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 * @rd_wait: reader wait point in case of empty pipe 33 * @wr_wait: writer wait point in case of full pipe 34 * @head: The point of buffer production 35 * @tail: The point of buffer consumption 36 * @max_usage: The maximum number of slots that may be used in the ring 37 * @ring_size: total number of buffers (should be a power of 2) 38 * @tmp_page: cached released page 39 * @readers: number of current readers of this pipe 40 * @writers: number of current writers of this pipe 41 * @files: number of struct file referring this pipe (protected by ->i_lock) 42 * @r_counter: reader counter 43 * @w_counter: writer counter 44 * @fasync_readers: reader side fasync 45 * @fasync_writers: writer side fasync 46 * @bufs: the circular array of pipe buffers 47 * @user: the user who created this pipe 48 **/ 49 struct pipe_inode_info { 50 struct mutex mutex; 51 wait_queue_head_t rd_wait, wr_wait; 52 unsigned int head; 53 unsigned int tail; 54 unsigned int max_usage; 55 unsigned int ring_size; 56 unsigned int readers; 57 unsigned int writers; 58 unsigned int files; 59 unsigned int r_counter; 60 unsigned int w_counter; 61 struct page *tmp_page; 62 struct fasync_struct *fasync_readers; 63 struct fasync_struct *fasync_writers; 64 struct pipe_buffer *bufs; 65 struct user_struct *user; 66 }; 67 68 /* 69 * Note on the nesting of these functions: 70 * 71 * ->confirm() 72 * ->steal() 73 * 74 * That is, ->steal() must be called on a confirmed buffer. 75 * See below for the meaning of each operation. Also see kerneldoc 76 * in fs/pipe.c for the pipe and generic variants of these hooks. 77 */ 78 struct pipe_buf_operations { 79 /* 80 * ->confirm() verifies that the data in the pipe buffer is there 81 * and that the contents are good. If the pages in the pipe belong 82 * to a file system, we may need to wait for IO completion in this 83 * hook. Returns 0 for good, or a negative error value in case of 84 * error. 85 */ 86 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *); 87 88 /* 89 * When the contents of this pipe buffer has been completely 90 * consumed by a reader, ->release() is called. 91 */ 92 void (*release)(struct pipe_inode_info *, struct pipe_buffer *); 93 94 /* 95 * Attempt to take ownership of the pipe buffer and its contents. 96 * ->steal() returns 0 for success, in which case the contents 97 * of the pipe (the buf->page) is locked and now completely owned 98 * by the caller. The page may then be transferred to a different 99 * mapping, the most often used case is insertion into different 100 * file address space cache. 101 */ 102 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *); 103 104 /* 105 * Get a reference to the pipe buffer. 106 */ 107 bool (*get)(struct pipe_inode_info *, struct pipe_buffer *); 108 }; 109 110 /** 111 * pipe_empty - Return true if the pipe is empty 112 * @head: The pipe ring head pointer 113 * @tail: The pipe ring tail pointer 114 */ 115 static inline bool pipe_empty(unsigned int head, unsigned int tail) 116 { 117 return head == tail; 118 } 119 120 /** 121 * pipe_occupancy - Return number of slots used in the pipe 122 * @head: The pipe ring head pointer 123 * @tail: The pipe ring tail pointer 124 */ 125 static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail) 126 { 127 return head - tail; 128 } 129 130 /** 131 * pipe_full - Return true if the pipe is full 132 * @head: The pipe ring head pointer 133 * @tail: The pipe ring tail pointer 134 * @limit: The maximum amount of slots available. 135 */ 136 static inline bool pipe_full(unsigned int head, unsigned int tail, 137 unsigned int limit) 138 { 139 return pipe_occupancy(head, tail) >= limit; 140 } 141 142 /** 143 * pipe_space_for_user - Return number of slots available to userspace 144 * @head: The pipe ring head pointer 145 * @tail: The pipe ring tail pointer 146 * @pipe: The pipe info structure 147 */ 148 static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail, 149 struct pipe_inode_info *pipe) 150 { 151 unsigned int p_occupancy, p_space; 152 153 p_occupancy = pipe_occupancy(head, tail); 154 if (p_occupancy >= pipe->max_usage) 155 return 0; 156 p_space = pipe->ring_size - p_occupancy; 157 if (p_space > pipe->max_usage) 158 p_space = pipe->max_usage; 159 return p_space; 160 } 161 162 /** 163 * pipe_buf_get - get a reference to a pipe_buffer 164 * @pipe: the pipe that the buffer belongs to 165 * @buf: the buffer to get a reference to 166 * 167 * Return: %true if the reference was successfully obtained. 168 */ 169 static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe, 170 struct pipe_buffer *buf) 171 { 172 return buf->ops->get(pipe, buf); 173 } 174 175 /** 176 * pipe_buf_release - put a reference to a pipe_buffer 177 * @pipe: the pipe that the buffer belongs to 178 * @buf: the buffer to put a reference to 179 */ 180 static inline void pipe_buf_release(struct pipe_inode_info *pipe, 181 struct pipe_buffer *buf) 182 { 183 const struct pipe_buf_operations *ops = buf->ops; 184 185 buf->ops = NULL; 186 ops->release(pipe, buf); 187 } 188 189 /** 190 * pipe_buf_confirm - verify contents of the pipe buffer 191 * @pipe: the pipe that the buffer belongs to 192 * @buf: the buffer to confirm 193 */ 194 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe, 195 struct pipe_buffer *buf) 196 { 197 return buf->ops->confirm(pipe, buf); 198 } 199 200 /** 201 * pipe_buf_steal - attempt to take ownership of a pipe_buffer 202 * @pipe: the pipe that the buffer belongs to 203 * @buf: the buffer to attempt to steal 204 */ 205 static inline int pipe_buf_steal(struct pipe_inode_info *pipe, 206 struct pipe_buffer *buf) 207 { 208 return buf->ops->steal(pipe, buf); 209 } 210 211 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual 212 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ 213 #define PIPE_SIZE PAGE_SIZE 214 215 /* Pipe lock and unlock operations */ 216 void pipe_lock(struct pipe_inode_info *); 217 void pipe_unlock(struct pipe_inode_info *); 218 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *); 219 220 extern unsigned int pipe_max_size; 221 extern unsigned long pipe_user_pages_hard; 222 extern unsigned long pipe_user_pages_soft; 223 224 /* Drop the inode semaphore and wait for a pipe event, atomically */ 225 void pipe_wait(struct pipe_inode_info *pipe); 226 227 struct pipe_inode_info *alloc_pipe_info(void); 228 void free_pipe_info(struct pipe_inode_info *); 229 230 /* Generic pipe buffer ops functions */ 231 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); 232 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); 233 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *); 234 int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *); 235 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *); 236 void pipe_buf_mark_unmergeable(struct pipe_buffer *buf); 237 238 extern const struct pipe_buf_operations nosteal_pipe_buf_ops; 239 240 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */ 241 long pipe_fcntl(struct file *, unsigned int, unsigned long arg); 242 struct pipe_inode_info *get_pipe_info(struct file *file); 243 244 int create_pipe_files(struct file **, int); 245 unsigned int round_pipe_size(unsigned long size); 246 247 #endif 248