linux-kernel - [PATCH 20/75] mm/gup: Convert gup_pte

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Date:   Fri,  4 Feb 2022 19:57:57 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        William Kucharski <william.kucharski@...cle.com>
Subject: [PATCH 20/75] mm/gup: Convert gup_pte_range() to use a folio

We still call try_grab_folio() once per PTE; a future patch could
optimise to just adjust the reference count for each page within
the folio.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: William Kucharski <william.kucharski@...cle.com>
---
 mm/gup.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 00227b2cb1cf..44281350db1a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2252,7 +2252,8 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 	ptem = ptep = pte_offset_map(&pmd, addr);
 	do {
 		pte_t pte = ptep_get_lockless(ptep);
-		struct page *head, *page;
+		struct page *page;
+		struct folio *folio;
 
 		/*
 		 * Similar to the PMD case below, NUMA hinting must take slow
@@ -2279,22 +2280,20 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 
-		head = try_grab_compound_head(page, 1, flags);
-		if (!head)
+		folio = try_grab_folio(page, 1, flags);
+		if (!folio)
 			goto pte_unmap;
 
 		if (unlikely(page_is_secretmem(page))) {
-			put_compound_head(head, 1, flags);
+			gup_put_folio(folio, 1, flags);
 			goto pte_unmap;
 		}
 
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
-			put_compound_head(head, 1, flags);
+			gup_put_folio(folio, 1, flags);
 			goto pte_unmap;
 		}
 
-		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-
 		/*
 		 * We need to make the page accessible if and only if we are
 		 * going to access its content (the FOLL_PIN case).  Please
@@ -2308,10 +2307,9 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 				goto pte_unmap;
 			}
 		}
-		SetPageReferenced(page);
+		folio_set_referenced(folio);
 		pages[*nr] = page;
 		(*nr)++;
-
 	} while (ptep++, addr += PAGE_SIZE, addr != end);
 
 	ret = 1;
-- 
2.34.1