
293
294 #endif
295
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