On Wed, 15 Sep 2021, Peter Xu wrote:
> The first_index/last_index parameters in zap_details are actually only used in
> unmap_mapping_range_tree(). At the meantime, this function is only called by
> unmap_mapping_pages() once. Instead of passing these two variables through the
> whole stack of page zapping code, remove them from zap_details and let them
> simply be parameters of unmap_mapping_range_tree(), which is inlined.
>
> Reviewed-by: Alistair Popple <apopple@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Liam Howlett <liam.howlett@xxxxxxxxxx>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
And this one is fine too, thanks. I don't know whether it saves anything
(ah yes, with args in registers not on the stack, should save a little),
but it's helpful to limit the scope of those indices.
You may wonder how they came to be in zap_details: that dates from the
days of remap_file_pages(): nonlinear vmas, in which the zapper needed
to check each pte_file()'s offset against first and last index, to
decide whether to zap or not. They should have been removed in 4.0.
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
> include/linux/mm.h | 2 --
> mm/memory.c | 31 ++++++++++++++++++-------------
> 2 files changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 73a52aba448f..d1126f731221 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1722,8 +1722,6 @@ extern void user_shm_unlock(size_t, struct ucounts *);
> */
> struct zap_details {
> struct address_space *check_mapping; /* Check page->mapping if set */
> - pgoff_t first_index; /* Lowest page->index to unmap */
> - pgoff_t last_index; /* Highest page->index to unmap */
> struct page *single_page; /* Locked page to be unmapped */
> };
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 7b095f07c4ef..a7e427177817 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3321,20 +3321,20 @@ static void unmap_mapping_range_vma(struct vm_area_struct *vma,
> }
>
> static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
> + pgoff_t first_index,
> + pgoff_t last_index,
> struct zap_details *details)
> {
> struct vm_area_struct *vma;
> pgoff_t vba, vea, zba, zea;
>
> - vma_interval_tree_foreach(vma, root,
> - details->first_index, details->last_index) {
> -
> + vma_interval_tree_foreach(vma, root, first_index, last_index) {
> vba = vma->vm_pgoff;
> vea = vba + vma_pages(vma) - 1;
> - zba = details->first_index;
> + zba = first_index;
> if (zba < vba)
> zba = vba;
> - zea = details->last_index;
> + zea = last_index;
> if (zea > vea)
> zea = vea;
>
> @@ -3360,18 +3360,22 @@ void unmap_mapping_page(struct page *page)
> {
> struct address_space *mapping = page->mapping;
> struct zap_details details = { };
> + pgoff_t first_index;
> + pgoff_t last_index;
>
> VM_BUG_ON(!PageLocked(page));
> VM_BUG_ON(PageTail(page));
>
> + first_index = page->index;
> + last_index = page->index + thp_nr_pages(page) - 1;
> +
> details.check_mapping = mapping;
> - details.first_index = page->index;
> - details.last_index = page->index + thp_nr_pages(page) - 1;
> details.single_page = page;
>
> i_mmap_lock_write(mapping);
> if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
> - unmap_mapping_range_tree(&mapping->i_mmap, &details);
> + unmap_mapping_range_tree(&mapping->i_mmap, first_index,
> + last_index, &details);
> i_mmap_unlock_write(mapping);
> }
>
> @@ -3391,16 +3395,17 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
> pgoff_t nr, bool even_cows)
> {
> struct zap_details details = { };
> + pgoff_t first_index = start;
> + pgoff_t last_index = start + nr - 1;
>
> details.check_mapping = even_cows ? NULL : mapping;
> - details.first_index = start;
> - details.last_index = start + nr - 1;
> - if (details.last_index < details.first_index)
> - details.last_index = ULONG_MAX;
> + if (last_index < first_index)
> + last_index = ULONG_MAX;
>
> i_mmap_lock_write(mapping);
> if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
> - unmap_mapping_range_tree(&mapping->i_mmap, &details);
> + unmap_mapping_range_tree(&mapping->i_mmap, first_index,
> + last_index, &details);
> i_mmap_unlock_write(mapping);
> }
>
> --
> 2.31.1
