diff options
| -rw-r--r-- | include/linux/slab.h | 30 | ||||
| -rw-r--r-- | mm/slab_common.c | 2 | ||||
| -rw-r--r-- | mm/slub.c | 6 |
3 files changed, 21 insertions, 17 deletions
diff --git a/include/linux/slab.h b/include/linux/slab.h index 2482992248dc..4554c04a9bd7 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -299,24 +299,26 @@ struct kmem_cache_args { unsigned int usersize; /** * @freeptr_offset: Custom offset for the free pointer - * in &SLAB_TYPESAFE_BY_RCU caches + * in caches with &SLAB_TYPESAFE_BY_RCU or @ctor * - * By default &SLAB_TYPESAFE_BY_RCU caches place the free pointer - * outside of the object. This might cause the object to grow in size. - * Cache creators that have a reason to avoid this can specify a custom - * free pointer offset in their struct where the free pointer will be - * placed. + * By default, &SLAB_TYPESAFE_BY_RCU and @ctor caches place the free + * pointer outside of the object. This might cause the object to grow + * in size. Cache creators that have a reason to avoid this can specify + * a custom free pointer offset in their data structure where the free + * pointer will be placed. * - * Note that placing the free pointer inside the object requires the - * caller to ensure that no fields are invalidated that are required to - * guard against object recycling (See &SLAB_TYPESAFE_BY_RCU for - * details). + * For caches with &SLAB_TYPESAFE_BY_RCU, the caller must ensure that + * the free pointer does not overlay fields required to guard against + * object recycling (See &SLAB_TYPESAFE_BY_RCU for details). * - * Using %0 as a value for @freeptr_offset is valid. If @freeptr_offset - * is specified, %use_freeptr_offset must be set %true. + * For caches with @ctor, the caller must ensure that the free pointer + * does not overlay fields initialized by the constructor. + * + * Currently, only caches with &SLAB_TYPESAFE_BY_RCU or @ctor + * may specify @freeptr_offset. * - * Note that @ctor currently isn't supported with custom free pointers - * as a @ctor requires an external free pointer. + * Using %0 as a value for @freeptr_offset is valid. If @freeptr_offset + * is specified, @use_freeptr_offset must be set %true. */ unsigned int freeptr_offset; /** diff --git a/mm/slab_common.c b/mm/slab_common.c index b6836f8500b6..027bf64c2e35 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -239,7 +239,7 @@ static struct kmem_cache *create_cache(const char *name, err = -EINVAL; if (args->use_freeptr_offset && (args->freeptr_offset >= object_size || - !(flags & SLAB_TYPESAFE_BY_RCU) || + (!(flags & SLAB_TYPESAFE_BY_RCU) && !args->ctor) || !IS_ALIGNED(args->freeptr_offset, __alignof__(freeptr_t)))) goto out; diff --git a/mm/slub.c b/mm/slub.c index 2c000dddcf74..1b7ed91a2f15 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7998,7 +7998,8 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s) s->inuse = size; if (((flags & SLAB_TYPESAFE_BY_RCU) && !args->use_freeptr_offset) || - (flags & SLAB_POISON) || s->ctor || + (flags & SLAB_POISON) || + (s->ctor && !args->use_freeptr_offset) || ((flags & SLAB_RED_ZONE) && (s->object_size < sizeof(void *) || slub_debug_orig_size(s)))) { /* @@ -8019,7 +8020,8 @@ static int calculate_sizes(struct kmem_cache_args *args, struct kmem_cache *s) */ s->offset = size; size += sizeof(void *); - } else if ((flags & SLAB_TYPESAFE_BY_RCU) && args->use_freeptr_offset) { + } else if (((flags & SLAB_TYPESAFE_BY_RCU) || s->ctor) && + args->use_freeptr_offset) { s->offset = args->freeptr_offset; } else { /* |