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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 : :
12 : : /**
13 : : * struct pipe_buffer - a linux kernel pipe buffer
14 : : * @page: the page containing the data for the pipe buffer
15 : : * @offset: offset of data inside the @page
16 : : * @len: length of data inside the @page
17 : : * @ops: operations associated with this buffer. See @pipe_buf_operations.
18 : : * @flags: pipe buffer flags. See above.
19 : : * @private: private data owned by the ops.
20 : : **/
21 : : struct pipe_buffer {
22 : : struct page *page;
23 : : unsigned int offset, len;
24 : : const struct pipe_buf_operations *ops;
25 : : unsigned int flags;
26 : : unsigned long private;
27 : : };
28 : :
29 : : /**
30 : : * struct pipe_inode_info - a linux kernel pipe
31 : : * @mutex: mutex protecting the whole thing
32 : : * @rd_wait: reader wait point in case of empty pipe
33 : : * @wr_wait: writer wait point in case of full pipe
34 : : * @head: The point of buffer production
35 : : * @tail: The point of buffer consumption
36 : : * @max_usage: The maximum number of slots that may be used in the ring
37 : : * @ring_size: total number of buffers (should be a power of 2)
38 : : * @tmp_page: cached released page
39 : : * @readers: number of current readers of this pipe
40 : : * @writers: number of current writers of this pipe
41 : : * @files: number of struct file referring this pipe (protected by ->i_lock)
42 : : * @r_counter: reader counter
43 : : * @w_counter: writer counter
44 : : * @fasync_readers: reader side fasync
45 : : * @fasync_writers: writer side fasync
46 : : * @bufs: the circular array of pipe buffers
47 : : * @user: the user who created this pipe
48 : : **/
49 : : struct pipe_inode_info {
50 : : struct mutex mutex;
51 : : wait_queue_head_t rd_wait, wr_wait;
52 : : unsigned int head;
53 : : unsigned int tail;
54 : : unsigned int max_usage;
55 : : unsigned int ring_size;
56 : : unsigned int readers;
57 : : unsigned int writers;
58 : : unsigned int files;
59 : : unsigned int r_counter;
60 : : unsigned int w_counter;
61 : : struct page *tmp_page;
62 : : struct fasync_struct *fasync_readers;
63 : : struct fasync_struct *fasync_writers;
64 : : struct pipe_buffer *bufs;
65 : : struct user_struct *user;
66 : : };
67 : :
68 : : /*
69 : : * Note on the nesting of these functions:
70 : : *
71 : : * ->confirm()
72 : : * ->steal()
73 : : *
74 : : * That is, ->steal() must be called on a confirmed buffer.
75 : : * See below for the meaning of each operation. Also see kerneldoc
76 : : * in fs/pipe.c for the pipe and generic variants of these hooks.
77 : : */
78 : : struct pipe_buf_operations {
79 : : /*
80 : : * ->confirm() verifies that the data in the pipe buffer is there
81 : : * and that the contents are good. If the pages in the pipe belong
82 : : * to a file system, we may need to wait for IO completion in this
83 : : * hook. Returns 0 for good, or a negative error value in case of
84 : : * error.
85 : : */
86 : : int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
87 : :
88 : : /*
89 : : * When the contents of this pipe buffer has been completely
90 : : * consumed by a reader, ->release() is called.
91 : : */
92 : : void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
93 : :
94 : : /*
95 : : * Attempt to take ownership of the pipe buffer and its contents.
96 : : * ->steal() returns 0 for success, in which case the contents
97 : : * of the pipe (the buf->page) is locked and now completely owned
98 : : * by the caller. The page may then be transferred to a different
99 : : * mapping, the most often used case is insertion into different
100 : : * file address space cache.
101 : : */
102 : : int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
103 : :
104 : : /*
105 : : * Get a reference to the pipe buffer.
106 : : */
107 : : bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
108 : : };
109 : :
110 : : /**
111 : : * pipe_empty - Return true if the pipe is empty
112 : : * @head: The pipe ring head pointer
113 : : * @tail: The pipe ring tail pointer
114 : : */
115 : 68053 : static inline bool pipe_empty(unsigned int head, unsigned int tail)
116 : : {
117 [ + + + + : 68053 : return head == tail;
+ + - + +
+ + + + +
- - ]
118 : : }
119 : :
120 : : /**
121 : : * pipe_occupancy - Return number of slots used in the pipe
122 : : * @head: The pipe ring head pointer
123 : : * @tail: The pipe ring tail pointer
124 : : */
125 : 22722 : static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
126 : : {
127 [ - + ]: 24 : return head - tail;
128 : : }
129 : :
130 : : /**
131 : : * pipe_full - Return true if the pipe is full
132 : : * @head: The pipe ring head pointer
133 : : * @tail: The pipe ring tail pointer
134 : : * @limit: The maximum amount of slots available.
135 : : */
136 : 22698 : static inline bool pipe_full(unsigned int head, unsigned int tail,
137 : : unsigned int limit)
138 : : {
139 [ + + + - : 22698 : return pipe_occupancy(head, tail) >= limit;
+ + - - -
- - - -
+ ]
140 : : }
141 : :
142 : : /**
143 : : * pipe_space_for_user - Return number of slots available to userspace
144 : : * @head: The pipe ring head pointer
145 : : * @tail: The pipe ring tail pointer
146 : : * @pipe: The pipe info structure
147 : : */
148 : 0 : static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
149 : : struct pipe_inode_info *pipe)
150 : : {
151 : 0 : unsigned int p_occupancy, p_space;
152 : :
153 : 0 : p_occupancy = pipe_occupancy(head, tail);
154 [ # # # # : 0 : if (p_occupancy >= pipe->max_usage)
# # ]
155 : : return 0;
156 : 0 : p_space = pipe->ring_size - p_occupancy;
157 : 0 : if (p_space > pipe->max_usage)
158 : : p_space = pipe->max_usage;
159 : : return p_space;
160 : : }
161 : :
162 : : /**
163 : : * pipe_buf_get - get a reference to a pipe_buffer
164 : : * @pipe: the pipe that the buffer belongs to
165 : : * @buf: the buffer to get a reference to
166 : : *
167 : : * Return: %true if the reference was successfully obtained.
168 : : */
169 : 0 : static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
170 : : struct pipe_buffer *buf)
171 : : {
172 : 0 : return buf->ops->get(pipe, buf);
173 : : }
174 : :
175 : : /**
176 : : * pipe_buf_release - put a reference to a pipe_buffer
177 : : * @pipe: the pipe that the buffer belongs to
178 : : * @buf: the buffer to put a reference to
179 : : */
180 : 38 : static inline void pipe_buf_release(struct pipe_inode_info *pipe,
181 : : struct pipe_buffer *buf)
182 : : {
183 : 38 : const struct pipe_buf_operations *ops = buf->ops;
184 : :
185 : 38 : buf->ops = NULL;
186 : 38 : ops->release(pipe, buf);
187 : 0 : }
188 : :
189 : : /**
190 : : * pipe_buf_confirm - verify contents of the pipe buffer
191 : : * @pipe: the pipe that the buffer belongs to
192 : : * @buf: the buffer to confirm
193 : : */
194 : 42 : static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
195 : : struct pipe_buffer *buf)
196 : : {
197 : 42 : return buf->ops->confirm(pipe, buf);
198 : : }
199 : :
200 : : /**
201 : : * pipe_buf_steal - attempt to take ownership of a pipe_buffer
202 : : * @pipe: the pipe that the buffer belongs to
203 : : * @buf: the buffer to attempt to steal
204 : : */
205 : 0 : static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
206 : : struct pipe_buffer *buf)
207 : : {
208 : 0 : return buf->ops->steal(pipe, buf);
209 : : }
210 : :
211 : : /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
212 : : memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
213 : : #define PIPE_SIZE PAGE_SIZE
214 : :
215 : : /* Pipe lock and unlock operations */
216 : : void pipe_lock(struct pipe_inode_info *);
217 : : void pipe_unlock(struct pipe_inode_info *);
218 : : void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
219 : :
220 : : extern unsigned int pipe_max_size;
221 : : extern unsigned long pipe_user_pages_hard;
222 : : extern unsigned long pipe_user_pages_soft;
223 : :
224 : : /* Drop the inode semaphore and wait for a pipe event, atomically */
225 : : void pipe_wait(struct pipe_inode_info *pipe);
226 : :
227 : : struct pipe_inode_info *alloc_pipe_info(void);
228 : : void free_pipe_info(struct pipe_inode_info *);
229 : :
230 : : /* Generic pipe buffer ops functions */
231 : : bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
232 : : int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
233 : : int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
234 : : int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
235 : : void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
236 : : void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
237 : :
238 : : extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
239 : :
240 : : /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
241 : : long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
242 : : struct pipe_inode_info *get_pipe_info(struct file *file);
243 : :
244 : : int create_pipe_files(struct file **, int);
245 : : unsigned int round_pipe_size(unsigned long size);
246 : :
247 : : #endif
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