1 #ifndef _LINUX_PIPE_FS_I_H 2 #define _LINUX_PIPE_FS_I_H 3 4 #define PIPEFS_MAGIC 0x50495045 5 6 #define PIPE_BUFFERS (16) 7 8 #define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */ 9 #define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */ 10 #define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */ 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 * @wait: reader/writer wait point in case of empty/full pipe 32 * @nrbufs: the number of non-empty pipe buffers in this pipe 33 * @curbuf: the current pipe buffer entry 34 * @tmp_page: cached released page 35 * @readers: number of current readers of this pipe 36 * @writers: number of current writers of this pipe 37 * @waiting_writers: number of writers blocked waiting for room 38 * @r_counter: reader counter 39 * @w_counter: writer counter 40 * @fasync_readers: reader side fasync 41 * @fasync_writers: writer side fasync 42 * @inode: inode this pipe is attached to 43 * @bufs: the circular array of pipe buffers 44 **/ 45 struct pipe_inode_info { 46 wait_queue_head_t wait; 47 unsigned int nrbufs, curbuf; 48 struct page *tmp_page; 49 unsigned int readers; 50 unsigned int writers; 51 unsigned int waiting_writers; 52 unsigned int r_counter; 53 unsigned int w_counter; 54 struct fasync_struct *fasync_readers; 55 struct fasync_struct *fasync_writers; 56 struct inode *inode; 57 struct pipe_buffer bufs[PIPE_BUFFERS]; 58 }; 59 60 /* 61 * Note on the nesting of these functions: 62 * 63 * ->confirm() 64 * ->steal() 65 * ... 66 * ->map() 67 * ... 68 * ->unmap() 69 * 70 * That is, ->map() must be called on a confirmed buffer, 71 * same goes for ->steal(). See below for the meaning of each 72 * operation. Also see kerneldoc in fs/pipe.c for the pipe 73 * and generic variants of these hooks. 74 */ 75 struct pipe_buf_operations { 76 /* 77 * This is set to 1, if the generic pipe read/write may coalesce 78 * data into an existing buffer. If this is set to 0, a new pipe 79 * page segment is always used for new data. 80 */ 81 int can_merge; 82 83 /* 84 * ->map() returns a virtual address mapping of the pipe buffer. 85 * The last integer flag reflects whether this should be an atomic 86 * mapping or not. The atomic map is faster, however you can't take 87 * page faults before calling ->unmap() again. So if you need to eg 88 * access user data through copy_to/from_user(), then you must get 89 * a non-atomic map. ->map() uses the KM_USER0 atomic slot for 90 * atomic maps, so you can't map more than one pipe_buffer at once 91 * and you have to be careful if mapping another page as source 92 * or destination for a copy (IOW, it has to use something else 93 * than KM_USER0). 94 */ 95 void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int); 96 97 /* 98 * Undoes ->map(), finishes the virtual mapping of the pipe buffer. 99 */ 100 void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *); 101 102 /* 103 * ->confirm() verifies that the data in the pipe buffer is there 104 * and that the contents are good. If the pages in the pipe belong 105 * to a file system, we may need to wait for IO completion in this 106 * hook. Returns 0 for good, or a negative error value in case of 107 * error. 108 */ 109 int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *); 110 111 /* 112 * When the contents of this pipe buffer has been completely 113 * consumed by a reader, ->release() is called. 114 */ 115 void (*release)(struct pipe_inode_info *, struct pipe_buffer *); 116 117 /* 118 * Attempt to take ownership of the pipe buffer and its contents. 119 * ->steal() returns 0 for success, in which case the contents 120 * of the pipe (the buf->page) is locked and now completely owned 121 * by the caller. The page may then be transferred to a different 122 * mapping, the most often used case is insertion into different 123 * file address space cache. 124 */ 125 int (*steal)(struct pipe_inode_info *, struct pipe_buffer *); 126 127 /* 128 * Get a reference to the pipe buffer. 129 */ 130 void (*get)(struct pipe_inode_info *, struct pipe_buffer *); 131 }; 132 133 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual 134 memory allocation, whereas PIPE_BUF makes atomicity guarantees. */ 135 #define PIPE_SIZE PAGE_SIZE 136 137 /* Drop the inode semaphore and wait for a pipe event, atomically */ 138 void pipe_wait(struct pipe_inode_info *pipe); 139 140 struct pipe_inode_info * alloc_pipe_info(struct inode * inode); 141 void free_pipe_info(struct inode * inode); 142 void __free_pipe_info(struct pipe_inode_info *); 143 144 /* Generic pipe buffer ops functions */ 145 void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int); 146 void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *); 147 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); 148 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); 149 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *); 150 151 #endif 152