include/linux/pipe_fs_i.h

   1 #ifndef _LINUX_PIPE_FS_I_H
   2 #define _LINUX_PIPE_FS_I_H
   3
   4 #define PIPEFS_MAGIC 0x50495045
   5
   6 #define PIPE_DEF_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 #define PIPE_BUF_FLAG_PACKET    0x08    /* read() as a packet */
  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  *      @wait: reader/writer wait point in case of empty/full pipe
  33  *      @nrbufs: the number of non-empty pipe buffers in this pipe
  34  *      @buffers: total number of buffers (should be a power of 2)
  35  *      @curbuf: the current pipe buffer entry
  36  *      @tmp_page: cached released page
  37  *      @readers: number of current readers of this pipe
  38  *      @writers: number of current writers of this pipe
  39  *      @waiting_writers: number of writers blocked waiting for room
  40  *      @r_counter: reader counter
  41  *      @w_counter: writer counter
  42  *      @fasync_readers: reader side fasync
  43  *      @fasync_writers: writer side fasync
  44  *      @inode: inode this pipe is attached to
  45  *      @bufs: the circular array of pipe buffers
  46  **/
  47 struct pipe_inode_info {
  48         wait_queue_head_t wait;
  49         unsigned int nrbufs, curbuf, buffers;
  50         unsigned int readers;
  51         unsigned int writers;
  52         unsigned int waiting_writers;
  53         unsigned int r_counter;
  54         unsigned int w_counter;
  55         struct page *tmp_page;
  56         struct fasync_struct *fasync_readers;
  57         struct fasync_struct *fasync_writers;
  58         struct inode *inode;
  59         struct pipe_buffer *bufs;
  60 };
  61
  62 /*
  63  * Note on the nesting of these functions:
  64  *
  65  * ->confirm()
  66  *      ->steal()
  67  *      ...
  68  *      ->map()
  69  *      ...
  70  *      ->unmap()
  71  *
  72  * That is, ->map() must be called on a confirmed buffer,
  73  * same goes for ->steal(). See below for the meaning of each
  74  * operation. Also see kerneldoc in fs/pipe.c for the pipe
  75  * and generic variants of these hooks.
  76  */
  77 struct pipe_buf_operations {
  78         /*
  79          * This is set to 1, if the generic pipe read/write may coalesce
  80          * data into an existing buffer. If this is set to 0, a new pipe
  81          * page segment is always used for new data.
  82          */
  83         int can_merge;
  84
  85         /*
  86          * ->map() returns a virtual address mapping of the pipe buffer.
  87          * The last integer flag reflects whether this should be an atomic
  88          * mapping or not. The atomic map is faster, however you can't take
  89          * page faults before calling ->unmap() again. So if you need to eg
  90          * access user data through copy_to/from_user(), then you must get
  91          * a non-atomic map. ->map() uses the KM_USER0 atomic slot for
  92          * atomic maps, so you can't map more than one pipe_buffer at once
  93          * and you have to be careful if mapping another page as source
  94          * or destination for a copy (IOW, it has to use something else
  95          * than KM_USER0).
  96          */
  97         void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int);
  98
  99         /*
 100          * Undoes ->map(), finishes the virtual mapping of the pipe buffer.
 101          */
 102         void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *);
 103
 104         /*
 105          * ->confirm() verifies that the data in the pipe buffer is there
 106          * and that the contents are good. If the pages in the pipe belong
 107          * to a file system, we may need to wait for IO completion in this
 108          * hook. Returns 0 for good, or a negative error value in case of
 109          * error.
 110          */
 111         int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 112
 113         /*
 114          * When the contents of this pipe buffer has been completely
 115          * consumed by a reader, ->release() is called.
 116          */
 117         void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
 118
 119         /*
 120          * Attempt to take ownership of the pipe buffer and its contents.
 121          * ->steal() returns 0 for success, in which case the contents
 122          * of the pipe (the buf->page) is locked and now completely owned
 123          * by the caller. The page may then be transferred to a different
 124          * mapping, the most often used case is insertion into different
 125          * file address space cache.
 126          */
 127         int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
 128
 129         /*
 130          * Get a reference to the pipe buffer.
 131          */
 132         void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 133 };
 134
 135 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
 136    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 137 #define PIPE_SIZE               PAGE_SIZE
 138
 139 /* Pipe lock and unlock operations */
 140 void pipe_lock(struct pipe_inode_info *);
 141 void pipe_unlock(struct pipe_inode_info *);
 142 void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 143
 144 extern unsigned int pipe_max_size, pipe_min_size;
 145 int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
 146
 147
 148 /* Drop the inode semaphore and wait for a pipe event, atomically */
 149 void pipe_wait(struct pipe_inode_info *pipe);
 150
 151 struct pipe_inode_info * alloc_pipe_info(struct inode * inode);
 152 void free_pipe_info(struct inode * inode);
 153 void __free_pipe_info(struct pipe_inode_info *);
 154
 155 /* Generic pipe buffer ops functions */
 156 void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int);
 157 void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *);
 158 void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 159 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 160 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 161 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 162
 163 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 164 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 165 struct pipe_inode_info *get_pipe_info(struct file *file);
 166
 167 #endif