Yin Fengwei <fengwei.yin@xxxxxxxxx> writes:
> Add function to do file page mapping based on folio and update
> filemap_map_pages() to use new function. So the filemap page
> mapping will deal with folio granularity instead of page
> granularity. This allow batched folio refcount update.
>
> Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> ---
> mm/filemap.c | 82 ++++++++++++++++++++++++++++++----------------------
> 1 file changed, 48 insertions(+), 34 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c915ded191f0..fe0c226c8b1e 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3351,6 +3351,43 @@ static inline struct folio *next_map_page(struct address_space *mapping,
> mapping, xas, end_pgoff);
> }
>
> +
> +static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
> + struct folio *folio, struct page *page, unsigned long addr,
> + int len)
As Matthew pointed out, we should rename 'len'. And some comments about
the meaning of the parameters should be good. For example,
/* Map sub-pages [start_page, start_page + nr_pages) of folio */
static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
struct folio *folio, struct page *start_page, unsigned int nr_pages,
unsigned long start)
Best Regards,
Huang, Ying
> +{
> + vm_fault_t ret = 0;
> + struct vm_area_struct *vma = vmf->vma;
> + struct file *file = vma->vm_file;
> + unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
> + int ref_count = 0, count = 0;
> +
> + do {
> + if (PageHWPoison(page))
> + continue;
> +
> + if (mmap_miss > 0)
> + mmap_miss--;
> +
> + if (!pte_none(*vmf->pte))
> + continue;
> +
> + if (vmf->address == addr)
> + ret = VM_FAULT_NOPAGE;
> +
> + ref_count++;
> +
> + do_set_pte(vmf, page, addr);
> + update_mmu_cache(vma, addr, vmf->pte);
> +
> + } while (vmf->pte++, page++, addr += PAGE_SIZE, ++count < len);
> +
> + folio_ref_add(folio, ref_count);
> + WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
> +
> + return ret;
> +}
> +
> vm_fault_t filemap_map_pages(struct vm_fault *vmf,
> pgoff_t start_pgoff, pgoff_t end_pgoff)
> {
> @@ -3361,9 +3398,9 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
> unsigned long addr;
> XA_STATE(xas, &mapping->i_pages, start_pgoff);
> struct folio *folio;
> - struct page *page;
> unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
> vm_fault_t ret = 0;
> + int len = 0;
>
> rcu_read_lock();
> folio = first_map_page(mapping, &xas, end_pgoff);
> @@ -3378,45 +3415,22 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
> addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
> do {
> -again:
> - page = folio_file_page(folio, xas.xa_index);
> - if (PageHWPoison(page))
> - goto unlock;
> -
> - if (mmap_miss > 0)
> - mmap_miss--;
> + struct page *page;
> + unsigned long end;
>
> + page = folio_file_page(folio, xas.xa_index);
> addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
> - vmf->pte += xas.xa_index - last_pgoff;
> + vmf->pte += xas.xa_index - last_pgoff - len;
> last_pgoff = xas.xa_index;
> + end = folio->index + folio_nr_pages(folio) - 1;
> + len = min(end, end_pgoff) - xas.xa_index + 1;
>
> - /*
> - * NOTE: If there're PTE markers, we'll leave them to be
> - * handled in the specific fault path, and it'll prohibit the
> - * fault-around logic.
> - */
> - if (!pte_none(*vmf->pte))
> - goto unlock;
> -
> - /* We're about to handle the fault */
> - if (vmf->address == addr)
> + if (VM_FAULT_NOPAGE ==
> + filemap_map_folio_range(vmf, folio, page, addr, len))
> ret = VM_FAULT_NOPAGE;
>
> - do_set_pte(vmf, page, addr);
> - /* no need to invalidate: a not-present page won't be cached */
> - update_mmu_cache(vma, addr, vmf->pte);
> - if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
> - xas.xa_index++;
> - folio_ref_inc(folio);
> - goto again;
> - }
> - folio_unlock(folio);
> - continue;
> -unlock:
> - if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
> - xas.xa_index++;
> - goto again;
> - }
> + xas.xa_index = end;
> +
> folio_unlock(folio);
> folio_put(folio);
> } while ((folio = next_map_page(mapping, &xas, end_pgoff)) != NULL);
