Commit 2b635dd3 authored by Will Deacon's avatar Will Deacon
Browse files

mm: Avoid modifying vmf.address in __collapse_huge_page_swapin() 



In preparation for const-ifying the anonymous struct field of
'struct vm_fault', rework __collapse_huge_page_swapin() to avoid
continuously updating vmf.address and instead populate a new
'struct vm_fault' on the stack for each page being processed.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 9d3af4b4

mm/khugepaged.c

+18 −19
Original line number Diff line number Diff line
@@ -991,38 +991,41 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, 


static bool __collapse_huge_page_swapin(struct mm_struct *mm,

					struct vm_area_struct *vma,

					unsigned long address, pmd_t *pmd,

					unsigned long haddr, pmd_t *pmd,

					int referenced)

{

	int swapped_in = 0;

	vm_fault_t ret = 0;

	unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);



	for (address = haddr; address < end; address += PAGE_SIZE) {

		struct vm_fault vmf = {

			.vma = vma,

			.address = address,

			.pgoff = linear_page_index(vma, haddr),

			.flags = FAULT_FLAG_ALLOW_RETRY,

			.pmd = pmd,

		.pgoff = linear_page_index(vma, address),

		};



		vmf.pte = pte_offset_map(pmd, address);

	for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;

			vmf.pte++, vmf.address += PAGE_SIZE) {

		vmf.orig_pte = *vmf.pte;

		if (!is_swap_pte(vmf.orig_pte))

		if (!is_swap_pte(vmf.orig_pte)) {

			pte_unmap(vmf.pte);

			continue;

		}

		swapped_in++;

		ret = do_swap_page(&vmf);



		/* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */

		if (ret & VM_FAULT_RETRY) {

			mmap_read_lock(mm);

			if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {

			if (hugepage_vma_revalidate(mm, haddr, &vma)) {

				/* vma is no longer available, don't continue to swapin */

				trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

				return false;

			}

			/* check if the pmd is still valid */

			if (mm_find_pmd(mm, address) != pmd) {

			if (mm_find_pmd(mm, haddr) != pmd) {

				trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

				return false;

			}
@@ -1031,11 +1034,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, 
			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

			return false;

		}

		/* pte is unmapped now, we need to map it */

		vmf.pte = pte_offset_map(pmd, vmf.address);

	}

	vmf.pte--;

	pte_unmap(vmf.pte);



	/* Drain LRU add pagevec to remove extra pin on the swapped in pages */

	if (swapped_in)