From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70166C32771 for ; Mon, 26 Sep 2022 10:08:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C47408E003B; Mon, 26 Sep 2022 06:08:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BF7978E0039; Mon, 26 Sep 2022 06:08:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ABEB68E003B; Mon, 26 Sep 2022 06:08:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 995C28E0039 for ; Mon, 26 Sep 2022 06:08:04 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 66053407DE for ; Mon, 26 Sep 2022 10:08:04 +0000 (UTC) X-FDA: 79953810888.19.D9B24AA Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [193.142.43.52]) by imf01.hostedemail.com (Postfix) with ESMTP id 0262740007 for ; Mon, 26 Sep 2022 10:08:02 +0000 (UTC) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1ocl1s-0003cn-G3; Mon, 26 Sep 2022 12:08:00 +0200 Date: Mon, 26 Sep 2022 12:08:00 +0200 From: Florian Westphal To: Michal Hocko Cc: Florian Westphal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, vbabka@suse.cz, akpm@linux-foundation.org, urezki@gmail.com, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, Martin Zaharinov Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC Message-ID: <20220926100800.GB12777@breakpoint.cc> References: <20220923103858.26729-1-fw@strlen.de> <20220923133512.GE22541@breakpoint.cc> <20220926075639.GA908@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf01.hostedemail.com: domain of fw@strlen.de designates 193.142.43.52 as permitted sender) smtp.mailfrom=fw@strlen.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1664186883; a=rsa-sha256; cv=none; b=Bs9Zdztwl2ix6tVZLAHX0sT86+lSsLV5EpdiU7lImSdcQqkgf4XQYnkXvTOBnVEyLDbtiP kFcL1A2OgFjW3J8k1DtjhF0t1Pn64Lx8Ot5lRb/NfA3HZU/wsKtPffgyepE45UYhguShzw ARD1Is/ancB1QV/B288wPNaodePSz7Q= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664186883; h=from:from:sender: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: in-reply-to:in-reply-to:references:references; bh=SiRq+tatfi+9Z8opZdccSUSqLGQKv1z7IuMuqPq3oSM=; b=Ew9IXbSYs0k1iWTYCvgMYe8GdzoMDhiW0FH9AhwF6VUd23eOrKfEWAa6Dg4DktnEZvE6c6 1yAhirYi+oCLupfHP3+B+tQkfY+kGwoBEYnd8uhaq8AXoSSozarms/8iHJK4j85lpLZIgW 6yc+mF4yS3qekv0NU05jsJnUaVZ5AkI= X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0262740007 X-Stat-Signature: 9swprnpsqzahbgknujjn5ykgyy74ratp Authentication-Results: imf01.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf01.hostedemail.com: domain of fw@strlen.de designates 193.142.43.52 as permitted sender) smtp.mailfrom=fw@strlen.de X-HE-Tag: 1664186882-302407 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: Michal Hocko wrote: > + old_tbl = rht_dereference_rcu(ht->tbl, ht); > + size = tbl->size; > + > + data = ERR_PTR(-EBUSY); > + > + if (rht_grow_above_75(ht, tbl)) > + size *= 2; > + /* Do not schedule more than one rehash */ > + else if (old_tbl != tbl) > + return data; > + > + data = ERR_PTR(-ENOMEM); > + > + rcu_read_unlock(); > + new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL); > + rcu_read_lock(); I don't think this is going to work, there can be callers that rely on rcu protected data structures getting free'd. Also, network stack assumes synchronize_rcu() means that all inflight packets have completed processing.