mm, rmap: check all VMAs that PTE-mapped THP can be part of

Current rmap code can miss a VMA that maps PTE-mapped THP if the first
suppage of the THP was unmapped from the VMA.

We need to walk rmap for the whole range of offsets that THP covers, not
only the first one.

vma_address() also need to be corrected to check the range instead of
the first subpage.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Kirill A. Shutemov <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: Andrea Arcangeli <[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]>

mm/internal.h

@@ -335,12 +335,15 @@ __vma_address(struct page *page, struct vm_area_struct *vma)
 static inline unsigned long
 vma_address(struct page *page, struct vm_area_struct *vma)
 {
-	unsigned long address = __vma_address(page, vma);
+	unsigned long start, end;
+
+	start = __vma_address(page, vma);
+	end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
 
 	/* page should be within @vma mapping range */
-	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+	VM_BUG_ON_VMA(end < vma->vm_start || start >= vma->vm_end, vma);
 
-	return address;
+	return max(start, vma->vm_start);
 }
 
 #else /* !CONFIG_MMU */

mm/rmap.c

@@ -1757,7 +1757,7 @@ static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
 		bool locked)
 {
 	struct anon_vma *anon_vma;
-	pgoff_t pgoff;
+	pgoff_t pgoff_start, pgoff_end;
 	struct anon_vma_chain *avc;
 	int ret = SWAP_AGAIN;
 
@@ -1771,8 +1771,10 @@ static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
 	if (!anon_vma)
 		return ret;
 
-	pgoff = page_to_pgoff(page);
-	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
+	pgoff_start = page_to_pgoff(page);
+	pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
+	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
+			pgoff_start, pgoff_end) {
 		struct vm_area_struct *vma = avc->vma;
 		unsigned long address = vma_address(page, vma);
 
@@ -1810,7 +1812,7 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
 		bool locked)
 {
 	struct address_space *mapping = page_mapping(page);
-	pgoff_t pgoff;
+	pgoff_t pgoff_start, pgoff_end;
 	struct vm_area_struct *vma;
 	int ret = SWAP_AGAIN;
 
@@ -1825,10 +1827,12 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
 	if (!mapping)
 		return ret;
 
-	pgoff = page_to_pgoff(page);
+	pgoff_start = page_to_pgoff(page);
+	pgoff_end = pgoff_start + hpage_nr_pages(page) - 1;
 	if (!locked)
 		i_mmap_lock_read(mapping);
-	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
+	vma_interval_tree_foreach(vma, &mapping->i_mmap,
+			pgoff_start, pgoff_end) {
 		unsigned long address = vma_address(page, vma);
 
 		cond_resched();