linux-kernel - [PATCH v2 4/7] mm/gup: remove gup_fast_pgd_leaf() and clean up the relevant codes

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Message-ID: <20250331081327.256412-5-bhe@redhat.com>
Date: Mon, 31 Mar 2025 16:13:24 +0800
From: Baoquan He <bhe@...hat.com>
To: akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	yanjun.zhu@...ux.dev,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH v2 4/7] mm/gup: remove gup_fast_pgd_leaf() and clean up the relevant codes

In the current kernel, only pud huge page is supported in some
architectures. P4d and pgd huge pages haven't been supported yet.
And in mm/gup.c, there's no pgd huge page handling in the
follow_page_mask() code path. Hence it doesn't make sense to have
gup_fast_pgd_leaf() in gup_fast code path.

Here remove gup_fast_pgd_leaf() and clean up the relevant codes.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/gup.c | 49 +++----------------------------------------------
 1 file changed, 3 insertions(+), 46 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index a15317cf6641..58cdc5605a4a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3168,46 +3168,6 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
 	return 1;
 }
 
-static int gup_fast_pgd_leaf(pgd_t orig, pgd_t *pgdp, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
-{
-	int refs;
-	struct page *page;
-	struct folio *folio;
-
-	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
-		return 0;
-
-	BUILD_BUG_ON(pgd_devmap(orig));
-
-	page = pgd_page(orig);
-	refs = record_subpages(page, PGDIR_SIZE, addr, end, pages + *nr);
-
-	folio = try_grab_folio_fast(page, refs, flags);
-	if (!folio)
-		return 0;
-
-	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
-		gup_put_folio(folio, refs, flags);
-		return 0;
-	}
-
-	if (!pgd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
-		gup_put_folio(folio, refs, flags);
-		return 0;
-	}
-
-	if (!gup_fast_folio_allowed(folio, flags)) {
-		gup_put_folio(folio, refs, flags);
-		return 0;
-	}
-
-	*nr += refs;
-	folio_set_referenced(folio);
-	return 1;
-}
-
 static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
 		unsigned long end, unsigned int flags, struct page **pages,
 		int *nr)
@@ -3302,12 +3262,9 @@ static void gup_fast_pgd_range(unsigned long addr, unsigned long end,
 		next = pgd_addr_end(addr, end);
 		if (pgd_none(pgd))
 			return;
-		if (unlikely(pgd_leaf(pgd))) {
-			if (!gup_fast_pgd_leaf(pgd, pgdp, addr, next, flags,
-					       pages, nr))
-				return;
-		} else if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
-					       pages, nr))
+		BUILD_BUG_ON(pgd_leaf(pgd));
+		if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
+					pages, nr))
 			return;
 	} while (pgdp++, addr = next, addr != end);
 }
-- 
2.41.0