From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 7DFD86B000E for ; Wed, 14 Feb 2018 16:29:41 -0500 (EST) Received: by mail-pl0-f69.google.com with SMTP id w24so11536592plq.11 for ; Wed, 14 Feb 2018 13:29:41 -0800 (PST) Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id b21si1812093pfe.31.2018.02.14.13.29.40 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 14 Feb 2018 13:29:40 -0800 (PST) Date: Wed, 14 Feb 2018 13:29:37 -0800 From: Matthew Wilcox Subject: Re: [PATCH v2 2/8] mm: Add kvmalloc_ab_c and kvzalloc_struct Message-ID: <20180214212937.GG20627@bombadil.infradead.org> References: <20180214201154.10186-1-willy@infradead.org> <20180214201154.10186-3-willy@infradead.org> <1518641152.3678.28.camel@perches.com> <20180214211203.GF20627@bombadil.infradead.org> <1518643449.3678.33.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1518643449.3678.33.camel@perches.com> Sender: owner-linux-mm@kvack.org List-ID: To: Joe Perches Cc: Andrew Morton , Matthew Wilcox , linux-mm@kvack.org, Kees Cook , linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com On Wed, Feb 14, 2018 at 01:24:09PM -0800, Joe Perches wrote: > On Wed, 2018-02-14 at 13:12 -0800, Matthew Wilcox wrote: > > On Wed, Feb 14, 2018 at 12:45:52PM -0800, Joe Perches wrote: > > > Perhaps kv[zm]alloc_buf_and_array is better naming. > > > > I think that's actively misleading. The programmer isn't allocating a > > buf, they're allocating a struct. kvzalloc_hdr_arr was the earlier name, > > and that made some sense; they're allocating an array with a header. > > But nobody thinks about it like that; they're allocating a structure > > with a variably sized array at the end of it. > > > > If C macros had decent introspection, I'd like it to be: > > > > sev = kvzalloc_struct(elems, GFP_KERNEL); > > > > and have the macro examine the structure pointed to by 'sev', check > > the last element was an array, calculate the size of the array element, > > and call kvzalloc_ab_c. But we don't live in that world, so I have to > > get the programmer to tell me the structure and the name of the last > > element in it. > > Look at your patch 4 > > - dev_dax = kzalloc(sizeof(*dev_dax) + sizeof(*res) * count, GFP_KERNEL); > + dev_dax = kvzalloc_struct(dev_dax, res, count, GFP_KERNEL); > > Here what is being allocated is exactly a struct > and an array. No, it's a struct *containing* an array. Look at patches 5 & 8 where I have to convert the structs to contain the array which was silently being allocated immediately after them. > And this doesn't compile either. Does for me. What error are you seeing? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org