248 lines
7.6 KiB
C
248 lines
7.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_PIPE_FS_I_H
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#define _LINUX_PIPE_FS_I_H
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#define PIPE_DEF_BUFFERS 16
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#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
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#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
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#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
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#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
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/**
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* struct pipe_buffer - a linux kernel pipe buffer
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* @page: the page containing the data for the pipe buffer
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* @offset: offset of data inside the @page
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* @len: length of data inside the @page
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* @ops: operations associated with this buffer. See @pipe_buf_operations.
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* @flags: pipe buffer flags. See above.
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* @private: private data owned by the ops.
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**/
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struct pipe_buffer {
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struct page *page;
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unsigned int offset, len;
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const struct pipe_buf_operations *ops;
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unsigned int flags;
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unsigned long private;
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};
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/**
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* struct pipe_inode_info - a linux kernel pipe
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* @mutex: mutex protecting the whole thing
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* @rd_wait: reader wait point in case of empty pipe
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* @wr_wait: writer wait point in case of full pipe
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* @head: The point of buffer production
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* @tail: The point of buffer consumption
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* @max_usage: The maximum number of slots that may be used in the ring
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* @ring_size: total number of buffers (should be a power of 2)
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* @tmp_page: cached released page
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* @readers: number of current readers of this pipe
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* @writers: number of current writers of this pipe
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* @files: number of struct file referring this pipe (protected by ->i_lock)
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* @r_counter: reader counter
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* @w_counter: writer counter
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* @fasync_readers: reader side fasync
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* @fasync_writers: writer side fasync
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* @bufs: the circular array of pipe buffers
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* @user: the user who created this pipe
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**/
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struct pipe_inode_info {
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struct mutex mutex;
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wait_queue_head_t rd_wait, wr_wait;
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unsigned int head;
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unsigned int tail;
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unsigned int max_usage;
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unsigned int ring_size;
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unsigned int readers;
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unsigned int writers;
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unsigned int files;
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unsigned int r_counter;
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unsigned int w_counter;
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struct page *tmp_page;
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struct fasync_struct *fasync_readers;
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struct fasync_struct *fasync_writers;
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struct pipe_buffer *bufs;
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struct user_struct *user;
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};
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/*
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* Note on the nesting of these functions:
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*
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* ->confirm()
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* ->steal()
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*
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* That is, ->steal() must be called on a confirmed buffer.
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* See below for the meaning of each operation. Also see kerneldoc
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* in fs/pipe.c for the pipe and generic variants of these hooks.
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*/
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struct pipe_buf_operations {
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/*
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* ->confirm() verifies that the data in the pipe buffer is there
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* and that the contents are good. If the pages in the pipe belong
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* to a file system, we may need to wait for IO completion in this
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* hook. Returns 0 for good, or a negative error value in case of
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* error.
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*/
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int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* When the contents of this pipe buffer has been completely
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* consumed by a reader, ->release() is called.
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*/
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void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* Attempt to take ownership of the pipe buffer and its contents.
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* ->steal() returns 0 for success, in which case the contents
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* of the pipe (the buf->page) is locked and now completely owned
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* by the caller. The page may then be transferred to a different
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* mapping, the most often used case is insertion into different
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* file address space cache.
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*/
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int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
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/*
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* Get a reference to the pipe buffer.
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*/
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bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
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};
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/**
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* pipe_empty - Return true if the pipe is empty
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* @head: The pipe ring head pointer
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* @tail: The pipe ring tail pointer
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*/
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static inline bool pipe_empty(unsigned int head, unsigned int tail)
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{
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return head == tail;
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}
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/**
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* pipe_occupancy - Return number of slots used in the pipe
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* @head: The pipe ring head pointer
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* @tail: The pipe ring tail pointer
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*/
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static inline unsigned int pipe_occupancy(unsigned int head, unsigned int tail)
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{
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return head - tail;
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}
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/**
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* pipe_full - Return true if the pipe is full
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* @head: The pipe ring head pointer
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* @tail: The pipe ring tail pointer
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* @limit: The maximum amount of slots available.
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*/
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static inline bool pipe_full(unsigned int head, unsigned int tail,
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unsigned int limit)
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{
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return pipe_occupancy(head, tail) >= limit;
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}
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/**
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* pipe_space_for_user - Return number of slots available to userspace
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* @head: The pipe ring head pointer
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* @tail: The pipe ring tail pointer
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* @pipe: The pipe info structure
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*/
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static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
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struct pipe_inode_info *pipe)
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{
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unsigned int p_occupancy, p_space;
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p_occupancy = pipe_occupancy(head, tail);
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if (p_occupancy >= pipe->max_usage)
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return 0;
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p_space = pipe->ring_size - p_occupancy;
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if (p_space > pipe->max_usage)
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p_space = pipe->max_usage;
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return p_space;
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}
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/**
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* pipe_buf_get - get a reference to a pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to get a reference to
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*
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* Return: %true if the reference was successfully obtained.
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*/
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static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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return buf->ops->get(pipe, buf);
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}
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/**
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* pipe_buf_release - put a reference to a pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to put a reference to
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*/
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static inline void pipe_buf_release(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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const struct pipe_buf_operations *ops = buf->ops;
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buf->ops = NULL;
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ops->release(pipe, buf);
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}
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/**
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* pipe_buf_confirm - verify contents of the pipe buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to confirm
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*/
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static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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return buf->ops->confirm(pipe, buf);
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}
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/**
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* pipe_buf_steal - attempt to take ownership of a pipe_buffer
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* @pipe: the pipe that the buffer belongs to
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* @buf: the buffer to attempt to steal
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*/
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static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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return buf->ops->steal(pipe, buf);
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}
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/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
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memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
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#define PIPE_SIZE PAGE_SIZE
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/* Pipe lock and unlock operations */
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void pipe_lock(struct pipe_inode_info *);
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void pipe_unlock(struct pipe_inode_info *);
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void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
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extern unsigned int pipe_max_size;
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extern unsigned long pipe_user_pages_hard;
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extern unsigned long pipe_user_pages_soft;
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/* Drop the inode semaphore and wait for a pipe event, atomically */
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void pipe_wait(struct pipe_inode_info *pipe);
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struct pipe_inode_info *alloc_pipe_info(void);
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void free_pipe_info(struct pipe_inode_info *);
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/* Generic pipe buffer ops functions */
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bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
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int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
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void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
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void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
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extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
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/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
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long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
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struct pipe_inode_info *get_pipe_info(struct file *file);
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int create_pipe_files(struct file **, int);
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unsigned int round_pipe_size(unsigned long size);
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#endif
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