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linux-sg2042/mm/migrate.c

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/*
* 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
*/
#include <linux/migrate.h>
#include <linux/export.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/nsproxy.h>
#include <linux/pagevec.h>
#include <linux/ksm.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 <linux/memcontrol.h>
#include <linux/syscalls.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
#include <linux/gfp.h>
#include <linux/balloon_compaction.h>
#include <asm/tlbflush.h>
#define CREATE_TRACE_POINTS
#include <trace/events/migrate.h>
#include "internal.h"
/*
* migrate_prep() needs to be called before we start compiling a list of pages
* to be migrated using isolate_lru_page(). If scheduling work on other CPUs is
* undesirable, use migrate_prep_local()
*/
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;
}
/* Do the necessary work of migrate_prep but not if it involves other CPUs */
int migrate_prep_local(void)
{
lru_add_drain();
return 0;
}
/*
* Add isolated pages on the list back to the LRU under page lock
* to avoid leaking evictable pages back onto unevictable list.
*/
void putback_lru_pages(struct list_head *l)
{
struct page *page;
struct page *page2;
list_for_each_entry_safe(page, page2, l, lru) {
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
putback_lru_page(page);
}
}
/*
* Put previously isolated pages back onto the appropriate lists
* from where they were once taken off for compaction/migration.
*
* This function shall be used instead of putback_lru_pages(),
* whenever the isolated pageset has been built by isolate_migratepages_range()
*/
void putback_movable_pages(struct list_head *l)
{
struct page *page;
struct page *page2;
list_for_each_entry_safe(page, page2, l, lru) {
list_del(&page->lru);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
if (unlikely(balloon_page_movable(page)))
balloon_page_putback(page);
else
putback_lru_page(page);
}
}
/*
* Restore a potential migration pte to a working pte entry
*/
static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
unsigned long addr, void *old)
{
struct mm_struct *mm = vma->vm_mm;
swp_entry_t entry;
pmd_t *pmd;
pte_t *ptep, pte;
spinlock_t *ptl;
if (unlikely(PageHuge(new))) {
ptep = huge_pte_offset(mm, addr);
if (!ptep)
goto out;
ptl = &mm->page_table_lock;
} else {
pmd = mm_find_pmd(mm, addr);
if (!pmd)
goto out;
if (pmd_trans_huge(*pmd))
goto out;
ptep = pte_offset_map(pmd, addr);
/*
* Peek to check is_swap_pte() before taking ptlock? No, we
* can race mremap's move_ptes(), which skips anon_vma lock.
*/
ptl = pte_lockptr(mm, pmd);
}
spin_lock(ptl);
pte = *ptep;
if (!is_swap_pte(pte))
goto unlock;
entry = pte_to_swp_entry(pte);
if (!is_migration_entry(entry) ||
migration_entry_to_page(entry) != old)
goto unlock;
get_page(new);
pte = pte_mkold(mk_pte(new, vma->vm_page_prot));
if (is_write_migration_entry(entry))
pte = pte_mkwrite(pte);
#ifdef CONFIG_HUGETLB_PAGE
if (PageHuge(new)) {
pte = pte_mkhuge(pte);
pte = arch_make_huge_pte(pte, vma, new, 0);
}
#endif
flush_dcache_page(new);
set_pte_at(mm, addr, ptep, pte);
if (PageHuge(new)) {
if (PageAnon(new))
hugepage_add_anon_rmap(new, vma, addr);
else
page_dup_rmap(new);
} else 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, ptep);
unlock:
pte_unmap_unlock(ptep, ptl);
out:
return SWAP_AGAIN;
}
/*
* 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)
{
rmap_walk(new, remove_migration_pte, old);
}
/*
* 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.
*/
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);
/*
* Once radix-tree replacement of page migration started, page_count
* *must* be zero. And, we don't want to call wait_on_page_locked()
* against a page without get_page().
* So, we use get_page_unless_zero(), here. Even failed, page fault
* will occur again.
*/
if (!get_page_unless_zero(page))
goto out;
pte_unmap_unlock(ptep, ptl);
wait_on_page_locked(page);
put_page(page);
return;
out:
pte_unmap_unlock(ptep, ptl);
}
#ifdef CONFIG_BLOCK
/* Returns true if all buffers are successfully locked */
static bool buffer_migrate_lock_buffers(struct buffer_head *head,
enum migrate_mode mode)
{
struct buffer_head *bh = head;
/* Simple case, sync compaction */
if (mode != MIGRATE_ASYNC) {
do {
get_bh(bh);
lock_buffer(bh);
bh = bh->b_this_page;
} while (bh != head);
return true;
}
/* async case, we cannot block on lock_buffer so use trylock_buffer */
do {
get_bh(bh);
if (!trylock_buffer(bh)) {
/*
* We failed to lock the buffer and cannot stall in
* async migration. Release the taken locks
*/
struct buffer_head *failed_bh = bh;
put_bh(failed_bh);
bh = head;
while (bh != failed_bh) {
unlock_buffer(bh);
put_bh(bh);
bh = bh->b_this_page;
}
return false;
}
bh = bh->b_this_page;
} while (bh != head);
return true;
}
#else
static inline bool buffer_migrate_lock_buffers(struct buffer_head *head,
enum migrate_mode mode)
{
return true;
}
#endif /* CONFIG_BLOCK */
/*
* 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/PagePrivate2 set.
*/
static int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page,
struct buffer_head *head, enum migrate_mode mode)
{
int expected_count = 0;
void **pslot;
if (!mapping) {
/* Anonymous page without mapping */
if (page_count(page) != 1)
return -EAGAIN;
return MIGRATEPAGE_SUCCESS;
}
spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
expected_count = 2 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
if (!page_freeze_refs(page, expected_count)) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
/*
* In the async migration case of moving a page with buffers, lock the
* buffers using trylock before the mapping is moved. If the mapping
* was moved, we later failed to lock the buffers and could not move
* the mapping back due to an elevated page count, we would have to
* block waiting on other references to be dropped.
*/
if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_unfreeze_refs(page, expected_count);
spin_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 */
if (PageSwapCache(page)) {
SetPageSwapCache(newpage);
set_page_private(newpage, page_private(page));
}
radix_tree_replace_slot(pslot, newpage);
/*
* Drop cache reference from old page by unfreezing
* to one less reference.
* We know this isn't the last reference.
*/
page_unfreeze_refs(page, expected_count - 1);
/*
* If moved to a different zone then also account
* the page for that zone. Other VM counters will be
* taken care of when we establish references to the
* new page and drop references to the old page.
*
* Note that anonymous pages are accounted for
* via NR_FILE_PAGES and NR_ANON_PAGES if they
* are mapped to swap space.
*/
__dec_zone_page_state(page, NR_FILE_PAGES);
__inc_zone_page_state(newpage, NR_FILE_PAGES);
if (!PageSwapCache(page) && PageSwapBacked(page)) {
__dec_zone_page_state(page, NR_SHMEM);
__inc_zone_page_state(newpage, NR_SHMEM);
}
spin_unlock_irq(&mapping->tree_lock);
return MIGRATEPAGE_SUCCESS;
}
/*
* The expected number of remaining references is the same as that
* of migrate_page_move_mapping().
*/
int migrate_huge_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page)
{
int expected_count;
void **pslot;
if (!mapping) {
if (page_count(page) != 1)
return -EAGAIN;
return MIGRATEPAGE_SUCCESS;
}
spin_lock_irq(&mapping->tree_lock);
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));
expected_count = 2 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
if (!page_freeze_refs(page, expected_count)) {
spin_unlock_irq(&mapping->tree_lock);
return -EAGAIN;
}
get_page(newpage);
radix_tree_replace_slot(pslot, newpage);
page_unfreeze_refs(page, expected_count - 1);
spin_unlock_irq(&mapping->tree_lock);
return MIGRATEPAGE_SUCCESS;
}
/*
* Copy the page to its new location
*/
void migrate_page_copy(struct page *newpage, struct page *page)
{
if (PageHuge(page) || PageTransHuge(page))
copy_huge_page(newpage, page);
else
copy_highpage(newpage, page);
if (PageError(page))
SetPageError(newpage);
if (PageReferenced(page))
SetPageReferenced(newpage);
if (PageUptodate(page))
SetPageUptodate(newpage);
if (TestClearPageActive(page)) {
VM_BUG_ON(PageUnevictable(page));
SetPageActive(newpage);
} else if (TestClearPageUnevictable(page))
SetPageUnevictable(newpage);
if (PageChecked(page))
SetPageChecked(newpage);
if (PageMappedToDisk(page))
SetPageMappedToDisk(newpage);
if (PageDirty(page)) {
clear_page_dirty_for_io(page);
/*
* Want to mark the page and the radix tree as dirty, and
* redo the accounting that clear_page_dirty_for_io undid,
* but we can't use set_page_dirty because that function
* is actually a signal that all of the page has become dirty.
* Whereas only part of our page may be dirty.
*/
if (PageSwapBacked(page))
SetPageDirty(newpage);
else
__set_page_dirty_nobuffers(newpage);
}
mlock_migrate_page(newpage, page);
ksm_migrate_page(newpage, page);
/*
* Please do not reorder this without considering how mm/ksm.c's
* get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache().
*/
ClearPageSwapCache(page);
ClearPagePrivate(page);
set_page_private(page, 0);
/*
* 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/PagePrivate2.
*
* Pages are locked upon entry and exit.
*/
int migrate_page(struct address_space *mapping,
struct page *newpage, struct page *page,
enum migrate_mode mode)
{
int rc;
BUG_ON(PageWriteback(page)); /* Writeback must be complete */
rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
migrate_page_copy(newpage, page);
return MIGRATEPAGE_SUCCESS;
}
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, enum migrate_mode mode)
{
struct buffer_head *bh, *head;
int rc;
if (!page_has_buffers(page))
return migrate_page(mapping, newpage, page, mode);
head = page_buffers(page);
rc = migrate_page_move_mapping(mapping, newpage, page, head, mode);
if (rc != MIGRATEPAGE_SUCCESS)
return rc;
/*
* In the async case, migrate_page_move_mapping locked the buffers
* with an IRQ-safe spinlock held. In the sync case, the buffers
* need to be locked now
*/
if (mode != MIGRATE_ASYNC)
BUG_ON(!buffer_migrate_lock_buffers(head, mode));
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 MIGRATEPAGE_SUCCESS;
}
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,
.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 != AOP_WRITEPAGE_ACTIVATE)
/* unlocked. Relock */
lock_page(page);
return (rc < 0) ? -EIO : -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, enum migrate_mode mode)
{
if (PageDirty(page)) {
/* Only writeback pages in full synchronous migration */
if (mode != MIGRATE_SYNC)
return -EBUSY;
return writeout(mapping, page);
}
/*
* Buffers may be managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (page_has_private(page) &&
!try_to_release_page(page, GFP_KERNEL))
return -EAGAIN;
return migrate_page(mapping, newpage, page, mode);
}
/*
* 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.
*
* Return value:
* < 0 - error code
* MIGRATEPAGE_SUCCESS - success
*/
static int move_to_new_page(struct page *newpage, struct page *page,
int remap_swapcache, enum migrate_mode mode)
{
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 (!trylock_page(newpage))
BUG();
/* Prepare mapping for the new page.*/
newpage->index = page->index;
newpage->mapping = page->mapping;
if (PageSwapBacked(page))
SetPageSwapBacked(newpage);
mapping = page_mapping(page);
if (!mapping)
rc = migrate_page(mapping, newpage, page, mode);
else if (mapping->a_ops->migratepage)
/*
* Most pages have a mapping and most filesystems provide a
* migratepage callback. Anonymous pages are part of swap
* space which also has its own migratepage callback. This
* is the most common path for page migration.
*/
rc = mapping->a_ops->migratepage(mapping,
newpage, page, mode);
else
rc = fallback_migrate_page(mapping, newpage, page, mode);
if (rc != MIGRATEPAGE_SUCCESS) {
newpage->mapping = NULL;
} else {
if (remap_swapcache)
remove_migration_ptes(page, newpage);
page->mapping = NULL;
}
unlock_page(newpage);
return rc;
}
static int __unmap_and_move(struct page *page, struct page *newpage,
int force, enum migrate_mode mode)
{
int rc = -EAGAIN;
int remap_swapcache = 1;
struct mem_cgroup *mem;
struct anon_vma *anon_vma = NULL;
if (!trylock_page(page)) {
if (!force || mode == MIGRATE_ASYNC)
goto out;
/*
* It's not safe for direct compaction to call lock_page.
* For example, during page readahead pages are added locked
* to the LRU. Later, when the IO completes the pages are
* marked uptodate and unlocked. However, the queueing
* could be merging multiple pages for one bio (e.g.
* mpage_readpages). If an allocation happens for the
* second or third page, the process can end up locking
* the same page twice and deadlocking. Rather than
* trying to be clever about what pages can be locked,
* avoid the use of lock_page for direct compaction
* altogether.
*/
if (current->flags & PF_MEMALLOC)
goto out;
lock_page(page);
}
/* charge against new page */
mem_cgroup_prepare_migration(page, newpage, &mem);
if (PageWriteback(page)) {
/*
* Only in the case of a full synchronous migration is it
* necessary to wait for PageWriteback. In the async case,
* the retry loop is too short and in the sync-light case,
* the overhead of stalling is too much
*/
if (mode != MIGRATE_SYNC) {
rc = -EBUSY;
goto uncharge;
}
if (!force)
goto uncharge;
wait_on_page_writeback(page);
}
/*
* By try_to_unmap(), page->mapcount goes down to 0 here. In this case,
* we cannot notice that anon_vma is freed while we migrates a page.
* This get_anon_vma() delays freeing anon_vma pointer until the end
* of migration. File cache pages are no problem because of page_lock()
* File Caches may use write_page() or lock_page() in migration, then,
* just care Anon page here.
*/
if (PageAnon(page) && !PageKsm(page)) {
/*
* Only page_lock_anon_vma_read() understands the subtleties of
* getting a hold on an anon_vma from outside one of its mms.
*/
anon_vma = page_get_anon_vma(page);
if (anon_vma) {
/*
* Anon page
*/
} else if (PageSwapCache(page)) {
/*
* We cannot be sure that the anon_vma of an unmapped
* swapcache page is safe to use because we don't
* know in advance if the VMA that this page belonged
* to still exists. If the VMA and others sharing the
* data have been freed, then the anon_vma could
* already be invalid.
*
* To avoid this possibility, swapcache pages get
* migrated but are not remapped when migration
* completes
*/
remap_swapcache = 0;
} else {
goto uncharge;
}
}
if (unlikely(balloon_page_movable(page))) {
/*
* A ballooned page does not need any special attention from
* physical to virtual reverse mapping procedures.
* Skip any attempt to unmap PTEs or to remap swap cache,
* in order to avoid burning cycles at rmap level, and perform
* the page migration right away (proteced by page lock).
*/
rc = balloon_page_migrate(newpage, page, mode);
goto uncharge;
}
/*
* Corner case handling:
* 1. When a new swap-cache page is read into, it is added to the LRU
* and treated as swapcache but it has no rmap yet.
* Calling try_to_unmap() against a page->mapping==NULL page will
* trigger a BUG. So handle it here.
* 2. An orphaned page (see truncate_complete_page) might have
* fs-private metadata. The page can be picked up due to memory
* offlining. Everywhere else except page reclaim, the page is
* invisible to the vm, so the page can not be migrated. So try to
* free the metadata, so the page can be freed.
*/
if (!page->mapping) {
VM_BUG_ON(PageAnon(page));
if (page_has_private(page)) {
try_to_free_buffers(page);
goto uncharge;
}
goto skip_unmap;
}
/* Establish migration ptes or remove ptes */
try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
skip_unmap:
if (!page_mapped(page))
rc = move_to_new_page(newpage, page, remap_swapcache, mode);
if (rc && remap_swapcache)
remove_migration_ptes(page, page);
/* Drop an anon_vma reference if we took one */
if (anon_vma)
put_anon_vma(anon_vma);
uncharge:
mem_cgroup_end_migration(mem, page, newpage,
(rc == MIGRATEPAGE_SUCCESS ||
rc == MIGRATEPAGE_BALLOON_SUCCESS));
unlock_page(page);
out:
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, enum migrate_mode mode)
{
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 out;
}
if (unlikely(PageTransHuge(page)))
if (unlikely(split_huge_page(page)))
goto out;
rc = __unmap_and_move(page, newpage, force, mode);
if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) {
/*
* A ballooned page has been migrated already.
* Now, it's the time to wrap-up counters,
* handle the page back to Buddy and return.
*/
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
balloon_page_free(page);
return MIGRATEPAGE_SUCCESS;
}
out:
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);
dec_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
putback_lru_page(page);
}
/*
* Move the new page to the LRU. If migration was not successful
* then this will free the page.
*/
putback_lru_page(newpage);
if (result) {
if (rc)
*result = rc;
else
*result = page_to_nid(newpage);
}
return rc;
}
/*
* Counterpart of unmap_and_move_page() for hugepage migration.
*
* This function doesn't wait the completion of hugepage I/O
* because there is no race between I/O and migration for hugepage.
* Note that currently hugepage I/O occurs only in direct I/O
* where no lock is held and PG_writeback is irrelevant,
* and writeback status of all subpages are counted in the reference
* count of the head page (i.e. if all subpages of a 2MB hugepage are
* under direct I/O, the reference of the head page is 512 and a bit more.)
* This means that when we try to migrate hugepage whose subpages are
* doing direct I/O, some references remain after try_to_unmap() and
* hugepage migration fails without data corruption.
*
* There is also no race when direct I/O is issued on the page under migration,
* because then pte is replaced with migration swap entry and direct I/O code
* will wait in the page fault for migration to complete.
*/
static int unmap_and_move_huge_page(new_page_t get_new_page,
unsigned long private, struct page *hpage,
int force, enum migrate_mode mode)
{
int rc = 0;
int *result = NULL;
struct page *new_hpage = get_new_page(hpage, private, &result);
struct anon_vma *anon_vma = NULL;
if (!new_hpage)
return -ENOMEM;
rc = -EAGAIN;
if (!trylock_page(hpage)) {
if (!force || mode != MIGRATE_SYNC)
goto out;
lock_page(hpage);
}
if (PageAnon(hpage))
anon_vma = page_get_anon_vma(hpage);
try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
if (!page_mapped(hpage))
rc = move_to_new_page(new_hpage, hpage, 1, mode);
if (rc)
remove_migration_ptes(hpage, hpage);
if (anon_vma)
put_anon_vma(anon_vma);
if (!rc)
hugetlb_cgroup_migrate(hpage, new_hpage);
unlock_page(hpage);
out:
put_page(new_hpage);
if (result) {
if (rc)
*result = rc;
else
*result = page_to_nid(new_hpage);
}
return rc;
}
/*
* migrate_pages - migrate the pages specified in a list, to the free pages
* supplied as the target for the page migration
*
* @from: The list of pages to be migrated.
* @get_new_page: The function used to allocate free pages to be used
* as the target of the page migration.
* @private: Private data to be passed on to get_new_page()
* @mode: The migration mode that specifies the constraints for
* page migration, if any.
* @reason: The reason for page migration.
*
* The function returns after 10 attempts or if no pages are movable any more
* because the list has become empty or no retryable pages exist any more.
* The caller should call putback_lru_pages() to return pages to the LRU
* or free list only if ret != 0.
*
* Returns the number of pages that were not migrated, or an error code.
*/
int migrate_pages(struct list_head *from, new_page_t get_new_page,
unsigned long private, enum migrate_mode mode, int reason)
{
int retry = 1;
int nr_failed = 0;
int nr_succeeded = 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, mode);
switch(rc) {
case -ENOMEM:
goto out;
case -EAGAIN:
retry++;
break;
case MIGRATEPAGE_SUCCESS:
nr_succeeded++;
break;
default:
/* Permanent failure */
nr_failed++;
break;
}
}
}
rc = nr_failed + retry;
out:
if (nr_succeeded)
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
if (nr_failed)
count_vm_events(PGMIGRATE_FAIL, nr_failed);
trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason);
if (!swapwrite)
current->flags &= ~PF_SWAPWRITE;
return rc;
}
int migrate_huge_page(struct page *hpage, new_page_t get_new_page,
unsigned long private, enum migrate_mode mode)
{
int pass, rc;
for (pass = 0; pass < 10; pass++) {
rc = unmap_and_move_huge_page(get_new_page, private,
hpage, pass > 2, mode);
switch (rc) {
case -ENOMEM:
goto out;
case -EAGAIN:
/* try again */
cond_resched();
break;
case MIGRATEPAGE_SUCCESS:
goto out;
default:
rc = -EIO;
goto out;
}
}
out:
return rc;
}
#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_exact_node(pm->node,
GFP_HIGHUSER_MOVABLE | 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.
* The pm array ends with node = MAX_NUMNODES.
*/
static int do_move_page_to_node_array(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
*/
for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
struct vm_area_struct *vma;
struct page *page;
err = -EFAULT;
vma = find_vma(mm, pp->addr);
if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma))
goto set_status;
page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = -ENOENT;
if (!page)
goto set_status;
/* Use PageReserved to check for zero page */
if (PageReserved(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);
if (!err) {
list_add_tail(&page->lru, &pagelist);
inc_zone_page_state(page, NR_ISOLATED_ANON +
page_is_file_cache(page));
}
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;
}
err = 0;
if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, new_page_node,
(unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL);
if (err)
putback_lru_pages(&pagelist);
}
up_read(&mm->mmap_sem);
return err;
}
/*
* Migrate an array of page address onto an array of nodes and fill
* the corresponding array of status.
*/
static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
struct page_to_node *pm;
unsigned long chunk_nr_pages;
unsigned long chunk_start;
int err;
err = -ENOMEM;
pm = (struct page_to_node *)__get_free_page(GFP_KERNEL);
if (!pm)
goto out;
migrate_prep();
/*
* Store a chunk of page_to_node array in a page,
* but keep the last one as a marker
*/
chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1;
for (chunk_start = 0;
chunk_start < nr_pages;
chunk_start += chunk_nr_pages) {
int j;
if (chunk_start + chunk_nr_pages > nr_pages)
chunk_nr_pages = nr_pages - chunk_start;
/* fill the chunk pm with addrs and nodes from user-space */
for (j = 0; j < chunk_nr_pages; j++) {
const void __user *p;
int node;
err = -EFAULT;
if (get_user(p, pages + j + chunk_start))
goto out_pm;
pm[j].addr = (unsigned long) p;
if (get_user(node, nodes + j + chunk_start))
goto out_pm;
err = -ENODEV;
if (node < 0 || node >= MAX_NUMNODES)
goto out_pm;
if (!node_state(node, N_MEMORY))
goto out_pm;
err = -EACCES;
if (!node_isset(node, task_nodes))
goto out_pm;
pm[j].node = node;
}
/* End marker for this chunk */
pm[chunk_nr_pages].node = MAX_NUMNODES;
/* Migrate this chunk */
err = do_move_page_to_node_array(mm, pm,
flags & MPOL_MF_MOVE_ALL);
if (err < 0)
goto out_pm;
/* Return status information */
for (j = 0; j < chunk_nr_pages; j++)
if (put_user(pm[j].status, status + j + chunk_start)) {
err = -EFAULT;
goto out_pm;
}
}
err = 0;
out_pm:
free_page((unsigned long)pm);
out:
return err;
}
/*
* Determine the nodes of an array of pages and store it in an array of status.
*/
static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
const void __user **pages, int *status)
{
unsigned long i;
down_read(&mm->mmap_sem);
for (i = 0; i < nr_pages; i++) {
unsigned long addr = (unsigned long)(*pages);
struct vm_area_struct *vma;
struct page *page;
int err = -EFAULT;
vma = find_vma(mm, addr);
if (!vma || addr < vma->vm_start)
goto set_status;
page = follow_page(vma, addr, 0);
err = PTR_ERR(page);
if (IS_ERR(page))
goto set_status;
err = -ENOENT;
/* Use PageReserved to check for zero page */
if (!page || PageReserved(page))
goto set_status;
err = page_to_nid(page);
set_status:
*status = err;
pages++;
status++;
}
up_read(&mm->mmap_sem);
}
/*
* Determine the nodes of a user array of pages and store it in
* a user array of status.
*/
static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
const void __user * __user *pages,
int __user *status)
{
#define DO_PAGES_STAT_CHUNK_NR 16
const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];
int chunk_status[DO_PAGES_STAT_CHUNK_NR];
while (nr_pages) {
unsigned long chunk_nr;
chunk_nr = nr_pages;
if (chunk_nr > DO_PAGES_STAT_CHUNK_NR)
chunk_nr = DO_PAGES_STAT_CHUNK_NR;
if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages)))
break;
do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);
if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status)))
break;
pages += chunk_nr;
status += chunk_nr;
nr_pages -= chunk_nr;
}
return nr_pages ? -EFAULT : 0;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
const void __user * __user *, pages,
const int __user *, nodes,
int __user *, status, int, flags)
{
const struct cred *cred = current_cred(), *tcred;
struct task_struct *task;
struct mm_struct *mm;
int err;
nodemask_t task_nodes;
/* 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 */
rcu_read_lock();
task = pid ? find_task_by_vpid(pid) : current;
if (!task) {
rcu_read_unlock();
return -ESRCH;
}
get_task_struct(task);
/*
* 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.
*/
tcred = __task_cred(task);
if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
!uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
!capable(CAP_SYS_NICE)) {
rcu_read_unlock();
err = -EPERM;
goto out;
}
rcu_read_unlock();
err = security_task_movememory(task);
if (err)
goto out;
task_nodes = cpuset_mems_allowed(task);
mm = get_task_mm(task);
put_task_struct(task);
if (!mm)
return -EINVAL;
if (nodes)
err = do_pages_move(mm, task_nodes, nr_pages, pages,
nodes, status, flags);
else
err = do_pages_stat(mm, nr_pages, pages, status);
mmput(mm);
return err;
out:
put_task_struct(task);
return err;
}
/*
* 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 && !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;
}
#ifdef CONFIG_NUMA_BALANCING
/*
* Returns true if this is a safe migration target node for misplaced NUMA
* pages. Currently it only checks the watermarks which crude
*/
static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
unsigned long nr_migrate_pages)
{
int z;
for (z = pgdat->nr_zones - 1; z >= 0; z--) {
struct zone *zone = pgdat->node_zones + z;
if (!populated_zone(zone))
continue;
if (zone->all_unreclaimable)
continue;
/* Avoid waking kswapd by allocating pages_to_migrate pages. */
if (!zone_watermark_ok(zone, 0,
high_wmark_pages(zone) +
nr_migrate_pages,
0, 0))
continue;
return true;
}
return false;
}
static struct page *alloc_misplaced_dst_page(struct page *page,
unsigned long data,
int **result)
{
int nid = (int) data;
struct page *newpage;
newpage = alloc_pages_exact_node(nid,
(GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
__GFP_NOMEMALLOC | __GFP_NORETRY |
__GFP_NOWARN) &
~GFP_IOFS, 0);
if (newpage)
page_nid_xchg_last(newpage, page_nid_last(page));
return newpage;
}
/*
* page migration rate limiting control.
* Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
* window of time. Default here says do not migrate more than 1280M per second.
* If a node is rate-limited then PTE NUMA updates are also rate-limited. However
* as it is faults that reset the window, pte updates will happen unconditionally
* if there has not been a fault since @pteupdate_interval_millisecs after the
* throttle window closed.
*/
static unsigned int migrate_interval_millisecs __read_mostly = 100;
static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
/* Returns true if NUMA migration is currently rate limited */
bool migrate_ratelimited(int node)
{
pg_data_t *pgdat = NODE_DATA(node);
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
msecs_to_jiffies(pteupdate_interval_millisecs)))
return false;
if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
return false;
return true;
}
/* Returns true if the node is migrate rate-limited after the update */
bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages)
{
bool rate_limited = false;
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
spin_lock(&pgdat->numabalancing_migrate_lock);
if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) {
pgdat->numabalancing_migrate_nr_pages = 0;
pgdat->numabalancing_migrate_next_window = jiffies +
msecs_to_jiffies(migrate_interval_millisecs);
}
if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
rate_limited = true;
else
pgdat->numabalancing_migrate_nr_pages += nr_pages;
spin_unlock(&pgdat->numabalancing_migrate_lock);
return rate_limited;
}
int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
{
int page_lru;
VM_BUG_ON(compound_order(page) && !PageTransHuge(page));
/* Avoid migrating to a node that is nearly full */
if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page)))
return 0;
if (isolate_lru_page(page))
return 0;
/*
* migrate_misplaced_transhuge_page() skips page migration's usual
* check on page_count(), so we must do it here, now that the page
* has been isolated: a GUP pin, or any other pin, prevents migration.
* The expected page count is 3: 1 for page's mapcount and 1 for the
* caller's pin and 1 for the reference taken by isolate_lru_page().
*/
if (PageTransHuge(page) && page_count(page) != 3) {
putback_lru_page(page);
return 0;
}
page_lru = page_is_file_cache(page);
mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru,
hpage_nr_pages(page));
/*
* Isolating the page has taken another reference, so the
* caller's reference can be safely dropped without the page
* disappearing underneath us during migration.
*/
put_page(page);
return 1;
}
/*
* Attempt to migrate a misplaced page to the specified destination
* node. Caller is expected to have an elevated reference count on
* the page that will be dropped by this function before returning.
*/
int migrate_misplaced_page(struct page *page, int node)
{
pg_data_t *pgdat = NODE_DATA(node);
int isolated;
int nr_remaining;
LIST_HEAD(migratepages);
/*
* Don't migrate pages that are mapped in multiple processes.
* TODO: Handle false sharing detection instead of this hammer
*/
if (page_mapcount(page) != 1)
goto out;
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
if (numamigrate_update_ratelimit(pgdat, 1))
goto out;
isolated = numamigrate_isolate_page(pgdat, page);
if (!isolated)
goto out;
list_add(&page->lru, &migratepages);
nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
node, MIGRATE_ASYNC, MR_NUMA_MISPLACED);
if (nr_remaining) {
putback_lru_pages(&migratepages);
isolated = 0;
} else
count_vm_numa_event(NUMA_PAGE_MIGRATE);
BUG_ON(!list_empty(&migratepages));
return isolated;
out:
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
/*
* Migrates a THP to a given target node. page must be locked and is unlocked
* before returning.
*/
int migrate_misplaced_transhuge_page(struct mm_struct *mm,
struct vm_area_struct *vma,
pmd_t *pmd, pmd_t entry,
unsigned long address,
struct page *page, int node)
{
unsigned long haddr = address & HPAGE_PMD_MASK;
pg_data_t *pgdat = NODE_DATA(node);
int isolated = 0;
struct page *new_page = NULL;
struct mem_cgroup *memcg = NULL;
int page_lru = page_is_file_cache(page);
/*
* Don't migrate pages that are mapped in multiple processes.
* TODO: Handle false sharing detection instead of this hammer
*/
if (page_mapcount(page) != 1)
goto out_dropref;
/*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
*/
if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR))
goto out_dropref;
new_page = alloc_pages_node(node,
(GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER);
if (!new_page)
goto out_fail;
page_nid_xchg_last(new_page, page_nid_last(page));
isolated = numamigrate_isolate_page(pgdat, page);
if (!isolated) {
put_page(new_page);
goto out_fail;
}
/* Prepare a page as a migration target */
__set_page_locked(new_page);
SetPageSwapBacked(new_page);
/* anon mapping, we can simply copy page->mapping to the new page: */
new_page->mapping = page->mapping;
new_page->index = page->index;
migrate_page_copy(new_page, page);
WARN_ON(PageLRU(new_page));
/* Recheck the target PMD */
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(*pmd, entry))) {
spin_unlock(&mm->page_table_lock);
/* Reverse changes made by migrate_page_copy() */
if (TestClearPageActive(new_page))
SetPageActive(page);
if (TestClearPageUnevictable(new_page))
SetPageUnevictable(page);
mlock_migrate_page(page, new_page);
unlock_page(new_page);
put_page(new_page); /* Free it */
unlock_page(page);
putback_lru_page(page);
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
isolated = 0;
goto out;
}
/*
* Traditional migration needs to prepare the memcg charge
* transaction early to prevent the old page from being
* uncharged when installing migration entries. Here we can
* save the potential rollback and start the charge transfer
* only when migration is already known to end successfully.
*/
mem_cgroup_prepare_migration(page, new_page, &memcg);
entry = mk_pmd(new_page, vma->vm_page_prot);
entry = pmd_mknonnuma(entry);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
entry = pmd_mkhuge(entry);
page_add_new_anon_rmap(new_page, vma, haddr);
set_pmd_at(mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, address, &entry);
page_remove_rmap(page);
/*
* Finish the charge transaction under the page table lock to
* prevent split_huge_page() from dividing up the charge
* before it's fully transferred to the new page.
*/
mem_cgroup_end_migration(memcg, page, new_page, true);
spin_unlock(&mm->page_table_lock);
unlock_page(new_page);
unlock_page(page);
put_page(page); /* Drop the rmap reference */
put_page(page); /* Drop the LRU isolation reference */
count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
out:
mod_zone_page_state(page_zone(page),
NR_ISOLATED_ANON + page_lru,
-HPAGE_PMD_NR);
return isolated;
out_fail:
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
out_dropref:
unlock_page(page);
put_page(page);
return 0;
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_NUMA */
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