[RFC PATCH] mm/slab: Avoid build bug for calls to kmalloc with a large constant

Dave Kleikamp
2024-11-01T20:18:43Z

When boot-time page size is enabled, the test against KMALLOC_MAX_CACHE_SIZE
is no longer optimized out with a constant size, so a build bug may
occur on a path that won't be reached.

Found compiling drivers/net/ethernet/qlogic/qed/qed_sriov.c

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
---

Ryan,

Please consider incorporating this fix or something similar into your
mm patch in the boot-time pages size patches.

include/linux/slab.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9848296ca6ba..a4c7507ab8ec 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -685,7 +685,8 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
if (size <= 1024 * 1024) return 20;
if (size <= 2 * 1024 * 1024) return 21;

- if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant)
+ if (!IS_ENABLED(CONFIG_ARM64_BOOT_TIME_PAGE_SIZE) &&
+ !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant)
BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
else
BUG();
--
2.47.0