mm: introduce page_vma_mapped_walk()

Introduce a new interface to check if a page is mapped into a vma.  It
aims to address shortcomings of page_check_address{,_transhuge}.

Existing interface is not able to handle PTE-mapped THPs: it only finds
the first PTE.  The rest lefted unnoticed.

page_vma_mapped_walk() iterates over all possible mapping of the page in
the vma.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Kirill A. Shutemov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 26 insertions, 0 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 15321fb1df6b..b76343610653 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -9,6 +9,7 @@
 #include <linux/mm.h>
 #include <linux/rwsem.h>
 #include <linux/memcontrol.h>
+#include <linux/highmem.h>
 
 /*
  * The anon_vma heads a list of private "related" vmas, to scan if
@@ -232,6 +233,31 @@ static inline bool page_check_address_transhuge(struct page *page,
 }
 #endif
 
+/* Avoid racy checks */
+#define PVMW_SYNC		(1 << 0)
+/* Look for migarion entries rather than present PTEs */
+#define PVMW_MIGRATION		(1 << 1)
+
+struct page_vma_mapped_walk {
+	struct page *page;
+	struct vm_area_struct *vma;
+	unsigned long address;
+	pmd_t *pmd;
+	pte_t *pte;
+	spinlock_t *ptl;
+	unsigned int flags;
+};
+
+static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
+{
+	if (pvmw->pte)
+		pte_unmap(pvmw->pte);
+	if (pvmw->ptl)
+		spin_unlock(pvmw->ptl);
+}
+
+bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
+
 /*
  * Used by swapoff to help locate where page is expected in vma.
  */