The patch titled
Subject: mm/rmap: introduce and use hugetlb_remove_rmap()
has been added to the -mm mm-unstable branch. Its filename is
mm-rmap-introduce-and-use-hugetlb_remove_rmap.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-introduce-and-use-hugetlb_remove_rmap.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/rmap: introduce and use hugetlb_remove_rmap()
Date: Wed, 20 Dec 2023 23:44:26 +0100
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@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 7 +++++++
mm/hugetlb.c | 4 ++--
mm/rmap.c | 18 +++++++++---------
3 files changed, 18 insertions(+), 11 deletions(-)
--- a/include/linux/rmap.h~mm-rmap-introduce-and-use-hugetlb_remove_rmap
+++ a/include/linux/rmap.h
@@ -211,6 +211,13 @@ void hugetlb_add_anon_rmap(struct folio
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) {
--- a/mm/hugetlb.c~mm-rmap-introduce-and-use-hugetlb_remove_rmap
+++ a/mm/hugetlb.c
@@ -5676,7 +5676,7 @@ void __unmap_hugepage_range(struct mmu_g
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);
--- a/mm/rmap.c~mm-rmap-introduce-and-use-hugetlb_remove_rmap
+++ a/mm/rmap.c
@@ -1480,15 +1480,9 @@ void page_remove_rmap(struct page *page,
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 foli
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 fo
*/
}
- 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);
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-rmap-rename-hugepage_add-to-hugetlb_add.patch
mm-rmap-introduce-and-use-hugetlb_remove_rmap.patch
mm-rmap-introduce-and-use-hugetlb_add_file_rmap.patch
mm-rmap-introduce-and-use-hugetlb_try_dup_anon_rmap.patch
mm-rmap-introduce-and-use-hugetlb_try_share_anon_rmap.patch
mm-rmap-add-hugetlb-sanity-checks-for-anon-rmap-handling.patch
mm-rmap-convert-folio_add_file_rmap_range-into-folio_add_file_rmap_.patch
mm-memory-page_add_file_rmap-folio_add_file_rmap_.patch
mm-huge_memory-page_add_file_rmap-folio_add_file_rmap_pmd.patch
mm-migrate-page_add_file_rmap-folio_add_file_rmap_pte.patch
mm-userfaultfd-page_add_file_rmap-folio_add_file_rmap_pte.patch
mm-rmap-remove-page_add_file_rmap.patch
mm-rmap-factor-out-adding-folio-mappings-into-__folio_add_rmap.patch
mm-rmap-introduce-folio_add_anon_rmap_.patch
mm-huge_memory-batch-rmap-operations-in-__split_huge_pmd_locked.patch
mm-huge_memory-page_add_anon_rmap-folio_add_anon_rmap_pmd.patch
mm-migrate-page_add_anon_rmap-folio_add_anon_rmap_pte.patch
mm-ksm-page_add_anon_rmap-folio_add_anon_rmap_pte.patch
mm-swapfile-page_add_anon_rmap-folio_add_anon_rmap_pte.patch
mm-memory-page_add_anon_rmap-folio_add_anon_rmap_pte.patch
mm-rmap-remove-page_add_anon_rmap.patch
mm-rmap-remove-rmap_compound.patch
mm-rmap-introduce-folio_remove_rmap_.patch
kernel-events-uprobes-page_remove_rmap-folio_remove_rmap_pte.patch
mm-huge_memory-page_remove_rmap-folio_remove_rmap_pmd.patch
mm-khugepaged-page_remove_rmap-folio_remove_rmap_pte.patch
mm-ksm-page_remove_rmap-folio_remove_rmap_pte.patch
mm-memory-page_remove_rmap-folio_remove_rmap_pte.patch
mm-migrate_device-page_remove_rmap-folio_remove_rmap_pte.patch
mm-rmap-page_remove_rmap-folio_remove_rmap_pte.patch
documentation-stop-referring-to-page_remove_rmap.patch
mm-rmap-remove-page_remove_rmap.patch
mm-rmap-convert-page_dup_file_rmap-to-folio_dup_file_rmap_.patch
mm-rmap-introduce-folio_try_dup_anon_rmap_.patch
mm-huge_memory-page_try_dup_anon_rmap-folio_try_dup_anon_rmap_pmd.patch
mm-memory-page_try_dup_anon_rmap-folio_try_dup_anon_rmap_pte.patch
mm-rmap-remove-page_try_dup_anon_rmap.patch
mm-convert-page_try_share_anon_rmap-to-folio_try_share_anon_rmap_.patch
mm-rmap-rename-compound_mapped-to-entirely_mapped.patch
mm-remove-one-last-reference-to-page_add__rmap.patch
