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a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=vUbySO9Y5rIA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=Uf9Hg8gT9vsuyMyUGiQA:9 a=CjuIK1q_8ugA:10 cc=ntf awl=host:12109 X-Proofpoint-ORIG-GUID: Dt17ORmz0vEVPQfGY_zCDNIdOd-I_edB X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTA4MDA3MCBTYWx0ZWRfX8GTaHF4JRU8o QIAGSCCCWvRJ85oJCjEp62wi+bBym/IzSLUxIgNZCDZ6AR82PSDHsj+aW6hrDDIccMrhkuFoBnJ th0J54wHAdO1RlQvFbWqUbqn35y3Gv5h2XSHZ6rbjaznNTwup7TYmxXz+a11S8ZLdSIx5rOr1Kh ifzDH2k0qWPFID6zBeoUaVB+NBJuZoVXapgcvQsDJdeI0S2mpKuAQsTVctBvD7x9y6y2sLFf4+S b9OhsOopFp59gn49bYi2pHd42F8G4s+nJSaatWuwgek1nW6RpP/Xn3Vmw9ihHaJdvrprq8/DBZE gF6TV8dlW8UMkI1JNsFDtqce38rL3tFER1XG284KmqNV7b4Ru9E5P8ES3oyO7E2T2eg7z60ttDY jvdAHFpPy3B0+ozP8bFuAHcv+UzvJU/EjwaQ2wDb5go2Yxvw1qkorb5BL3vzUQtqGMneKMeRTVt tUHEe7tlVlYFollif+CL/3gSr6QfF691WdrTnx28= On Thu, Jan 08, 2026 at 05:52:27PM +0800, Hao Li wrote: > On Thu, Jan 08, 2026 at 05:41:00PM +0900, Harry Yoo wrote: > > On Thu, Jan 08, 2026 at 01:52:09PM +0800, Hao Li wrote: > > > On Mon, Jan 05, 2026 at 05:02:30PM +0900, Harry Yoo wrote: > > > > When a cache has high s->align value and s->object_size is not aligned > > > > to it, each object ends up with some unused space because of alignment. > > > > If this wasted space is big enough, we can use it to store the > > > > slabobj_ext metadata instead of wasting it. > > > > > > Hi, Harry, > > > > Hi Hao, > > > > > When we save obj_ext in s->size space, it seems that slab_ksize() might > > > be missing the corresponding handling. > > > > Oops. > > > > > It still returns s->size, which could cause callers of slab_ksize() > > > to see unexpected data (i.e. obj_ext), or even overwrite the obj_ext data. > > > > Yes indeed. > > Great point, thanks! > > > > I'll fix it by checking if the slab has obj_exts within the object > > layout and returning s->object_size if so. > > Makes sense - I think there's one more nuance worth capturing. > slab_ksize() seems to compute the maximum safe size by applying layout > constraints from most-restrictive to least-restrictive: > redzones/poison/KASAN clamp it to object_size, tail metadata > (SLAB_TYPESAFE_BY_RCU / SLAB_STORE_USER) clamps it to inuse, and only > when nothing metadata lives does it return s->size. Hmm, you're right. s->object_size is more restrictive than it should be. > With that ordering in mind, SLAB_OBJ_EXT_IN_OBJ should behave like > another "tail metadata" cap: put the check right before `return s->size`, > and if it's set, return s->inuse instead. Curious what you think. Good point, and that will work. Will do. Thanks! -- Cheers, Harry / Hyeonggon