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 #ifdef CONFIG_WATCH_QUEUE 66 bool note_loss; 67 #endif 68 unsigned int nr_accounted; 69 unsigned int readers; 70 unsigned int writers; 71 unsigned int files; 72 unsigned int r_counter; 73 unsigned int w_counter; 74 bool poll_usage; 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_empty - Return true if the pipe is empty 129 * @head: The pipe ring head pointer 130 * @tail: The pipe ring tail pointer 131 */ 132 static inline bool pipe_empty(unsigned int head, unsigned int tail) 133 { 134 return head == tail; 135 } 136 137 /** 138 * pipe_occupancy - Return number of slots used in the pipe 139 * @head: The pipe ring head pointer 140 * @tail: The pipe ring tail pointer 141 */ 142 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail) 143 { 144 return head - tail; 145 } 146 147 /** 148 * pipe_full - Return true if the pipe is full 149 * @head: The pipe ring head pointer 150 * @tail: The pipe ring tail pointer 151 * @limit: The maximum amount of slots available. 152 */ 153 static inline bool pipe_full(unsigned int head, unsigned int tail, 154 unsigned int limit) 155 { 156 return pipe_occupancy(head, tail) >= limit; 157 } 158 159 /** 160 * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring 161 * @pipe: The pipe to access 162 * @slot: The slot of interest 163 */ 164 static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe, 165 unsigned int slot) 166 { 167 return &pipe->bufs[slot & (pipe->ring_size - 1)]; 168 } 169 170 /** 171 * pipe_head_buf - Return the pipe buffer at the head of the pipe ring 172 * @pipe: The pipe to access 173 */ 174 static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe) 175 { 176 return pipe_buf(pipe, pipe->head); 177 } 178 179 /** 180 * pipe_buf_get - get a reference to a pipe_buffer 181 * @pipe: the pipe that the buffer belongs to 182 * @buf: the buffer to get a reference to 183 * 184 * Return: %true if the reference was successfully obtained. 185 */ 186 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe, 187 struct pipe_buffer *buf) 188 { 189 return buf->ops->get(pipe, buf); 190 } 191 192 /** 193 * pipe_buf_release - put a reference to a pipe_buffer 194 * @pipe: the pipe that the buffer belongs to 195 * @buf: the buffer to put a reference to 196 */ 197 static inline void pipe_buf_release(struct pipe_inode_info *pipe, 198 struct pipe_buffer *buf) 199 { 200 const struct pipe_buf_operations *ops = buf->ops; 201 202 buf->ops = NULL; 203 ops->release(pipe, buf); 204 } 205 206 /** 207 * pipe_buf_confirm - verify contents of the pipe buffer 208 * @pipe: the pipe that the buffer belongs to 209 * @buf: the buffer to confirm 210 */ 211 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe, 212 struct pipe_buffer *buf) 213 { 214 if (!buf->ops->confirm) 215 return 0; 216 return buf->ops->confirm(pipe, buf); 217 } 218 219 /** 220 * pipe_buf_try_steal - attempt to take ownership of a pipe_buffer 221 * @pipe: the pipe that the buffer belongs to 222 * @buf: the buffer to attempt to steal 223 */ 224 static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe, 225 struct pipe_buffer *buf) 226 { 227 if (!buf->ops->try_steal) 228 return false; 229 return buf->ops->try_steal(pipe, buf); 230 } 231 232 static inline void pipe_discard_from(struct pipe_inode_info *pipe, 233 unsigned int old_head) 234 { 235 unsigned int mask = pipe->ring_size - 1; 236 237 while (pipe->head > old_head) 238 pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]); 239 } 240 241 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual 242 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ 243 #define PIPE_SIZE PAGE_SIZE 244 245 /* Pipe lock and unlock operations */ 246 void pipe_lock(struct pipe_inode_info *); 247 void pipe_unlock(struct pipe_inode_info *); 248 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *); 249 250 /* Wait for a pipe to be readable/writable while dropping the pipe lock */ 251 void pipe_wait_readable(struct pipe_inode_info *); 252 void pipe_wait_writable(struct pipe_inode_info *); 253 254 struct pipe_inode_info *alloc_pipe_info(void); 255 void free_pipe_info(struct pipe_inode_info *); 256 257 /* Generic pipe buffer ops functions */ 258 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); 259 bool generic_pipe_buf_try_steal(struct pipe_inode_info *, struct pipe_buffer *); 260 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *); 261 262 extern const struct pipe_buf_operations nosteal_pipe_buf_ops; 263 264 unsigned long account_pipe_buffers(struct user_struct *user, 265 unsigned long old, unsigned long new); 266 bool too_many_pipe_buffers_soft(unsigned long user_bufs); 267 bool too_many_pipe_buffers_hard(unsigned long user_bufs); 268 bool pipe_is_unprivileged_user(void); 269 270 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */ 271 int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots); 272 long pipe_fcntl(struct file *, unsigned int, unsigned int arg); 273 struct pipe_inode_info *get_pipe_info(struct file *file, bool for_splice); 274 275 int create_pipe_files(struct file **, int); 276 unsigned int round_pipe_size(unsigned int size); 277 278 #endif 279