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  *      @poll_usage: is this pipe used for epoll, which has crazy wakeups?
  52  *      @fasync_readers: reader side fasync
  53  *      @fasync_writers: writer side fasync
  54  *      @bufs: the circular array of pipe buffers
  55  *      @user: the user who created this pipe
  56  *      @watch_queue: If this pipe is a watch_queue, this is the stuff for that
  57  **/
  58 struct pipe_inode_info {
  59         struct mutex mutex;
  60         wait_queue_head_t rd_wait, wr_wait;
  61         unsigned int head;
  62         unsigned int tail;
  63         unsigned int max_usage;
  64         unsigned int ring_size;
  65         unsigned int nr_accounted;
  66         unsigned int readers;
  67         unsigned int writers;
  68         unsigned int files;
  69         unsigned int r_counter;
  70         unsigned int w_counter;
  71         bool poll_usage;
  72 #ifdef CONFIG_WATCH_QUEUE
  73         bool note_loss;
  74 #endif
  75         struct page *tmp_page;
  76         struct fasync_struct *fasync_readers;
  77         struct fasync_struct *fasync_writers;
  78         struct pipe_buffer *bufs;
  79         struct user_struct *user;
  80 #ifdef CONFIG_WATCH_QUEUE
  81         struct watch_queue *watch_queue;
  82 #endif
  83 };
  84
  85 /*
  86  * Note on the nesting of these functions:
  87  *
  88  * ->confirm()
  89  *      ->try_steal()
  90  *
  91  * That is, ->try_steal() must be called on a confirmed buffer.  See below for
  92  * the meaning of each operation.  Also see the kerneldoc in fs/pipe.c for the
  93  * pipe and generic variants of these hooks.
  94  */
  95 struct pipe_buf_operations {
  96         /*
  97          * ->confirm() verifies that the data in the pipe buffer is there
  98          * and that the contents are good. If the pages in the pipe belong
  99          * to a file system, we may need to wait for IO completion in this
 100          * hook. Returns 0 for good, or a negative error value in case of
 101          * error.  If not present all pages are considered good.
 102          */
 103         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 104
 105         /*
 106          * When the contents of this pipe buffer has been completely
 107          * consumed by a reader, ->release() is called.
 108          */
 109         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 110
 111         /*
 112          * Attempt to take ownership of the pipe buffer and its contents.
 113          * ->try_steal() returns %true for success, in which case the contents
 114          * of the pipe (the buf->page) is locked and now completely owned by the
 115          * caller. The page may then be transferred to a different mapping, the
 116          * most often used case is insertion into different file address space
 117          * cache.
 118          */
 119         bool (*try_steal)(struct pipe_inode_info *, struct pipe_buffer *);
 120
 121         /*
 122          * Get a reference to the pipe buffer.
 123          */
 124         bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 125 };
 126
 127 /**
 128  * pipe_has_watch_queue - Check whether the pipe is a watch_queue,
 129  * i.e. it was created with O_NOTIFICATION_PIPE
 130  * @pipe: The pipe to check
 131  *
 132  * Return: true if pipe is a watch queue, false otherwise.
 133  */
 134 static inline bool pipe_has_watch_queue(const struct pipe_inode_info *pipe)
 135 {
 136 #ifdef CONFIG_WATCH_QUEUE
 137         return pipe->watch_queue != NULL;
 138 #else
 139         return false;
 140 #endif
 141 }
 142
 143 /**
 144  * pipe_empty - Return true if the pipe is empty
 145  * @head: The pipe ring head pointer
 146  * @tail: The pipe ring tail pointer
 147  */
 148 static inline bool pipe_empty(unsigned int head, unsigned int tail)
 149 {
 150         return head == tail;
 151 }
 152
 153 /**
 154  * pipe_occupancy - Return number of slots used in the pipe
 155  * @head: The pipe ring head pointer
 156  * @tail: The pipe ring tail pointer
 157  */
 158 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
 159 {
 160         return head - tail;
 161 }
 162
 163 /**
 164  * pipe_full - Return true if the pipe is full
 165  * @head: The pipe ring head pointer
 166  * @tail: The pipe ring tail pointer
 167  * @limit: The maximum amount of slots available.
 168  */
 169 static inline bool pipe_full(unsigned int head, unsigned int tail,
 170                              unsigned int limit)
 171 {
 172         return pipe_occupancy(head, tail) >= limit;
 173 }
 174
 175 /**
 176  * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
 177  * @pipe: The pipe to access
 178  * @slot: The slot of interest
 179  */
 180 static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
 181                                            unsigned int slot)
 182 {
 183         return &pipe->bufs[slot & (pipe->ring_size - 1)];
 184 }
 185
 186 /**
 187  * pipe_head_buf - Return the pipe buffer at the head of the pipe ring
 188  * @pipe: The pipe to access
 189  */
 190 static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe)
 191 {
 192         return pipe_buf(pipe, pipe->head);
 193 }
 194
 195 /**
 196  * pipe_buf_get - get a reference to a pipe_buffer
 197  * @pipe:       the pipe that the buffer belongs to
 198  * @buf:        the buffer to get a reference to
 199  *
 200  * Return: %true if the reference was successfully obtained.
 201  */
 202 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
 203                                 struct pipe_buffer *buf)
 204 {
 205         return buf->ops->get(pipe, buf);
 206 }
 207
 208 /**
 209  * pipe_buf_release - put a reference to a pipe_buffer
 210  * @pipe:       the pipe that the buffer belongs to
 211  * @buf:        the buffer to put a reference to
 212  */
 213 static inline void pipe_buf_release(struct pipe_inode_info *pipe,
 214                                     struct pipe_buffer *buf)
 215 {
 216         const struct pipe_buf_operations *ops = buf->ops;
 217
 218         buf->ops = NULL;
 219         ops->release(pipe, buf);
 220 }
 221
 222 /**
 223  * pipe_buf_confirm - verify contents of the pipe buffer
 224  * @pipe:       the pipe that the buffer belongs to
 225  * @buf:        the buffer to confirm
 226  */
 227 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 228                                    struct pipe_buffer *buf)
 229 {
 230         if (!buf->ops->confirm)
 231                 return 0;
 232         return buf->ops->confirm(pipe, buf);
 233 }
 234
 235 /**
 236  * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer
 237  * @pipe:       the pipe that the buffer belongs to
 238  * @buf:        the buffer to attempt to steal
 239  */
 240 static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
 241                 struct pipe_buffer *buf)
 242 {
 243         if (!buf->ops->try_steal)
 244                 return false;
 245         return buf->ops->try_steal(pipe, buf);
 246 }
 247
 248 static inline void pipe_discard_from(struct pipe_inode_info *pipe,
 249                 unsigned int old_head)
 250 {
 251         unsigned int mask = pipe->ring_size - 1;
 252
 253         while (pipe->head > old_head)
 254                 pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
 255 }
 256
 257 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 258    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 259 #define PIPE_SIZE               PAGE_SIZE
 260
 261 /* Pipe lock and unlock operations */
 262 void pipe_lock(struct pipe_inode_info *);
 263 void pipe_unlock(struct pipe_inode_info *);
 264 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 265
 266 /* Wait for a pipe to be readable/writable while dropping the pipe lock */
 267 void pipe_wait_readable(struct pipe_inode_info *);
 268 void pipe_wait_writable(struct pipe_inode_info *);
 269
 270 struct pipe_inode_info *alloc_pipe_info(void);
 271 void free_pipe_info(struct pipe_inode_info *);
 272
 273 /* Generic pipe buffer ops functions */
 274 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 275 bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *);
 276 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 277
 278 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
 279
 280 unsigned long account_pipe_buffers(struct user_struct *user,
 281                                    unsigned long old, unsigned long new);
 282 bool too_many_pipe_buffers_soft(unsigned long user_bufs);
 283 bool too_many_pipe_buffers_hard(unsigned long user_bufs);
 284 bool pipe_is_unprivileged_user(void);
 285
 286 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 287 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots);
 288 long pipe_fcntl(struct file *, unsigned int, unsigned int arg);
 289 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice);
 290
 291 int create_pipe_files(struct file **, int);
 292 unsigned int round_pipe_size(unsigned int size);
 293
 294 #endif