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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7EDC0C4321E for ; Wed, 30 Nov 2022 08:23:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234569AbiK3IXc (ORCPT ); Wed, 30 Nov 2022 03:23:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234772AbiK3IXN (ORCPT ); Wed, 30 Nov 2022 03:23:13 -0500 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96678282 for ; Wed, 30 Nov 2022 00:23:12 -0800 (PST) X-UUID: e15af86f09524a93b1bb2e33569ce7fc-20221130 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:CC:To:From; bh=1ih/5AZ7VH4p7skGfYkFy1TDMephGSqfFTBm8ZbhGsk=; b=FcII+bSoo/NSaB5tOGDmAEsu7MGK95o6KlK8dPvz3utWjM39luFj66v5AwcXxcYbBXDUzJ4or5BA7khTg4kYXgfTcSdSCD8hq3Wu1ZNo/KtbHQ4kdUl14790zpL6nAd9B/GeZQuGKjInwYHTiLY2xQX88A5m1+BeWJ3c2POv8Yk=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.14,REQID:986dd338-f3c8-46fc-a91d-0f4026fa5e46,IP:0,U RL:0,TC:0,Content:0,EDM:0,RT:0,SF:45,FILE:0,BULK:0,RULE:Release_Ham,ACTION :release,TS:45 X-CID-INFO: VERSION:1.1.14,REQID:986dd338-f3c8-46fc-a91d-0f4026fa5e46,IP:0,URL :0,TC:0,Content:0,EDM:0,RT:0,SF:45,FILE:0,BULK:0,RULE:Release_Ham,ACTION:r elease,TS:45 X-CID-META: VersionHash:dcaaed0,CLOUDID:f52c216c-41fe-47b6-8eb4-ec192dedaf7d,B ulkID:221130162307VUMOZIKQ,BulkQuantity:0,Recheck:0,SF:28|17|19|48|102,TC: nil,Content:0,EDM:-3,IP:nil,URL:0,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0 X-UUID: e15af86f09524a93b1bb2e33569ce7fc-20221130 Received: from mtkmbs13n1.mediatek.inc [(172.21.101.193)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1755579773; Wed, 30 Nov 2022 16:23:07 +0800 Received: from mtkmbs11n1.mediatek.inc (172.21.101.185) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.792.15; Wed, 30 Nov 2022 16:23:06 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs11n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.792.15 via Frontend Transport; Wed, 30 Nov 2022 16:23:06 +0800 From: Andrew Yang To: CC: , , , , , , Subject: Re: [PATCH v2] mm/writeback: fix dereferencing NULL mapping->host Date: Wed, 30 Nov 2022 16:23:03 +0800 Message-ID: <20221130082303.30859-2-andrew.yang@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20221130082303.30859-1-andrew.yang@mediatek.com> References: <20221129095620.4c1a8056@gandalf.local.home> <20221130082303.30859-1-andrew.yang@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2022-11-29 at 09:56 -0500, Steven Rostedt wrote: > On Tue, 29 Nov 2022 11:32:59 +0800 > Andrew Yang wrote: > > > From: "andrew.yang" > > > > Check before dereferencing mapping->host > > > > Signed-off-by: andrew.yang > > --- > > include/trace/events/writeback.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/trace/events/writeback.h > > b/include/trace/events/writeback.h > > index 86b2a82da546..56f6e114d3ed 100644 > > --- a/include/trace/events/writeback.h > > +++ b/include/trace/events/writeback.h > > @@ -68,7 +68,7 @@ DECLARE_EVENT_CLASS(writeback_folio_template, > > strscpy_pad(__entry->name, > > bdi_dev_name(mapping ? > > inode_to_bdi(mapping->host) : > > NULL), 32); > > - __entry->ino = mapping ? mapping->host->i_ino : 0; > > + __entry->ino = mapping && mapping->host ? mapping- > > >host->i_ino : 0; > > I hate remembering precedence. Can we add parenthesis around this to > be > clear? > > __entry->ino = (mapping && mapping->host) ? mapping- > >host->i_ino : 0; > > Thanks, > > -- Steve > > > > __entry->index = folio->index; > > ), > > > > Sure, that's a good suggestion