text: /*
   * linux/include/linux/nfs_page.h
   *
   * Copyright (C) 2000 Trond Myklebust
   *
   * NFS page cache wrapper.
   */
  
  #ifndef _LINUX_NFS_PAGE_H
  #define _LINUX_NFS_PAGE_H
  
  
  #include <linux/list.h>
  #include <linux/pagemap.h>
  #include <linux/wait.h>
  #include <linux/nfs_fs_sb.h>
  #include <linux/sunrpc/auth.h>
  #include <linux/nfs_xdr.h>
  
  #include <asm/atomic.h>
  
  /*
   * Valid flags for the radix tree
   */
  #define NFS_PAGE_TAG_DIRTY	0
  #define NFS_PAGE_TAG_WRITEBACK	1
  
  /*
   * Valid flags for a dirty buffer
   */
  #define PG_BUSY			0
  #define PG_NEED_COMMIT		1
  #define PG_NEED_RESCHED		2
  
  struct nfs_inode;
  struct nfs_page {
  	struct list_head	wb_list,	/* Defines state of page: */
  				*wb_list_head;	/*      read/write/commit */
  	struct page		*wb_page;	/* page to read in/write out */
  	struct nfs_open_context	*wb_context;	/* File state context info */
  	atomic_t		wb_complete;	/* i/os we're waiting for */
  	unsigned long		wb_index;	/* Offset >> PAGE_CACHE_SHIFT */
  	unsigned int		wb_offset,	/* Offset & ~PAGE_CACHE_MASK */
  				wb_pgbase,	/* Start of page data */
  				wb_bytes;	/* Length of request */
  	atomic_t		wb_count;	/* reference count */
  	unsigned long		wb_flags;
  	struct nfs_writeverf	wb_verf;	/* Commit cookie */
  };
  
  #define NFS_WBACK_BUSY(req)	(test_bit(PG_BUSY,&(req)->wb_flags))
  #define NFS_NEED_COMMIT(req)	(test_bit(PG_NEED_COMMIT,&(req)->wb_flags))
  #define NFS_NEED_RESCHED(req)	(test_bit(PG_NEED_RESCHED,&(req)->wb_flags))
  
  extern	struct nfs_page *nfs_create_request(struct nfs_open_context *ctx,
  					    struct inode *inode,
  					    struct page *page,
  					    unsigned int offset,
  					    unsigned int count);
  extern	void nfs_clear_request(struct nfs_page *req);
  extern	void nfs_release_request(struct nfs_page *req);
  
  
  extern  int nfs_scan_lock_dirty(struct nfs_inode *nfsi, struct list_head *dst,
  				unsigned long idx_start, unsigned int npages);
  extern	int nfs_scan_list(struct list_head *, struct list_head *,
  			  unsigned long, unsigned int);
  extern	int nfs_coalesce_requests(struct list_head *, struct list_head *,
  				  unsigned int);
  extern  int nfs_wait_on_request(struct nfs_page *);
  extern	void nfs_unlock_request(struct nfs_page *req);
  extern  int nfs_set_page_writeback_locked(struct nfs_page *req);
  extern  void nfs_clear_page_writeback(struct nfs_page *req);
  
  
  /*
   * Lock the page of an asynchronous request without incrementing the wb_count
   */
  static inline int
  nfs_lock_request_dontget(struct nfs_page *req)
  {
  	return !test_and_set_bit(PG_BUSY, &req->wb_flags);
  }
  
  /*
   * Lock the page of an asynchronous request
   */
  static inline int
  nfs_lock_request(struct nfs_page *req)
  {
  	if (test_and_set_bit(PG_BUSY, &req->wb_flags))
  		return 0;
  	atomic_inc(&req->wb_count);
  	return 1;
  }
  
  /**
   * nfs_list_add_request - Insert a request into a list
   * @req: request
   * @head: head of list into which to insert the request.
   */
  static inline void
  nfs_list_add_request(struct nfs_page *req, struct list_head *head)
  {
  	list_add_tail(&req->wb_list, head);
  	req->wb_list_head = head;
  }
  
  
  /**
   * nfs_list_remove_request - Remove a request from its wb_list
   * @req: request
   */
  static inline void
  nfs_list_remove_request(struct nfs_page *req)
  {
  	if (list_empty(&req->wb_list))
  		return;
  	list_del_init(&req->wb_list);
  	req->wb_list_head = NULL;
  }
  
  static inline int
  nfs_defer_commit(struct nfs_page *req)
  {
  	return !test_and_set_bit(PG_NEED_COMMIT, &req->wb_flags);
  }
  
  static inline void
  nfs_clear_commit(struct nfs_page *req)
  {
  	smp_mb__before_clear_bit();
  	clear_bit(PG_NEED_COMMIT, &req->wb_flags);
  	smp_mb__after_clear_bit();
  }
  
  static inline int
  nfs_defer_reschedule(struct nfs_page *req)
  {
  	return !test_and_set_bit(PG_NEED_RESCHED, &req->wb_flags);
  }
  
  static inline void
  nfs_clear_reschedule(struct nfs_page *req)
  {
  	smp_mb__before_clear_bit();
  	clear_bit(PG_NEED_RESCHED, &req->wb_flags);
  	smp_mb__after_clear_bit();
  }
  
  static inline struct nfs_page *
  nfs_list_entry(struct list_head *head)
  {
  	return list_entry(head, struct nfs_page, wb_list);
  }
  
  static inline
  loff_t req_offset(struct nfs_page *req)
  {
  	return (((loff_t)req->wb_index) << PAGE_CACHE_SHIFT) + req->wb_offset;
  }
  
  #endif /* _LINUX_NFS_PAGE_H */
  