mm/slab: drop the OBJEXTS_NOSPIN_ALLOC flag from enum objext_flags

OBJEXTS_NOSPIN_ALLOC was used to remember whether a slabobj_ext vector
was allocated via kmalloc_nolock(), so that free_slab_obj_exts() could
call kfree_nolock() instead of kfree().

Now that kfree() supports freeing kmalloc_nolock() objects, this flag is
no longer needed. Instead, pass the allow_spin parameter down to
free_slab_obj_exts() to determine whether kfree_nolock() or kfree()
should be called in the free path, and free one bit in
enum objext_flags.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Hao Li <hao.li@linux.dev>
Link: https://patch.msgid.link/20260210044642.139482-3-harry.yoo@oracle.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0651865a4564fab9feb5c1d1aa24bd9543826cbe..bb789ec4a2a289611dd725d10f0dbc02107f6c89 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -359,8 +359,7 @@ enum objext_flags {
         * MEMCG_DATA_OBJEXTS.
         */
        OBJEXTS_ALLOC_FAIL = __OBJEXTS_ALLOC_FAIL,
-       /* slabobj_ext vector allocated with kmalloc_nolock() */
-       OBJEXTS_NOSPIN_ALLOC = __FIRST_OBJEXT_FLAG,
+       __OBJEXTS_FLAG_UNUSED = __FIRST_OBJEXT_FLAG,
        /* 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 3f64a6b94571acdd47669aa431466573eba76cfa..18c30872d1962ffb97a0ad9b9f27c56c0bfa2d44 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2190,8 +2190,6 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
                        virt_to_slab(vec)->slab_cache == s);
 
        new_exts = (unsigned long)vec;
-       if (unlikely(!allow_spin))
-               new_exts |= OBJEXTS_NOSPIN_ALLOC;
 #ifdef CONFIG_MEMCG
        new_exts |= MEMCG_DATA_OBJEXTS;
 #endif
@@ -2229,7 +2227,7 @@ retry:
        return 0;
 }
 
-static inline void free_slab_obj_exts(struct slab *slab)
+static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)
 {
        struct slabobj_ext *obj_exts;
 
@@ -2257,10 +2255,10 @@ static inline void free_slab_obj_exts(struct slab *slab)
         * the extension for obj_exts is expected to be NULL.
         */
        mark_objexts_empty(obj_exts);
-       if (unlikely(READ_ONCE(slab->obj_exts) & OBJEXTS_NOSPIN_ALLOC))
-               kfree_nolock(obj_exts);
-       else
+       if (allow_spin)
                kfree(obj_exts);
+       else
+               kfree_nolock(obj_exts);
        slab->obj_exts = 0;
 }
 
@@ -2324,7 +2322,7 @@ static int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
        return 0;
 }
 
-static inline void free_slab_obj_exts(struct slab *slab)
+static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin)
 {
 }
 
@@ -3404,14 +3402,14 @@ static __always_inline void account_slab(struct slab *slab, int order,
 }
 
 static __always_inline void unaccount_slab(struct slab *slab, int order,
-                                          struct kmem_cache *s)
+                                          struct kmem_cache *s, bool allow_spin)
 {
        /*
         * The slab object extensions should now be freed regardless of
         * whether mem_alloc_profiling_enabled() or not because profiling
         * might have been disabled after slab->obj_exts got allocated.
         */
-       free_slab_obj_exts(slab);
+       free_slab_obj_exts(slab, allow_spin);
 
        mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),
                            -(PAGE_SIZE << order));
@@ -3515,7 +3513,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab, bool allow_spin
        page->mapping = NULL;
        __ClearPageSlab(page);
        mm_account_reclaimed_pages(pages);
-       unaccount_slab(slab, order, s);
+       unaccount_slab(slab, order, s, allow_spin);
        if (allow_spin)
                free_frozen_pages(page, order);
        else