linux-kernel - [PATCH RFC 1/6] mm/treewide: Remove pgd

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Message-ID: <20240717220219.3743374-2-peterx@redhat.com>
Date: Wed, 17 Jul 2024 18:02:14 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: Vlastimil Babka <vbabka@...e.cz>,
	peterx@...hat.com,
	David Hildenbrand <david@...hat.com>,
	Oscar Salvador <osalvador@...e.de>,
	linux-s390@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Michal Hocko <mhocko@...nel.org>,
	linux-riscv@...ts.infradead.org,
	sparclinux@...r.kernel.org,
	Alex Williamson <alex.williamson@...hat.com>,
	Jason Gunthorpe <jgg@...dia.com>,
	x86@...nel.org,
	Alistair Popple <apopple@...dia.com>,
	linuxppc-dev@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org,
	Ryan Roberts <ryan.roberts@....com>,
	Hugh Dickins <hughd@...gle.com>,
	Axel Rasmussen <axelrasmussen@...gle.com>
Subject: [PATCH RFC 1/6] mm/treewide: Remove pgd_devmap()

It's always 0 for all archs, and there's no sign to even support p4d entry
in the near future.  Remove it until it's needed for real.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/arm64/include/asm/pgtable.h             | 5 -----
 arch/powerpc/include/asm/book3s/64/pgtable.h | 5 -----
 arch/x86/include/asm/pgtable.h               | 5 -----
 include/linux/pgtable.h                      | 4 ----
 mm/gup.c                                     | 2 --
 5 files changed, 21 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index f8efbc128446..5d5d1b18b837 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1119,11 +1119,6 @@ static inline int pud_devmap(pud_t pud)
 {
 	return 0;
 }
-
-static inline int pgd_devmap(pgd_t pgd)
-{
-	return 0;
-}
 #endif
 
 #ifdef CONFIG_PAGE_TABLE_CHECK
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 5da92ba68a45..051b1b6d729c 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1431,11 +1431,6 @@ static inline int pud_devmap(pud_t pud)
 {
 	return pte_devmap(pud_pte(pud));
 }
-
-static inline int pgd_devmap(pgd_t pgd)
-{
-	return 0;
-}
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 701593c53f3b..0d234f48ceeb 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -311,11 +311,6 @@ static inline int pud_devmap(pud_t pud)
 	return 0;
 }
 #endif
-
-static inline int pgd_devmap(pgd_t pgd)
-{
-	return 0;
-}
 #endif
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2289e9f7aa1b..0a904300ac90 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1626,10 +1626,6 @@ static inline int pud_devmap(pud_t pud)
 {
 	return 0;
 }
-static inline int pgd_devmap(pgd_t pgd)
-{
-	return 0;
-}
 #endif
 
 #if !defined(CONFIG_TRANSPARENT_HUGEPAGE) || \
diff --git a/mm/gup.c b/mm/gup.c
index 54d0dc3831fb..b023bcd38235 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3149,8 +3149,6 @@ static int gup_fast_pgd_leaf(pgd_t orig, pgd_t *pgdp, unsigned long addr,
 	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);
 
-- 
2.45.0