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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 **/
26struct 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
42typedef unsigned int pipe_index_t;
43#else
44typedef unsigned short pipe_index_t;
45#endif
46
47/**
48 * struct pipe_index - pipe indeces
49 * @head: The point of buffer production
50 * @tail: The point of buffer consumption
51 * @head_tail: unsigned long union of @head and @tail
52 */
53union 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 * @pipe_index: the pipe indeces
67 * @note_loss: The next read() should insert a data-lost message
68 * @max_usage: The maximum number of slots that may be used in the ring
69 * @ring_size: total number of buffers (should be a power of 2)
70 * @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
71 * @tmp_page: cached released page
72 * @readers: number of current readers of this pipe
73 * @writers: number of current writers of this pipe
74 * @files: number of struct file referring this pipe (protected by ->i_lock)
75 * @r_counter: reader counter
76 * @w_counter: writer counter
77 * @poll_usage: is this pipe used for epoll, which has crazy wakeups?
78 * @fasync_readers: reader side fasync
79 * @fasync_writers: writer side fasync
80 * @bufs: the circular array of pipe buffers
81 * @user: the user who created this pipe
82 * @watch_queue: If this pipe is a watch_queue, this is the stuff for that
83 **/
84struct pipe_inode_info {
85 struct mutex mutex;
86 wait_queue_head_t rd_wait, wr_wait;
87
88 union pipe_index;
89
90 unsigned int max_usage;
91 unsigned int ring_size;
92 unsigned int nr_accounted;
93 unsigned int readers;
94 unsigned int writers;
95 unsigned int files;
96 unsigned int r_counter;
97 unsigned int w_counter;
98 bool poll_usage;
99#ifdef CONFIG_WATCH_QUEUE
100 bool note_loss;
101#endif
102 struct page *tmp_page[2];
103 struct fasync_struct *fasync_readers;
104 struct fasync_struct *fasync_writers;
105 struct pipe_buffer *bufs;
106 struct user_struct *user;
107#ifdef CONFIG_WATCH_QUEUE
108 struct watch_queue *watch_queue;
109#endif
110};
111
112/*
113 * Note on the nesting of these functions:
114 *
115 * ->confirm()
116 * ->try_steal()
117 *
118 * That is, ->try_steal() must be called on a confirmed buffer. See below for
119 * the meaning of each operation. Also see the kerneldoc in fs/pipe.c for the
120 * pipe and generic variants of these hooks.
121 */
122struct pipe_buf_operations {
123 /*
124 * ->confirm() verifies that the data in the pipe buffer is there
125 * and that the contents are good. If the pages in the pipe belong
126 * to a file system, we may need to wait for IO completion in this
127 * hook. Returns 0 for good, or a negative error value in case of
128 * error. If not present all pages are considered good.
129 */
130 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
131
132 /*
133 * When the contents of this pipe buffer has been completely
134 * consumed by a reader, ->release() is called.
135 */
136 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
137
138 /*
139 * Attempt to take ownership of the pipe buffer and its contents.
140 * ->try_steal() returns %true for success, in which case the contents
141 * of the pipe (the buf->page) is locked and now completely owned by the
142 * caller. The page may then be transferred to a different mapping, the
143 * most often used case is insertion into different file address space
144 * cache.
145 */
146 bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
147
148 /*
149 * Get a reference to the pipe buffer.
150 */
151 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
152};
153
154/**
155 * pipe_has_watch_queue - Check whether the pipe is a watch_queue,
156 * i.e. it was created with O_NOTIFICATION_PIPE
157 * @pipe: The pipe to check
158 *
159 * Return: true if pipe is a watch queue, false otherwise.
160 */
161static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
162{
163#ifdef CONFIG_WATCH_QUEUE
164 return pipe->watch_queue != NULL;
165#else
166 return false;
167#endif
168}
169
170/**
171 * pipe_occupancy - Return number of slots used in the pipe
172 * @head: The pipe ring head pointer
173 * @tail: The pipe ring tail pointer
174 */
175static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
176{
177 return (pipe_index_t)(head - tail);
178}
179
180/**
181 * pipe_empty - Return true if the pipe is empty
182 * @head: The pipe ring head pointer
183 * @tail: The pipe ring tail pointer
184 */
185static inline bool pipe_empty(unsigned int head, unsigned int tail)
186{
187 return !pipe_occupancy(head, tail);
188}
189
190/**
191 * pipe_full - Return true if the pipe is full
192 * @head: The pipe ring head pointer
193 * @tail: The pipe ring tail pointer
194 * @limit: The maximum amount of slots available.
195 */
196static inline bool pipe_full(unsigned int head, unsigned int tail,
197 unsigned int limit)
198{
199 return pipe_occupancy(head, tail) >= limit;
200}
201
202/**
203 * pipe_is_full - Return true if the pipe is full
204 * @pipe: the pipe
205 */
206static inline bool pipe_is_full(const struct pipe_inode_info *pipe)
207{
208 return pipe_full(head: pipe->head, tail: pipe->tail, limit: pipe->max_usage);
209}
210
211/**
212 * pipe_is_empty - Return true if the pipe is empty
213 * @pipe: the pipe
214 */
215static inline bool pipe_is_empty(const struct pipe_inode_info *pipe)
216{
217 return pipe_empty(head: pipe->head, tail: pipe->tail);
218}
219
220/**
221 * pipe_buf_usage - Return how many pipe buffers are in use
222 * @pipe: the pipe
223 */
224static inline unsigned int pipe_buf_usage(const struct pipe_inode_info *pipe)
225{
226 return pipe_occupancy(head: pipe->head, tail: pipe->tail);
227}
228
229/**
230 * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
231 * @pipe: The pipe to access
232 * @slot: The slot of interest
233 */
234static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
235 unsigned int slot)
236{
237 return &pipe->bufs[slot & (pipe->ring_size - 1)];
238}
239
240/**
241 * pipe_head_buf - Return the pipe buffer at the head of the pipe ring
242 * @pipe: The pipe to access
243 */
244static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe)
245{
246 return pipe_buf(pipe, slot: pipe->head);
247}
248
249/**
250 * pipe_buf_get - get a reference to a pipe_buffer
251 * @pipe: the pipe that the buffer belongs to
252 * @buf: the buffer to get a reference to
253 *
254 * Return: %true if the reference was successfully obtained.
255 */
256static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
257 struct pipe_buffer *buf)
258{
259 return buf->ops->get(pipe, buf);
260}
261
262/**
263 * pipe_buf_release - put a reference to a pipe_buffer
264 * @pipe: the pipe that the buffer belongs to
265 * @buf: the buffer to put a reference to
266 */
267static inline void pipe_buf_release(struct pipe_inode_info *pipe,
268 struct pipe_buffer *buf)
269{
270 const struct pipe_buf_operations *ops = buf->ops;
271
272 buf->ops = NULL;
273 ops->release(pipe, buf);
274}
275
276/**
277 * pipe_buf_confirm - verify contents of the pipe buffer
278 * @pipe: the pipe that the buffer belongs to
279 * @buf: the buffer to confirm
280 */
281static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
282 struct pipe_buffer *buf)
283{
284 if (!buf->ops->confirm)
285 return 0;
286 return buf->ops->confirm(pipe, buf);
287}
288
289/**
290 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
291 * @pipe: the pipe that the buffer belongs to
292 * @buf: the buffer to attempt to steal
293 */
294static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
295 struct pipe_buffer *buf)
296{
297 if (!buf->ops->try_steal)
298 return false;
299 return buf->ops->try_steal(pipe, buf);
300}
301
302/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
303 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
304#define PIPE_SIZE PAGE_SIZE
305
306/* Pipe lock and unlock operations */
307void pipe_lock(struct pipe_inode_info *);
308void pipe_unlock(struct pipe_inode_info *);
309void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
310
311/* Wait for a pipe to be readable/writable while dropping the pipe lock */
312void pipe_wait_readable(struct pipe_inode_info *);
313void pipe_wait_writable(struct pipe_inode_info *);
314
315struct pipe_inode_info *alloc_pipe_info(void);
316void free_pipe_info(struct pipe_inode_info *);
317
318/* Generic pipe buffer ops functions */
319bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
320bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
321void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
322
323extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
324
325unsigned long account_pipe_buffers(struct user_struct *user,
326 unsigned long old, unsigned long new);
327bool too_many_pipe_buffers_soft(unsigned long user_bufs);
328bool too_many_pipe_buffers_hard(unsigned long user_bufs);
329bool pipe_is_unprivileged_user(void);
330
331/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
332int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
333long pipe_fcntl(struct file *, unsigned int, unsigned int arg);
334struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
335
336int create_pipe_files(struct file **, int);
337unsigned int round_pipe_size(unsigned int size);
338
339#endif
340

source code of linux/include/linux/pipe_fs_i.h