+ mm-rmap-introduce-and-use-hugetlb_add_file_rmap.patch added to mm-unstable branch

+ mm-rmap-introduce-and-use-hugetlb_add_file_rmap.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/rmap: introduce and use hugetlb_add_file_rmap()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-rmap-introduce-and-use-hugetlb_add_file_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_add_file_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@redhat.com>
Subject: mm/rmap: introduce and use hugetlb_add_file_rmap()
Date: Wed, 20 Dec 2023 23:44:27 +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.

Right now we're using page_dup_file_rmap() in some cases where "ordinary"
rmap code would have used page_add_file_rmap().  So let's introduce and
use hugetlb_add_file_rmap() instead.  We won't be adding a
"hugetlb_dup_file_rmap()" functon for the fork() case, as it would be
doing the same: "dup" is just an optimization for "add".

What remains is a single page_dup_file_rmap() call in fork() code.

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

Link: https://lkml.kernel.org/r/20231220224504.646757-4-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: Muchun Song <songmuchun@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rmap.h |    8 ++++++++
 mm/hugetlb.c         |    6 +++---
 mm/migrate.c         |    2 +-
 mm/rmap.c            |    1 +
 4 files changed, 13 insertions(+), 4 deletions(-)

--- a/include/linux/rmap.h~mm-rmap-introduce-and-use-hugetlb_add_file_rmap
+++ a/include/linux/rmap.h
@@ -211,6 +211,14 @@ 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_add_file_rmap(struct folio *folio)
+{
+	VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
+	VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
+
+	atomic_inc(&folio->_entire_mapcount);
+}
+
 static inline void hugetlb_remove_rmap(struct folio *folio)
 {
 	VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
--- a/mm/hugetlb.c~mm-rmap-introduce-and-use-hugetlb_add_file_rmap
+++ a/mm/hugetlb.c
@@ -5408,7 +5408,7 @@ again:
 			 * sleep during the process.
 			 */
 			if (!folio_test_anon(pte_folio)) {
-				page_dup_file_rmap(&pte_folio->page, true);
+				hugetlb_add_file_rmap(pte_folio);
 			} else if (page_try_dup_anon_rmap(&pte_folio->page,
 							  true, src_vma)) {
 				pte_t src_pte_old = entry;
@@ -6279,7 +6279,7 @@ static vm_fault_t hugetlb_no_page(struct
 	if (anon_rmap)
 		hugetlb_add_new_anon_rmap(folio, vma, haddr);
 	else
-		page_dup_file_rmap(&folio->page, true);
+		hugetlb_add_file_rmap(folio);
 	new_pte = make_huge_pte(vma, &folio->page, ((vma->vm_flags & VM_WRITE)
 				&& (vma->vm_flags & VM_SHARED)));
 	/*
@@ -6730,7 +6730,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_
 		goto out_release_unlock;
 
 	if (folio_in_pagecache)
-		page_dup_file_rmap(&folio->page, true);
+		hugetlb_add_file_rmap(folio);
 	else
 		hugetlb_add_new_anon_rmap(folio, dst_vma, dst_addr);
 
--- a/mm/migrate.c~mm-rmap-introduce-and-use-hugetlb_add_file_rmap
+++ a/mm/migrate.c
@@ -252,7 +252,7 @@ static bool remove_migration_pte(struct
 				hugetlb_add_anon_rmap(folio, vma, pvmw.address,
 						      rmap_flags);
 			else
-				page_dup_file_rmap(new, true);
+				hugetlb_add_file_rmap(folio);
 			set_huge_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte,
 					psize);
 		} else
--- a/mm/rmap.c~mm-rmap-introduce-and-use-hugetlb_add_file_rmap
+++ a/mm/rmap.c
@@ -1395,6 +1395,7 @@ void folio_add_file_rmap_range(struct fo
 	unsigned int nr_pmdmapped = 0, first;
 	int nr = 0;
 
+	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
 	VM_WARN_ON_FOLIO(compound && !folio_test_pmd_mappable(folio), folio);
 
 	/* Is page being mapped by PTE? Is this its first map to be added? */
_

Patches currently in -mm which might be from david@redhat.com 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