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 **/
  20struct 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 *      @wait: reader/writer wait point in case of empty/full pipe
  31 *      @nrbufs: the number of non-empty pipe buffers in this pipe
  32 *      @buffers: total number of buffers (should be a power of 2)
  33 *      @curbuf: the current pipe buffer entry
  34 *      @tmp_page: cached released page
  35 *      @readers: number of current readers of this pipe
  36 *      @writers: number of current writers of this pipe
  37 *      @waiting_writers: number of writers blocked waiting for room
  38 *      @r_counter: reader counter
  39 *      @w_counter: writer counter
  40 *      @fasync_readers: reader side fasync
  41 *      @fasync_writers: writer side fasync
  42 *      @inode: inode this pipe is attached to
  43 *      @bufs: the circular array of pipe buffers
  44 **/
  45struct pipe_inode_info {
  46        wait_queue_head_t wait;
  47        unsigned int nrbufs, curbuf, buffers;
  48        unsigned int readers;
  49        unsigned int writers;
  50        unsigned int waiting_writers;
  51        unsigned int r_counter;
  52        unsigned int w_counter;
  53        struct page *tmp_page;
  54        struct fasync_struct *fasync_readers;
  55        struct fasync_struct *fasync_writers;
  56        struct inode *inode;
  57        struct pipe_buffer *bufs;
  58};
  59
  60/*
  61 * Note on the nesting of these functions:
  62 *
  63 * ->confirm()
  64 *      ->steal()
  65 *      ...
  66 *      ->map()
  67 *      ...
  68 *      ->unmap()
  69 *
  70 * That is, ->map() must be called on a confirmed buffer,
  71 * same goes for ->steal(). See below for the meaning of each
  72 * operation. Also see kerneldoc in fs/pipe.c for the pipe
  73 * and generic variants of these hooks.
  74 */
  75struct pipe_buf_operations {
  76        /*
  77         * This is set to 1, if the generic pipe read/write may coalesce
  78         * data into an existing buffer. If this is set to 0, a new pipe
  79         * page segment is always used for new data.
  80         */
  81        int can_merge;
  82
  83        /*
  84         * ->map() returns a virtual address mapping of the pipe buffer.
  85         * The last integer flag reflects whether this should be an atomic
  86         * mapping or not. The atomic map is faster, however you can't take
  87         * page faults before calling ->unmap() again. So if you need to eg
  88         * access user data through copy_to/from_user(), then you must get
  89         * a non-atomic map. ->map() uses the kmap_atomic slot for
  90         * atomic maps, you have to be careful if mapping another page as
  91         * source or destination for a copy.
  92         */
  93        void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int);
  94
  95        /*
  96         * Undoes ->map(), finishes the virtual mapping of the pipe buffer.
  97         */
  98        void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *);
  99
 100        /*
 101         * ->confirm() verifies that the data in the pipe buffer is there
 102         * and that the contents are good. If the pages in the pipe belong
 103         * to a file system, we may need to wait for IO completion in this
 104         * hook. Returns 0 for good, or a negative error value in case of
 105         * error.
 106         */
 107        int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 108
 109        /*
 110         * When the contents of this pipe buffer has been completely
 111         * consumed by a reader, ->release() is called.
 112         */
 113        void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 114
 115        /*
 116         * Attempt to take ownership of the pipe buffer and its contents.
 117         * ->steal() returns 0 for success, in which case the contents
 118         * of the pipe (the buf->page) is locked and now completely owned
 119         * by the caller. The page may then be transferred to a different
 120         * mapping, the most often used case is insertion into different
 121         * file address space cache.
 122         */
 123        int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
 124
 125        /*
 126         * Get a reference to the pipe buffer.
 127         */
 128        void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 129};
 130
 131/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 132   memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 133#define PIPE_SIZE               PAGE_SIZE
 134
 135/* Pipe lock and unlock operations */
 136void pipe_lock(struct pipe_inode_info *);
 137void pipe_unlock(struct pipe_inode_info *);
 138void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 139
 140extern unsigned int pipe_max_size, pipe_min_size;
 141int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
 142
 143
 144/* Drop the inode semaphore and wait for a pipe event, atomically */
 145void pipe_wait(struct pipe_inode_info *pipe);
 146
 147struct pipe_inode_info * alloc_pipe_info(struct inode * inode);
 148void free_pipe_info(struct inode * inode);
 149void __free_pipe_info(struct pipe_inode_info *);
 150
 151/* Generic pipe buffer ops functions */
 152void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int);
 153void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *);
 154void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 155int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 156int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 157void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 158
 159/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 160long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 161struct pipe_inode_info *get_pipe_info(struct file *file);
 162
 163int create_pipe_files(struct file **, int);
 164
 165#endif
 166
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