[PATCH v3 1/4] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap()

From: Ryan Roberts <ryan.roberts@arm.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Yin Fengwei <fengwei.yin@intel.com>,
	David Hildenbrand <david@redhat.com>, Yu Zhao <yuzhao@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Yang Shi <shy828301@gmail.com>,
	"Huang, Ying" <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
	Luis Chamberlain <mcgrof@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 1/4] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap()
Date: Fri, 14 Jul 2023 17:17:30 +0100	[thread overview]
Message-ID: <20230714161733.4144503-1-ryan.roberts@arm.com> (raw)
In-Reply-To: <20230714160407.4142030-1-ryan.roberts@arm.com>

In preparation for FLEXIBLE_THP support, improve
folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
passed to it. In this case, all contained pages are accounted using the
order-0 folio (or base page) scheme.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
---
 mm/rmap.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 0c0d8857dfce..f293d072368a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1278,31 +1278,45 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
  * This means the inc-and-test can be bypassed.
  * The folio does not have to be locked.
  *
- * If the folio is large, it is accounted as a THP.  As the folio
+ * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
  * is new, it's assumed to be mapped exclusively by a single process.
  */
 void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
 		unsigned long address)
 {
-	int nr;
+	int nr = folio_nr_pages(folio);

-	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+	VM_BUG_ON_VMA(address < vma->vm_start ||
+			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
 	__folio_set_swapbacked(folio);

-	if (likely(!folio_test_pmd_mappable(folio))) {
+	if (!folio_test_large(folio)) {
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_mapcount, 0);
-		nr = 1;
+		__page_set_anon_rmap(folio, &folio->page, vma, address, 1);
+	} else if (!folio_test_pmd_mappable(folio)) {
+		int i;
+
+		for (i = 0; i < nr; i++) {
+			struct page *page = folio_page(folio, i);
+
+			/* increment count (starts at -1) */
+			atomic_set(&page->_mapcount, 0);
+			__page_set_anon_rmap(folio, page, vma,
+					address + (i << PAGE_SHIFT), 1);
+		}
+
+		/* increment count (starts at 0) */
+		atomic_set(&folio->_nr_pages_mapped, nr);
 	} else {
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_entire_mapcount, 0);
 		atomic_set(&folio->_nr_pages_mapped, COMPOUND_MAPPED);
-		nr = folio_nr_pages(folio);
+		__page_set_anon_rmap(folio, &folio->page, vma, address, 1);
 		__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
 	}

 	__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
-	__page_set_anon_rmap(folio, &folio->page, vma, address, 1);
 }

 /**
--
2.25.1


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