linux-2.6.33/get_user_pages()(mmu) 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/get_user_pages()(mmu) へ行く。
  • 1 (2013-03-03 (日) 04:59:53)

参照元†

• linux-2.6.33/get_user_pages()

説明†

• パス: linux-2.6.33/mm/memory.c

• FIXME: これは何？
  • 説明

引数†

• struct task_struct *tsk
  • linux-2.6.33/task_struct
• struct mm_struct *mm
  • linux-2.6.33/mm_struct
• unsigned long start
• int nr_pages
• int write
• int force
• struct page **pages
  • linux-2.6.33/page
• struct vm_area_struct **vmas
  • linux-2.6.33/vm_area_struct

返り値†

• int

参考†

実装†

/**
 * get_user_pages() - pin user pages in memory
 * @tsk:	task_struct of target task
 * @mm:		mm_struct of target mm
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to by the caller
 * @force:	whether to force write access even if user mapping is
 *		readonly. This will result in the page being COWed even
 *		in MAP_SHARED mappings. You do not want this.
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long. Or NULL, if caller
 *		only intends to ensure the pages are faulted in.
 * @vmas:	array of pointers to vmas corresponding to each page.
 *		Or NULL if the caller does not require them.
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno. Each page returned must be released
 * with a put_page() call when it is finished with. vmas will only
 * remain valid while mmap_sem is held.
 *
 * Must be called with mmap_sem held for read or write.
 *
 * get_user_pages walks a process's page tables and takes a reference to
 * each struct page that each user address corresponds to at a given
 * instant. That is, it takes the page that would be accessed if a user
 * thread accesses the given user virtual address at that instant.
 *
 * This does not guarantee that the page exists in the user mappings when
 * get_user_pages returns, and there may even be a completely different
 * page there in some cases (eg. if mmapped pagecache has been invalidated
 * and subsequently re faulted). However it does guarantee that the page
 * won't be freed completely. And mostly callers simply care that the page
 * contains data that was valid *at some point in time*. Typically, an IO
 * or similar operation cannot guarantee anything stronger anyway because
 * locks can't be held over the syscall boundary.
 *
 * If write=0, the page must not be written to. If the page is written to,
 * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
 * after the page is finished with, and before put_page is called.
 *
 * get_user_pages is typically used for fewer-copy IO operations, to get a
 * handle on the memory by some means other than accesses via the user virtual
 * addresses. The pages may be submitted for DMA to devices or accessed via
 * their kernel linear mapping (via the kmap APIs). Care should be taken to
 * use the correct cache flushing APIs.
 *
 * See also get_user_pages_fast, for performance critical applications.
 */
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
		unsigned long start, int nr_pages, int write, int force,
		struct page **pages, struct vm_area_struct **vmas)
{
	int flags = FOLL_TOUCH;

	if (pages)
		flags |= FOLL_GET;
	if (write)
		flags |= FOLL_WRITE;
	if (force)
		flags |= FOLL_FORCE;

• • linux-2.6.33/FOLL_TOUCH

• linux-2.6.33/FOLL_GET

• • linux-2.6.33/FOLL_WRITE

• linux-2.6.33/FOLL_FORCE

	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);

• • linux-2.6.33/__get_user_pages()

}
EXPORT_SYMBOL(get_user_pages);

• ライセンスに関係なくシンボルを公開する。
  • linux-2.6.33/EXPORT_SYMBOL()

コメント†