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Tue, 19 Mar 2019 10:51:11 -0700 (PDT) Received: from ltop.local ([2a02:a03f:4049:a600:52:6fcd:af3b:582e]) by smtp.gmail.com with ESMTPSA id w8sm3238240ejj.27.2019.03.19.10.51.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Mar 2019 10:51:10 -0700 (PDT) Date: Tue, 19 Mar 2019 18:51:08 +0100 From: Luc Van Oostenryck To: Matthew Wilcox Cc: Souptick Joarder , akpm@linux-foundation.org, mike.kravetz@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org Subject: Re: [PATCH] include/linux/hugetlb.h: Convert to use vm_fault_t Message-ID: <20190319175107.oxwjf72hpcqqmo3l@ltop.local> References: <20190318162604.GA31553@jordon-HP-15-Notebook-PC> <20190319032022.GR19508@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190319032022.GR19508@bombadil.infradead.org> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 18, 2019 at 08:20:22PM -0700, Matthew Wilcox wrote: > On Mon, Mar 18, 2019 at 09:56:05PM +0530, Souptick Joarder wrote: > > >> mm/memory.c:3968:21: sparse: incorrect type in assignment (different > > >> base types) @@ expected restricted vm_fault_t [usertype] ret @@ > > >> got e] ret @@ > > mm/memory.c:3968:21: expected restricted vm_fault_t [usertype] ret > > mm/memory.c:3968:21: got int > > I think this may be a sparse bug. > > Compare: > > +++ b/mm/memory.c > @@ -3964,6 +3964,9 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > if (flags & FAULT_FLAG_USER) > mem_cgroup_enter_user_fault(); > > + ret = 0; > + ret = ({ BUG(); 0; }); > + ret = 1; > if (unlikely(is_vm_hugetlb_page(vma))) > ret = hugetlb_fault(vma->vm_mm, vma, address, flags); > else > > ../mm/memory.c:3968:13: sparse: warning: incorrect type in assignment (different base types) > ../mm/memory.c:3968:13: sparse: expected restricted vm_fault_t [assigned] [usertype] ret > ../mm/memory.c:3968:13: sparse: got int > ../mm/memory.c:3969:13: sparse: warning: incorrect type in assignment (different base types) > ../mm/memory.c:3969:13: sparse: expected restricted vm_fault_t [assigned] [usertype] ret > ../mm/memory.c:3969:13: sparse: got int > > vm_fault_t is __bitwise: > > include/linux/mm_types.h:typedef __bitwise unsigned int vm_fault_t; > > so simply assigning 0 to ret should work (and does on line 3967), but > sparse doesn't seem to like it as part of a ({ .. }) expression. This is the expected behaviour. The constant 0 is magic regarding bitwise types but ({ ...; 0; }) is not, it is just an ordinary expression of type 'int'. So, IMHO, Souptick's patch is the right thing to do. Best regards, -- Luc Van Oostenryck