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 X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00F7EC83004 for ; Wed, 29 Apr 2020 18:25:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B6D5422202 for ; Wed, 29 Apr 2020 18:25:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="h0NgVJZn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6D5422202 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4DD468E0005; Wed, 29 Apr 2020 14:25:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 48D438E0001; Wed, 29 Apr 2020 14:25:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3A4E08E0005; Wed, 29 Apr 2020 14:25:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0130.hostedemail.com [216.40.44.130]) by kanga.kvack.org (Postfix) with ESMTP id 1F7C38E0001 for ; Wed, 29 Apr 2020 14:25:25 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id D0EFF180AD815 for ; Wed, 29 Apr 2020 18:25:24 +0000 (UTC) X-FDA: 76761720168.14.soap81_68f4f4c4b8049 X-HE-Tag: soap81_68f4f4c4b8049 X-Filterd-Recvd-Size: 3239 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Apr 2020 18:25:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=mk8Z9sCY0AhAexl6PYPVinqKRa9QYElOCdGLIqmtc8Y=; b=h0NgVJZnMQxSMXEuqfJICAC3T9 DVTnQvYxycKsv119y9J9+OnK1xPBqKoOR2PzIMa+JPHZwiYWXb4EMkeDgGRU2AX5x0vdOMVmgOmSE 8eWtvR4CrHy/U2yEyWpy2SBgyZ/tKI2xbT7qpHjwOT3x+1mXJLdnuBHtSnaiVPx3lnW7fL0HLCoer 29gnZMWOkrivqfvC//UzEW8RHJmYHhDxbsAYgo35Goc1Khg5XZ9dIfEOm24XjJVFDS02HP8OFBot/ wvNgnzAQtcHCHkX4ANTRtpwbAjyrfCGobZGvRfPs5bApZTRz1dot8UtI4KoccJkt/8ho14puFjqGZ /VKECLDw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTrOO-0006rY-LW; Wed, 29 Apr 2020 18:25:08 +0000 Date: Wed, 29 Apr 2020 11:25:08 -0700 From: Matthew Wilcox To: Markus Elfring Cc: Waiman Long , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Kees Cook , Changbin Du , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/slub: Fix incorrect interpretation of s->offset Message-ID: <20200429182508.GU29705@bombadil.infradead.org> References: <20200429135328.26976-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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, Apr 29, 2020 at 06:42:55PM +0200, Markus Elfring wrote: > > In a couple of places in the slub memory allocator, the code uses > > "s->offset" as a check to see if the free pointer is put right after the > > object. That check is no longer true with commit 3202fa62fb43 ("slub: > > relocate freelist pointer to middle of object"). > > Will any further collateral evolution become interesting? What do you mean by this question? > > +static inline unsigned int get_info_end(struct kmem_cache *s) > > +{ > > + if (freeptr_outside_object(s)) > > + return s->inuse + sizeof(void *); > > + else > > + return s->inuse; > > +} > > How do you think about the following source code variants? > > + return freeptr_outside_object(s) > + ? s->inuse + sizeof(void *) > + : s->inuse; That is less clear than the version Wayman posted. > > static struct track *get_track(struct kmem_cache *s, void *object, > > enum track_item alloc) > > { > > struct track *p; > > > > - if (s->offset) > > - p = object + s->offset + sizeof(void *); > > - else > > - p = object + s->inuse; > > + p = object + get_info_end(s); > > > > return p + alloc; > > } > > + struct track *p = object + get_info_end(s); > > return p + alloc; Yes, I think that's an improvement.