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 * Really only alpha needs 32-bit fields, but
36 * might as well do it for 64-bit architectures
37 * since that's what we've historically done,
38 * and it makes 'head_tail' always be a simple
39 * 'unsigned long'.
40 */
41 #ifdef CONFIG_64BIT
42 typedef unsigned int pipe_index_t;
43 #else
44 typedef unsigned short pipe_index_t;
45 #endif
46
47 /*
48 * We have to declare this outside 'struct pipe_inode_info',
49 * but then we can't use 'union pipe_index' for an anonymous
50 * union, so we end up having to duplicate this declaration
51 * below. Annoying.
52 */
53 union pipe_index {
54 unsigned long head_tail;
55 struct {
56 pipe_index_t head;
57 pipe_index_t tail;
58 };
59 };
60
61 /**
62 * struct pipe_inode_info - a linux kernel pipe
63 * @mutex: mutex protecting the whole thing
64 * @rd_wait: reader wait point in case of empty pipe
65 * @wr_wait: writer wait point in case of full pipe
66 * @head: The point of buffer production
67 * @tail: The point of buffer consumption
68 * @head_tail: unsigned long union of @head and @tail
69 * @note_loss: The next read() should insert a data-lost message
70 * @max_usage: The maximum number of slots that may be used in the ring
71 * @ring_size: total number of buffers (should be a power of 2)
72 * @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
73 * @tmp_page: cached released page
74 * @readers: number of current readers of this pipe
75 * @writers: number of current writers of this pipe
76 * @files: number of struct file referring this pipe (protected by ->i_lock)
77 * @r_counter: reader counter
78 * @w_counter: writer counter
79 * @poll_usage: is this pipe used for epoll, which has crazy wakeups?
80 * @fasync_readers: reader side fasync
81 * @fasync_writers: writer side fasync
82 * @bufs: the circular array of pipe buffers
83 * @user: the user who created this pipe
84 * @watch_queue: If this pipe is a watch_queue, this is the stuff for that
85 **/
86 struct pipe_inode_info {
87 struct mutex mutex;
88 wait_queue_head_t rd_wait, wr_wait;
89
90 /* This has to match the 'union pipe_index' above */
91 union {
92 unsigned long head_tail;
93 struct {
94 pipe_index_t head;
95 pipe_index_t tail;
96 };
97 };
98
99 unsigned int max_usage;
100 unsigned int ring_size;
101 unsigned int nr_accounted;
102 unsigned int readers;
103 unsigned int writers;
104 unsigned int files;
105 unsigned int r_counter;
106 unsigned int w_counter;
107 bool poll_usage;
108 #ifdef CONFIG_WATCH_QUEUE
109 bool note_loss;
110 #endif
111 struct page *tmp_page;
112 struct fasync_struct *fasync_readers;
113 struct fasync_struct *fasync_writers;
114 struct pipe_buffer *bufs;
115 struct user_struct *user;
116 #ifdef CONFIG_WATCH_QUEUE
117 struct watch_queue *watch_queue;
118 #endif
119 };
120
121 /*
122 * Note on the nesting of these functions:
123 *
124 * ->confirm()
125 * ->try_steal()
126 *
127 * That is, ->try_steal() must be called on a confirmed buffer. See below for
128 * the meaning of each operation. Also see the kerneldoc in fs/pipe.c for the
129 * pipe and generic variants of these hooks.
130 */
131 struct pipe_buf_operations {
132 /*
133 * ->confirm() verifies that the data in the pipe buffer is there
134 * and that the contents are good. If the pages in the pipe belong
135 * to a file system, we may need to wait for IO completion in this
136 * hook. Returns 0 for good, or a negative error value in case of
137 * error. If not present all pages are considered good.
138 */
139 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
140
141 /*
142 * When the contents of this pipe buffer has been completely
143 * consumed by a reader, ->release() is called.
144 */
145 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
146
147 /*
148 * Attempt to take ownership of the pipe buffer and its contents.
149 * ->try_steal() returns %true for success, in which case the contents
150 * of the pipe (the buf->page) is locked and now completely owned by the
151 * caller. The page may then be transferred to a different mapping, the
152 * most often used case is insertion into different file address space
153 * cache.
154 */
155 bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
156
157 /*
158 * Get a reference to the pipe buffer.
159 */
160 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
161 };
162
163 /**
164 * pipe_has_watch_queue - Check whether the pipe is a watch_queue,
165 * i.e. it was created with O_NOTIFICATION_PIPE
166 * @pipe: The pipe to check
167 *
168 * Return: true if pipe is a watch queue, false otherwise.
169 */
pipe_has_watch_queue(const struct pipe_inode_info * pipe)170 static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
171 {
172 #ifdef CONFIG_WATCH_QUEUE
173 return pipe->watch_queue != NULL;
174 #else
175 return false;
176 #endif
177 }
178
179 /**
180 * pipe_occupancy - Return number of slots used in the pipe
181 * @head: The pipe ring head pointer
182 * @tail: The pipe ring tail pointer
183 */
pipe_occupancy(unsigned int head,unsigned int tail)184 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
185 {
186 return (pipe_index_t)(head - tail);
187 }
188
189 /**
190 * pipe_empty - Return true if the pipe is empty
191 * @head: The pipe ring head pointer
192 * @tail: The pipe ring tail pointer
193 */
pipe_empty(unsigned int head,unsigned int tail)194 static inline bool pipe_empty(unsigned int head, unsigned int tail)
195 {
196 return !pipe_occupancy(head, tail);
197 }
198
199 /**
200 * pipe_full - Return true if the pipe is full
201 * @head: The pipe ring head pointer
202 * @tail: The pipe ring tail pointer
203 * @limit: The maximum amount of slots available.
204 */
pipe_full(unsigned int head,unsigned int tail,unsigned int limit)205 static inline bool pipe_full(unsigned int head, unsigned int tail,
206 unsigned int limit)
207 {
208 return pipe_occupancy(head, tail) >= limit;
209 }
210
211 /**
212 * pipe_is_full - Return true if the pipe is full
213 * @pipe: the pipe
214 */
pipe_is_full(const struct pipe_inode_info * pipe)215 static inline bool pipe_is_full(const struct pipe_inode_info *pipe)
216 {
217 return pipe_full(pipe->head, pipe->tail, pipe->max_usage);
218 }
219
220 /**
221 * pipe_is_empty - Return true if the pipe is empty
222 * @pipe: the pipe
223 */
pipe_is_empty(const struct pipe_inode_info * pipe)224 static inline bool pipe_is_empty(const struct pipe_inode_info *pipe)
225 {
226 return pipe_empty(pipe->head, pipe->tail);
227 }
228
229 /**
230 * pipe_buf_usage - Return how many pipe buffers are in use
231 * @pipe: the pipe
232 */
pipe_buf_usage(const struct pipe_inode_info * pipe)233 static inline unsigned int pipe_buf_usage(const struct pipe_inode_info *pipe)
234 {
235 return pipe_occupancy(pipe->head, pipe->tail);
236 }
237
238 /**
239 * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
240 * @pipe: The pipe to access
241 * @slot: The slot of interest
242 */
pipe_buf(const struct pipe_inode_info * pipe,unsigned int slot)243 static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
244 unsigned int slot)
245 {
246 return &pipe->bufs[slot & (pipe->ring_size - 1)];
247 }
248
249 /**
250 * pipe_head_buf - Return the pipe buffer at the head of the pipe ring
251 * @pipe: The pipe to access
252 */
pipe_head_buf(const struct pipe_inode_info * pipe)253 static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe)
254 {
255 return pipe_buf(pipe, pipe->head);
256 }
257
258 /**
259 * pipe_buf_get - get a reference to a pipe_buffer
260 * @pipe: the pipe that the buffer belongs to
261 * @buf: the buffer to get a reference to
262 *
263 * Return: %true if the reference was successfully obtained.
264 */
pipe_buf_get(struct pipe_inode_info * pipe,struct pipe_buffer * buf)265 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
266 struct pipe_buffer *buf)
267 {
268 return buf->ops->get(pipe, buf);
269 }
270
271 /**
272 * pipe_buf_release - put a reference to a pipe_buffer
273 * @pipe: the pipe that the buffer belongs to
274 * @buf: the buffer to put a reference to
275 */
pipe_buf_release(struct pipe_inode_info * pipe,struct pipe_buffer * buf)276 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
277 struct pipe_buffer *buf)
278 {
279 const struct pipe_buf_operations *ops = buf->ops;
280
281 buf->ops = NULL;
282 ops->release(pipe, buf);
283 }
284
285 /**
286 * pipe_buf_confirm - verify contents of the pipe buffer
287 * @pipe: the pipe that the buffer belongs to
288 * @buf: the buffer to confirm
289 */
pipe_buf_confirm(struct pipe_inode_info * pipe,struct pipe_buffer * buf)290 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
291 struct pipe_buffer *buf)
292 {
293 if (!buf->ops->confirm)
294 return 0;
295 return buf->ops->confirm(pipe, buf);
296 }
297
298 /**
299 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
300 * @pipe: the pipe that the buffer belongs to
301 * @buf: the buffer to attempt to steal
302 */
pipe_buf_try_steal(struct pipe_inode_info * pipe,struct pipe_buffer * buf)303 static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
304 struct pipe_buffer *buf)
305 {
306 if (!buf->ops->try_steal)
307 return false;
308 return buf->ops->try_steal(pipe, buf);
309 }
310
311 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
312 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
313 #define PIPE_SIZE PAGE_SIZE
314
315 /* Pipe lock and unlock operations */
316 void pipe_lock(struct pipe_inode_info *);
317 void pipe_unlock(struct pipe_inode_info *);
318 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
319
320 /* Wait for a pipe to be readable/writable while dropping the pipe lock */
321 void pipe_wait_readable(struct pipe_inode_info *);
322 void pipe_wait_writable(struct pipe_inode_info *);
323
324 struct pipe_inode_info *alloc_pipe_info(void);
325 void free_pipe_info(struct pipe_inode_info *);
326
327 /* Generic pipe buffer ops functions */
328 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
329 bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
330 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
331
332 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
333
334 unsigned long account_pipe_buffers(struct user_struct *user,
335 unsigned long old, unsigned long new);
336 bool too_many_pipe_buffers_soft(unsigned long user_bufs);
337 bool too_many_pipe_buffers_hard(unsigned long user_bufs);
338 bool pipe_is_unprivileged_user(void);
339
340 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
341 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
342 long pipe_fcntl(struct file *, unsigned int, unsigned int arg);
343 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
344
345 int create_pipe_files(struct file **, int);
346 unsigned int round_pipe_size(unsigned int size);
347
348 #endif
349