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#ifndef _LINUX_PIPE_FS_I_H
#define _LINUX_PIPE_FS_I_H
#define PIPEFS_MAGIC 0x50495045
#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
* struct pipe_buffer - a linux kernel pipe buffer
* @page: the page containing the data for the pipe buffer
* @offset: offset of data inside the @page
* @len: length of data inside the @page
* @ops: operations associated with this buffer. See @pipe_buf_operations.
* @flags: pipe buffer flags. See above.
* @private: private data owned by the ops.
struct pipe_buffer {
struct page *page;
unsigned int offset, len;
const struct pipe_buf_operations *ops;
unsigned int flags;
unsigned long private;
* struct pipe_inode_info - a linux kernel pipe
* @wait: reader/writer wait point in case of empty/full pipe
* @nrbufs: the number of non-empty pipe buffers in this pipe
* @curbuf: the current pipe buffer entry
* @tmp_page: cached released page
* @readers: number of current readers of this pipe
* @writers: number of current writers of this pipe
* @waiting_writers: number of writers blocked waiting for room
* @r_counter: reader counter
* @w_counter: writer counter
* @fasync_readers: reader side fasync
* @fasync_writers: writer side fasync
* @inode: inode this pipe is attached to
* @bufs: the circular array of pipe buffers
struct pipe_inode_info {
wait_queue_head_t wait;
unsigned int nrbufs, curbuf, buffers;
unsigned int readers;
unsigned int writers;
unsigned int waiting_writers;
unsigned int r_counter;
unsigned int w_counter;
struct page *tmp_page;
struct fasync_struct *fasync_readers;
struct fasync_struct *fasync_writers;
struct inode *inode;
struct pipe_buffer *bufs;
* Note on the nesting of these functions:
* ->confirm()
* ->steal()
* ...
* ->map()
* ...
* ->unmap()
* That is, ->map() must be called on a confirmed buffer,
* same goes for ->steal(). See below for the meaning of each
* operation. Also see kerneldoc in fs/pipe.c for the pipe
* and generic variants of these hooks.
struct pipe_buf_operations {
* This is set to 1, if the generic pipe read/write may coalesce
* data into an existing buffer. If this is set to 0, a new pipe
* page segment is always used for new data.
int can_merge;
* ->map() returns a virtual address mapping of the pipe buffer.
* The last integer flag reflects whether this should be an atomic
* mapping or not. The atomic map is faster, however you can't take
* page faults before calling ->unmap() again. So if you need to eg
* access user data through copy_to/from_user(), then you must get
* a non-atomic map. ->map() uses the KM_USER0 atomic slot for
* atomic maps, so you can't map more than one pipe_buffer at once
* and you have to be careful if mapping another page as source
* or destination for a copy (IOW, it has to use something else
* than KM_USER0).
void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int);
* Undoes ->map(), finishes the virtual mapping of the pipe buffer.
void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *);
* ->confirm() verifies that the data in the pipe buffer is there
* and that the contents are good. If the pages in the pipe belong
* to a file system, we may need to wait for IO completion in this
* hook. Returns 0 for good, or a negative error value in case of
* error.
int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
* When the contents of this pipe buffer has been completely
* consumed by a reader, ->release() is called.
void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
* Attempt to take ownership of the pipe buffer and its contents.
* ->steal() returns 0 for success, in which case the contents
* of the pipe (the buf->page) is locked and now completely owned
* by the caller. The page may then be transferred to a different
* mapping, the most often used case is insertion into different
* file address space cache.
int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
* Get a reference to the pipe buffer.
void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
/* Pipe lock and unlock operations */
void pipe_lock(struct pipe_inode_info *);
void pipe_unlock(struct pipe_inode_info *);
void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
extern unsigned int pipe_max_size, pipe_min_size;
int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
/* Drop the inode semaphore and wait for a pipe event, atomically */
void pipe_wait(struct pipe_inode_info *pipe);
struct pipe_inode_info * alloc_pipe_info(struct inode * inode);
void free_pipe_info(struct inode * inode);
void __free_pipe_info(struct pipe_inode_info *);
/* Generic pipe buffer ops functions */
void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int);
void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *);
void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
struct pipe_inode_info *get_pipe_info(struct file *file);