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 * @wait: reader/writer wait point in case of empty/full pipe
33 * @nrbufs: the number of non-empty pipe buffers in this pipe
34 * @buffers: total number of buffers (should be a power of 2)
35 * @curbuf: the current pipe buffer entry
36 * @tmp_page: cached released page
37 * @readers: number of current readers of this pipe
38 * @writers: number of current writers of this pipe
39 * @files: number of struct file referring this pipe (protected by ->i_lock)
40 * @waiting_writers: number of writers blocked waiting for room
41 * @r_counter: reader counter
42 * @w_counter: writer counter
43 * @fasync_readers: reader side fasync
44 * @fasync_writers: writer side fasync
45 * @bufs: the circular array of pipe buffers
46 * @user: the user who created this pipe
47 **/
48 struct pipe_inode_info {
49 struct mutex mutex;
50 wait_queue_head_t wait;
51 unsigned int nrbufs, curbuf, buffers;
52 unsigned int readers;
53 unsigned int writers;
54 unsigned int files;
55 unsigned int waiting_writers;
56 unsigned int r_counter;
57 unsigned int w_counter;
58 struct page *tmp_page;
59 struct fasync_struct *fasync_readers;
60 struct fasync_struct *fasync_writers;
61 struct pipe_buffer *bufs;
62 struct user_struct *user;
63 };
64
65 /*
66 * Note on the nesting of these functions:
67 *
68 * ->confirm()
69 * ->steal()
70 *
71 * That is, ->steal() must be called on a confirmed buffer.
72 * See below for the meaning of each operation. Also see kerneldoc
73 * in fs/pipe.c for the pipe and generic variants of these hooks.
74 */
75 struct pipe_buf_operations {
76 /*
77 * ->confirm() verifies that the data in the pipe buffer is there
78 * and that the contents are good. If the pages in the pipe belong
79 * to a file system, we may need to wait for IO completion in this
80 * hook. Returns 0 for good, or a negative error value in case of
81 * error.
82 */
83 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
84
85 /*
86 * When the contents of this pipe buffer has been completely
87 * consumed by a reader, ->release() is called.
88 */
89 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
90
91 /*
92 * Attempt to take ownership of the pipe buffer and its contents.
93 * ->steal() returns 0 for success, in which case the contents
94 * of the pipe (the buf->page) is locked and now completely owned
95 * by the caller. The page may then be transferred to a different
96 * mapping, the most often used case is insertion into different
97 * file address space cache.
98 */
99 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
100
101 /*
102 * Get a reference to the pipe buffer.
103 */
104 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
105 };
106
107 /**
108 * pipe_buf_get - get a reference to a pipe_buffer
109 * @pipe: the pipe that the buffer belongs to
110 * @buf: the buffer to get a reference to
111 *
112 * Return: %true if the reference was successfully obtained.
113 */
pipe_buf_get(struct pipe_inode_info * pipe,struct pipe_buffer * buf)114 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
115 struct pipe_buffer *buf)
116 {
117 return buf->ops->get(pipe, buf);
118 }
119
120 /**
121 * pipe_buf_release - put a reference to a pipe_buffer
122 * @pipe: the pipe that the buffer belongs to
123 * @buf: the buffer to put a reference to
124 */
pipe_buf_release(struct pipe_inode_info * pipe,struct pipe_buffer * buf)125 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
126 struct pipe_buffer *buf)
127 {
128 const struct pipe_buf_operations *ops = buf->ops;
129
130 buf->ops = NULL;
131 ops->release(pipe, buf);
132 }
133
134 /**
135 * pipe_buf_confirm - verify contents of the pipe buffer
136 * @pipe: the pipe that the buffer belongs to
137 * @buf: the buffer to confirm
138 */
pipe_buf_confirm(struct pipe_inode_info * pipe,struct pipe_buffer * buf)139 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
140 struct pipe_buffer *buf)
141 {
142 return buf->ops->confirm(pipe, buf);
143 }
144
145 /**
146 * pipe_buf_steal - attempt to take ownership of a pipe_buffer
147 * @pipe: the pipe that the buffer belongs to
148 * @buf: the buffer to attempt to steal
149 */
pipe_buf_steal(struct pipe_inode_info * pipe,struct pipe_buffer * buf)150 static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
151 struct pipe_buffer *buf)
152 {
153 return buf->ops->steal(pipe, buf);
154 }
155
156 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
157 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
158 #define PIPE_SIZE PAGE_SIZE
159
160 /* Pipe lock and unlock operations */
161 void pipe_lock(struct pipe_inode_info *);
162 void pipe_unlock(struct pipe_inode_info *);
163 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
164
165 extern unsigned int pipe_max_size;
166 extern unsigned long pipe_user_pages_hard;
167 extern unsigned long pipe_user_pages_soft;
168
169 /* Drop the inode semaphore and wait for a pipe event, atomically */
170 void pipe_wait(struct pipe_inode_info *pipe);
171
172 struct pipe_inode_info *alloc_pipe_info(void);
173 void free_pipe_info(struct pipe_inode_info *);
174
175 /* Generic pipe buffer ops functions */
176 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
177 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
178 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
179 int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
180 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
181 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
182
183 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
184
185 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
186 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
187 struct pipe_inode_info *get_pipe_info(struct file *file);
188
189 int create_pipe_files(struct file **, int);
190 unsigned int round_pipe_size(unsigned long size);
191
192 #endif
193
