From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 44E816B0038 for ; Tue, 28 Feb 2017 15:28:31 -0500 (EST) Received: by mail-lf0-f69.google.com with SMTP id a6so11372207lfa.1 for ; Tue, 28 Feb 2017 12:28:31 -0800 (PST) Received: from mail-lf0-x244.google.com (mail-lf0-x244.google.com. [2a00:1450:4010:c07::244]) by mx.google.com with ESMTPS id f2si1552471ljb.73.2017.02.28.12.28.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Feb 2017 12:28:29 -0800 (PST) Received: by mail-lf0-x244.google.com with SMTP id z127so1823768lfa.2 for ; Tue, 28 Feb 2017 12:28:29 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20170228193539.GT29622@ZenIV.linux.org.uk> References: <20170227215008.21457-1-lstoakes@gmail.com> <20170228090110.m4pxtjlbgaft7oet@phenom.ffwll.local> <20170228193539.GT29622@ZenIV.linux.org.uk> From: Lorenzo Stoakes Date: Tue, 28 Feb 2017 20:28:08 +0000 Message-ID: Subject: Re: [PATCH RESEND] drm/via: use get_user_pages_unlocked() Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Al Viro Cc: Linux Kernel Mailing List , dri-devel@lists.freedesktop.org, linux-mm On 28 February 2017 at 19:35, Al Viro wrote: > On Tue, Feb 28, 2017 at 10:01:10AM +0100, Daniel Vetter wrote: > >> > + ret = get_user_pages_unlocked((unsigned long)xfer->mem_addr, >> > + vsg->num_pages, vsg->pages, >> > + (vsg->direction == DMA_FROM_DEVICE) ? FOLL_WRITE : 0); > > Umm... Why not > ret = get_user_pages_fast((unsigned long)xfer->mem_addr, > vsg->num_pages, > vsg->direction == DMA_FROM_DEVICE, > vsg->pages); > > IOW, do you really need a warranty that ->mmap_sem will be grabbed and > released? Daniel will be better placed to answer in this specific case, but more generally is there any reason why we can't just use get_user_pages_fast() in all such cases? These patches were simply a mechanical/cautious replacement for code that is more or less exactly equivalent but if this would make sense perhaps it'd be worth using gup_fast() where possible? -- Lorenzo Stoakes https://ljs.io -- 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