xref: /linux/include/linux/pipe_fs_i.h (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
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  */
pipe_has_watch_queue(const struct pipe_inode_info * pipe)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  */
pipe_empty(unsigned int head,unsigned int tail)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  */
pipe_occupancy(unsigned int head,unsigned int tail)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  */
pipe_full(unsigned int head,unsigned int tail,unsigned int limit)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  */
pipe_buf(const struct pipe_inode_info * pipe,unsigned int slot)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  */
pipe_head_buf(const struct pipe_inode_info * pipe)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  */
pipe_buf_get(struct pipe_inode_info * pipe,struct pipe_buffer * buf)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  */
pipe_buf_release(struct pipe_inode_info * pipe,struct pipe_buffer * buf)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  */
pipe_buf_confirm(struct pipe_inode_info * pipe,struct pipe_buffer * buf)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  */
pipe_buf_try_steal(struct pipe_inode_info * pipe,struct pipe_buffer * buf)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 
pipe_discard_from(struct pipe_inode_info * pipe,unsigned int old_head)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