1 #ifndef _LINUX_PIPE_FS_I_H
2 #define _LINUX_PIPE_FS_I_H
4 #define PIPE_DEF_BUFFERS 16
6 #define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
7 #define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
8 #define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
9 #define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
12 * struct pipe_buffer - a linux kernel pipe buffer
13 * @page: the page containing the data for the pipe buffer
14 * @offset: offset of data inside the @page
15 * @len: length of data inside the @page
16 * @ops: operations associated with this buffer. See @pipe_buf_operations.
17 * @flags: pipe buffer flags. See above.
18 * @private: private data owned by the ops.
22 unsigned int offset, len;
23 const struct pipe_buf_operations *ops;
25 unsigned long private;
29 * struct pipe_inode_info - a linux kernel pipe
30 * @mutex: mutex protecting the whole thing
31 * @wait: reader/writer wait point in case of empty/full pipe
32 * @nrbufs: the number of non-empty pipe buffers in this pipe
33 * @buffers: total number of buffers (should be a power of 2)
34 * @curbuf: the current pipe buffer entry
35 * @tmp_page: cached released page
36 * @readers: number of current readers of this pipe
37 * @writers: number of current writers of this pipe
38 * @files: number of struct file referring this pipe (protected by ->i_lock)
39 * @waiting_writers: number of writers blocked waiting for room
40 * @r_counter: reader counter
41 * @w_counter: writer counter
42 * @fasync_readers: reader side fasync
43 * @fasync_writers: writer side fasync
44 * @bufs: the circular array of pipe buffers
45 * @user: the user who created this pipe
47 struct pipe_inode_info {
49 wait_queue_head_t wait;
50 unsigned int nrbufs, curbuf, buffers;
54 unsigned int waiting_writers;
55 unsigned int r_counter;
56 unsigned int w_counter;
57 struct page *tmp_page;
58 struct fasync_struct *fasync_readers;
59 struct fasync_struct *fasync_writers;
60 struct pipe_buffer *bufs;
61 struct user_struct *user;
65 * Note on the nesting of these functions:
74 * That is, ->map() must be called on a confirmed buffer,
75 * same goes for ->steal(). See below for the meaning of each
76 * operation. Also see kerneldoc in fs/pipe.c for the pipe
77 * and generic variants of these hooks.
79 struct pipe_buf_operations {
81 * This is set to 1, if the generic pipe read/write may coalesce
82 * data into an existing buffer. If this is set to 0, a new pipe
83 * page segment is always used for new data.
88 * ->confirm() verifies that the data in the pipe buffer is there
89 * and that the contents are good. If the pages in the pipe belong
90 * to a file system, we may need to wait for IO completion in this
91 * hook. Returns 0 for good, or a negative error value in case of
94 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
97 * When the contents of this pipe buffer has been completely
98 * consumed by a reader, ->release() is called.
100 void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
103 * Attempt to take ownership of the pipe buffer and its contents.
104 * ->steal() returns 0 for success, in which case the contents
105 * of the pipe (the buf->page) is locked and now completely owned
106 * by the caller. The page may then be transferred to a different
107 * mapping, the most often used case is insertion into different
108 * file address space cache.
110 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
113 * Get a reference to the pipe buffer.
115 void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
119 * pipe_buf_get - get a reference to a pipe_buffer
120 * @pipe: the pipe that the buffer belongs to
121 * @buf: the buffer to get a reference to
123 static inline void pipe_buf_get(struct pipe_inode_info *pipe,
124 struct pipe_buffer *buf)
126 buf->ops->get(pipe, buf);
130 * pipe_buf_release - put a reference to a pipe_buffer
131 * @pipe: the pipe that the buffer belongs to
132 * @buf: the buffer to put a reference to
134 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
135 struct pipe_buffer *buf)
137 const struct pipe_buf_operations *ops = buf->ops;
140 ops->release(pipe, buf);
144 * pipe_buf_confirm - verify contents of the pipe buffer
145 * @pipe: the pipe that the buffer belongs to
146 * @buf: the buffer to confirm
148 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
149 struct pipe_buffer *buf)
151 return buf->ops->confirm(pipe, buf);
155 * pipe_buf_steal - attempt to take ownership of a pipe_buffer
156 * @pipe: the pipe that the buffer belongs to
157 * @buf: the buffer to attempt to steal
159 static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
160 struct pipe_buffer *buf)
162 return buf->ops->steal(pipe, buf);
165 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
166 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
167 #define PIPE_SIZE PAGE_SIZE
169 /* Pipe lock and unlock operations */
170 void pipe_lock(struct pipe_inode_info *);
171 void pipe_unlock(struct pipe_inode_info *);
172 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
174 extern unsigned int pipe_max_size, pipe_min_size;
175 extern unsigned long pipe_user_pages_hard;
176 extern unsigned long pipe_user_pages_soft;
177 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
179 /* Drop the inode semaphore and wait for a pipe event, atomically */
180 void pipe_wait(struct pipe_inode_info *pipe);
182 struct pipe_inode_info *alloc_pipe_info(void);
183 void free_pipe_info(struct pipe_inode_info *);
185 /* Generic pipe buffer ops functions */
186 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
187 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
188 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
189 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
191 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
193 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
194 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
195 struct pipe_inode_info *get_pipe_info(struct file *file);
197 int create_pipe_files(struct file **, int);