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