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09:30, Harry Yoo wrote: > > On Mon, Jan 26, 2026 at 08:36:16AM +0100, Vlastimil Babka wrote: > > /* > > * Calculate the allocation size for slabobj_ext array. > > * > > * When memory allocation profiling is enabled, the obj_exts array > > * could be allocated from the same slab it's being allocated for. > > * This would prevent the slab from ever being freed because it would > > * always contain at least one allocated object (its own obj_exts array). > > * > > * To avoid this, increase the allocation size when we detect the array > > * would come from the same cache, forcing it to use a different cache. > > */ > > static inline size_t obj_exts_alloc_size(struct kmem_cache *s, > > struct slab *slab, gfp_t gfp) > > { > > size_t sz = sizeof(struct slabobj_ext) * slab->objects; > > struct kmem_cache *obj_exts_cache; > > > > /* > > * slabobj_ext array for KMALLOC_CGROUP allocations > > * are served from KMALLOC_NORMAL caches. > > */ > > if (!mem_alloc_profiling_enabled()) > > return sz; > > > > if (sz > KMALLOC_MAX_CACHE_SIZE) > > return sz; > > > > if (!is_kmalloc_normal(s)) > > return sz; > > > > obj_exts_cache = kmalloc_slab(sz, NULL, gfp, 0); > > /* > > * Random kmalloc caches have multiple caches per size, and the cache > > Maybe start with something like "We can't simply compare s with > obj_exts_cache, because..." > > > * is selected by the caller address. Since caller address may differ > > * between kmalloc_slab() and actual allocation, bump size when both > > * are normal kmalloc caches of same size. > > As we don't test the other for normal kmalloc(), anymore this now reads as > if we forgot to. Ok, something like this: "We can't simply compare s with obj_exts_cache, because random kmalloc caches have multiple caches per size, selected by caller address. Since caller address may differ between kmalloc_slab() and actual allocation, bump size when sizes are equal." > > */ > > if (s->size == obj_exts_cache->size) > > return s->object_size + 1; > > Why switch to size from object_size for the checks? I'd be worried that due > to debugging etc this can yield wrong results? Oops, sorry. copied from wrong version of the patch. Yeah I initially compared size and then switched to object_size for the reason you mentioned. > > > > return sz; > > } -- Cheers, Harry / Hyeonggon