On 2024/6/3 12:44, Lance Yang wrote:
On Thu, May 30, 2024 at 10:04 AM Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:Add large folio mapping establishment support for finish_fault() as a preparation, to support multi-size THP allocation of anonymous shmem pages in the following patches. Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> --- mm/memory.c | 58 ++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 48 insertions(+), 10 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index eef4e482c0c2..435187ff7ea4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4831,9 +4831,12 @@ vm_fault_t finish_fault(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct page *page; + struct folio *folio; vm_fault_t ret; bool is_cow = (vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED); + int type, nr_pages, i; + unsigned long addr = vmf->address; /* Did we COW the page? */ if (is_cow) @@ -4864,24 +4867,59 @@ vm_fault_t finish_fault(struct vm_fault *vmf) return VM_FAULT_OOM; } + folio = page_folio(page); + nr_pages = folio_nr_pages(folio); + + /* + * Using per-page fault to maintain the uffd semantics, and same + * approach also applies to non-anonymous-shmem faults to avoid + * inflating the RSS of the process. + */ + if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) { + nr_pages = 1; + } else if (nr_pages > 1) { + pgoff_t idx = folio_page_idx(folio, page); + /* The page offset of vmf->address within the VMA. */ + pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff; + + /* + * Fallback to per-page fault in case the folio size in page + * cache beyond the VMA limits. + */ + if (unlikely(vma_off < idx || + vma_off + (nr_pages - idx) > vma_pages(vma))) { + nr_pages = 1; + } else { + /* Now we can set mappings for the whole large folio. */ + addr = vmf->address - idx * PAGE_SIZE; + page = &folio->page; + } + } + vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); + addr, &vmf->ptl); if (!vmf->pte) return VM_FAULT_NOPAGE; /* Re-check under ptl */ - if (likely(!vmf_pte_changed(vmf))) { - struct folio *folio = page_folio(page); - int type = is_cow ? MM_ANONPAGES : mm_counter_file(folio); - - set_pte_range(vmf, folio, page, 1, vmf->address); - add_mm_counter(vma->vm_mm, type, 1); - ret = 0; - } else { - update_mmu_tlb(vma, vmf->address, vmf->pte); + if (nr_pages == 1 && unlikely(vmf_pte_changed(vmf))) { + update_mmu_tlb(vma, addr, vmf->pte); ret = VM_FAULT_NOPAGE; + goto unlock; + } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) { + for (i = 0; i < nr_pages; i++) + update_mmu_tlb(vma, addr + PAGE_SIZE * i, vmf->pte + i);Just a friendly reminder: Bang has added the update_mmu_tlb_range()[1] batch function to update TLB in batches, so we can use it instead of the update_mmu_tlb() loop. [1] https://lore.kernel.org/linux-mm/20240522061204.117421-1-libang.li@xxxxxxxxxxxx/
Good point, I will use the new helper instead.
