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