linux-kernel - [PATCH 04/11] powerpc: mm: Call ctor/dtor for kernel PTEs

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Message-ID: <20250317141700.3701581-5-kevin.brodsky@arm.com>
Date: Mon, 17 Mar 2025 14:16:53 +0000
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Andreas Larsson <andreas@...sler.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"David S. Miller" <davem@...emloft.net>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Mark Rutland <mark.rutland@....com>,
	Matthew Wilcox <willy@...radead.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Qi Zheng <zhengqi.arch@...edance.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Will Deacon <will@...nel.org>,
	Yang Shi <yang@...amperecomputing.com>,
	linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-csky@...r.kernel.org,
	linux-m68k@...ts.linux-m68k.org,
	linux-openrisc@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	sparclinux@...r.kernel.org
Subject: [PATCH 04/11] powerpc: mm: Call ctor/dtor for kernel PTEs

The generic implementation of pte_{alloc_one,free}_kernel now calls
the [cd]tor, without initialising the ptlock needlessly as
pagetable_pte_ctor() skips it for init_mm.

On powerpc, all functions related to PTE allocation are implemented
by common helpers, which are passed a boolean to differentiate user
from kernel pgtables. This patch aligns the powerpc implementation
with the generic one by calling pagetable_pte_[cd]tor()
unconditionally in those helpers.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/powerpc/mm/pgtable-frag.c | 30 +++++++++++++-----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
index 387e9b1fe12c..77e55eac16e4 100644
--- a/arch/powerpc/mm/pgtable-frag.c
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -56,19 +56,17 @@ static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
 {
 	void *ret = NULL;
 	struct ptdesc *ptdesc;
+	gfp_t gfp = PGALLOC_GFP;
 
-	if (!kernel) {
-		ptdesc = pagetable_alloc(PGALLOC_GFP | __GFP_ACCOUNT, 0);
-		if (!ptdesc)
-			return NULL;
-		if (!pagetable_pte_ctor(mm, ptdesc)) {
-			pagetable_free(ptdesc);
-			return NULL;
-		}
-	} else {
-		ptdesc = pagetable_alloc(PGALLOC_GFP, 0);
-		if (!ptdesc)
-			return NULL;
+	if (!kernel)
+		gfp |= __GFP_ACCOUNT;
+
+	ptdesc = pagetable_alloc(gfp, 0);
+	if (!ptdesc)
+		return NULL;
+	if (!pagetable_pte_ctor(mm, ptdesc)) {
+		pagetable_free(ptdesc);
+		return NULL;
 	}
 
 	atomic_set(&ptdesc->pt_frag_refcount, 1);
@@ -124,12 +122,10 @@ void pte_fragment_free(unsigned long *table, int kernel)
 
 	BUG_ON(atomic_read(&ptdesc->pt_frag_refcount) <= 0);
 	if (atomic_dec_and_test(&ptdesc->pt_frag_refcount)) {
-		if (kernel)
-			pagetable_free(ptdesc);
-		else if (folio_test_clear_active(ptdesc_folio(ptdesc)))
-			call_rcu(&ptdesc->pt_rcu_head, pte_free_now);
-		else
+		if (kernel || !folio_test_clear_active(ptdesc_folio(ptdesc)))
 			pte_free_now(&ptdesc->pt_rcu_head);
+		else
+			call_rcu(&ptdesc->pt_rcu_head, pte_free_now);
 	}
 }
 
-- 
2.47.0