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 #define PIPE_BUF_FLAG_CAN_MERGE 0x10    /* can merge buffers */
  12 #define PIPE_BUF_FLAG_WHOLE     0x20    /* read() must return entire buffer or error */
  13 #ifdef CONFIG_WATCH_QUEUE
  14 #define PIPE_BUF_FLAG_LOSS      0x40    /* Message loss happened after this buffer */
  15 #endif
  16
  17 /**
  18  *      struct pipe_buffer - a linux kernel pipe buffer
  19  *      @page: the page containing the data for the pipe buffer
  20  *      @offset: offset of data inside the @page
  21  *      @len: length of data inside the @page
  22  *      @ops: operations associated with this buffer. See @pipe_buf_operations.
  23  *      @flags: pipe buffer flags. See above.
  24  *      @private: private data owned by the ops.
  25  **/
  26 struct pipe_buffer {
  27         struct page *page;
  28         unsigned int offset, len;
  29         const struct pipe_buf_operations *ops;
  30         unsigned int flags;
  31         unsigned long private;
  32 };
  33
  34 /**
  35  *      struct pipe_inode_info - a linux kernel pipe
  36  *      @mutex: mutex protecting the whole thing
  37  *      @rd_wait: reader wait point in case of empty pipe
  38  *      @wr_wait: writer wait point in case of full pipe
  39  *      @head: The point of buffer production
  40  *      @tail: The point of buffer consumption
  41  *      @note_loss: The next read() should insert a data-lost message
  42  *      @max_usage: The maximum number of slots that may be used in the ring
  43  *      @ring_size: total number of buffers (should be a power of 2)
  44  *      @nr_accounted: The amount this pipe accounts for in user->pipe_bufs
  45  *      @tmp_page: cached released page
  46  *      @readers: number of current readers of this pipe
  47  *      @writers: number of current writers of this pipe
  48  *      @files: number of struct file referring this pipe (protected by ->i_lock)
  49  *      @r_counter: reader counter
  50  *      @w_counter: writer counter
  51  *      @fasync_readers: reader side fasync
  52  *      @fasync_writers: writer side fasync
  53  *      @bufs: the circular array of pipe buffers
  54  *      @user: the user who created this pipe
  55  *      @watch_queue: If this pipe is a watch_queue, this is the stuff for that
  56  **/
  57 struct pipe_inode_info {
  58         struct mutex mutex;
  59         wait_queue_head_t rd_wait, wr_wait;
  60         unsigned int head;
  61         unsigned int tail;
  62         unsigned int max_usage;
  63         unsigned int ring_size;
  64 #ifdef CONFIG_WATCH_QUEUE
  65         bool note_loss;
  66 #endif
  67         unsigned int nr_accounted;
  68         unsigned int readers;
  69         unsigned int writers;
  70         unsigned int files;
  71         unsigned int r_counter;
  72         unsigned int w_counter;
  73         struct page *tmp_page;
  74         struct fasync_struct *fasync_readers;
  75         struct fasync_struct *fasync_writers;
  76         struct pipe_buffer *bufs;
  77         struct user_struct *user;
  78 #ifdef CONFIG_WATCH_QUEUE
  79         struct watch_queue *watch_queue;
  80 #endif
  81 };
  82
  83 /*
  84  * Note on the nesting of these functions:
  85  *
  86  * ->confirm()
  87  *      ->try_steal()
  88  *
  89  * That is, ->try_steal() must be called on a confirmed buffer.  See below for
  90  * the meaning of each operation.  Also see the kerneldoc in fs/pipe.c for the
  91  * pipe and generic variants of these hooks.
  92  */
  93 struct pipe_buf_operations {
  94         /*
  95          * ->confirm() verifies that the data in the pipe buffer is there
  96          * and that the contents are good. If the pages in the pipe belong
  97          * to a file system, we may need to wait for IO completion in this
  98          * hook. Returns 0 for good, or a negative error value in case of
  99          * error.  If not present all pages are considered good.
 100          */
 101         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 102
 103         /*
 104          * When the contents of this pipe buffer has been completely
 105          * consumed by a reader, ->release() is called.
 106          */
 107         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 108
 109         /*
 110          * Attempt to take ownership of the pipe buffer and its contents.
 111          * ->try_steal() returns %true for success, in which case the contents
 112          * of the pipe (the buf->page) is locked and now completely owned by the
 113          * caller. The page may then be transferred to a different mapping, the
 114          * most often used case is insertion into different file address space
 115          * cache.
 116          */
 117         bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
 118
 119         /*
 120          * Get a reference to the pipe buffer.
 121          */
 122         bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 123 };
 124
 125 /**
 126  * pipe_empty - Return true if the pipe is empty
 127  * @head: The pipe ring head pointer
 128  * @tail: The pipe ring tail pointer
 129  */
 130 static inline bool pipe_empty(unsigned int head, unsigned int tail)
 131 {
 132         return head == tail;
 133 }
 134
 135 /**
 136  * pipe_occupancy - Return number of slots used in the pipe
 137  * @head: The pipe ring head pointer
 138  * @tail: The pipe ring tail pointer
 139  */
 140 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
 141 {
 142         return head - tail;
 143 }
 144
 145 /**
 146  * pipe_full - Return true if the pipe is full
 147  * @head: The pipe ring head pointer
 148  * @tail: The pipe ring tail pointer
 149  * @limit: The maximum amount of slots available.
 150  */
 151 static inline bool pipe_full(unsigned int head, unsigned int tail,
 152                              unsigned int limit)
 153 {
 154         return pipe_occupancy(head, tail) >= limit;
 155 }
 156
 157 /**
 158  * pipe_space_for_user - Return number of slots available to userspace
 159  * @head: The pipe ring head pointer
 160  * @tail: The pipe ring tail pointer
 161  * @pipe: The pipe info structure
 162  */
 163 static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
 164                                                struct pipe_inode_info *pipe)
 165 {
 166         unsigned int p_occupancy, p_space;
 167
 168         p_occupancy = pipe_occupancy(head, tail);
 169         if (p_occupancy >= pipe->max_usage)
 170                 return 0;
 171         p_space = pipe->ring_size - p_occupancy;
 172         if (p_space > pipe->max_usage)
 173                 p_space = pipe->max_usage;
 174         return p_space;
 175 }
 176
 177 /**
 178  * pipe_buf_get - get a reference to a pipe_buffer
 179  * @pipe:       the pipe that the buffer belongs to
 180  * @buf:        the buffer to get a reference to
 181  *
 182  * Return: %true if the reference was successfully obtained.
 183  */
 184 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
 185                                 struct pipe_buffer *buf)
 186 {
 187         return buf->ops->get(pipe, buf);
 188 }
 189
 190 /**
 191  * pipe_buf_release - put a reference to a pipe_buffer
 192  * @pipe:       the pipe that the buffer belongs to
 193  * @buf:        the buffer to put a reference to
 194  */
 195 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
 196                                     struct pipe_buffer *buf)
 197 {
 198         const struct pipe_buf_operations *ops = buf->ops;
 199
 200         buf->ops = NULL;
 201         ops->release(pipe, buf);
 202 }
 203
 204 /**
 205  * pipe_buf_confirm - verify contents of the pipe buffer
 206  * @pipe:       the pipe that the buffer belongs to
 207  * @buf:        the buffer to confirm
 208  */
 209 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 210                                    struct pipe_buffer *buf)
 211 {
 212         if (!buf->ops->confirm)
 213                 return 0;
 214         return buf->ops->confirm(pipe, buf);
 215 }
 216
 217 /**
 218  * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
 219  * @pipe:       the pipe that the buffer belongs to
 220  * @buf:        the buffer to attempt to steal
 221  */
 222 static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
 223                 struct pipe_buffer *buf)
 224 {
 225         if (!buf->ops->try_steal)
 226                 return false;
 227         return buf->ops->try_steal(pipe, buf);
 228 }
 229
 230 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 231    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 232 #define PIPE_SIZE               PAGE_SIZE
 233
 234 /* Pipe lock and unlock operations */
 235 void pipe_lock(struct pipe_inode_info *);
 236 void pipe_unlock(struct pipe_inode_info *);
 237 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 238
 239 extern unsigned int pipe_max_size;
 240 extern unsigned long pipe_user_pages_hard;
 241 extern unsigned long pipe_user_pages_soft;
 242
 243 /* Wait for a pipe to be readable/writable while dropping the pipe lock */
 244 void pipe_wait_readable(struct pipe_inode_info *);
 245 void pipe_wait_writable(struct pipe_inode_info *);
 246
 247 struct pipe_inode_info *alloc_pipe_info(void);
 248 void free_pipe_info(struct pipe_inode_info *);
 249
 250 /* Generic pipe buffer ops functions */
 251 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 252 bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
 253 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 254
 255 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
 256
 257 #ifdef CONFIG_WATCH_QUEUE
 258 unsigned long account_pipe_buffers(struct user_struct *user,
 259                                    unsigned long old, unsigned long new);
 260 bool too_many_pipe_buffers_soft(unsigned long user_bufs);
 261 bool too_many_pipe_buffers_hard(unsigned long user_bufs);
 262 bool pipe_is_unprivileged_user(void);
 263 #endif
 264
 265 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 266 #ifdef CONFIG_WATCH_QUEUE
 267 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
 268 #endif
 269 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 270 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
 271
 272 int create_pipe_files(struct file **, int);
 273 unsigned int round_pipe_size(unsigned long size);
 274
 275 #endif