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[209.85.208.173]) by smtp.gmail.com with ESMTPSA id 5sm629701lfa.98.2021.01.14.11.09.17 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Jan 2021 11:09:18 -0800 (PST) Received: by mail-lj1-f173.google.com with SMTP id p13so7740181ljg.2 for ; Thu, 14 Jan 2021 11:09:17 -0800 (PST) X-Received: by 2002:a2e:6f17:: with SMTP id k23mr3659547ljc.411.1610651357370; Thu, 14 Jan 2021 11:09:17 -0800 (PST) MIME-Version: 1.0 References: <20210114175934.13070-1-will@kernel.org> <20210114175934.13070-5-will@kernel.org> <20210114190021.GB13135@willie-the-truck> In-Reply-To: <20210114190021.GB13135@willie-the-truck> From: Linus Torvalds Date: Thu, 14 Jan 2021 11:09:01 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault' To: Will Deacon 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 Content-Type: text/plain; charset="UTF-8" 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, 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? Linus