include/linux/pipe_fs_i.h

   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  **/
  21 struct 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  **/
  48 struct 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  */
  75 struct 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          * ->confirm() verifies that the data in the pipe buffer is there
  85          * and that the contents are good. If the pages in the pipe belong
  86          * to a file system, we may need to wait for IO completion in this
  87          * hook. Returns 0 for good, or a negative error value in case of
  88          * error.
  89          */
  90         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
  91
  92         /*
  93          * When the contents of this pipe buffer has been completely
  94          * consumed by a reader, ->release() is called.
  95          */
  96         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
  97
  98         /*
  99          * Attempt to take ownership of the pipe buffer and its contents.
 100          * ->steal() returns 0 for success, in which case the contents
 101          * of the pipe (the buf->page) is locked and now completely owned
 102          * by the caller. The page may then be transferred to a different
 103          * mapping, the most often used case is insertion into different
 104          * file address space cache.
 105          */
 106         int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
 107
 108         /*
 109          * Get a reference to the pipe buffer.
 110          */
 111         void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 112 };
 113
 114 /**
 115  * pipe_buf_get - get a reference to a pipe_buffer
 116  * @pipe:       the pipe that the buffer belongs to
 117  * @buf:        the buffer to get a reference to
 118  */
 119 static inline void pipe_buf_get(struct pipe_inode_info *pipe,
 120                                 struct pipe_buffer *buf)
 121 {
 122         buf->ops->get(pipe, buf);
 123 }
 124
 125 /**
 126  * pipe_buf_release - put a reference to a pipe_buffer
 127  * @pipe:       the pipe that the buffer belongs to
 128  * @buf:        the buffer to put a reference to
 129  */
 130 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
 131                                     struct pipe_buffer *buf)
 132 {
 133         const struct pipe_buf_operations *ops = buf->ops;
 134
 135         buf->ops = NULL;
 136         ops->release(pipe, buf);
 137 }
 138
 139 /**
 140  * pipe_buf_confirm - verify contents of the pipe buffer
 141  * @pipe:       the pipe that the buffer belongs to
 142  * @buf:        the buffer to confirm
 143  */
 144 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 145                                    struct pipe_buffer *buf)
 146 {
 147         return buf->ops->confirm(pipe, buf);
 148 }
 149
 150 /**
 151  * pipe_buf_steal - attempt to take ownership of a pipe_buffer
 152  * @pipe:       the pipe that the buffer belongs to
 153  * @buf:        the buffer to attempt to steal
 154  */
 155 static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
 156                                  struct pipe_buffer *buf)
 157 {
 158         return buf->ops->steal(pipe, buf);
 159 }
 160
 161 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 162    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 163 #define PIPE_SIZE               PAGE_SIZE
 164
 165 /* Pipe lock and unlock operations */
 166 void pipe_lock(struct pipe_inode_info *);
 167 void pipe_unlock(struct pipe_inode_info *);
 168 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 169
 170 extern unsigned int pipe_max_size;
 171 extern unsigned long pipe_user_pages_hard;
 172 extern unsigned long pipe_user_pages_soft;
 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 unsigned int round_pipe_size(unsigned long size);
 194
 195 #endif