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Wed, 29 Oct 2025 11:19:37 -0700 (PDT) Message-ID: Date: Wed, 29 Oct 2025 19:19:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH V3 7/7] mm/slab: place slabobj_ext metadata in unused space within s->size To: Harry Yoo , akpm@linux-foundation.org, vbabka@suse.cz Cc: andreyknvl@gmail.com, cl@linux.com, dvyukov@google.com, glider@google.com, hannes@cmpxchg.org, linux-mm@kvack.org, mhocko@kernel.org, muchun.song@linux.dev, rientjes@google.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, surenb@google.com, vincenzo.frascino@arm.com, yeoreum.yun@arm.com, tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251027122847.320924-1-harry.yoo@oracle.com> <20251027122847.320924-8-harry.yoo@oracle.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: <20251027122847.320924-8-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Stat-Signature: e7nxo5qm138c3okmrp8fzit5g5pwdixr X-Rspam-User: X-Rspamd-Queue-Id: 9E6954000C X-HE-Tag: 1761761980-934492 X-HE-Meta: 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 dA16VSs6 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/27/25 1:28 PM, Harry Yoo wrote: > slab->obj_exts |= MEMCG_DATA_OBJEXTS; > slab_set_stride(slab, sizeof(struct slabobj_ext)); > + } else if (obj_exts_in_object(s)) { > + unsigned int offset = obj_exts_offset_in_object(s); > + > + slab->obj_exts = (unsigned long)slab_address(slab); > + slab->obj_exts += s->red_left_pad; > + slab->obj_exts += obj_exts_offset_in_object(s); > + if (IS_ENABLED(CONFIG_MEMCG)) > + slab->obj_exts |= MEMCG_DATA_OBJEXTS; > + slab_set_stride(slab, s->size); > + > + for_each_object(addr, s, slab_address(slab), slab->objects) { > + kasan_unpoison_range(addr + offset, > + sizeof(struct slabobj_ext)); Is this leftover from previous version? Otherwise I don't get why we unpoison this. > + memset(addr + offset, 0, sizeof(struct slabobj_ext)); > + } > } > metadata_access_disable(); > }