linux-2.6.33/page_cache_async_readahead() の履歴(No.1)

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-2.6.33/page_cache_async_readahead() へ行く。
  • 1 (2010-08-17 (火) 16:53:28)

参照元†

• linux-2.6.33/do_generic_file_read()

説明†

• パス: linux-2.6.33/mm/readahead.c

• FIXME: これは何？
  • 説明

引数†

• struct address_space *mapping
  • linux-2.6.33/address_space
• struct file_ra_state *ra
  • linux-2.6.33/file_ra_state
• struct file *filp
  • linux-2.6.33/file
• struct page *page
  • linux-2.6.33/page
• pgoff_t offset
• unsigned long req_size

返り値†

• なし

参考†

実装†

/**
 * page_cache_async_readahead - file readahead for marked pages
 * @mapping: address_space which holds the pagecache and I/O vectors
 * @ra: file_ra_state which holds the readahead state
 * @filp: passed on to ->readpage() and ->readpages()
 * @page: the page at @offset which has the PG_readahead flag set
 * @offset: start offset into @mapping, in pagecache page-sized units
 * @req_size: hint: total size of the read which the caller is performing in
 *            pagecache pages
 *
 * page_cache_async_ondemand() should be called when a page is used which
 * has the PG_readahead flag; this is a marker to suggest that the application
 * has used up enough of the readahead window that we should start pulling in
 * more pages.
 */
void
page_cache_async_readahead(struct address_space *mapping,
			   struct file_ra_state *ra, struct file *filp,
			   struct page *page, pgoff_t offset,
			   unsigned long req_size)
{
	/* no read-ahead */
	if (!ra->ra_pages)
		return;

	/*
	 * Same bit is used for PG_readahead and PG_reclaim.
	 */
	if (PageWriteback(page))
		return;

	ClearPageReadahead(page);

	/*
	 * Defer asynchronous read-ahead on IO congestion.
	 */
	if (bdi_read_congested(mapping->backing_dev_info))
		return;

	/* do read-ahead */
	ondemand_readahead(mapping, ra, filp, true, offset, req_size);

#ifdef CONFIG_BLOCK
	/*
	 * Normally the current page is !uptodate and lock_page() will be
	 * immediately called to implicitly unplug the device. However this
	 * is not always true for RAID conifgurations, where data arrives
	 * not strictly in their submission order. In this case we need to
	 * explicitly kick off the IO.
	 */
	if (PageUptodate(page))
		blk_run_backing_dev(mapping->backing_dev_info, NULL);
#endif
}
EXPORT_SYMBOL_GPL(page_cache_async_readahead);

• カーネルのシンボルテーブル（GPL 用）にエクスポートする。
• linux-2.6.33/EXPORT_SYMBOL_GPL()

コメント†