linux-kernel - [PATCH v1 3/5] mm/rmap: introduce and use hugetlb_add_file

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Message-ID: <20231128145205.215026-4-david@redhat.com>
Date:   Tue, 28 Nov 2023 15:52:03 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <muchun.song@...ux.dev>
Subject: [PATCH v1 3/5] mm/rmap: introduce and use hugetlb_add_file_rmap()

hugetlb rmap handling differs quite a lot from "ordinary" rmap code, and
we already have dedicated functions for adding anon hugetlb folios and
removing hugetlb folios.

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".

While this is a cleanup, this will also make it easier to change rmap
handling for partially-mappable folios.

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

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/rmap.h | 7 +++++++
 mm/hugetlb.c         | 6 +++---
 mm/migrate.c         | 2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index e8d1dc1d5361..0a81e8420a96 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -208,6 +208,13 @@ 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_add_file_rmap(struct 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)
 {
 	atomic_dec(&folio->_entire_mapcount);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d17bb53b19ff..541a8f38cfdc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5401,7 +5401,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 			 * 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;
@@ -6272,7 +6272,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 	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)));
 	/*
@@ -6723,7 +6723,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 		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);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 4cb849fa0dd2..de9d94b99ab7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -252,7 +252,7 @@ static bool remove_migration_pte(struct folio *folio,
 				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
-- 
2.41.0