*参照元 [#s349cecf]
#backlinks
*説明 [#y52440fa]
-パス: [[linux-2.6.33/mm/memory.c]]
-FIXME: これは何？
--説明
**引数 [#n1a0f89f]
-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 [#fc697fcd]
-int
--
**参考 [#w3dda315]
*実装 [#s9e9b0c6]
/**
* 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 [#g74a94be]
![[PukiWiki]](image/pukiwiki.png "[PukiWiki]")
