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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 203F3C433E0 for ; Thu, 14 Jan 2021 19:42:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC5522399C for ; Thu, 14 Jan 2021 19:42:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730301AbhANTmR (ORCPT ); Thu, 14 Jan 2021 14:42:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:33714 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730177AbhANTmQ (ORCPT ); Thu, 14 Jan 2021 14:42:16 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3987F239EF; Thu, 14 Jan 2021 19:41:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610653295; bh=j72ES8sG143mJE4qoXOz2HxLviBlz2SE24DDEx8XP0o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GTupvysEJQdFamE1YxFEmpRUIuOtDSMco9l+VnAqtDreicebY/e5TFTBV9T5lPwJ+ 6W98Bz9ewmb/e7mc6z4cmTGMvJcALkWW4pn/lVbGNshU51fDceDJu4+NDs5qAvnbAe 8Q5ISSNEjsp8luCkE7n0yHHwg/NVITpnY62NAYheMibO6W3ZZZpOaJ1q/a2GO5hiMI OtadQ5JviuBgoZEv46qUSwHKJtrMv4lr9Roo1oP/94omk3v5kzX5ks27TPQg3anIkz aflwvl5gc9Ezt6aWY2gqecU5AmLW5R2yS+PCkuE//tZGOHmaq5EKszKubPvzUJcJTj PV2DQLD3R1zxg== Date: Thu, 14 Jan 2021 19:41:29 +0000 From: Will Deacon To: Linus Torvalds , ndesaulniers@google.com Cc: Linux Kernel Mailing List , Linux-MM , Linux ARM , Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , "Kirill A . Shutemov" , Vinayak Menon , Hugh Dickins , Android Kernel Team Subject: Re: [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault' Message-ID: <20210114194129.GA13314@willie-the-truck> References: <20210114175934.13070-1-will@kernel.org> <20210114175934.13070-5-will@kernel.org> <20210114190021.GB13135@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 14, 2021 at 11:09:01AM -0800, Linus Torvalds wrote: > On Thu, Jan 14, 2021 at 11:00 AM Will Deacon wrote: > > > > I tried that initially, but I found that I had to make all of the > > members const to get it to work, at which point the anonymous struct > > wasn't really adding anything. Did I just botch the syntax? > > I'm not sure what you tried. But this stupid test-case sure works for me: > > struct hello { > const struct { > unsigned long address; > }; > unsigned int flags; > }; > > extern int fn(struct hello *); > > int test(void) > { > struct hello a = { > .address = 1, > }; > a.flags = 0; > return fn(&a); > } > > and because "address" is in that unnamed constant struct, you can only > set it within that initializer, and cannot do > > a.address = 0; > > without an error (the way you _can_ do "a.flags = 0"). > > I don't see naming the struct making a difference - apart from forcing > that big rename patch, of course. > > But maybe we're talking about different issues? Urgh... We _are_ both on the same page, and your reply above had me thinking I've lost the plot, so I went back to the start. Check out v5.11-rc3 and apply this patch: diff --git a/include/linux/mm.h b/include/linux/mm.h index ecdf8a8cd6ae..1eb950865450 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -514,11 +514,14 @@ static inline bool fault_flag_allow_retry_first(unsigned int flags) * pgoff should be used in favour of virtual_address, if possible. */ struct vm_fault { - struct vm_area_struct *vma; /* Target VMA */ + const struct { + struct vm_area_struct *vma; /* Target VMA */ + gfp_t gfp_mask; /* gfp mask to be used for allocations */ + pgoff_t pgoff; /* Logical page offset based on vma */ + unsigned long address; /* Faulting virtual address */ + }; + unsigned int flags; /* FAULT_FLAG_xxx flags */ - gfp_t gfp_mask; /* gfp mask to be used for allocations */ - pgoff_t pgoff; /* Logical page offset based on vma */ - unsigned long address; /* Faulting virtual address */ pmd_t *pmd; /* Pointer to pmd entry matching * the 'address' */ pud_t *pud; /* Pointer to pud entry matching Sure enough, an arm64 defconfig builds perfectly alright with that change, but it really shouldn't. I'm using clang 11.0.5, so I had another go with GCC 9.2.1 and bang: mm/filemap.c: In function ‘filemap_map_pages’: mm/filemap.c:2963:16: error: assignment of member ‘address’ in read-only object 2963 | vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT; | ^~ make[1]: *** [scripts/Makefile.build:279: mm/filemap.o] Error 1 make[1]: *** Waiting for unfinished jobs.... make: *** [Makefile:1805: mm] Error 2 make: *** Waiting for unfinished jobs.... Nick -- any clue what's happening here? We would like that const anonymous struct to behave like a const struct member, as the alternative (naming the thing) results in a lot of refactoring churn. Cheers, Will 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=-10.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 91F6FC433E0 for ; Thu, 14 Jan 2021 19:46:21 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4DBB72343B for ; Thu, 14 Jan 2021 19:46:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DBB72343B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ZqnEbGV3YNGH5HBrdVjPq9MXsjVd2xD+2Mle3wjHBAk=; b=PVhz3PDQBFfzc3RHIVqLd32qP OThKzmRn2zCFgr/AAMxi+fVXWx4uFjeb6856uMU2l7930cyykrDE6ZrtAZS1WqIA7oXhepG6DkDM1 gvyAHn7CkOrSXj2zS0LthOzmdOKTcYK0BhtNWhCcxVi03Vf0cdjqt/krlEqkUp9hA32P4n41KSNFX s0yEwReY/X84Tugy2LXD1MVQyIzfGQ3gtCgUXtlZ9o20T74lbmMOMDgQfk9+Utdm0eVlWjIL1XmEI wTp6UCqkAMke8z8b082CpVmdQuLhuviQ/1/JVk+lhqm9QmxoqHGjlw1G+vpGl2qEUa1i8uP2U6fti x9fgTBlNg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l08Xk-0000fG-4v; Thu, 14 Jan 2021 19:44:28 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l08V0-0006Mc-Pn for linux-arm-kernel@lists.infradead.org; Thu, 14 Jan 2021 19:41:43 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3987F239EF; Thu, 14 Jan 2021 19:41:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610653295; bh=j72ES8sG143mJE4qoXOz2HxLviBlz2SE24DDEx8XP0o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=GTupvysEJQdFamE1YxFEmpRUIuOtDSMco9l+VnAqtDreicebY/e5TFTBV9T5lPwJ+ 6W98Bz9ewmb/e7mc6z4cmTGMvJcALkWW4pn/lVbGNshU51fDceDJu4+NDs5qAvnbAe 8Q5ISSNEjsp8luCkE7n0yHHwg/NVITpnY62NAYheMibO6W3ZZZpOaJ1q/a2GO5hiMI OtadQ5JviuBgoZEv46qUSwHKJtrMv4lr9Roo1oP/94omk3v5kzX5ks27TPQg3anIkz aflwvl5gc9Ezt6aWY2gqecU5AmLW5R2yS+PCkuE//tZGOHmaq5EKszKubPvzUJcJTj PV2DQLD3R1zxg== Date: Thu, 14 Jan 2021 19:41:29 +0000 From: Will Deacon To: Linus Torvalds , ndesaulniers@google.com Subject: Re: [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault' Message-ID: <20210114194129.GA13314@willie-the-truck> References: <20210114175934.13070-1-will@kernel.org> <20210114175934.13070-5-will@kernel.org> <20210114190021.GB13135@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210114_144139_204404_DA162C56 X-CRM114-Status: GOOD ( 26.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jan Kara , Minchan Kim , Catalin Marinas , Hugh Dickins , Linux Kernel Mailing List , Linux-MM , Vinayak Menon , "Kirill A . Shutemov" , Andrew Morton , Android Kernel Team , Linux ARM Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCBKYW4gMTQsIDIwMjEgYXQgMTE6MDk6MDFBTSAtMDgwMCwgTGludXMgVG9ydmFsZHMg d3JvdGU6Cj4gT24gVGh1LCBKYW4gMTQsIDIwMjEgYXQgMTE6MDAgQU0gV2lsbCBEZWFjb24gPHdp bGxAa2VybmVsLm9yZz4gd3JvdGU6Cj4gPgo+ID4gSSB0cmllZCB0aGF0IGluaXRpYWxseSwgYnV0 IEkgZm91bmQgdGhhdCBJIGhhZCB0byBtYWtlIGFsbCBvZiB0aGUKPiA+IG1lbWJlcnMgY29uc3Qg dG8gZ2V0IGl0IHRvIHdvcmssIGF0IHdoaWNoIHBvaW50IHRoZSBhbm9ueW1vdXMgc3RydWN0Cj4g PiB3YXNuJ3QgcmVhbGx5IGFkZGluZyBhbnl0aGluZy4gRGlkIEkganVzdCBib3RjaCB0aGUgc3lu dGF4Pwo+IAo+IEknbSBub3Qgc3VyZSB3aGF0IHlvdSB0cmllZC4gQnV0IHRoaXMgc3R1cGlkIHRl c3QtY2FzZSBzdXJlIHdvcmtzIGZvciBtZToKPiAKPiAgICAgc3RydWN0IGhlbGxvIHsKPiAgICAg ICAgIGNvbnN0IHN0cnVjdCB7Cj4gICAgICAgICAgICAgICAgIHVuc2lnbmVkIGxvbmcgYWRkcmVz czsKPiAgICAgICAgIH07Cj4gICAgICAgICB1bnNpZ25lZCBpbnQgZmxhZ3M7Cj4gICAgIH07Cj4g Cj4gICAgIGV4dGVybiBpbnQgZm4oc3RydWN0IGhlbGxvICopOwo+IAo+ICAgICBpbnQgdGVzdCh2 b2lkKQo+ICAgICB7Cj4gICAgICAgICBzdHJ1Y3QgaGVsbG8gYSA9IHsKPiAgICAgICAgICAgICAg ICAgLmFkZHJlc3MgPSAxLAo+ICAgICAgICAgfTsKPiAgICAgICAgIGEuZmxhZ3MgPSAwOwo+ICAg ICAgICAgcmV0dXJuIGZuKCZhKTsKPiAgICAgfQo+IAo+IGFuZCBiZWNhdXNlICJhZGRyZXNzIiBp cyBpbiB0aGF0IHVubmFtZWQgY29uc3RhbnQgc3RydWN0LCB5b3UgY2FuIG9ubHkKPiBzZXQgaXQg d2l0aGluIHRoYXQgaW5pdGlhbGl6ZXIsIGFuZCBjYW5ub3QgZG8KPiAKPiAgICAgICAgIGEuYWRk cmVzcyA9IDA7Cj4gCj4gd2l0aG91dCBhbiBlcnJvciAodGhlIHdheSB5b3UgX2Nhbl8gZG8gImEu ZmxhZ3MgPSAwIikuCj4gCj4gSSBkb24ndCBzZWUgbmFtaW5nIHRoZSBzdHJ1Y3QgbWFraW5nIGEg ZGlmZmVyZW5jZSAtIGFwYXJ0IGZyb20gZm9yY2luZwo+IHRoYXQgYmlnIHJlbmFtZSBwYXRjaCwg b2YgY291cnNlLgo+IAo+IEJ1dCBtYXliZSB3ZSdyZSB0YWxraW5nIGFib3V0IGRpZmZlcmVudCBp c3N1ZXM/CgpVcmdoLi4uCgpXZSBfYXJlXyBib3RoIG9uIHRoZSBzYW1lIHBhZ2UsIGFuZCB5b3Vy IHJlcGx5IGFib3ZlIGhhZCBtZSB0aGlua2luZyBJJ3ZlCmxvc3QgdGhlIHBsb3QsIHNvIEkgd2Vu dCBiYWNrIHRvIHRoZSBzdGFydC4gQ2hlY2sgb3V0IHY1LjExLXJjMyBhbmQgYXBwbHkKdGhpcyBw YXRjaDoKCgpkaWZmIC0tZ2l0IGEvaW5jbHVkZS9saW51eC9tbS5oIGIvaW5jbHVkZS9saW51eC9t bS5oCmluZGV4IGVjZGY4YThjZDZhZS4uMWViOTUwODY1NDUwIDEwMDY0NAotLS0gYS9pbmNsdWRl L2xpbnV4L21tLmgKKysrIGIvaW5jbHVkZS9saW51eC9tbS5oCkBAIC01MTQsMTEgKzUxNCwxNCBA QCBzdGF0aWMgaW5saW5lIGJvb2wgZmF1bHRfZmxhZ19hbGxvd19yZXRyeV9maXJzdCh1bnNpZ25l ZCBpbnQgZmxhZ3MpCiAgKiBwZ29mZiBzaG91bGQgYmUgdXNlZCBpbiBmYXZvdXIgb2YgdmlydHVh bF9hZGRyZXNzLCBpZiBwb3NzaWJsZS4KICAqLwogc3RydWN0IHZtX2ZhdWx0IHsKLSAgICAgICBz dHJ1Y3Qgdm1fYXJlYV9zdHJ1Y3QgKnZtYTsgICAgIC8qIFRhcmdldCBWTUEgKi8KKyAgICAgICBj b25zdCBzdHJ1Y3QgeworICAgICAgICAgICAgICAgc3RydWN0IHZtX2FyZWFfc3RydWN0ICp2bWE7 ICAgICAvKiBUYXJnZXQgVk1BICovCisgICAgICAgICAgICAgICBnZnBfdCBnZnBfbWFzazsgICAg ICAgICAgICAgICAgIC8qIGdmcCBtYXNrIHRvIGJlIHVzZWQgZm9yIGFsbG9jYXRpb25zICovCisg ICAgICAgICAgICAgICBwZ29mZl90IHBnb2ZmOyAgICAgICAgICAgICAgICAgIC8qIExvZ2ljYWwg cGFnZSBvZmZzZXQgYmFzZWQgb24gdm1hICovCisgICAgICAgICAgICAgICB1bnNpZ25lZCBsb25n IGFkZHJlc3M7ICAgICAgICAgIC8qIEZhdWx0aW5nIHZpcnR1YWwgYWRkcmVzcyAqLworICAgICAg IH07CisKICAgICAgICB1bnNpZ25lZCBpbnQgZmxhZ3M7ICAgICAgICAgICAgIC8qIEZBVUxUX0ZM QUdfeHh4IGZsYWdzICovCi0gICAgICAgZ2ZwX3QgZ2ZwX21hc2s7ICAgICAgICAgICAgICAgICAv KiBnZnAgbWFzayB0byBiZSB1c2VkIGZvciBhbGxvY2F0aW9ucyAqLwotICAgICAgIHBnb2ZmX3Qg cGdvZmY7ICAgICAgICAgICAgICAgICAgLyogTG9naWNhbCBwYWdlIG9mZnNldCBiYXNlZCBvbiB2 bWEgKi8KLSAgICAgICB1bnNpZ25lZCBsb25nIGFkZHJlc3M7ICAgICAgICAgIC8qIEZhdWx0aW5n IHZpcnR1YWwgYWRkcmVzcyAqLwogICAgICAgIHBtZF90ICpwbWQ7ICAgICAgICAgICAgICAgICAg ICAgLyogUG9pbnRlciB0byBwbWQgZW50cnkgbWF0Y2hpbmcKICAgICAgICAgICAgICAgICAgICAg ICAgICAgICAgICAgICAgICAgICAqIHRoZSAnYWRkcmVzcycgKi8KICAgICAgICBwdWRfdCAqcHVk OyAgICAgICAgICAgICAgICAgICAgIC8qIFBvaW50ZXIgdG8gcHVkIGVudHJ5IG1hdGNoaW5nCgoK U3VyZSBlbm91Z2gsIGFuIGFybTY0IGRlZmNvbmZpZyBidWlsZHMgcGVyZmVjdGx5IGFscmlnaHQg d2l0aCB0aGF0IGNoYW5nZSwKYnV0IGl0IHJlYWxseSBzaG91bGRuJ3QuIEknbSB1c2luZyBjbGFu ZyAxMS4wLjUsIHNvIEkgaGFkIGFub3RoZXIgZ28gd2l0aApHQ0MgOS4yLjEgYW5kIGJhbmc6Cgpt bS9maWxlbWFwLmM6IEluIGZ1bmN0aW9uIOKAmGZpbGVtYXBfbWFwX3BhZ2Vz4oCZOgptbS9maWxl bWFwLmM6Mjk2MzoxNjogZXJyb3I6IGFzc2lnbm1lbnQgb2YgbWVtYmVyIOKAmGFkZHJlc3PigJkg aW4gcmVhZC1vbmx5IG9iamVjdAogMjk2MyB8ICAgdm1mLT5hZGRyZXNzICs9ICh4YXMueGFfaW5k ZXggLSBsYXN0X3Bnb2ZmKSA8PCBQQUdFX1NISUZUOwogICAgICB8ICAgICAgICAgICAgICAgIF5+ Cm1ha2VbMV06ICoqKiBbc2NyaXB0cy9NYWtlZmlsZS5idWlsZDoyNzk6IG1tL2ZpbGVtYXAub10g RXJyb3IgMQptYWtlWzFdOiAqKiogV2FpdGluZyBmb3IgdW5maW5pc2hlZCBqb2JzLi4uLgptYWtl OiAqKiogW01ha2VmaWxlOjE4MDU6IG1tXSBFcnJvciAyCm1ha2U6ICoqKiBXYWl0aW5nIGZvciB1 bmZpbmlzaGVkIGpvYnMuLi4uCgpOaWNrIC0tIGFueSBjbHVlIHdoYXQncyBoYXBwZW5pbmcgaGVy ZT8gV2Ugd291bGQgbGlrZSB0aGF0IGNvbnN0IGFub255bW91cwpzdHJ1Y3QgdG8gYmVoYXZlIGxp a2UgYSBjb25zdCBzdHJ1Y3QgbWVtYmVyLCBhcyB0aGUgYWx0ZXJuYXRpdmUgKG5hbWluZyB0aGUK dGhpbmcpIHJlc3VsdHMgaW4gYSBsb3Qgb2YgcmVmYWN0b3JpbmcgY2h1cm4uCgpDaGVlcnMsCgpX aWxsCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwpsaW51 eC1hcm0ta2VybmVsIG1haWxpbmcgbGlzdApsaW51eC1hcm0ta2VybmVsQGxpc3RzLmluZnJhZGVh ZC5vcmcKaHR0cDovL2xpc3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9saXN0aW5mby9saW51eC1h cm0ta2VybmVsCg==