BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
}
-static int shrink_huge_zero_page(struct shrinker *shrink,
- struct shrink_control *sc)
+static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
+ struct shrink_control *sc)
{
- if (!sc->nr_to_scan)
- /* we can free zero page only if last reference remains */
- return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
+ /* we can free zero page only if last reference remains */
+ return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
+}
+static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
struct page *zero_page = xchg(&huge_zero_page, NULL);
BUG_ON(zero_page == NULL);
__free_page(zero_page);
+ return HPAGE_PMD_NR;
}
return 0;
}
static struct shrinker huge_zero_page_shrinker = {
- .shrink = shrink_huge_zero_page,
+ .count_objects = shrink_huge_zero_page_count,
+ .scan_objects = shrink_huge_zero_page_scan,
.seeks = DEFAULT_SEEKS,
};
{
struct page *page;
unsigned long haddr = address & HPAGE_PMD_MASK;
- pte_t *pte;
- if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
- if (unlikely(anon_vma_prepare(vma)))
- return VM_FAULT_OOM;
- if (unlikely(khugepaged_enter(vma)))
+ if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
+ return VM_FAULT_FALLBACK;
+ if (unlikely(anon_vma_prepare(vma)))
+ return VM_FAULT_OOM;
+ if (unlikely(khugepaged_enter(vma)))
+ return VM_FAULT_OOM;
+ if (!(flags & FAULT_FLAG_WRITE) &&
+ transparent_hugepage_use_zero_page()) {
+ pgtable_t pgtable;
+ struct page *zero_page;
+ bool set;
+ pgtable = pte_alloc_one(mm, haddr);
+ if (unlikely(!pgtable))
return VM_FAULT_OOM;
- if (!(flags & FAULT_FLAG_WRITE) &&
- transparent_hugepage_use_zero_page()) {
- pgtable_t pgtable;
- struct page *zero_page;
- bool set;
- pgtable = pte_alloc_one(mm, haddr);
- if (unlikely(!pgtable))
- return VM_FAULT_OOM;
- zero_page = get_huge_zero_page();
- if (unlikely(!zero_page)) {
- pte_free(mm, pgtable);
- count_vm_event(THP_FAULT_FALLBACK);
- goto out;
- }
- spin_lock(&mm->page_table_lock);
- set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
- zero_page);
- spin_unlock(&mm->page_table_lock);
- if (!set) {
- pte_free(mm, pgtable);
- put_huge_zero_page();
- }
- return 0;
- }
- page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
- vma, haddr, numa_node_id(), 0);
- if (unlikely(!page)) {
+ zero_page = get_huge_zero_page();
+ if (unlikely(!zero_page)) {
+ pte_free(mm, pgtable);
count_vm_event(THP_FAULT_FALLBACK);
- goto out;
+ return VM_FAULT_FALLBACK;
}
- count_vm_event(THP_FAULT_ALLOC);
- if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
- put_page(page);
- goto out;
- }
- if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
- page))) {
- mem_cgroup_uncharge_page(page);
- put_page(page);
- goto out;
+ spin_lock(&mm->page_table_lock);
+ set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
+ zero_page);
+ spin_unlock(&mm->page_table_lock);
+ if (!set) {
+ pte_free(mm, pgtable);
+ put_huge_zero_page();
}
-
return 0;
}
-out:
- /*
- * Use __pte_alloc instead of pte_alloc_map, because we can't
- * run pte_offset_map on the pmd, if an huge pmd could
- * materialize from under us from a different thread.
- */
- if (unlikely(pmd_none(*pmd)) &&
- unlikely(__pte_alloc(mm, vma, pmd, address)))
- return VM_FAULT_OOM;
- /* if an huge pmd materialized from under us just retry later */
- if (unlikely(pmd_trans_huge(*pmd)))
- return 0;
- /*
- * A regular pmd is established and it can't morph into a huge pmd
- * from under us anymore at this point because we hold the mmap_sem
- * read mode and khugepaged takes it in write mode. So now it's
- * safe to run pte_offset_map().
- */
- pte = pte_offset_map(pmd, address);
- return handle_pte_fault(mm, vma, address, pte, pmd, flags);
+ page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
+ vma, haddr, numa_node_id(), 0);
+ if (unlikely(!page)) {
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+ if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
+ put_page(page);
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+ if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) {
+ mem_cgroup_uncharge_page(page);
+ put_page(page);
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+
+ count_vm_event(THP_FAULT_ALLOC);
+ return 0;
}
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
new_page = NULL;
if (unlikely(!new_page)) {
- count_vm_event(THP_FAULT_FALLBACK);
if (is_huge_zero_pmd(orig_pmd)) {
ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
address, pmd, orig_pmd, haddr);
split_huge_page(page);
put_page(page);
}
+ count_vm_event(THP_FAULT_FALLBACK);
goto out;
}
- count_vm_event(THP_FAULT_ALLOC);
if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
put_page(new_page);
split_huge_page(page);
put_page(page);
}
+ count_vm_event(THP_FAULT_FALLBACK);
ret |= VM_FAULT_OOM;
goto out;
}
+ count_vm_event(THP_FAULT_ALLOC);
+
if (is_huge_zero_pmd(orig_pmd))
clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
else
int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd, pmd_t *pmdp)
{
+ struct anon_vma *anon_vma = NULL;
struct page *page;
unsigned long haddr = addr & HPAGE_PMD_MASK;
int target_nid;
int current_nid = -1;
- bool migrated;
+ bool migrated, page_locked;
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(pmd, *pmdp)))
goto out_unlock;
page = pmd_page(pmd);
- get_page(page);
current_nid = page_to_nid(page);
count_vm_numa_event(NUMA_HINT_FAULTS);
if (current_nid == numa_node_id())
count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
+ /*
+ * Acquire the page lock to serialise THP migrations but avoid dropping
+ * page_table_lock if at all possible
+ */
+ page_locked = trylock_page(page);
target_nid = mpol_misplaced(page, vma, haddr);
if (target_nid == -1) {
- put_page(page);
- goto clear_pmdnuma;
+ /* If the page was locked, there are no parallel migrations */
+ if (page_locked) {
+ unlock_page(page);
+ goto clear_pmdnuma;
+ }
+
+ /* Otherwise wait for potential migrations and retry fault */
+ spin_unlock(&mm->page_table_lock);
+ wait_on_page_locked(page);
+ goto out;
}
- /* Acquire the page lock to serialise THP migrations */
+ /* Page is misplaced, serialise migrations and parallel THP splits */
+ get_page(page);
spin_unlock(&mm->page_table_lock);
- lock_page(page);
+ if (!page_locked) {
+ lock_page(page);
+ page_locked = true;
+ }
+ anon_vma = page_lock_anon_vma_read(page);
/* Confirm the PTE did not while locked */
spin_lock(&mm->page_table_lock);
put_page(page);
goto out_unlock;
}
- spin_unlock(&mm->page_table_lock);
/* Migrate the THP to the requested node */
+ spin_unlock(&mm->page_table_lock);
migrated = migrate_misplaced_transhuge_page(mm, vma,
pmdp, pmd, addr, page, target_nid);
if (!migrated)
goto check_same;
task_numa_fault(target_nid, HPAGE_PMD_NR, true);
+ if (anon_vma)
+ page_unlock_anon_vma_read(anon_vma);
return 0;
check_same:
spin_lock(&mm->page_table_lock);
- if (unlikely(!pmd_same(pmd, *pmdp)))
+ if (unlikely(!pmd_same(pmd, *pmdp))) {
+ /* Someone else took our fault */
+ current_nid = -1;
goto out_unlock;
+ }
clear_pmdnuma:
pmd = pmd_mknonnuma(pmd);
set_pmd_at(mm, haddr, pmdp, pmd);
update_mmu_cache_pmd(vma, addr, pmdp);
out_unlock:
spin_unlock(&mm->page_table_lock);
+
+out:
+ if (anon_vma)
+ page_unlock_anon_vma_read(anon_vma);
+
if (current_nid != -1)
task_numa_fault(current_nid, HPAGE_PMD_NR, false);
return 0;
mmun_start = haddr;
mmun_end = haddr + HPAGE_PMD_SIZE;
+again:
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_trans_huge(*pmd))) {
split_huge_page(page);
put_page(page);
- BUG_ON(pmd_trans_huge(*pmd));
+
+ /*
+ * We don't always have down_write of mmap_sem here: a racing
+ * do_huge_pmd_wp_page() might have copied-on-write to another
+ * huge page before our split_huge_page() got the anon_vma lock.
+ */
+ if (unlikely(pmd_trans_huge(*pmd)))
+ goto again;
}
void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,