xref: /linux/include/linux/pipe_fs_i.h (revision 00a7d39898c8010bfd5ff62af31ca5db34421b38)
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