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DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.cz:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On 12/6/24 23:52, Suren Baghdasaryan wrote: > There is no real reason to prevent freeptr_offset usage when a slab > cache has a ctor. The only real limitation is that any field unioned > with the free pointer and initialized by ctor will be overwritten since > free pointer is set after @ctor invocation. Document this limitation > and enable usage of freeptr_offset with ctor. > > Suggested-by: Vlastimil Babka > Signed-off-by: Suren Baghdasaryan Reviewed-by: Vlastimil Babka > --- > include/linux/slab.h | 5 +++-- > mm/slub.c | 2 +- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 681b685b6c4e..6bad744bef5e 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -305,8 +305,9 @@ struct kmem_cache_args { > * Using %0 as a value for @freeptr_offset is valid. If @freeptr_offset > * is specified, %use_freeptr_offset must be set %true. > * > - * Note that @ctor currently isn't supported with custom free pointers > - * as a @ctor requires an external free pointer. > + * Note that fields unioned with free pointer cannot be initialized by > + * @ctor since free pointer is set after @ctor invocation, so those > + * values will be overwritten. > */ > unsigned int freeptr_offset; > /** > diff --git a/mm/slub.c b/mm/slub.c > index 870a1d95521d..f62c829b7b6b 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5462,7 +5462,7 @@ 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)))) { > /*