Received-SPF: pass (google.com: domain of linux-kernel+bounces-65949-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org,
	David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Wilcox <willy@infradead.org>,
	Ryan Roberts <ryan.roberts@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Yin Fengwei <fengwei.yin@intel.com>,
	Michal Hocko <mhocko@suse.com>,
	Will Deacon <will@kernel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Nick Piggin <npiggin@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-arch@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org
Subject: [PATCH v3 03/10] mm/memory: further separate anon and pagecache folio handling in zap_present_pte()
Date: Wed, 14 Feb 2024 21:44:28 +0100
Message-ID: <20240214204435.167852-4-david@redhat.com>
In-Reply-To: <20240214204435.167852-1-david@redhat.com>
References: <20240214204435.167852-1-david@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

We don't need up-to-date accessed-dirty information for anon folios and can
simply work with the ptent we already have. Also, we know the RSS counter
we want to update.

We can safely move arch_check_zapped_pte() + tlb_remove_tlb_entry() +
zap_install_uffd_wp_if_needed() after updating the folio and RSS.

While at it, only call zap_install_uffd_wp_if_needed() if there is even
any chance that pte_install_uffd_wp_if_needed() would do *something*.
That is, just don't bother if uffd-wp does not apply.

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/memory.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 4da6923709b2..7a3ebb6e5909 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1552,12 +1552,9 @@ static inline void zap_present_pte(struct mmu_gather *tlb,
 	folio = page_folio(page);
 	if (unlikely(!should_zap_folio(details, folio)))
 		return;
-	ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
-	arch_check_zapped_pte(vma, ptent);
-	tlb_remove_tlb_entry(tlb, pte, addr);
-	zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
 
 	if (!folio_test_anon(folio)) {
+		ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
 		if (pte_dirty(ptent)) {
 			folio_mark_dirty(folio);
 			if (tlb_delay_rmap(tlb)) {
@@ -1567,8 +1564,17 @@ static inline void zap_present_pte(struct mmu_gather *tlb,
 		}
 		if (pte_young(ptent) && likely(vma_has_recency(vma)))
 			folio_mark_accessed(folio);
+		rss[mm_counter(folio)]--;
+	} else {
+		/* We don't need up-to-date accessed/dirty bits. */
+		ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
+		rss[MM_ANONPAGES]--;
 	}
-	rss[mm_counter(folio)]--;
+	arch_check_zapped_pte(vma, ptent);
+	tlb_remove_tlb_entry(tlb, pte, addr);
+	if (unlikely(userfaultfd_pte_wp(vma, ptent)))
+		zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
+
 	if (!delay_rmap) {
 		folio_remove_rmap_pte(folio, page, vma);
 		if (unlikely(page_mapcount(page) < 0))
-- 
2.43.0