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 4087AC433F5 for ; Sat, 12 Mar 2022 10:24:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 761328D0002; Sat, 12 Mar 2022 05:24:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 710318D0001; Sat, 12 Mar 2022 05:24:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D7FC8D0002; Sat, 12 Mar 2022 05:24:48 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0186.hostedemail.com [216.40.44.186]) by kanga.kvack.org (Postfix) with ESMTP id 4B6BE8D0001 for ; Sat, 12 Mar 2022 05:24:48 -0500 (EST) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id AA58D181CC404 for ; Sat, 12 Mar 2022 10:24:47 +0000 (UTC) X-FDA: 79235350614.31.E624ED8 Received: from rere.qmqm.pl (rere.qmqm.pl [91.227.64.183]) by imf23.hostedemail.com (Postfix) with ESMTP id A9F9A14001D for ; Sat, 12 Mar 2022 10:24:46 +0000 (UTC) Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 4KFzSW2sKzzJS; Sat, 12 Mar 2022 11:24:43 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1647080684; bh=+QR/+RJkyH6iOL9WdEejK5XbutH1cp/++rV5+5TNCEU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fJup2gIGRswfLU52LqyF/nMo3l2iimuu1mZSzsQTuQKGumuX731elm4pQaQoiTA7R MP+HtyE9Dd01XZHadk64vHmOtW7A/XXhdC00IVxtKHeUwUMK+Wmays+UTb155qlIRr ERo2qs8gvRUeRgaHCGixncnt2KIuYg/0uqjni0UXn0NGN4a69IkL+NN0rhmhKXNWqn VXp1Uibi8oRExJlWeKWM1RGkoMm61+GyqDBjYs4Ua8u1U1J1yLdyzWv8L2e0pOKHBr 9u5OEs+uczVfBM15y8Ps2Y7TkiyAyfEx917KnhoA0XXx6AnOvWUPIa7r4H4JgieC+1 2XDC/8ptw0Fgg== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.5 at mail Date: Sat, 12 Mar 2022 11:24:40 +0100 From: =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= To: Linus Torvalds Cc: Xiaomeng Tong , Arnd Bergmann , Greg Kroah-Hartman , Jakob Koschel , Jann Horn , Kees Cook , Linux Kbuild mailing list , Linux Kernel Mailing List , Linux-MM , Netdev Subject: Re: [PATCH 2/6] list: add new MACROs to make iterator invisiable Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: A9F9A14001D X-Stat-Signature: 59x4pz381wcm6hpnyz7sby8uqifpjkfu X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=rere.qmqm.pl header.s=1 header.b=fJup2gIG; dmarc=pass (policy=reject) header.from=rere.qmqm.pl; spf=pass (imf23.hostedemail.com: domain of mirq-linux@rere.qmqm.pl designates 91.227.64.183 as permitted sender) smtp.mailfrom=mirq-linux@rere.qmqm.pl X-Rspamd-Server: rspam02 X-HE-Tag: 1647080686-269856 Content-Transfer-Encoding: quoted-printable 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 Thu, Mar 10, 2022 at 04:46:33PM -0800, Linus Torvalds wrote: > On Thu, Mar 10, 2022 at 3:54 PM Micha=B3 Miros=B3aw wrote: > > > > If the macro implementation doesn't have to be pretty, maybe it could= go > > a step further and remember the list_head's offset? That would look > > something like following (expanding on your patch; not compile tested= ): >=20 > Oh, I thought of it. >=20 > It gets complicated. [...] It seems that it's not that bad if we don't require checking whether a list_head of an entry is only ever used with a single list parent. The source type is not needed for the macros, and it turns out that pre-decla= ring the offset type is also not needed. I compile-tested the code below on godbolt.org with -std=3Dc11: struct list_head { struct list_head *prev, *next; }; #define offsetof __builtin_offsetof #define typeof __typeof #define list_traversal_head(name,type,target_member) \ union { \ struct list_head name; \ type *name##_traversal_type; \ char (*name##_list_head_offset)[offsetof(type, target_member)]; \ } #define self_list_ref_offset_type(type,target_member) \ type##__##target_member##__offset__ #define define_self_list_ref_offset(type,target_member) \ self_list_ref_offset_type(type,target_member) \ { char ignoreme__[offsetof(type, target_member)]; } #define self_list_traversal_head(name,type,target_member) \ union { \ struct list_head name; \ type *name##_traversal_type; \ self_list_ref_offset_type(type,target_member) *name##_list_head_offset;= \ } #define list_traversal_entry(ptr, head) \ (typeof(*head##_traversal_type))((void *)ptr - sizeof(**head##_list_head= _offset)) #define list_traversal_entry_head(ptr, head) \ ((struct list_head *)((void *)ptr + sizeof(**head##_list_head_offset))) #define list_traversal_entry_is_head(ptr, head) \ (list_traversal_entry_head(ptr, head) =3D=3D (head)) #define list_traversal_next_entry(ptr, head) \ list_traversal_entry(list_traversal_entry_head(ptr, head)->next, head) #define list_traverse(pos, head) \ for (typeof(*head##_traversal_type) pos =3D list_traversal_entry((hea= d)->next, head); \ !list_traversal_entry_is_head(pos, head); \ pos =3D list_traversal_next_entry(pos,head)) struct entry { self_list_traversal_head(self_list, struct entry, child_head); struct list_head child_head; }; define_self_list_ref_offset(struct entry, child_head); void bar(struct entry *b); void foo(struct entry *a) { list_traverse(pos, &a->self_list) { bar(pos); } } --=20 Micha=B3 Miros=B3aw