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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1760476412; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=axJZtnDZWi6vaVYeCAyW3be+cBc21q2dMi5KM6Ov1x0=; b=P9hWH24o8Wx6LHWvdKijhu1xCOvFjsaC/PBwLdkkPa6OAx9qiRsTFFedEOfwaQYzfpWQNq mXgym1dK/eMLi9IhC3iu2ILRPW0CBHu0KtGL8WoNaQZ9DupifEEUhWcsd0AxnOzDoYbHp9 y0qWQHLvNacRjJtYwdmWQjXSaR4Oa1Y= From: Roman Gushchin To: Hao Ge Cc: Vlastimil Babka , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Shakeel Butt , Michal Hocko , Muchun Song , Suren Baghdasaryan , Harry Yoo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Subject: Re: [PATCH v3] slab: Add check for memcg_data != OBJEXTS_ALLOC_FAIL in folio_memcg_kmem In-Reply-To: <20251014152751.499376-1-hao.ge@linux.dev> (Hao Ge's message of "Tue, 14 Oct 2025 23:27:51 +0800") References: <20251014152751.499376-1-hao.ge@linux.dev> Date: Tue, 14 Oct 2025 14:13:25 -0700 Message-ID: <87y0pddw5m.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Stat-Signature: scgufwe6huzhurxiziktsifhaceijxie X-Rspam-User: X-Rspamd-Queue-Id: DA975180003 X-HE-Tag: 1760476415-825443 X-HE-Meta: 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 4Y+fB/8Y zqDOjkUvmkGFSl4BN1i30zBpfXbJ6kem/nl24WRx9WXvdhJhp7yp6h5zjIzsVtTGtwIfZnvads/PYYqn0hxfqTmWPb0gVzos4SIzKYSTJw+e5AcbmfU9lDsI3oNenHjqX3YYu4rZsdVxdVnHyDSM5MoFK28LJqMaqahEu+0q7c9biy3n5hrmHiAidVT+z31oORN4SRXZFlSgJ9iEH8WlEnBnnOKQjk0+28GlWRaqQ2LbxICcYghN+zAwZh3P8KNJ9Ze3F2Xj26Nod80vmDyQLfPVggmpOnIQ2E53OW8unw/6iDpsraj5eRyNPFg== 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: Hao Ge writes: > From: Hao Ge > > Since OBJEXTS_ALLOC_FAIL and MEMCG_DATA_OBJEXTS currently share > the same bit position, we cannot determine whether memcg_data still > points to the slabobj_ext vector simply by checking > folio->memcg_data & MEMCG_DATA_OBJEXTS. > > If obj_exts allocation failed, slab->obj_exts is set to OBJEXTS_ALLOC_FAIL, > and during the release of the associated folio, the BUG check is triggered > because it was mistakenly assumed that a valid folio->memcg_data > was not cleared before freeing the folio. > > So let's check for memcg_data != OBJEXTS_ALLOC_FAIL in folio_memcg_kmem. > > Fixes: 7612833192d5 ("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") > Suggested-by: Harry Yoo > Signed-off-by: Hao Ge > --- > v3: Simplify the solution, per Harry's suggestion in the v1 comments > Add Suggested-by: Harry Yoo Acked-by: Roman Gushchin Thanks!