From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) by kanga.kvack.org (Postfix) with ESMTP id BC64E6B0010 for ; Wed, 3 Oct 2018 16:00:51 -0400 (EDT) Received: by mail-pf1-f200.google.com with SMTP id r81-v6so4058264pfk.11 for ; Wed, 03 Oct 2018 13:00:51 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id m16-v6si2220841pgd.48.2018.10.03.13.00.50 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 03 Oct 2018 13:00:50 -0700 (PDT) Date: Wed, 3 Oct 2018 13:00:03 -0700 From: Matthew Wilcox Subject: Re: [PATCH v2] mm: Introduce new function vm_insert_kmem_page Message-ID: <20181003200003.GA9965@bombadil.infradead.org> References: <20181003185854.GA1174@jordon-HP-15-Notebook-PC> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181003185854.GA1174@jordon-HP-15-Notebook-PC> Sender: owner-linux-mm@kvack.org List-ID: To: Souptick Joarder Cc: linux@armlinux.org.uk, miguel.ojeda.sandonis@gmail.com, robin@protonic.nl, stefanr@s5r6.in-berlin.de, hjc@rock-chips.com, heiko@sntech.de, airlied@linux.ie, robin.murphy@arm.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, m.szyprowski@samsung.com, keescook@chromium.org, treding@nvidia.com, mhocko@suse.com, dan.j.williams@intel.com, kirill.shutemov@linux.intel.com, mark.rutland@arm.com, aryabinin@virtuozzo.com, dvyukov@google.com, kstewart@linuxfoundation.org, tchibo@google.com, riel@redhat.com, minchan@kernel.org, peterz@infradead.org, ying.huang@intel.com, ak@linux.intel.com, rppt@linux.vnet.ibm.com, linux@dominikbrodowski.net, arnd@arndb.de, cpandya@codeaurora.org, hannes@cmpxchg.org, joe@perches.com, mcgrof@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux1394-devel@lists.sourceforge.net, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, linux-mm@kvack.org On Thu, Oct 04, 2018 at 12:28:54AM +0530, Souptick Joarder wrote: > These are the approaches which could have been taken to handle > this scenario - > > * Replace vm_insert_page with vmf_insert_page and then write few > extra lines of code to convert VM_FAULT_CODE to errno which > makes driver users more complex ( also the reverse mapping errno to > VM_FAULT_CODE have been cleaned up as part of vm_fault_t migration , > not preferred to introduce anything similar again) > > * Maintain both vm_insert_page and vmf_insert_page and use it in > respective places. But it won't gurantee that vm_insert_page will > never be used in #PF context. > > * Introduce a similar API like vm_insert_page, convert all non #PF > consumer to use it and finally remove vm_insert_page by converting > it to vmf_insert_page. > > And the 3rd approach was taken by introducing vm_insert_kmem_page(). > > In short, vmf_insert_page will be used in page fault handlers > context and vm_insert_kmem_page will be used to map kernel > memory to user vma outside page fault handlers context. As far as I can tell, vm_insert_kmem_page() is line-for-line identical with vm_insert_page(). Seriously, here's a diff I just did: -static int insert_page(struct vm_area_struct *vma, unsigned long addr, - struct page *page, pgprot_t prot) +static int insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, + struct page *page, pgprot_t prot) - /* Ok, finally just insert the thing.. */ -int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, +int vm_insert_kmem_page(struct vm_area_struct *vma, unsigned long addr, - return insert_page(vma, addr, page, vma->vm_page_prot); + return insert_kmem_page(vma, addr, page, vma->vm_page_prot); -EXPORT_SYMBOL(vm_insert_page); +EXPORT_SYMBOL(vm_insert_kmem_page); What on earth are you trying to do?