+ mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level-fix.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/rmap: always inline __folio_rmap_sanity_checks()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level-fix.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Nathan Chancellor <nathan@kernel.org>
Subject: mm/rmap: always inline __folio_rmap_sanity_checks()
Date: Thu, 14 Aug 2025 13:05:22 -0700

Commit 5e901e249ad1 ("mm/rmap: convert "enum rmap_level" to "enum
pgtable_level"") changed VM_WARN_ON_ONCE, a run time warning, into
BUILD_BUG, a compile time error. After this adjustment, certain builds
with older versions of clang (such as arm64 allmodconfig) started
failing to build with:

  In file included from mm/rmap.c:63:
  In file included from include/linux/ksm.h:14:
  include/linux/rmap.h:440:3: error: call to __compiletime_assert_890 declared with 'error' attribute: BUILD_BUG failed
                  BUILD_BUG();
                  ^
  ...
  <scratch space>:21:1: note: expanded from here
  __compiletime_assert_890
  ^

While __folio_rmap_sanity_checks() is marked 'inline', the compiler may
not always honor it, such as when sanitizers or other instrumentation is
enabled.  If __folio_rmap_sanity_checks() is not inlined, there is no
way the compiler can eliminate the default cause.

Mark __folio_rmap_sanity_checks() as __always_inline to allow the
BUILD_BUG() to work consistently, which clears up the error.

Link: https://lkml.kernel.org/r/20250814-rmap-fix-build_bug-conversion-v1-1-fb7b10a0b362@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rmap.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/rmap.h~mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level-fix
+++ a/include/linux/rmap.h
@@ -394,7 +394,7 @@ typedef int __bitwise rmap_t;
 /* The anonymous (sub)page is exclusive to a single process. */
 #define RMAP_EXCLUSIVE		((__force rmap_t)BIT(0))
 
-static inline void __folio_rmap_sanity_checks(const struct folio *folio,
+static __always_inline void __folio_rmap_sanity_checks(const struct folio *folio,
 		const struct page *page, int nr_pages, enum pgtable_level level)
 {
 	/* hugetlb folios are handled separately. */
_

Patches currently in -mm which might be from nathan@kernel.org are

mm-rmap-convert-enum-rmap_level-to-enum-pgtable_level-fix.patch