[PATCH 39/40] codetag: debug: introduce OBJEXTS_ALLOC_FAIL to mark failed slab_ext allocations

Suren Baghdasaryan
2023-05-01T17:03:41Z

If slabobj_ext vector allocation for a slab object fails and later on it
succeeds for another object in the same slab, the slabobj_ext for the
original object will be NULL and will be flagged in case when
CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled.
Mark failed slabobj_ext vector allocations using a new objext_flags flag
stored in the lower bits of slab->obj_exts. When new allocation succeeds
it marks all tag references in the same slabobj_ext vector as empty to
avoid warnings implemented by CONFIG_MEM_ALLOC_PROFILING_DEBUG checks.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
include/linux/memcontrol.h | 4 +++-
mm/slab_common.c | 27 +++++++++++++++++++++++++--
2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index c7f21b15b540..3eb8975c1462 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -356,8 +356,10 @@ enum page_memcg_data_flags {
#endif /* CONFIG_MEMCG */

enum objext_flags {
+ /* slabobj_ext vector failed to allocate */
+ OBJEXTS_ALLOC_FAIL = __FIRST_OBJEXT_FLAG,
/* the next bit after the last actual flag */
- __NR_OBJEXTS_FLAGS = __FIRST_OBJEXT_FLAG,
+ __NR_OBJEXTS_FLAGS = (__FIRST_OBJEXT_FLAG << 1),
};

#define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 89265f825c43..5b7e096b70a5 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -217,21 +217,44 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
{
unsigned int objects = objs_per_slab(s, slab);
unsigned long obj_exts;
- void *vec;
+ struct slabobj_ext *vec;

gfp &= ~OBJCGS_CLEAR_MASK;
/* Prevent recursive extension vector allocation */
gfp |= __GFP_NO_OBJ_EXT;
vec = kcalloc_node(objects, sizeof(struct slabobj_ext), gfp,
slab_nid(slab));
- if (!vec)
+ if (!vec) {
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+ if (new_slab) {
+ /* Mark vectors which failed to allocate */
+ slab->obj_exts = OBJEXTS_ALLOC_FAIL;
+#ifdef CONFIG_MEMCG
+ slab->obj_exts |= MEMCG_DATA_OBJEXTS;
+#endif
+ }
+#endif
return -ENOMEM;
+ }

obj_exts = (unsigned long)vec;
#ifdef CONFIG_MEMCG
obj_exts |= MEMCG_DATA_OBJEXTS;
#endif
if (new_slab) {
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+ /*
+ * If vector previously failed to allocate then we have live
+ * objects with no tag reference. Mark all references in this
+ * vector as empty to avoid warnings later on.
+ */
+ if (slab->obj_exts & OBJEXTS_ALLOC_FAIL) {
+ unsigned int i;
+
+ for (i = 0; i < objects; i++)
+ set_codetag_empty(&vec[i].ref);
+ }
+#endif
/*
* If the slab is brand new and nobody can yet access its
* obj_exts, no synchronization is required and obj_exts can
--
2.40.1.495.gc816e09b53d-goog