From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (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 4DD593B531D for ; Mon, 27 Apr 2026 10:55:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777287312; cv=none; b=brVRjOA6z3b7nLTcXZDzdHH+zz8QIfhrMCoOjs468eRvLzbj8wyjyiqVFoqAbq+sZbCYDvINwncXSU6U/M0JRAyu6IYV74JhG0S6xV+4NGzfg93XPiZ4rdKd1BceFbJtTWaiDGMqcaz39Vg/RIc/8nfzwCHaqTYw75A9IvG+M34= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777287312; c=relaxed/simple; bh=/w4RUftOiWKG0B9T+XnElTFIM5A507TdHnwLVG/6FMs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gIedb9nK9tIjGYtp4o2aEFah5Pz3vg/tllq6j1KfHH4rvqz5K7KsQ+qmTu7ECPweJcZaF26Xt6afKGXhgXA/UTGhwgn+FhPM5iXbvC+k88DDqm9OU5JD0VEdy10TjUaQ057fCcLSy1eZLF4rMQTnY1pHMslbpwF90seKGpQkPCU= 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=vaMgGQQ7; arc=none smtp.client-ip=91.218.175.170 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="vaMgGQQ7" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777287307; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=01pnW2uMOPcCj5rJaZLF3XU0HpXGu/ejkcw5Amteq3k=; b=vaMgGQQ7gF+2VqyK2PHIai6pYu6HfSISoVSFz98mGUuSjh+1gSIes28GJnt5DZAkRLBQSq gFVoXSjF7QKRBEiqHffysKmWeO4bpkWGKW1ttjvAtlHe19ZrtVpGCE/KKt/YQLFN25RaVG jeNlGGytB6UYbm4m59D7aiyiAvlTJ40= Date: Mon, 27 Apr 2026 18:54:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [syzbot] [mm?] WARNING: bad unlock balance in do_wp_page To: Andrew Morton Cc: shakeel.butt@linux.dev, syzbot , Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, surenb@google.com, syzkaller-bugs@googlegroups.com, vbabka@kernel.org, Muchun Song References: <69edca15.170a0220.38e3f1.0000.GAE@google.com> <20260426034938.db29d74982a8eb8463f8cf3a@linux-foundation.org> <20260426105532.43768b24a42744f1b52fdff2@linux-foundation.org> <3591c663-a4a9-4c22-97cf-b58b2e7d8a41@linux.dev> <20260427034352.6ca48156d613319aac415290@linux-foundation.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <20260427034352.6ca48156d613319aac415290@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 4/27/26 6:43 PM, Andrew Morton wrote: > On Mon, 27 Apr 2026 15:24:10 +0800 Qi Zheng wrote: > >> >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -805,10 +805,15 @@ static long memcg_state_val_in_pages(int idx, long >> val) >> * Used in mod_memcg_state() and mod_memcg_lruvec_state() to avoid >> race with >> * reparenting of non-hierarchical state_locals. >> */ >> -static inline struct mem_cgroup *get_non_dying_memcg_start(struct >> mem_cgroup *memcg) >> +static inline struct mem_cgroup *get_non_dying_memcg_start(struct >> mem_cgroup *memcg, >> + bool *locked) > > Sometimes this is called "locked", sometimes "rcu_locked". Let's be > consistent please. OK. > >> { >> - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { >> + *locked = false; >> return memcg; >> + } > > I was thinking we could use a single bit in the task_struct for this: Maybe this isn't the good idea. It feels a bit weird to add a new member to task_struct just to fix a minor bug in mm. :( > > --- a/mm/memcontrol.c~a > +++ a/mm/memcontrol.c > @@ -810,6 +810,8 @@ static inline struct mem_cgroup *get_non > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return memcg; > > + current->foo = 1; > + > rcu_read_lock(); > > while (memcg_is_dying(memcg)) > @@ -820,9 +822,11 @@ static inline struct mem_cgroup *get_non > > static inline void get_non_dying_memcg_end(void) > { > - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > + if (current->foo == 0) > return; > > + current->foo = 0; > + > rcu_read_unlock(); > } > #else > _ > > That doesn't work if get_non_dying_memcg_start/get_non_dying_memcg_end > calls can nest? If they can nest then we'd need a counter in the > task_struct. >