[PATCH 5.4 and earlier only] mm: Fix '.data.once' orphan section warning

From: Nathan Chancellor <nathan@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sasha Levin <sashal@kernel.org>
Cc: Hugh Dickins <hughd@google.com>,
	llvm@lists.linux.dev, stable@vger.kernel.org,
	Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH 5.4 and earlier only] mm: Fix '.data.once' orphan section warning
Date: Mon, 28 Nov 2022 15:53:46 -0700	[thread overview]
Message-ID: <20221128225345.9383-1-nathan@kernel.org> (raw)

Portions of upstream commit a4055888629b ("mm/memcg: warning on !memcg
after readahead page charged") were backported as commit cfe575954ddd
("mm: add VM_WARN_ON_ONCE_PAGE() macro"). Unfortunately, the backport
did not account for the lack of commit 33def8498fdd ("treewide: Convert
macro and uses of __section(foo) to __section("foo")") in kernels prior
to 5.10, resulting in the following orphan section warnings on PowerPC
clang builds with CONFIG_DEBUG_VM=y:

  powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
  powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'
  powerpc64le-linux-gnu-ld: warning: orphan section `".data.once"' from `mm/huge_memory.o' being placed in section `".data.once"'

This is a difference between how clang and gcc handle macro
stringification, which was resolved for the kernel by not stringifying
the argument to the __section() macro. Since that change was deemed not
suitable for the stable kernels by commit 59f89518f510 ("once: fix
section mismatch on clang builds"), do that same thing as that change
and remove the quotes from the argument to __section().

Fixes: cfe575954ddd ("mm: add VM_WARN_ON_ONCE_PAGE() macro")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---

As far as I can tell, this should be applied to 5.4 and earlier. It
should apply cleanly but let me know if not.

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

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 5d0767cb424a..4ed52879ce55 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -38,7 +38,7 @@ void dump_mm(const struct mm_struct *mm);
 		}							\
 	} while (0)
 #define VM_WARN_ON_ONCE_PAGE(cond, page)	({			\
-	static bool __section(".data.once") __warned;			\
+	static bool __section(.data.once) __warned;			\
 	int __ret_warn_once = !!(cond);					\
 									\
 	if (unlikely(__ret_warn_once && !__warned)) {			\

base-commit: 4d2a309b5c28a2edc0900542d22fec3a5a22243b
-- 
2.38.1

