From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 96969314A8E for ; Tue, 14 Oct 2025 14:09:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760450949; cv=none; b=M5QGO0sNOv4qM8v3X7CAVCaMK1WMcUZV97N1+wcHnA43Fhze90OR+HEQ0EG4uw58neAMpgBvkkWJo7YcA3XuTxWZbM9aoJGU1PljWj3VldOzPNMhM69epro11I8R6TddhvrN631Hv/oQxFvki1+YrVASD21gHcILLBexPiqFtaw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760450949; c=relaxed/simple; bh=PBU4fhmS7xNaU4hsexHHxQh75ZgP+S8EWiuxCN5cjGw=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=K/8OiNuhzSx00WKt8NGcKSgdUylGw4baQvOd1d0jssH3ZpgUwK69o/ldNZ4703psX3eWj4A6vCl6jBTEwlibE+mh3rWS8wWIlaMR2QgyHZmyr6tpIKWxbw/7htqJiafGMNVJ6hTrEGqA4ioafTOAg3PB0/CRPwW5jnwbb/LJo1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=qmHUBqwK; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="qmHUBqwK" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1760450944; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=HTt/KzKieiee5hMQF+Yl+hZuVbxPhLlk+WHV6D9guo8=; b=qmHUBqwKWNT5vYFudzOiUF4zcASTLZYuSKIEBYKIYVECM3evlnYbwtVC8+wujvSBGhkRvY OyuizPA56TwSUlr7qmo4GZLrjp3R+5oetCgXTIS7kckygImIJsFsBocWRNnvc2skNg4ZEq Ug6JIGrNsyZQALcEojvwDxh6J+Z7bGw= From: Hao Ge To: Vlastimil Babka , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Shakeel Butt , Michal Hocko , Roman Gushchin , Muchun Song , Suren Baghdasaryan Cc: Harry Yoo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Subject: [PATCH v2] slab: Add check for memcg_data's upper bits in folio_memcg_kmem Date: Tue, 14 Oct 2025 22:08:15 +0800 Message-Id: <20251014140815.383823-1-hao.ge@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Hao Ge This is because OBJEXTS_ALLOC_FAIL and OBJEXTS_ALLOC_FAIL currently share the same bit position. Therefore, we cannot simply determine whether memcg_data still points to the slabobj_ext vector by checking folio->memcg_data & MEMCG_DATA_OBJEXTS. We can distinguish between these two cases by checking whether the upper bits set: 1) MEMCG_DATA_OBJEXTS is set, but upper bits are not set, so it should mean obj_exts allocation failed (OBJEXTS_ALLOC_FAIL), thus do not report error, or 2) MEMCG_DATA_OBJEXTS is set, and upper bits are also set, so someone did not clear a valid folio->memcg_data before freeing the folio (report error). So let's add check for memcg_data's upper bits in folio_memcg_kmem. Fixes: 7612833192d5 ("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") Signed-off-by: Hao Ge --- v2: Per Vlastimil and Harry's suggestion, instead of introducing a new bit, implement this by checking if the highest bit is set. Many thanks to Vlastimil and Harry. --- include/linux/memcontrol.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 873e510d6f8d..f9f7ba14be04 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -534,7 +534,9 @@ static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *ob static inline bool folio_memcg_kmem(struct folio *folio) { VM_BUG_ON_PGFLAGS(PageTail(&folio->page), &folio->page); - VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS, folio); + VM_BUG_ON_FOLIO((folio->memcg_data & MEMCG_DATA_OBJEXTS) && + (folio->memcg_data & ~(ULONG_MAX >> 1)), + folio); return folio->memcg_data & MEMCG_DATA_KMEM; } -- 2.25.1