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 5099FC433EF for ; Wed, 13 Jul 2022 10:07:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D0DD7940122; Wed, 13 Jul 2022 06:07:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C96769400E5; Wed, 13 Jul 2022 06:07:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B36C4940122; Wed, 13 Jul 2022 06:07:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 9FF1D9400E5 for ; Wed, 13 Jul 2022 06:07:43 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 7929C12015C for ; Wed, 13 Jul 2022 10:07:43 +0000 (UTC) X-FDA: 79681650006.20.CABF2F2 Received: from gentwo.de (gentwo.de [161.97.139.209]) by imf19.hostedemail.com (Postfix) with ESMTP id CDD321A0076 for ; Wed, 13 Jul 2022 10:07:41 +0000 (UTC) Received: by gentwo.de (Postfix, from userid 1001) id CB054B00418; Wed, 13 Jul 2022 12:07:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.de; s=default; t=1657706859; bh=SeRKe3yf26MO72QyT8L5XOyRs4a5maEIynSyHOtqHmI=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=KfjqqhlJ+qL4z2DVAzkCyK3gUGScWGTsPAWcs3B+248mSEHsLroKOpBYT58vskshA HhDD8TPqp5LgUL7hh9w0lxfU6BdzJiaLFQuGF/Uk8dvqVPKr++46gU1OwJ8X6+9+8o 3llasYq85WgGUZZaprYp0qBiYZ5Vt8Blt+AWJKK5Wuhd3AGRiEh2D2tOOGc6POyAFg JJPvvxUmvPWLo0Cp7ZFMTMvzzwdSsPrmtUW7HIQ/y+999X5Arba1dZZQlmHcDXmCEY oBbRbph2PYTXaaVhIZRjem5Jil5RUErOMQFc5CH0LOZkSlDgtQKYeiImI6nKf7HDtQ UbwnKwniLgl8g== Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id C88D1B00149; Wed, 13 Jul 2022 12:07:39 +0200 (CEST) Date: Wed, 13 Jul 2022 12:07:39 +0200 (CEST) From: Christoph Lameter To: Hyeonggon Yoo <42.hyeyoo@gmail.com> cc: Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Joe Perches , Vasily Averin , Matthew WilCox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Marco Elver Subject: Re: [PATCH 16/16] mm/sl[au]b: check if large object is valid in __ksize() In-Reply-To: Message-ID: References: <20220712133946.307181-1-42.hyeyoo@gmail.com> <20220712133946.307181-17-42.hyeyoo@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657706862; a=rsa-sha256; cv=none; b=t9wzJZtXKixRB/CfWezt5NQWH7b5HeWDJD1hzLevaBCI0jtcLKansp4/7AKNTowmUNVtbG LL8AyL4UVYXRjOTeAALKVitV6HKeX+PpWk6UQVFZYccb7eHfsFxEm0HGQpz81iWioLjcX0 hwXSHDRmFFseZNcipknn0LTo/QSw+Vg= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=gentwo.de header.s=default header.b=KfjqqhlJ; spf=pass (imf19.hostedemail.com: domain of cl@gentwo.de designates 161.97.139.209 as permitted sender) smtp.mailfrom=cl@gentwo.de; dmarc=pass (policy=none) header.from=gentwo.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657706862; 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:dkim-signature; bh=V6txJ8kJFqlTavM48Tri7b4ZlEseDN4jP6+HK4Ak3BQ=; b=2BPVUgigayusvCY1jkhJUZd6ZLaHjB/vRPUs1nKMgTZ4PElQTh+2RVYM3GfIhIaUBdqz9/ GbfzFXfRf22BNxDUuKJx+vcz8dwlykhDtbMszrLhHbHeY1fhxQ+SOjTGf7VDlsEtn0SG1y DwtuRk5XO8zgjm0ZIDi07Cy1ZFEZho4= X-Rspamd-Queue-Id: CDD321A0076 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gentwo.de header.s=default header.b=KfjqqhlJ; spf=pass (imf19.hostedemail.com: domain of cl@gentwo.de designates 161.97.139.209 as permitted sender) smtp.mailfrom=cl@gentwo.de; dmarc=pass (policy=none) header.from=gentwo.de X-Rspamd-Server: rspam02 X-Rspam-User: X-Stat-Signature: rbspoaxf9gxdgngkq15urtx4dwbjtonc X-HE-Tag: 1657706861-631633 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: On Wed, 13 Jul 2022, Hyeonggon Yoo wrote: > > Why return 0 if there is an error and why bother the callers with these > > checks. BUG()? > > I thought BUG should be used when there is no other solution. Spurios returns of 0 that the caller has to check for is a solution? > > I guess this is an error since the order-0 page cannot come from slab > > allocations. > > comment in ksize() says: > "The caller must guarantee that objp points to a valid object > previously allocated with either kmalloc() or kmem_cache_alloc()." > > It should not be used on order-0 page that is not allocated from slab. No? I guess we would need to check. Code could exist that does this. Getting a 0 size would be surprising too here. BUG()? Or WARN() and return PAGE_SIZE.