linux-kernel - [PATCH v2 11/20] mm/rmap: use folio_large_nr

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Message-ID: <20250224165603.1434404-12-david@redhat.com>
Date: Mon, 24 Feb 2025 17:55:53 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-doc@...r.kernel.org,
	cgroups@...r.kernel.org,
	linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	linux-api@...r.kernel.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	Tejun Heo <tj@...nel.org>,
	Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	Jonathan Corbet <corbet@....net>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Muchun Song <muchun.song@...ux.dev>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Jann Horn <jannh@...gle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH v2 11/20] mm/rmap: use folio_large_nr_pages() in add/remove functions

Let's just use the "large" variant in code where we are sure that we
have a large folio in our hands: this way we are sure that we don't
perform any unnecessary "large" checks.

While at it, convert the VM_BUG_ON_VMA to a VM_WARN_ON_ONCE.

Maybe in the future there will not be a difference in that regard
between large and small folios; in that case, unifying the handling again
will be easy. E.g., folio_large_nr_pages() will simply translate to
folio_nr_pages() until we replace all instances.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/rmap.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 08846b7eced60..c9922928616ee 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1274,7 +1274,7 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
 		if (first) {
 			nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
 			if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
-				nr_pages = folio_nr_pages(folio);
+				nr_pages = folio_large_nr_pages(folio);
 				/*
 				 * We only track PMD mappings of PMD-sized
 				 * folios separately.
@@ -1522,14 +1522,11 @@ void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
 void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 		unsigned long address, rmap_t flags)
 {
-	const int nr = folio_nr_pages(folio);
 	const bool exclusive = flags & RMAP_EXCLUSIVE;
-	int nr_pmdmapped = 0;
+	int nr = 1, nr_pmdmapped = 0;
 
 	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
 	VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
-	VM_BUG_ON_VMA(address < vma->vm_start ||
-			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
 
 	/*
 	 * VM_DROPPABLE mappings don't swap; instead they're just dropped when
@@ -1547,6 +1544,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 	} else if (!folio_test_pmd_mappable(folio)) {
 		int i;
 
+		nr = folio_large_nr_pages(folio);
 		for (i = 0; i < nr; i++) {
 			struct page *page = folio_page(folio, i);
 
@@ -1559,6 +1557,7 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 		folio_set_large_mapcount(folio, nr, vma);
 		atomic_set(&folio->_nr_pages_mapped, nr);
 	} else {
+		nr = folio_large_nr_pages(folio);
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_entire_mapcount, 0);
 		folio_set_large_mapcount(folio, 1, vma);
@@ -1568,6 +1567,9 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 		nr_pmdmapped = nr;
 	}
 
+	VM_WARN_ON_ONCE(address < vma->vm_start ||
+			address + (nr << PAGE_SHIFT) > vma->vm_end);
+
 	__folio_mod_stat(folio, nr, nr_pmdmapped);
 	mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1);
 }
@@ -1681,7 +1683,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
 		if (last) {
 			nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
 			if (likely(nr < ENTIRELY_MAPPED)) {
-				nr_pages = folio_nr_pages(folio);
+				nr_pages = folio_large_nr_pages(folio);
 				if (level == RMAP_LEVEL_PMD)
 					nr_pmdmapped = nr_pages;
 				nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
-- 
2.48.1