summaryrefslogtreecommitdiff
path: root/include/linux/pipe_fs_i.h
blob: 5d2705f1d01c3d7c2574b0a705aecf0ba27ddedf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PIPE_FS_I_H
#define _LINUX_PIPE_FS_I_H

#define PIPE_DEF_BUFFERS	16

#define PIPE_BUF_FLAG_LRU	0x01	/* page is on the LRU */
#define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
#define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
#define PIPE_BUF_FLAG_PACKET	0x08	/* read() as a packet */
#define PIPE_BUF_FLAG_CAN_MERGE	0x10	/* can merge buffers */
#define PIPE_BUF_FLAG_WHOLE	0x20	/* read() must return entire buffer or error */
#ifdef CONFIG_WATCH_QUEUE
#define PIPE_BUF_FLAG_LOSS	0x40	/* Message loss happened after this buffer */
#endif

/**
 *	struct pipe_buffer - a linux kernel pipe buffer
 *	@page: the page containing the data for the pipe buffer
 *	@offset: offset of data inside the @page
 *	@len: length of data inside the @page
 *	@ops: operations associated with this buffer. See @pipe_buf_operations.
 *	@flags: pipe buffer flags. See above.
 *	@private: private data owned by the ops.
 **/
struct pipe_buffer {
	struct page *page;
	unsigned int offset, len;
	const struct pipe_buf_operations *ops;
	unsigned int flags;
	unsigned long private;
};

/**
 *	struct pipe_inode_info - a linux kernel pipe
 *	@mutex: mutex protecting the whole thing
 *	@rd_wait: reader wait point in case of empty pipe
 *	@wr_wait: writer wait point in case of full pipe
 *	@head: The point of buffer production
 *	@tail: The point of buffer consumption
 *	@note_loss: The next read() should insert a data-lost message
 *	@max_usage: The maximum number of slots that may be used in the ring
 *	@ring_size: total number of buffers (should be a power of 2)
 *	@nr_accounted: The amount this pipe accounts for in user->pipe_bufs
 *	@tmp_page: cached released page
 *	@readers: number of current readers of this pipe
 *	@writers: number of current writers of this pipe
 *	@files: number of struct file referring this pipe (protected by ->i_lock)
 *	@r_counter: reader counter
 *	@w_counter: writer counter
 *	@fasync_readers: reader side fasync
 *	@fasync_writers: writer side fasync
 *	@bufs: the circular array of pipe buffers
 *	@user: the user who created this pipe
 *	@watch_queue: If this pipe is a watch_queue, this is the stuff for that
 **/
struct pipe_inode_info {
	struct mutex mutex;
	wait_queue_head_t rd_wait, wr_wait;
	unsigned int head;
	unsigned int tail;
	unsigned int max_usage;
	unsigned int ring_size;
#ifdef CONFIG_WATCH_QUEUE
	bool note_loss;
#endif
	unsigned int nr_accounted;
	unsigned int readers;
	unsigned int writers;
	unsigned int files;
	unsigned int r_counter;
	unsigned int w_counter;
	struct page *tmp_page;
	struct fasync_struct *fasync_readers;
	struct fasync_struct *fasync_writers;
	struct pipe_buffer *bufs;
	struct user_struct *user;
#ifdef CONFIG_WATCH_QUEUE
	struct watch_queue *watch_queue;
#endif
};

/*
 * Note on the nesting of these functions:
 *
 * ->confirm()
 *	->try_steal()
 *
 * That is, ->try_steal() must be called on a confirmed buffer.  See below for
 * the meaning of each operation.  Also see the kerneldoc in fs/pipe.c for the
 * pipe and generic variants of these hooks.
 */
struct pipe_buf_operations {
	/*
	 * ->confirm() verifies that the data in the pipe buffer is there
	 * and that the contents are good. If the pages in the pipe belong
	 * to a file system, we may need to wait for IO completion in this
	 * hook. Returns 0 for good, or a negative error value in case of
	 * error.  If not present all pages are considered good.
	 */
	int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);

	/*
	 * When the contents of this pipe buffer has been completely
	 * consumed by a reader, ->release() is called.
	 */
	void (*release)(struct pipe_inode_info *, struct pipe_buffer *);

	/*
	 * Attempt to take ownership of the pipe buffer and its contents.
	 * ->try_steal() returns %true for success, in which case the contents
	 * of the pipe (the buf->page) is locked and now completely owned by the
	 * caller. The page may then be transferred to a different mapping, the
	 * most often used case is insertion into different file address space
	 * cache.
	 */
	bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);

	/*
	 * Get a reference to the pipe buffer.
	 */
	bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
};

/**
 * pipe_empty - Return true if the pipe is empty
 * @head: The pipe ring head pointer
 * @tail: The pipe ring tail pointer
 */
static inline bool pipe_empty(unsigned int head, unsigned int tail)
{
	return head == tail;
}

/**
 * pipe_occupancy - Return number of slots used in the pipe
 * @head: The pipe ring head pointer
 * @tail: The pipe ring tail pointer
 */
static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
{
	return head - tail;
}

/**
 * pipe_full - Return true if the pipe is full
 * @head: The pipe ring head pointer
 * @tail: The pipe ring tail pointer
 * @limit: The maximum amount of slots available.
 */
static inline bool pipe_full(unsigned int head, unsigned int tail,
			     unsigned int limit)
{
	return pipe_occupancy(head, tail) >= limit;
}

/**
 * pipe_space_for_user - Return number of slots available to userspace
 * @head: The pipe ring head pointer
 * @tail: The pipe ring tail pointer
 * @pipe: The pipe info structure
 */
static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
					       struct pipe_inode_info *pipe)
{
	unsigned int p_occupancy, p_space;

	p_occupancy = pipe_occupancy(head, tail);
	if (p_occupancy >= pipe->max_usage)
		return 0;
	p_space = pipe->ring_size - p_occupancy;
	if (p_space > pipe->max_usage)
		p_space = pipe->max_usage;
	return p_space;
}

/**
 * pipe_buf_get - get a reference to a pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to get a reference to
 *
 * Return: %true if the reference was successfully obtained.
 */
static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
				struct pipe_buffer *buf)
{
	return buf->ops->get(pipe, buf);
}

/**
 * pipe_buf_release - put a reference to a pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to put a reference to
 */
static inline void pipe_buf_release(struct pipe_inode_info *pipe,
				    struct pipe_buffer *buf)
{
	const struct pipe_buf_operations *ops = buf->ops;

	buf->ops = NULL;
	ops->release(pipe, buf);
}

/**
 * pipe_buf_confirm - verify contents of the pipe buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to confirm
 */
static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
				   struct pipe_buffer *buf)
{
	if (!buf->ops->confirm)
		return 0;
	return buf->ops->confirm(pipe, buf);
}

/**
 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
 * @pipe:	the pipe that the buffer belongs to
 * @buf:	the buffer to attempt to steal
 */
static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
		struct pipe_buffer *buf)
{
	if (!buf->ops->try_steal)
		return false;
	return buf->ops->try_steal(pipe, buf);
}

/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
   memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
#define PIPE_SIZE		PAGE_SIZE

/* Pipe lock and unlock operations */
void pipe_lock(struct pipe_inode_info *);
void pipe_unlock(struct pipe_inode_info *);
void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);

extern unsigned int pipe_max_size;
extern unsigned long pipe_user_pages_hard;
extern unsigned long pipe_user_pages_soft;

/* Wait for a pipe to be readable/writable while dropping the pipe lock */
void pipe_wait_readable(struct pipe_inode_info *);
void pipe_wait_writable(struct pipe_inode_info *);

struct pipe_inode_info *alloc_pipe_info(void);
void free_pipe_info(struct pipe_inode_info *);

/* Generic pipe buffer ops functions */
bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);

extern const struct pipe_buf_operations nosteal_pipe_buf_ops;

#ifdef CONFIG_WATCH_QUEUE
unsigned long account_pipe_buffers(struct user_struct *user,
				   unsigned long old, unsigned long new);
bool too_many_pipe_buffers_soft(unsigned long user_bufs);
bool too_many_pipe_buffers_hard(unsigned long user_bufs);
bool pipe_is_unprivileged_user(void);
#endif

/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
#ifdef CONFIG_WATCH_QUEUE
int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
#endif
long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);

int create_pipe_files(struct file **, int);
unsigned int round_pipe_size(unsigned long size);

#endif