X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=mm%2Frmap.c;h=38a336e2eea1e104a654052834ef93e252340d18;hb=99765cc7e393c8637abaaf0c73f28ec63370d35c;hp=0feeef860a8f5b5d61081234f40e8e149e2696f5;hpb=15953654cc312429740fd58fb37a5a3d63a54376;p=pandora-kernel.git

diff --git a/mm/rmap.c b/mm/rmap.c
index 0feeef860a8f..38a336e2eea1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -250,7 +250,7 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain)
 	list_del(&anon_vma_chain->same_anon_vma);
 
 	/* We must garbage collect the anon_vma if it's empty */
-	empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma);
+	empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);
 	spin_unlock(&anon_vma->lock);
 
 	if (empty)
@@ -274,7 +274,7 @@ static void anon_vma_ctor(void *data)
 	struct anon_vma *anon_vma = data;
 
 	spin_lock_init(&anon_vma->lock);
-	ksm_refcount_init(anon_vma);
+	anonvma_external_refcount_init(anon_vma);
 	INIT_LIST_HEAD(&anon_vma->head);
 }
 
@@ -1131,6 +1131,20 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
 	return ret;
 }
 
+static bool is_vma_temporary_stack(struct vm_area_struct *vma)
+{
+	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
+
+	if (!maybe_stack)
+		return false;
+
+	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
+						VM_STACK_INCOMPLETE_SETUP)
+		return true;
+
+	return false;
+}
+
 /**
  * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
  * rmap method
@@ -1159,7 +1173,21 @@ static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
 
 	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
 		struct vm_area_struct *vma = avc->vma;
-		unsigned long address = vma_address(page, vma);
+		unsigned long address;
+
+		/*
+		 * During exec, a temporary VMA is setup and later moved.
+		 * The VMA is moved under the anon_vma lock but not the
+		 * page tables leading to a race where migration cannot
+		 * find the migration ptes. Rather than increasing the
+		 * locking requirements of exec(), migration skips
+		 * temporary VMAs until after exec() completes.
+		 */
+		if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
+				is_vma_temporary_stack(vma))
+			continue;
+
+		address = vma_address(page, vma);
 		if (address == -EFAULT)
 			continue;
 		ret = try_to_unmap_one(page, vma, address, flags);
@@ -1355,10 +1383,8 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
 	/*
 	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
 	 * because that depends on page_mapped(); but not all its usages
-	 * are holding mmap_sem, which also gave the necessary guarantee
-	 * (that this anon_vma's slab has not already been destroyed).
-	 * This needs to be reviewed later: avoiding page_lock_anon_vma()
-	 * is risky, and currently limits the usefulness of rmap_walk().
+	 * are holding mmap_sem. Users without mmap_sem are required to
+	 * take a reference count to prevent the anon_vma disappearing
 	 */
 	anon_vma = page_anon_vma(page);
 	if (!anon_vma)