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TOMOYO Linux Cross Reference
Linux/include/linux/pipe_fs_i.h

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  1 #ifndef _LINUX_PIPE_FS_I_H
  2 #define _LINUX_PIPE_FS_I_H
  3 
  4 #define PIPE_DEF_BUFFERS        16
  5 
  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 */
 10 
 11 /**
 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.
 19  **/
 20 struct pipe_buffer {
 21         struct page *page;
 22         unsigned int offset, len;
 23         const struct pipe_buf_operations *ops;
 24         unsigned int flags;
 25         unsigned long private;
 26 };
 27 
 28 /**
 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
 46  **/
 47 struct pipe_inode_info {
 48         struct mutex mutex;
 49         wait_queue_head_t wait;
 50         unsigned int nrbufs, curbuf, buffers;
 51         unsigned int readers;
 52         unsigned int writers;
 53         unsigned int files;
 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;
 62 };
 63 
 64 /*
 65  * Note on the nesting of these functions:
 66  *
 67  * ->confirm()
 68  *      ->steal()
 69  *
 70  * That is, ->steal() must be called on a confirmed buffer.
 71  * See below for the meaning of each operation. Also see kerneldoc
 72  * in fs/pipe.c for the pipe and generic variants of these hooks.
 73  */
 74 struct pipe_buf_operations {
 75         /*
 76          * This is set to 1, if the generic pipe read/write may coalesce
 77          * data into an existing buffer. If this is set to 0, a new pipe
 78          * page segment is always used for new data.
 79          */
 80         int can_merge;
 81 
 82         /*
 83          * ->confirm() verifies that the data in the pipe buffer is there
 84          * and that the contents are good. If the pages in the pipe belong
 85          * to a file system, we may need to wait for IO completion in this
 86          * hook. Returns 0 for good, or a negative error value in case of
 87          * error.
 88          */
 89         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 90 
 91         /*
 92          * When the contents of this pipe buffer has been completely
 93          * consumed by a reader, ->release() is called.
 94          */
 95         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 96 
 97         /*
 98          * Attempt to take ownership of the pipe buffer and its contents.
 99          * ->steal() returns 0 for success, in which case the contents
100          * of the pipe (the buf->page) is locked and now completely owned
101          * by the caller. The page may then be transferred to a different
102          * mapping, the most often used case is insertion into different
103          * file address space cache.
104          */
105         int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
106 
107         /*
108          * Get a reference to the pipe buffer.
109          */
110         void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
111 };
112 
113 /**
114  * pipe_buf_get - get a reference to a pipe_buffer
115  * @pipe:       the pipe that the buffer belongs to
116  * @buf:        the buffer to get a reference to
117  */
118 static inline void pipe_buf_get(struct pipe_inode_info *pipe,
119                                 struct pipe_buffer *buf)
120 {
121         buf->ops->get(pipe, buf);
122 }
123 
124 /**
125  * pipe_buf_release - put a reference to a pipe_buffer
126  * @pipe:       the pipe that the buffer belongs to
127  * @buf:        the buffer to put a reference to
128  */
129 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
130                                     struct pipe_buffer *buf)
131 {
132         const struct pipe_buf_operations *ops = buf->ops;
133 
134         buf->ops = NULL;
135         ops->release(pipe, buf);
136 }
137 
138 /**
139  * pipe_buf_confirm - verify contents of the pipe buffer
140  * @pipe:       the pipe that the buffer belongs to
141  * @buf:        the buffer to confirm
142  */
143 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
144                                    struct pipe_buffer *buf)
145 {
146         return buf->ops->confirm(pipe, buf);
147 }
148 
149 /**
150  * pipe_buf_steal - attempt to take ownership of a pipe_buffer
151  * @pipe:       the pipe that the buffer belongs to
152  * @buf:        the buffer to attempt to steal
153  */
154 static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
155                                  struct pipe_buffer *buf)
156 {
157         return buf->ops->steal(pipe, buf);
158 }
159 
160 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
161    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
162 #define PIPE_SIZE               PAGE_SIZE
163 
164 /* Pipe lock and unlock operations */
165 void pipe_lock(struct pipe_inode_info *);
166 void pipe_unlock(struct pipe_inode_info *);
167 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
168 
169 extern unsigned int pipe_max_size, pipe_min_size;
170 extern unsigned long pipe_user_pages_hard;
171 extern unsigned long pipe_user_pages_soft;
172 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
173 
174 /* Drop the inode semaphore and wait for a pipe event, atomically */
175 void pipe_wait(struct pipe_inode_info *pipe);
176 
177 struct pipe_inode_info *alloc_pipe_info(void);
178 void free_pipe_info(struct pipe_inode_info *);
179 
180 /* Generic pipe buffer ops functions */
181 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
182 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
183 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
184 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
185 
186 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
187 
188 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
189 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
190 struct pipe_inode_info *get_pipe_info(struct file *file);
191 
192 int create_pipe_files(struct file **, int);
193 
194 #endif
195 

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