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