ACPI: fix acpi_find_child_device() invocation in acpi_preset_companion()

[mirror_ubuntu-bionic-kernel.git] / include / linux / page-flags.h

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 584b14c774c181e85eac69be4f5a3ad037cb75d4..a6b15f20328c818efa403541e36fcde8b7dba118 100644 (file)
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -18,7 +18,7 @@
  * Various page->flags bits:
  *
  * PG_reserved is set for special pages, which can never be swapped out. Some
- * of them might not even exist (eg empty_bad_page)...
+ * of them might not even exist...
  *
  * The PG_private bitflag is set on pagecache pages if they contain filesystem
  * specific data (which is normally at page->private). It can be used by
@@ -565,12 +565,28 @@ static inline int PageTransCompound(struct page *page)
  *
  * Unlike PageTransCompound, this is safe to be called only while
  * split_huge_pmd() cannot run from under us, like if protected by the
- * MMU notifier, otherwise it may result in page->_mapcount < 0 false
+ * MMU notifier, otherwise it may result in page->_mapcount check false
  * positives.
+ *
+ * We have to treat page cache THP differently since every subpage of it
+ * would get _mapcount inc'ed once it is PMD mapped.  But, it may be PTE
+ * mapped in the current process so comparing subpage's _mapcount to
+ * compound_mapcount to filter out PTE mapped case.
  */
 static inline int PageTransCompoundMap(struct page *page)
 {
-       return PageTransCompound(page) && atomic_read(&page->_mapcount) < 0;
+       struct page *head;
+
+       if (!PageTransCompound(page))
+               return 0;
+
+       if (PageAnon(page))
+               return atomic_read(&page->_mapcount) < 0;
+
+       head = compound_head(page);
+       /* File THP is PMD mapped and not PTE mapped */
+       return atomic_read(&page->_mapcount) ==
+              atomic_read(compound_mapcount_ptr(head));
 }
 
 /*