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mm/rmap: introduce and use hugetlb_remove_rmap() 

hugetlb rmap handling differs quite a lot from "ordinary" rmap code.  For
example, hugetlb currently only supports entire mappings, and treats any
mapping as mapped using a single "logical PTE".  Let's move it out of the
way so we can overhaul our "ordinary" rmap.  implementation/interface.

Let's introduce and use hugetlb_remove_rmap() and remove the hugetlb code
from page_remove_rmap().  This effectively removes one check on the
small-folio path as well.

Add sanity checks that we end up with the right folios in the right
functions.

Note: all possible candidates that need care are page_remove_rmap() that
      pass compound=true.

Link: https://lkml.kernel.org/r/20231220224504.646757-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2023-12-20 23:44:26 +01:00 committed by Andrew Morton
parent 9d5fafd5d8
commit e135826b2d
3 changed files with 18 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/rmap.h
View File

@ -211,6 +211,13 @@ void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *,
void hugetlb_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
unsigned long address);
static inline void hugetlb_remove_rmap(struct folio *folio)
{
VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
atomic_dec(&folio->_entire_mapcount);
}
static inline void __page_dup_rmap(struct page *page, bool compound)
{
if (compound) {

4
mm/hugetlb.c
View File

@ -5676,7 +5676,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
make_pte_marker(PTE_MARKER_UFFD_WP),
sz);
hugetlb_count_sub(pages_per_huge_page(h), mm);
page_remove_rmap(page, vma, true);
hugetlb_remove_rmap(page_folio(page));
spin_unlock(ptl);
tlb_remove_page_size(tlb, page, huge_page_size(h));
@ -5987,7 +5987,7 @@ retry_avoidcopy:
/* Break COW or unshare */
huge_ptep_clear_flush(vma, haddr, ptep);
page_remove_rmap(&old_folio->page, vma, true);
hugetlb_remove_rmap(old_folio);
hugetlb_add_new_anon_rmap(new_folio, vma, haddr);
if (huge_pte_uffd_wp(pte))
newpte = huge_pte_mkuffd_wp(newpte);

18
mm/rmap.c
View File

@ -1480,15 +1480,9 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
bool last;
enum node_stat_item idx;
VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
VM_BUG_ON_PAGE(compound && !PageHead(page), page);
/* Hugetlb pages are not counted in NR_*MAPPED */
if (unlikely(folio_test_hugetlb(folio))) {
/* hugetlb pages are always mapped with pmds */
atomic_dec(&folio->_entire_mapcount);
return;
}
/* Is page being unmapped by PTE? Is this its last map to be removed? */
if (likely(!compound)) {
last = atomic_add_negative(-1, &page->_mapcount);
@ -1846,7 +1840,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
dec_mm_counter(mm, mm_counter_file(&folio->page));
}
discard:
page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
if (unlikely(folio_test_hugetlb(folio)))
hugetlb_remove_rmap(folio);
else
page_remove_rmap(subpage, vma, false);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put(folio);
@ -2199,7 +2196,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
*/
}
page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
if (unlikely(folio_test_hugetlb(folio)))
hugetlb_remove_rmap(folio);
else
page_remove_rmap(subpage, vma, false);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put(folio);