android_kernel_xiaomi_sm8350/mm/migrate.c
Nick Piggin 7cf9c2c76c [PATCH] radix-tree: RCU lockless readside
Make radix tree lookups safe to be performed without locks.  Readers are
protected against nodes being deleted by using RCU based freeing.  Readers
are protected against new node insertion by using memory barriers to ensure
the node itself will be properly written before it is visible in the radix
tree.

Each radix tree node keeps a record of their height (above leaf nodes).
This height does not change after insertion -- when the radix tree is
extended, higher nodes are only inserted in the top.  So a lookup can take
the pointer to what is *now* the root node, and traverse down it even if
the tree is concurrently extended and this node becomes a subtree of a new
root.

"Direct" pointers (tree height of 0, where root->rnode points directly to
the data item) are handled by using the low bit of the pointer to signal
whether rnode is a direct pointer or a pointer to a radix tree node.

When a reader wants to traverse the next branch, they will take a copy of
the pointer.  This pointer will be either NULL (and the branch is empty) or
non-NULL (and will point to a valid node).

[akpm@osdl.org: cleanups]
[Lee.Schermerhorn@hp.com: bugfixes, comments, simplifications]
[clameter@sgi.com: build fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07 08:39:25 -08:00

1005 lines
21 KiB
C

/*
* Memory Migration functionality - linux/mm/migration.c
*
* Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter
*
* Page migration was first developed in the context of the memory hotplug
* project. The main authors of the migration code are:
*
* IWAMOTO Toshihiro <iwamoto@valinux.co.jp>
* Hirokazu Takahashi <taka@valinux.co.jp>
* Dave Hansen <haveblue@us.ibm.com>
* Christoph Lameter <clameter@sgi.com>
*/
#include <linux/migrate.h>
#include <linux/module.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include <linux/mm_inline.h>
#include <linux/pagevec.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/writeback.h>
#include <linux/mempolicy.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include "internal.h"
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
/*
* Isolate one page from the LRU lists. If successful put it onto
* the indicated list with elevated page count.
*
* Result:
* -EBUSY: page not on LRU list
* 0: page removed from LRU list and added to the specified list.
*/
int isolate_lru_page(struct page *page, struct list_head *pagelist)
{
int ret = -EBUSY;
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (PageLRU(page)) {
ret = 0;
get_page(page);
ClearPageLRU(page);
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
list_add_tail(&page->lru, pagelist);
}
spin_unlock_irq(&zone->lru_lock);
}
return ret;
}
/*
* migrate_prep() needs to be called before we start compiling a list of pages
* to be migrated using isolate_lru_page().
*/
int migrate_prep(void)
{
/*
* Clear the LRU lists so pages can be isolated.
* Note that pages may be moved off the LRU after we have
* drained them. Those pages will fail to migrate like other
* pages that may be busy.
*/
lru_add_drain_all();
return 0;
}
static inline void move_to_lru(struct page *page)
{
if (PageActive(page)) {
/*
* lru_cache_add_active checks that
* the PG_active bit is off.
*/
ClearPageActive(page);
lru_cache_add_active(page);
} else {
lru_cache_add(page);
}
put_page(page);
}
/*
* Add isolated pages on the list back to the LRU.
*
* returns the number of pages put back.
*/
int putback_lru_pages(struct list_head *l)
{
struct page *page;
struct page *page2;
int count = 0;
list_for_each_entry_safe(page, page2, l, lru) {
list_del(&page->lru);
move_to_lru(page);
count++;
}
return count;
}
static inline int is_swap_pte(pte_t pte)
{
return !pte_none(pte) && !pte_present(pte) && !pte_file(pte);
}
/*
* Restore a potential migration pte to a working pte entry
*/
static void remove_migration_pte(struct vm_area_struct *vma,
struct page *old, struct page *new)
{
struct mm_struct *mm = vma->vm_mm;
swp_entry_t entry;
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *ptep, pte;
spinlock_t *ptl;
unsigned long addr = page_address_in_vma(new, vma);
if (addr == -EFAULT)
return;
pgd = pgd_offset(mm, addr);
if (!pgd_present(*pgd))
return;
pud = pud_offset(pgd, addr);
if (!pud_present(*pud))
return;
pmd = pmd_offset(pud, addr);
if (!pmd_present(*pmd))
return;
ptep = pte_offset_map(pmd, addr);
if (!is_swap_pte(*ptep)) {
pte_unmap(ptep);
return;
}
ptl = pte_lockptr(mm, pmd);
spin_lock(ptl);
pte = *ptep;
if (!is_swap_pte(pte))
goto out;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old)
goto out;
get_page(new);
pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
if (is_write_migration_entry(entry))
pte = pte_mkwrite(pte);
set_pte_at(mm, addr, ptep, pte);
if (PageAnon(new))
page_add_anon_rmap(new, vma, addr);
else
page_add_file_rmap(new);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, addr, pte);
lazy_mmu_prot_update(pte);
out:
pte_unmap_unlock(ptep, ptl);
}
/*
* Note that remove_file_migration_ptes will only work on regular mappings,
* Nonlinear mappings do not use migration entries.
*/
static void remove_file_migration_ptes(struct page *old, struct page *new)
{
struct vm_area_struct *vma;
struct address_space *mapping = page_mapping(new);
struct prio_tree_iter iter;
pgoff_t pgoff = new->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
if (!mapping)
return;
spin_lock(&mapping->i_mmap_lock);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff)
remove_migration_pte(vma, old, new);
spin_unlock(&mapping->i_mmap_lock);
}
/*
* Must hold mmap_sem lock on at least one of the vmas containing
* the page so that the anon_vma cannot vanish.
*/
static void remove_anon_migration_ptes(struct page *old, struct page *new)
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
unsigned long mapping;
mapping = (unsigned long)new->mapping;
if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
return;
/*
* We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
*/
anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
spin_lock(&anon_vma->lock);
list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
remove_migration_pte(vma, old, new);
spin_unlock(&anon_vma->lock);
}
/*
* Get rid of all migration entries and replace them by
* references to the indicated page.
*/
static void remove_migration_ptes(struct page *old, struct page *new)
{
if (PageAnon(new))
remove_anon_migration_ptes(old, new);
else
remove_file_migration_ptes(old, new);
}
/*
* Something used the pte of a page under migration. We need to
* get to the page and wait until migration is finished.
* When we return from this function the fault will be retried.
*
* This function is called from do_swap_page().
*/
void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address)
{
pte_t *ptep, pte;
spinlock_t *ptl;
swp_entry_t entry;
struct page *page;
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
pte = *ptep;
if (!is_swap_pte(pte))
goto out;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry))
goto out;
page = migration_entry_to_page(entry);
get_page(page);
pte_unmap_unlock(ptep, ptl);
wait_on_page_locked(page);
put_page(page);
return;
out:
pte_unmap_unlock(ptep, ptl);
}
/*
* Replace the page in the mapping.
*
* The number of remaining references must be:
* 1 for anonymous pages without a mapping
* 2 for pages with a mapping
* 3 for pages with a mapping and PagePrivate set.
*/
static int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page)
{
void **pslot;
if (!mapping) {
/* Anonymous page */
if (page_count(page) != 1)
return -EAGAIN;
return 0;
}
write_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
if (page_count(page) != 2 + !!PagePrivate(page) ||
(struct page *)radix_tree_deref_slot(pslot) != page) {
write_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* Now we know that no one else is looking at the page.
*/
get_page(newpage); /* add cache reference */
#ifdef CONFIG_SWAP
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
#endif
radix_tree_replace_slot(pslot, newpage);
/*
* Drop cache reference from old page.
* We know this isn't the last reference.
*/
__put_page(page);
write_unlock_irq(&mapping->tree_lock);
return 0;
}
/*
* Copy the page to its new location
*/
static void migrate_page_copy(struct page *newpage, struct page *page)
{
copy_highpage(newpage, page);
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
SetPageReferenced(newpage);
if (PageUptodate(page))
SetPageUptodate(newpage);
if (PageActive(page))
SetPageActive(newpage);
if (PageChecked(page))
SetPageChecked(newpage);
if (PageMappedToDisk(page))
SetPageMappedToDisk(newpage);
if (PageDirty(page)) {
clear_page_dirty_for_io(page);
set_page_dirty(newpage);
}
#ifdef CONFIG_SWAP
ClearPageSwapCache(page);
#endif
ClearPageActive(page);
ClearPagePrivate(page);
set_page_private(page, 0);
page->mapping = NULL;
/*
* If any waiters have accumulated on the new page then
* wake them up.
*/
if (PageWriteback(newpage))
end_page_writeback(newpage);
}
/************************************************************
* Migration functions
***********************************************************/
/* Always fail migration. Used for mappings that are not movable */
int fail_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page)
{
return -EIO;
}
EXPORT_SYMBOL(fail_migrate_page);
/*
* Common logic to directly migrate a single page suitable for
* pages that do not use PagePrivate.
*
* Pages are locked upon entry and exit.
*/
int migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page)
{
int rc;
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
rc = migrate_page_move_mapping(mapping, newpage, page);
if (rc)
return rc;
migrate_page_copy(newpage, page);
return 0;
}
EXPORT_SYMBOL(migrate_page);
#ifdef CONFIG_BLOCK
/*
* Migration function for pages with buffers. This function can only be used
* if the underlying filesystem guarantees that no other references to "page"
* exist.
*/
int buffer_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page)
{
struct buffer_head *bh, *head;
int rc;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page);
head = page_buffers(page);
rc = migrate_page_move_mapping(mapping, newpage, page);
if (rc)
return rc;
bh = head;
do {
get_bh(bh);
lock_buffer(bh);
bh = bh->b_this_page;
} while (bh != head);
ClearPagePrivate(page);
set_page_private(newpage, page_private(page));
set_page_private(page, 0);
put_page(page);
get_page(newpage);
bh = head;
do {
set_bh_page(bh, newpage, bh_offset(bh));
bh = bh->b_this_page;
} while (bh != head);
SetPagePrivate(newpage);
migrate_page_copy(newpage, page);
bh = head;
do {
unlock_buffer(bh);
put_bh(bh);
bh = bh->b_this_page;
} while (bh != head);
return 0;
}
EXPORT_SYMBOL(buffer_migrate_page);
#endif
/*
* Writeback a page to clean the dirty state
*/
static int writeout(struct address_space *mapping, struct page *page)
{
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = 1,
.range_start = 0,
.range_end = LLONG_MAX,
.nonblocking = 1,
.for_reclaim = 1
};
int rc;
if (!mapping->a_ops->writepage)
/* No write method for the address space */
return -EINVAL;
if (!clear_page_dirty_for_io(page))
/* Someone else already triggered a write */
return -EAGAIN;
/*
* A dirty page may imply that the underlying filesystem has
* the page on some queue. So the page must be clean for
* migration. Writeout may mean we loose the lock and the
* page state is no longer what we checked for earlier.
* At this point we know that the migration attempt cannot
* be successful.
*/
remove_migration_ptes(page, page);
rc = mapping->a_ops->writepage(page, &wbc);
if (rc < 0)
/* I/O Error writing */
return -EIO;
if (rc != AOP_WRITEPAGE_ACTIVATE)
/* unlocked. Relock */
lock_page(page);
return -EAGAIN;
}
/*
* Default handling if a filesystem does not provide a migration function.
*/
static int fallback_migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page)
{
if (PageDirty(page))
return writeout(mapping, page);
/*
* Buffers may be managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (PagePrivate(page) &&
!try_to_release_page(page, GFP_KERNEL))
return -EAGAIN;
return migrate_page(mapping, newpage, page);
}
/*
* Move a page to a newly allocated page
* The page is locked and all ptes have been successfully removed.
*
* The new page will have replaced the old page if this function
* is successful.
*/
static int move_to_new_page(struct page *newpage, struct page *page)
{
struct address_space *mapping;
int rc;
/*
* Block others from accessing the page when we get around to
* establishing additional references. We are the only one
* holding a reference to the new page at this point.
*/
if (TestSetPageLocked(newpage))
BUG();
/* Prepare mapping for the new page.*/
newpage->index = page->index;
newpage->mapping = page->mapping;
mapping = page_mapping(page);
if (!mapping)
rc = migrate_page(mapping, newpage, page);
else if (mapping->a_ops->migratepage)
/*
* Most pages have a mapping and most filesystems
* should provide a migration function. Anonymous
* pages are part of swap space which also has its
* own migration function. This is the most common
* path for page migration.
*/
rc = mapping->a_ops->migratepage(mapping,
newpage, page);
else
rc = fallback_migrate_page(mapping, newpage, page);
if (!rc)
remove_migration_ptes(page, newpage);
else
newpage->mapping = NULL;
unlock_page(newpage);
return rc;
}
/*
* Obtain the lock on page, remove all ptes and migrate the page
* to the newly allocated page in newpage.
*/
static int unmap_and_move(new_page_t get_new_page, unsigned long private,
struct page *page, int force)
{
int rc = 0;
int *result = NULL;
struct page *newpage = get_new_page(page, private, &result);
if (!newpage)
return -ENOMEM;
if (page_count(page) == 1)
/* page was freed from under us. So we are done. */
goto move_newpage;
rc = -EAGAIN;
if (TestSetPageLocked(page)) {
if (!force)
goto move_newpage;
lock_page(page);
}
if (PageWriteback(page)) {
if (!force)
goto unlock;
wait_on_page_writeback(page);
}
/*
* Establish migration ptes or remove ptes
*/
try_to_unmap(page, 1);
if (!page_mapped(page))
rc = move_to_new_page(newpage, page);
if (rc)
remove_migration_ptes(page, page);
unlock:
unlock_page(page);
if (rc != -EAGAIN) {
/*
* A page that has been migrated has all references
* removed and will be freed. A page that has not been
* migrated will have kepts its references and be
* restored.
*/
list_del(&page->lru);
move_to_lru(page);
}
move_newpage:
/*
* Move the new page to the LRU. If migration was not successful
* then this will free the page.
*/
move_to_lru(newpage);
if (result) {
if (rc)
*result = rc;
else
*result = page_to_nid(newpage);
}
return rc;
}
/*
* migrate_pages
*
* The function takes one list of pages to migrate and a function
* that determines from the page to be migrated and the private data
* the target of the move and allocates the page.
*
* The function returns after 10 attempts or if no pages
* are movable anymore because to has become empty
* or no retryable pages exist anymore. All pages will be
* retruned to the LRU or freed.
*
* Return: Number of pages not migrated or error code.
*/
int migrate_pages(struct list_head *from,
new_page_t get_new_page, unsigned long private)
{
int retry = 1;
int nr_failed = 0;
int pass = 0;
struct page *page;
struct page *page2;
int swapwrite = current->flags & PF_SWAPWRITE;
int rc;
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
for(pass = 0; pass < 10 && retry; pass++) {
retry = 0;
list_for_each_entry_safe(page, page2, from, lru) {
cond_resched();
rc = unmap_and_move(get_new_page, private,
page, pass > 2);
switch(rc) {
case -ENOMEM:
goto out;
case -EAGAIN:
retry++;
break;
case 0:
break;
default:
/* Permanent failure */
nr_failed++;
break;
}
}
}
rc = 0;
out:
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
putback_lru_pages(from);
if (rc)
return rc;
return nr_failed + retry;
}
#ifdef CONFIG_NUMA
/*
* Move a list of individual pages
*/
struct page_to_node {
unsigned long addr;
struct page *page;
int node;
int status;
};
static struct page *new_page_node(struct page *p, unsigned long private,
int **result)
{
struct page_to_node *pm = (struct page_to_node *)private;
while (pm->node != MAX_NUMNODES && pm->page != p)
pm++;
if (pm->node == MAX_NUMNODES)
return NULL;
*result = &pm->status;
return alloc_pages_node(pm->node, GFP_HIGHUSER | GFP_THISNODE, 0);
}
/*
* Move a set of pages as indicated in the pm array. The addr
* field must be set to the virtual address of the page to be moved
* and the node number must contain a valid target node.
*/
static int do_move_pages(struct mm_struct *mm, struct page_to_node *pm,
int migrate_all)
{
int err;
struct page_to_node *pp;
LIST_HEAD(pagelist);
down_read(&mm->mmap_sem);
/*
* Build a list of pages to migrate
*/
migrate_prep();
for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
struct vm_area_struct *vma;
struct page *page;
/*
* A valid page pointer that will not match any of the
* pages that will be moved.
*/
pp->page = ZERO_PAGE(0);
err = -EFAULT;
vma = find_vma(mm, pp->addr);
if (!vma)
goto set_status;
page = follow_page(vma, pp->addr, FOLL_GET);
err = -ENOENT;
if (!page)
goto set_status;
if (PageReserved(page)) /* Check for zero page */
goto put_and_set;
pp->page = page;
err = page_to_nid(page);
if (err == pp->node)
/*
* Node already in the right place
*/
goto put_and_set;
err = -EACCES;
if (page_mapcount(page) > 1 &&
!migrate_all)
goto put_and_set;
err = isolate_lru_page(page, &pagelist);
put_and_set:
/*
* Either remove the duplicate refcount from
* isolate_lru_page() or drop the page ref if it was
* not isolated.
*/
put_page(page);
set_status:
pp->status = err;
}
if (!list_empty(&pagelist))
err = migrate_pages(&pagelist, new_page_node,
(unsigned long)pm);
else
err = -ENOENT;
up_read(&mm->mmap_sem);
return err;
}
/*
* Determine the nodes of a list of pages. The addr in the pm array
* must have been set to the virtual address of which we want to determine
* the node number.
*/
static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm)
{
down_read(&mm->mmap_sem);
for ( ; pm->node != MAX_NUMNODES; pm++) {
struct vm_area_struct *vma;
struct page *page;
int err;
err = -EFAULT;
vma = find_vma(mm, pm->addr);
if (!vma)
goto set_status;
page = follow_page(vma, pm->addr, 0);
err = -ENOENT;
/* Use PageReserved to check for zero page */
if (!page || PageReserved(page))
goto set_status;
err = page_to_nid(page);
set_status:
pm->status = err;
}
up_read(&mm->mmap_sem);
return 0;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
int err = 0;
int i;
struct task_struct *task;
nodemask_t task_nodes;
struct mm_struct *mm;
struct page_to_node *pm = NULL;
/* Check flags */
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
return -EINVAL;
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
return -EPERM;
/* Find the mm_struct */
read_lock(&tasklist_lock);
task = pid ? find_task_by_pid(pid) : current;
if (!task) {
read_unlock(&tasklist_lock);
return -ESRCH;
}
mm = get_task_mm(task);
read_unlock(&tasklist_lock);
if (!mm)
return -EINVAL;
/*
* Check if this process has the right to modify the specified
* process. The right exists if the process has administrative
* capabilities, superuser privileges or the same
* userid as the target process.
*/
if ((current->euid != task->suid) && (current->euid != task->uid) &&
(current->uid != task->suid) && (current->uid != task->uid) &&
!capable(CAP_SYS_NICE)) {
err = -EPERM;
goto out2;
}
err = security_task_movememory(task);
if (err)
goto out2;
task_nodes = cpuset_mems_allowed(task);
/* Limit nr_pages so that the multiplication may not overflow */
if (nr_pages >= ULONG_MAX / sizeof(struct page_to_node) - 1) {
err = -E2BIG;
goto out2;
}
pm = vmalloc((nr_pages + 1) * sizeof(struct page_to_node));
if (!pm) {
err = -ENOMEM;
goto out2;
}
/*
* Get parameters from user space and initialize the pm
* array. Return various errors if the user did something wrong.
*/
for (i = 0; i < nr_pages; i++) {
const void *p;
err = -EFAULT;
if (get_user(p, pages + i))
goto out;
pm[i].addr = (unsigned long)p;
if (nodes) {
int node;
if (get_user(node, nodes + i))
goto out;
err = -ENODEV;
if (!node_online(node))
goto out;
err = -EACCES;
if (!node_isset(node, task_nodes))
goto out;
pm[i].node = node;
} else
pm[i].node = 0; /* anything to not match MAX_NUMNODES */
}
/* End marker */
pm[nr_pages].node = MAX_NUMNODES;
if (nodes)
err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL);
else
err = do_pages_stat(mm, pm);
if (err >= 0)
/* Return status information */
for (i = 0; i < nr_pages; i++)
if (put_user(pm[i].status, status + i))
err = -EFAULT;
out:
vfree(pm);
out2:
mmput(mm);
return err;
}
#endif
/*
* Call migration functions in the vma_ops that may prepare
* memory in a vm for migration. migration functions may perform
* the migration for vmas that do not have an underlying page struct.
*/
int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
const nodemask_t *from, unsigned long flags)
{
struct vm_area_struct *vma;
int err = 0;
for(vma = mm->mmap; vma->vm_next && !err; vma = vma->vm_next) {
if (vma->vm_ops && vma->vm_ops->migrate) {
err = vma->vm_ops->migrate(vma, to, from, flags);
if (err)
break;
}
}
return err;
}