LXR linux/include/linux/pipe_fs

   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 **/
  21struct 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 **/
  48struct 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 */
  75struct 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 */
 114static 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 */
 125static 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 */
 139static 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 */
 150static 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 */
 161void pipe_lock(struct pipe_inode_info *);
 162void pipe_unlock(struct pipe_inode_info *);
 163void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 164
 165extern unsigned int pipe_max_size;
 166extern unsigned long pipe_user_pages_hard;
 167extern unsigned long pipe_user_pages_soft;
 168
 169/* Drop the inode semaphore and wait for a pipe event, atomically */
 170void pipe_wait(struct pipe_inode_info *pipe);
 171
 172struct pipe_inode_info *alloc_pipe_info(void);
 173void free_pipe_info(struct pipe_inode_info *);
 174
 175/* Generic pipe buffer ops functions */
 176bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 177int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 178int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 179int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
 180void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 181void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
 182
 183extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
 184
 185/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 186long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 187struct pipe_inode_info *get_pipe_info(struct file *file);
 188
 189int create_pipe_files(struct file **, int);
 190unsigned int round_pipe_size(unsigned long size);
 191
 192#endif
 193