On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
Let's define page_mapped() to be true for compound pages if any
sub-pages of the compound page is mapped (with PMD or PTE).
On other hand page_mapcount() return mapcount for this particular small
page.
This will make cases like page_get_anon_vma() behave correctly once we
allow huge pages to be mapped with PTE.
Most users outside core-mm should use page_mapcount() instead of
page_mapped().
Does "should" mean that they do that now, or just that you would like
them to? Should there be a warning before the function then?
Signed-off-by: Kirill A. Shutemov <[email protected]>
Tested-by: Sasha Levin <[email protected]>
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -909,7 +909,16 @@ static inline pgoff_t page_file_index(struct page *page)
(not shown in the diff)
* Return true if this page is mapped into pagetables.
*/
Expand the comment? Especially if you put compound_head() there.
static inline int page_mapped(struct page *page)
Convert to proper bool while at it?
{
- return atomic_read(&(page)->_mapcount) + compound_mapcount(page) >= 0;
+ int i;
+ if (likely(!PageCompound(page)))
+ return atomic_read(&page->_mapcount) >= 0;
+ if (compound_mapcount(page))
+ return 1;
+ for (i = 0; i < hpage_nr_pages(page); i++) {
+ if (atomic_read(&page[i]._mapcount) >= 0)
+ return 1;
+ }
+ return 0;
}
/*
--
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