linux-kernel - [PATCH 3/3] fixup! mm/arch: provide pud

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Date: Tue,  2 Apr 2024 21:32:49 -0400
From: peterx@...hat.com
To: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Huacai Chen <chenhuacai@...nel.org>,
	peterx@...hat.com,
	David Hildenbrand <david@...hat.com>,
	Jason Gunthorpe <jgg@...dia.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	WANG Xuerui <kernel@...0n.name>,
	Ryan Roberts <ryan.roberts@....com>,
	loongarch@...ts.linux.dev
Subject: [PATCH 3/3] fixup! mm/arch: provide pud_pfn() fallback

From: Peter Xu <peterx@...hat.com>

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 include/linux/pgtable.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index fa8f92f6e2d7..0f4b2faa1d71 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1882,9 +1882,13 @@ typedef unsigned int pgtbl_mod_mask;
  * code.  Now it happens too for pud_pfn (and can happen for larger
  * mappings too in the future; we're not there yet).  Instead of defining
  * it for all archs (like pmd_pfn), provide a fallback.
+ *
+ * Note that returning 0 here means any arch that didn't define this can
+ * get severely wrong when it hits a real pud leaf.  It's arch's
+ * responsibility to properly define it when a huge pud is possible.
  */
 #ifndef pud_pfn
-#define pud_pfn(x) ({ BUILD_BUG(); 0; })
+#define pud_pfn(x) 0
 #endif
 
 /*
-- 
2.44.0