From: Alexei Starovoitov <ast@xxxxxxxxxx>
Since the combination of valid upper bits in slab->obj_exts with
OBJEXTS_ALLOC_FAIL bit can never happen,
use OBJEXTS_ALLOC_FAIL == (1ull << 0) as a magic sentinel
instead of (1ull << 2) to free up bit 2.
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/memcontrol.h | 10 ++++++++--
mm/slub.c | 2 +-
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 785173aa0739..d254c0b96d0d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -341,17 +341,23 @@ enum page_memcg_data_flags {
__NR_MEMCG_DATA_FLAGS = (1UL << 2),
};
+#define __OBJEXTS_ALLOC_FAIL MEMCG_DATA_OBJEXTS
#define __FIRST_OBJEXT_FLAG __NR_MEMCG_DATA_FLAGS
#else /* CONFIG_MEMCG */
+#define __OBJEXTS_ALLOC_FAIL (1UL << 0)
#define __FIRST_OBJEXT_FLAG (1UL << 0)
#endif /* CONFIG_MEMCG */
enum objext_flags {
- /* slabobj_ext vector failed to allocate */
- OBJEXTS_ALLOC_FAIL = __FIRST_OBJEXT_FLAG,
+ /*
+ * Use bit 0 with zero other bits to signal that slabobj_ext vector
+ * failed to allocate. The same bit 0 with valid upper bits means
+ * MEMCG_DATA_OBJEXTS.
+ */
+ OBJEXTS_ALLOC_FAIL = __OBJEXTS_ALLOC_FAIL,
/* the next bit after the last actual flag */
__NR_OBJEXTS_FLAGS = (__FIRST_OBJEXT_FLAG << 1),
};
diff --git a/mm/slub.c b/mm/slub.c
index 212161dc0f29..61841ba72120 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2051,7 +2051,7 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts,
* objects with no tag reference. Mark all references in this
* vector as empty to avoid warnings later on.
*/
- if (obj_exts & OBJEXTS_ALLOC_FAIL) {
+ if (obj_exts == OBJEXTS_ALLOC_FAIL) {
unsigned int i;
for (i = 0; i < objects; i++)
--
2.47.3
