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 *      @head: The point of buffer production
  34 *      @tail: The point of buffer consumption
  35 *      @max_usage: The maximum number of slots that may be used in the ring
  36 *      @ring_size: total number of buffers (should be a power of 2)
  37 *      @tmp_page: cached released page
  38 *      @readers: number of current readers of this pipe
  39 *      @writers: number of current writers of this pipe
  40 *      @files: number of struct file referring this pipe (protected by ->i_lock)
  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 head;
  52        unsigned int tail;
  53        unsigned int max_usage;
  54        unsigned int ring_size;
  55        unsigned int readers;
  56        unsigned int writers;
  57        unsigned int files;
  58        unsigned int r_counter;
  59        unsigned int w_counter;
  60        struct page *tmp_page;
  61        struct fasync_struct *fasync_readers;
  62        struct fasync_struct *fasync_writers;
  63        struct pipe_buffer *bufs;
  64        struct user_struct *user;
  65};
  66
  67/*
  68 * Note on the nesting of these functions:
  69 *
  70 * ->confirm()
  71 *      ->steal()
  72 *
  73 * That is, ->steal() must be called on a confirmed buffer.
  74 * See below for the meaning of each operation. Also see kerneldoc
  75 * in fs/pipe.c for the pipe and generic variants of these hooks.
  76 */
  77struct pipe_buf_operations {
  78        /*
  79         * ->confirm() verifies that the data in the pipe buffer is there
  80         * and that the contents are good. If the pages in the pipe belong
  81         * to a file system, we may need to wait for IO completion in this
  82         * hook. Returns 0 for good, or a negative error value in case of
  83         * error.
  84         */
  85        int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
  86
  87        /*
  88         * When the contents of this pipe buffer has been completely
  89         * consumed by a reader, ->release() is called.
  90         */
  91        void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
  92
  93        /*
  94         * Attempt to take ownership of the pipe buffer and its contents.
  95         * ->steal() returns 0 for success, in which case the contents
  96         * of the pipe (the buf->page) is locked and now completely owned
  97         * by the caller. The page may then be transferred to a different
  98         * mapping, the most often used case is insertion into different
  99         * file address space cache.
 100         */
 101        int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
 102
 103        /*
 104         * Get a reference to the pipe buffer.
 105         */
 106        bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 107};
 108
 109/**
 110 * pipe_empty - Return true if the pipe is empty
 111 * @head: The pipe ring head pointer
 112 * @tail: The pipe ring tail pointer
 113 */
 114static inline bool pipe_empty(unsigned int head, unsigned int tail)
 115{
 116        return head == tail;
 117}
 118
 119/**
 120 * pipe_occupancy - Return number of slots used in the pipe
 121 * @head: The pipe ring head pointer
 122 * @tail: The pipe ring tail pointer
 123 */
 124static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
 125{
 126        return head - tail;
 127}
 128
 129/**
 130 * pipe_full - Return true if the pipe is full
 131 * @head: The pipe ring head pointer
 132 * @tail: The pipe ring tail pointer
 133 * @limit: The maximum amount of slots available.
 134 */
 135static inline bool pipe_full(unsigned int head, unsigned int tail,
 136                             unsigned int limit)
 137{
 138        return pipe_occupancy(head, tail) >= limit;
 139}
 140
 141/**
 142 * pipe_space_for_user - Return number of slots available to userspace
 143 * @head: The pipe ring head pointer
 144 * @tail: The pipe ring tail pointer
 145 * @pipe: The pipe info structure
 146 */
 147static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
 148                                               struct pipe_inode_info *pipe)
 149{
 150        unsigned int p_occupancy, p_space;
 151
 152        p_occupancy = pipe_occupancy(head, tail);
 153        if (p_occupancy >= pipe->max_usage)
 154                return 0;
 155        p_space = pipe->ring_size - p_occupancy;
 156        if (p_space > pipe->max_usage)
 157                p_space = pipe->max_usage;
 158        return p_space;
 159}
 160
 161/**
 162 * pipe_buf_get - get a reference to a pipe_buffer
 163 * @pipe:       the pipe that the buffer belongs to
 164 * @buf:        the buffer to get a reference to
 165 *
 166 * Return: %true if the reference was successfully obtained.
 167 */
 168static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
 169                                struct pipe_buffer *buf)
 170{
 171        return buf->ops->get(pipe, buf);
 172}
 173
 174/**
 175 * pipe_buf_release - put a reference to a pipe_buffer
 176 * @pipe:       the pipe that the buffer belongs to
 177 * @buf:        the buffer to put a reference to
 178 */
 179static inline void pipe_buf_release(struct pipe_inode_info *pipe,
 180                                    struct pipe_buffer *buf)
 181{
 182        const struct pipe_buf_operations *ops = buf->ops;
 183
 184        buf->ops = NULL;
 185        ops->release(pipe, buf);
 186}
 187
 188/**
 189 * pipe_buf_confirm - verify contents of the pipe buffer
 190 * @pipe:       the pipe that the buffer belongs to
 191 * @buf:        the buffer to confirm
 192 */
 193static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 194                                   struct pipe_buffer *buf)
 195{
 196        return buf->ops->confirm(pipe, buf);
 197}
 198
 199/**
 200 * pipe_buf_steal - attempt to take ownership of a pipe_buffer
 201 * @pipe:       the pipe that the buffer belongs to
 202 * @buf:        the buffer to attempt to steal
 203 */
 204static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
 205                                 struct pipe_buffer *buf)
 206{
 207        return buf->ops->steal(pipe, buf);
 208}
 209
 210/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 211   memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 212#define PIPE_SIZE               PAGE_SIZE
 213
 214/* Pipe lock and unlock operations */
 215void pipe_lock(struct pipe_inode_info *);
 216void pipe_unlock(struct pipe_inode_info *);
 217void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 218
 219extern unsigned int pipe_max_size;
 220extern unsigned long pipe_user_pages_hard;
 221extern unsigned long pipe_user_pages_soft;
 222
 223/* Drop the inode semaphore and wait for a pipe event, atomically */
 224void pipe_wait(struct pipe_inode_info *pipe);
 225
 226struct pipe_inode_info *alloc_pipe_info(void);
 227void free_pipe_info(struct pipe_inode_info *);
 228
 229/* Generic pipe buffer ops functions */
 230bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 231int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 232int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 233int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
 234void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 235void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
 236
 237extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
 238
 239/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 240long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 241struct pipe_inode_info *get_pipe_info(struct file *file);
 242
 243int create_pipe_files(struct file **, int);
 244unsigned int round_pipe_size(unsigned long size);
 245
 246#endif
 247