Merge branch 'x86/core' into core/percpu

18 files changed, 167 insertions, 76 deletions

diff --git a/mm/fremap.c b/mm/fremap.c
index 736ba7f3306..b6ec85abbb3 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -198,7 +198,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 			flags &= MAP_NONBLOCK;
 			get_file(file);
 			addr = mmap_region(file, start, size,
-					flags, vma->vm_flags, pgoff, 1);
+					flags, vma->vm_flags, pgoff);
 			fput(file);
 			if (IS_ERR_VALUE(addr)) {
 				err = addr;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 618e9830408..107da3d809a 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2269,12 +2269,18 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
 
 int hugetlb_reserve_pages(struct inode *inode,
 					long from, long to,
-					struct vm_area_struct *vma)
+					struct vm_area_struct *vma,
+					int acctflag)
 {
 	long ret, chg;
 	struct hstate *h = hstate_inode(inode);
 
-	if (vma && vma->vm_flags & VM_NORESERVE)
+	/*
+	 * Only apply hugepage reservation if asked. At fault time, an
+	 * attempt will be made for VM_NORESERVE to allocate a page
+	 * and filesystem quota without using reserves
+	 */
+	if (acctflag & VM_NORESERVE)
 		return 0;
 
 	/*
@@ -2299,13 +2305,31 @@ int hugetlb_reserve_pages(struct inode *inode,
 	if (chg < 0)
 		return chg;
 
+	/* There must be enough filesystem quota for the mapping */
 	if (hugetlb_get_quota(inode->i_mapping, chg))
 		return -ENOSPC;
+
+	/*
+	 * Check enough hugepages are available for the reservation.
+	 * Hand back the quota if there are not
+	 */
 	ret = hugetlb_acct_memory(h, chg);
 	if (ret < 0) {
 		hugetlb_put_quota(inode->i_mapping, chg);
 		return ret;
 	}
+
+	/*
+	 * Account for the reservations made. Shared mappings record regions
+	 * that have reservations as they are shared by multiple VMAs.
+	 * When the last VMA disappears, the region map says how much
+	 * the reservation was and the page cache tells how much of
+	 * the reservation was consumed. Private mappings are per-VMA and
+	 * only the consumed reservations are tracked. When the VMA
+	 * disappears, the original reservation is the VMA size and the
+	 * consumed reservations are stored in the map. Hence, nothing
+	 * else has to be done for private mappings here
+	 */
 	if (!vma || vma->vm_flags & VM_SHARED)
 		region_add(&inode->i_mapping->private_list, from, to);
 	return 0;
diff --git a/mm/migrate.c b/mm/migrate.c
index 2bb4e1d6352..a9eff3f092f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1129,7 +1129,7 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
  	struct vm_area_struct *vma;
  	int err = 0;
 
- 	for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) {
+	for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
  		if (vma->vm_ops && vma->vm_ops->migrate) {
  			err = vma->vm_ops->migrate(vma, to, from, flags);
  			if (err)
diff --git a/mm/mlock.c b/mm/mlock.c
index 028ec482fdd..cbe9e0581b7 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -311,7 +311,10 @@ long mlock_vma_pages_range(struct vm_area_struct *vma,
 			is_vm_hugetlb_page(vma) ||
 			vma == get_gate_vma(current))) {
 
-		return __mlock_vma_pages_range(vma, start, end, 1);
+		__mlock_vma_pages_range(vma, start, end, 1);
+
+		/* Hide errors from mmap() and other callers */
+		return 0;
 	}
 
 	/*
@@ -657,7 +660,7 @@ void *alloc_locked_buffer(size_t size)
 	return buffer;
 }
 
-void free_locked_buffer(void *buffer, size_t size)
+void release_locked_buffer(void *buffer, size_t size)
 {
 	unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
@@ -667,6 +670,11 @@ void free_locked_buffer(void *buffer, size_t size)
 	current->mm->locked_vm -= pgsz;
 
 	up_write(&current->mm->mmap_sem);
+}
+
+void free_locked_buffer(void *buffer, size_t size)
+{
+	release_locked_buffer(buffer, size);
 
 	kfree(buffer);
 }
diff --git a/mm/mmap.c b/mm/mmap.c
index 214b6a258ee..00ced3ee49a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -918,7 +918,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 	struct inode *inode;
 	unsigned int vm_flags;
 	int error;
-	int accountable = 1;
 	unsigned long reqprot = prot;
 
 	/*
@@ -1019,8 +1018,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 					return -EPERM;
 				vm_flags &= ~VM_MAYEXEC;
 			}
-			if (is_file_hugepages(file))
-				accountable = 0;
 
 			if (!file->f_op || !file->f_op->mmap)
 				return -ENODEV;
@@ -1053,8 +1050,7 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 	if (error)
 		return error;
 
-	return mmap_region(file, addr, len, flags, vm_flags, pgoff,
-			   accountable);
+	return mmap_region(file, addr, len, flags, vm_flags, pgoff);
 }
 EXPORT_SYMBOL(do_mmap_pgoff);
 
@@ -1092,17 +1088,23 @@ int vma_wants_writenotify(struct vm_area_struct *vma)
 
 /*
  * We account for memory if it's a private writeable mapping,
- * and VM_NORESERVE wasn't set.
+ * not hugepages and VM_NORESERVE wasn't set.
  */
-static inline int accountable_mapping(unsigned int vm_flags)
+static inline int accountable_mapping(struct file *file, unsigned int vm_flags)
 {
+	/*
+	 * hugetlb has its own accounting separate from the core VM
+	 * VM_HUGETLB may not be set yet so we cannot check for that flag.
+	 */
+	if (file && is_file_hugepages(file))
+		return 0;
+
 	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
 }
 
 unsigned long mmap_region(struct file *file, unsigned long addr,
 			  unsigned long len, unsigned long flags,
-			  unsigned int vm_flags, unsigned long pgoff,
-			  int accountable)
+			  unsigned int vm_flags, unsigned long pgoff)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma, *prev;
@@ -1128,18 +1130,22 @@ munmap_back:
 
 	/*
 	 * Set 'VM_NORESERVE' if we should not account for the
-	 * memory use of this mapping. We only honor MAP_NORESERVE
-	 * if we're allowed to overcommit memory.
+	 * memory use of this mapping.
 	 */
-	if ((flags & MAP_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER)
-		vm_flags |= VM_NORESERVE;
-	if (!accountable)
-		vm_flags |= VM_NORESERVE;
+	if ((flags & MAP_NORESERVE)) {
+		/* We honor MAP_NORESERVE if allowed to overcommit */
+		if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
+			vm_flags |= VM_NORESERVE;
+
+		/* hugetlb applies strict overcommit unless MAP_NORESERVE */
+		if (file && is_file_hugepages(file))
+			vm_flags |= VM_NORESERVE;
+	}
 
 	/*
 	 * Private writable mapping: check memory availability
 	 */
-	if (accountable_mapping(vm_flags)) {
+	if (accountable_mapping(file, vm_flags)) {
 		charged = len >> PAGE_SHIFT;
 		if (security_vm_enough_memory(charged))
 			return -ENOMEM;
@@ -2078,12 +2084,8 @@ void exit_mmap(struct mm_struct *mm)
 	unsigned long end;
 
 	/* mm's last user has gone, and its about to be pulled down */
-	arch_exit_mmap(mm);
 	mmu_notifier_release(mm);
 
-	if (!mm->mmap)	/* Can happen if dup_mmap() received an OOM */
-		return;
-
 	if (mm->locked_vm) {
 		vma = mm->mmap;
 		while (vma) {
@@ -2092,7 +2094,13 @@ void exit_mmap(struct mm_struct *mm)
 			vma = vma->vm_next;
 		}
 	}
+
+	arch_exit_mmap(mm);
+
 	vma = mm->mmap;
+	if (!vma)	/* Can happen if dup_mmap() received an OOM */
+		return;
+
 	lru_add_drain();
 	flush_cache_mm(mm);
 	tlb = tlb_gather_mmu(mm, 1);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index abe2694e13f..258197b76fb 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -151,10 +151,11 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 	/*
 	 * If we make a private mapping writable we increase our commit;
 	 * but (without finer accounting) cannot reduce our commit if we
-	 * make it unwritable again.
+	 * make it unwritable again. hugetlb mapping were accounted for
+	 * even if read-only so there is no need to account for them here
 	 */
 	if (newflags & VM_WRITE) {
-		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|
+		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
 						VM_SHARED|VM_NORESERVE))) {
 			charged = nrpages;
 			if (security_vm_enough_memory(charged))
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dc32dae01e5..74dc57c7434 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -209,7 +209,7 @@ int dirty_bytes_handler(struct ctl_table *table, int write,
 		struct file *filp, void __user *buffer, size_t *lenp,
 		loff_t *ppos)
 {
-	int old_bytes = vm_dirty_bytes;
+	unsigned long old_bytes = vm_dirty_bytes;
 	int ret;
 
 	ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos);
@@ -240,7 +240,7 @@ void bdi_writeout_inc(struct backing_dev_info *bdi)
 }
 EXPORT_SYMBOL_GPL(bdi_writeout_inc);
 
-static inline void task_dirty_inc(struct task_struct *tsk)
+void task_dirty_inc(struct task_struct *tsk)
 {
 	prop_inc_single(&vm_dirties, &tsk->dirties);
 }
@@ -1051,20 +1051,23 @@ continue_unlock:
 				}
  			}
 
-			if (nr_to_write > 0)
+			if (nr_to_write > 0) {
 				nr_to_write--;
-			else if (wbc->sync_mode == WB_SYNC_NONE) {
-				/*
-				 * We stop writing back only if we are not
-				 * doing integrity sync. In case of integrity
-				 * sync we have to keep going because someone
-				 * may be concurrently dirtying pages, and we
-				 * might have synced a lot of newly appeared
-				 * dirty pages, but have not synced all of the
-				 * old dirty pages.
-				 */
-				done = 1;
-				break;
+				if (nr_to_write == 0 &&
+				    wbc->sync_mode == WB_SYNC_NONE) {
+					/*
+					 * We stop writing back only if we are
+					 * not doing integrity sync. In case of
+					 * integrity sync we have to keep going
+					 * because someone may be concurrently
+					 * dirtying pages, and we might have
+					 * synced a lot of newly appeared dirty
+					 * pages, but have not synced all of the
+					 * old dirty pages.
+					 */
+					done = 1;
+					break;
+				}
 			}
 
 			if (wbc->nonblocking && bdi_write_congested(bdi)) {
@@ -1076,7 +1079,7 @@ continue_unlock:
 		pagevec_release(&pvec);
 		cond_resched();
 	}
-	if (!cycled) {
+	if (!cycled && !done) {
 		/*
 		 * range_cyclic:
 		 * We hit the last page and there is more work to be done: wrap
@@ -1227,6 +1230,7 @@ int __set_page_dirty_nobuffers(struct page *page)
 				__inc_zone_page_state(page, NR_FILE_DIRTY);
 				__inc_bdi_stat(mapping->backing_dev_info,
 						BDI_RECLAIMABLE);
+				task_dirty_inc(current);
 				task_io_account_write(PAGE_CACHE_SIZE);
 			}
 			radix_tree_tag_set(&mapping->page_tree,
@@ -1259,7 +1263,7 @@ EXPORT_SYMBOL(redirty_page_for_writepage);
  * If the mapping doesn't provide a set_page_dirty a_op, then
  * just fall through and assume that it wants buffer_heads.
  */
-static int __set_page_dirty(struct page *page)
+int set_page_dirty(struct page *page)
 {
 	struct address_space *mapping = page_mapping(page);
 
@@ -1277,14 +1281,6 @@ static int __set_page_dirty(struct page *page)
 	}
 	return 0;
 }
-
-int set_page_dirty(struct page *page)
-{
-	int ret = __set_page_dirty(page);
-	if (ret)
-		task_dirty_inc(current);
-	return ret;
-}
 EXPORT_SYMBOL(set_page_dirty);
 
 /*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5675b307385..5c44ed49ca9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2989,7 +2989,7 @@ static int __meminit next_active_region_index_in_nid(int index, int nid)
  * was used and there are no special requirements, this is a convenient
  * alternative
  */
-int __meminit early_pfn_to_nid(unsigned long pfn)
+int __meminit __early_pfn_to_nid(unsigned long pfn)
 {
 	int i;
 
@@ -3000,10 +3000,33 @@ int __meminit early_pfn_to_nid(unsigned long pfn)
 		if (start_pfn <= pfn && pfn < end_pfn)
 			return early_node_map[i].nid;
 	}
+	/* This is a memory hole */
+	return -1;
+}
+#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */
+
+int __meminit early_pfn_to_nid(unsigned long pfn)
+{
+	int nid;
 
+	nid = __early_pfn_to_nid(pfn);
+	if (nid >= 0)
+		return nid;
+	/* just returns 0 */
 	return 0;
 }
-#endif /* CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID */
+
+#ifdef CONFIG_NODES_SPAN_OTHER_NODES
+bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
+{
+	int nid;
+
+	nid = __early_pfn_to_nid(pfn);
+	if (nid >= 0 && nid != node)
+		return false;
+	return true;
+}
+#endif
 
 /* Basic iterator support to walk early_node_map[] */
 #define for_each_active_range_index_in_nid(i, nid) \
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 7006a11350c..ceecfbb143f 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -114,7 +114,8 @@ static int __init_refok init_section_page_cgroup(unsigned long pfn)
 		nid = page_to_nid(pfn_to_page(pfn));
 		table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
 		if (slab_is_available()) {
-			base = kmalloc_node(table_size, GFP_KERNEL, nid);
+			base = kmalloc_node(table_size,
+					GFP_KERNEL | __GFP_NOWARN, nid);
 			if (!base)
 				base = vmalloc_node(table_size, nid);
 		} else {
diff --git a/mm/page_io.c b/mm/page_io.c
index dc6ce0afbde..3023c475e04 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -111,7 +111,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 		goto out;
 	}
 	if (wbc->sync_mode == WB_SYNC_ALL)
-		rw |= (1 << BIO_RW_SYNC);
+		rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
 	count_vm_event(PSWPOUT);
 	set_page_writeback(page);
 	unlock_page(page);
diff --git a/mm/rmap.c b/mm/rmap.c
index ac4af8cffbf..16521664010 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1072,7 +1072,8 @@ static int try_to_unmap_file(struct page *page, int unlock, int migration)
 	spin_lock(&mapping->i_mmap_lock);
 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 		if (MLOCK_PAGES && unlikely(unlock)) {
-			if (!(vma->vm_flags & VM_LOCKED))
+			if (!((vma->vm_flags & VM_LOCKED) &&
+						page_mapped_in_vma(page, vma)))
 				continue;	/* must visit all vmas */
 			ret = SWAP_MLOCK;
 		} else {
diff --git a/mm/slab.c b/mm/slab.c
index ddc41f337d5..4d00855629c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4457,3 +4457,4 @@ size_t ksize(const void *objp)
 
 	return obj_size(virt_to_cache(objp));
 }
+EXPORT_SYMBOL(ksize);
diff --git a/mm/slob.c b/mm/slob.c
index bf7e8fc3aed..52bc8a2bd9e 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -521,6 +521,7 @@ size_t ksize(const void *block)
 	} else
 		return sp->page.private;
 }
+EXPORT_SYMBOL(ksize);
 
 struct kmem_cache {
 	unsigned int size, align;
diff --git a/mm/slub.c b/mm/slub.c
index bdc9abb08a2..0280eee6cf3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2736,6 +2736,7 @@ size_t ksize(const void *object)
 	 */
 	return s->size;
 }
+EXPORT_SYMBOL(ksize);
 
 void kfree(const void *x)
 {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7e6304dfafa..312fafe0ab6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -635,7 +635,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 
 		if (!bdev) {
 			if (bdev_p)
-				*bdev_p = sis->bdev;
+				*bdev_p = bdget(sis->bdev->bd_dev);
 
 			spin_unlock(&swap_lock);
 			return i;
@@ -647,7 +647,7 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 					struct swap_extent, list);
 			if (se->start_block == offset) {
 				if (bdev_p)
-					*bdev_p = sis->bdev;
+					*bdev_p = bdget(sis->bdev->bd_dev);
 
 				spin_unlock(&swap_lock);
 				bdput(bdev);
diff --git a/mm/util.c b/mm/util.c
index cb00b748ce4..37eaccdf305 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -129,6 +129,26 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
 }
 EXPORT_SYMBOL(krealloc);
 
+/**
+ * kzfree - like kfree but zero memory
+ * @p: object to free memory of
+ *
+ * The memory of the object @p points to is zeroed before freed.
+ * If @p is %NULL, kzfree() does nothing.
+ */
+void kzfree(const void *p)
+{
+	size_t ks;
+	void *mem = (void *)p;
+
+	if (unlikely(ZERO_OR_NULL_PTR(mem)))
+		return;
+	ks = ksize(mem);
+	memset(mem, 0, ks);
+	kfree(mem);
+}
+EXPORT_SYMBOL(kzfree);
+
 /*
  * strndup_user - duplicate an existing string from user space
  * @s: The string to duplicate
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 75f49d312e8..903cad46e79 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1012,6 +1012,8 @@ void __init vmalloc_init(void)
 void unmap_kernel_range(unsigned long addr, unsigned long size)
 {
 	unsigned long end = addr + size;
+
+	flush_cache_vunmap(addr, end);
 	vunmap_page_range(addr, end);
 	flush_tlb_kernel_range(addr, end);
 }
@@ -1106,6 +1108,14 @@ struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
 }
 EXPORT_SYMBOL_GPL(__get_vm_area);
 
+struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
+				       unsigned long start, unsigned long end,
+				       void *caller)
+{
+	return __get_vm_area_node(size, flags, start, end, -1, GFP_KERNEL,
+				  caller);
+}
+
 /**
  *	get_vm_area  -  reserve a contiguous kernel virtual area
  *	@size:		size of the area
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9a27c44aa32..6177e3bcd66 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2057,31 +2057,31 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
 				      int pass, struct scan_control *sc)
 {
 	struct zone *zone;
-	unsigned long nr_to_scan, ret = 0;
-	enum lru_list l;
+	unsigned long ret = 0;
 
 	for_each_zone(zone) {
+		enum lru_list l;
 
 		if (!populated_zone(zone))
 			continue;
-
 		if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
 			continue;
 
 		for_each_evictable_lru(l) {
+			enum zone_stat_item ls = NR_LRU_BASE + l;
+			unsigned long lru_pages = zone_page_state(zone, ls);
+
 			/* For pass = 0, we don't shrink the active list */
-			if (pass == 0 &&
-				(l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
+			if (pass == 0 && (l == LRU_ACTIVE_ANON ||
+						l == LRU_ACTIVE_FILE))
 				continue;
 
-			zone->lru[l].nr_scan +=
-				(zone_page_state(zone, NR_LRU_BASE + l)
-								>> prio) + 1;
+			zone->lru[l].nr_scan += (lru_pages >> prio) + 1;
 			if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
+				unsigned long nr_to_scan;
+
 				zone->lru[l].nr_scan = 0;
-				nr_to_scan = min(nr_pages,
-					zone_page_state(zone,
-							NR_LRU_BASE + l));
+				nr_to_scan = min(nr_pages, lru_pages);
 				ret += shrink_list(l, nr_to_scan, zone,
 								sc, prio);
 				if (ret >= nr_pages)
@@ -2089,7 +2089,6 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
 			}
 		}
 	}
-
 	return ret;
 }
 
@@ -2112,7 +2111,6 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 		.may_swap = 0,
 		.swap_cluster_max = nr_pages,
 		.may_writepage = 1,
-		.swappiness = vm_swappiness,
 		.isolate_pages = isolate_pages_global,
 	};
 
@@ -2146,10 +2144,8 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
 		int prio;
 
 		/* Force reclaiming mapped pages in the passes #3 and #4 */
-		if (pass > 2) {
+		if (pass > 2)
 			sc.may_swap = 1;
-			sc.swappiness = 100;
-		}
 
 		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
 			unsigned long nr_to_scan = nr_pages - ret;