include/linux/pipe_fs_i.h

   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