Revert "Revert "mm: thp: make the THP mapcount atomic against __split_huge_pmd_locked()"" (ddc9e8e8) · Commits · e / devices / android_kernel_fairphone_FP3

mm/huge_memory.c

+28 −3

Original line number	Diff line number	Diff line
		@@ -1755,6 +1755,8 @@ void __split_huge_pmd(struct vm_area_struct vma, pmd_t pmd,
		spinlock_t *ptl;
		struct mm_struct *mm = vma->vm_mm;
		unsigned long haddr = address & HPAGE_PMD_MASK;
		bool was_locked = false;
		pmd_t _pmd;

		mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
		ptl = pmd_lock(mm, pmd);
		@@ -1764,11 +1766,32 @@ void __split_huge_pmd(struct vm_area_struct vma, pmd_t pmd,
		* pmd against. Otherwise we can end up replacing wrong page.
		*/
		VM_BUG_ON(freeze && !page);
		if (page && page != pmd_page(*pmd))
		if (page) {
		VM_WARN_ON_ONCE(!PageLocked(page));
		was_locked = true;
		if (page != pmd_page(*pmd))
		goto out;
		}

		repeat:
		if (pmd_trans_huge(*pmd)) {
		if (!page) {
		page = pmd_page(*pmd);
		if (unlikely(!trylock_page(page))) {
		get_page(page);
		_pmd = *pmd;
		spin_unlock(ptl);
		lock_page(page);
		spin_lock(ptl);
		if (unlikely(!pmd_same(*pmd, _pmd))) {
		unlock_page(page);
		put_page(page);
		page = NULL;
		goto repeat;
		}
		put_page(page);
		}
		}
		if (PageMlocked(page))
		clear_page_mlock(page);
		} else if (!pmd_devmap(*pmd))
		@@ -1776,6 +1799,8 @@ void __split_huge_pmd(struct vm_area_struct vma, pmd_t pmd,
		__split_huge_pmd_locked(vma, pmd, haddr, freeze);
		out:
		spin_unlock(ptl);
		if (!was_locked && page)
		unlock_page(page);
		mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
		}