On 1/31/2023 11:34 AM, Huang, Ying wrote:
> 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)
Yes. I will address this in next version series. Thanks.
Regards
Yin, Fengwei
>
> 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);
