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;