include/linux/pipe_fs_i.h

   1 #ifndef _LINUX_PIPE_FS_I_H
   2 #define _LINUX_PIPE_FS_I_H
   3
   4 #define PIPE_DEF_BUFFERS        16
   5
   6 #define PIPE_BUF_FLAG_LRU       0x01    /* page is on the LRU */
   7 #define PIPE_BUF_FLAG_ATOMIC    0x02    /* was atomically mapped */
   8 #define PIPE_BUF_FLAG_GIFT      0x04    /* page is a gift */
   9
  10 /**
  11  *      struct pipe_buffer - a linux kernel pipe buffer
  12  *      @page: the page containing the data for the pipe buffer
  13  *      @offset: offset of data inside the @page
  14  *      @len: length of data inside the @page
  15  *      @ops: operations associated with this buffer. See @pipe_buf_operations.
  16  *      @flags: pipe buffer flags. See above.
  17  *      @private: private data owned by the ops.
  18  **/
  19 struct pipe_buffer {
  20         struct page *page;
  21         unsigned int offset, len;
  22         const struct pipe_buf_operations *ops;
  23         unsigned int flags;
  24         unsigned long private;
  25 };
  26
  27 /**
  28  *      struct pipe_inode_info - a linux kernel pipe
  29  *      @wait: reader/writer wait point in case of empty/full pipe
  30  *      @nrbufs: the number of non-empty pipe buffers in this pipe
  31  *      @buffers: total number of buffers (should be a power of 2)
  32  *      @curbuf: the current pipe buffer entry
  33  *      @tmp_page: cached released page
  34  *      @readers: number of current readers of this pipe
  35  *      @writers: number of current writers of this pipe
  36  *      @waiting_writers: number of writers blocked waiting for room
  37  *      @r_counter: reader counter
  38  *      @w_counter: writer counter
  39  *      @fasync_readers: reader side fasync
  40  *      @fasync_writers: writer side fasync
  41  *      @inode: inode this pipe is attached to
  42  *      @bufs: the circular array of pipe buffers
  43  **/
  44 struct pipe_inode_info {
  45         wait_queue_head_t wait;
  46         unsigned int nrbufs, curbuf, buffers;
  47         unsigned int readers;
  48         unsigned int writers;
  49         unsigned int waiting_writers;
  50         unsigned int r_counter;
  51         unsigned int w_counter;
  52         struct page *tmp_page;
  53         struct fasync_struct *fasync_readers;
  54         struct fasync_struct *fasync_writers;
  55         struct inode *inode;
  56         struct pipe_buffer *bufs;
  57 };
  58
  59 /*
  60  * Note on the nesting of these functions:
  61  *
  62  * ->confirm()
  63  *      ->steal()
  64  *      ...
  65  *      ->map()
  66  *      ...
  67  *      ->unmap()
  68  *
  69  * That is, ->map() must be called on a confirmed buffer,
  70  * same goes for ->steal(). See below for the meaning of each
  71  * operation. Also see kerneldoc in fs/pipe.c for the pipe
  72  * and generic variants of these hooks.
  73  */
  74 struct pipe_buf_operations {
  75         /*
  76          * This is set to 1, if the generic pipe read/write may coalesce
  77          * data into an existing buffer. If this is set to 0, a new pipe
  78          * page segment is always used for new data.
  79          */
  80         int can_merge;
  81
  82         /*
  83          * ->map() returns a virtual address mapping of the pipe buffer.
  84          * The last integer flag reflects whether this should be an atomic
  85          * mapping or not. The atomic map is faster, however you can't take
  86          * page faults before calling ->unmap() again. So if you need to eg
  87          * access user data through copy_to/from_user(), then you must get
  88          * a non-atomic map. ->map() uses the KM_USER0 atomic slot for
  89          * atomic maps, so you can't map more than one pipe_buffer at once
  90          * and you have to be careful if mapping another page as source
  91          * or destination for a copy (IOW, it has to use something else
  92          * than KM_USER0).
  93          */
  94         void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int);
  95
  96         /*
  97          * Undoes ->map(), finishes the virtual mapping of the pipe buffer.
  98          */
  99         void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *);
 100
 101         /*
 102          * ->confirm() verifies that the data in the pipe buffer is there
 103          * and that the contents are good. If the pages in the pipe belong
 104          * to a file system, we may need to wait for IO completion in this
 105          * hook. Returns 0 for good, or a negative error value in case of
 106          * error.
 107          */
 108         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 109
 110         /*
 111          * When the contents of this pipe buffer has been completely
 112          * consumed by a reader, ->release() is called.
 113          */
 114         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 115
 116         /*
 117          * Attempt to take ownership of the pipe buffer and its contents.
 118          * ->steal() returns 0 for success, in which case the contents
 119          * of the pipe (the buf->page) is locked and now completely owned
 120          * by the caller. The page may then be transferred to a different
 121          * mapping, the most often used case is insertion into different
 122          * file address space cache.
 123          */
 124         int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
 125
 126         /*
 127          * Get a reference to the pipe buffer.
 128          */
 129         void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 130 };
 131
 132 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 133    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 134 #define PIPE_SIZE               PAGE_SIZE
 135
 136 /* Pipe lock and unlock operations */
 137 void pipe_lock(struct pipe_inode_info *);
 138 void pipe_unlock(struct pipe_inode_info *);
 139 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 140
 141 extern unsigned int pipe_max_size, pipe_min_size;
 142 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
 143
 144
 145 /* Drop the inode semaphore and wait for a pipe event, atomically */
 146 void pipe_wait(struct pipe_inode_info *pipe);
 147
 148 struct pipe_inode_info * alloc_pipe_info(struct inode * inode);
 149 void free_pipe_info(struct inode * inode);
 150 void __free_pipe_info(struct pipe_inode_info *);
 151
 152 /* Generic pipe buffer ops functions */
 153 void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int);
 154 void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *);
 155 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 156 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 157 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 158 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 159
 160 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 161 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 162 struct pipe_inode_info *get_pipe_info(struct file *file);
 163
 164 #endif