linux-kernel - [PATCH v2 06/19] mm/pagewalk: Check pfnmap for folio_walk

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Message-ID: <20240826204353.2228736-7-peterx@redhat.com>
Date: Mon, 26 Aug 2024 16:43:40 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: Gavin Shan <gshan@...hat.com>,
	Catalin Marinas <catalin.marinas@....com>,
	x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alistair Popple <apopple@...dia.com>,
	kvm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Sean Christopherson <seanjc@...gle.com>,
	peterx@...hat.com,
	Oscar Salvador <osalvador@...e.de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Borislav Petkov <bp@...en8.de>,
	Zi Yan <ziy@...dia.com>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Yan Zhao <yan.y.zhao@...el.com>,
	Will Deacon <will@...nel.org>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Alex Williamson <alex.williamson@...hat.com>
Subject: [PATCH v2 06/19] mm/pagewalk: Check pfnmap for folio_walk_start()

Teach folio_walk_start() to recognize special pmd/pud mappings, and fail
them properly as it means there's no folio backing them.

Cc: David Hildenbrand <david@...hat.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/pagewalk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index cd79fb3b89e5..12be5222d70e 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -753,7 +753,7 @@ struct folio *folio_walk_start(struct folio_walk *fw,
 		fw->pudp = pudp;
 		fw->pud = pud;
 
-		if (!pud_present(pud) || pud_devmap(pud)) {
+		if (!pud_present(pud) || pud_devmap(pud) || pud_special(pud)) {
 			spin_unlock(ptl);
 			goto not_found;
 		} else if (!pud_leaf(pud)) {
@@ -783,7 +783,7 @@ struct folio *folio_walk_start(struct folio_walk *fw,
 		fw->pmdp = pmdp;
 		fw->pmd = pmd;
 
-		if (pmd_none(pmd)) {
+		if (pmd_none(pmd) || pmd_special(pmd)) {
 			spin_unlock(ptl);
 			goto not_found;
 		} else if (!pmd_leaf(pmd)) {
-- 
2.45.0