From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id BA6116B0038 for ; Wed, 1 Mar 2017 03:43:31 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id e15so13775215wmd.6 for ; Wed, 01 Mar 2017 00:43:31 -0800 (PST) Received: from mail-wm0-x241.google.com (mail-wm0-x241.google.com. [2a00:1450:400c:c09::241]) by mx.google.com with ESMTPS id g16si21036242wmg.156.2017.03.01.00.43.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Mar 2017 00:43:30 -0800 (PST) Received: by mail-wm0-x241.google.com with SMTP id m70so6049025wma.1 for ; Wed, 01 Mar 2017 00:43:30 -0800 (PST) Date: Wed, 1 Mar 2017 09:43:26 +0100 From: Daniel Vetter Subject: Re: [PATCH RESEND] drm/via: use get_user_pages_unlocked() Message-ID: <20170301084326.tdz32zvjg62znclq@phenom.ffwll.local> References: <20170227215008.21457-1-lstoakes@gmail.com> <20170228090110.m4pxtjlbgaft7oet@phenom.ffwll.local> <20170228193539.GT29622@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Lorenzo Stoakes Cc: Al Viro , Linux Kernel Mailing List , dri-devel@lists.freedesktop.org, linux-mm On Tue, Feb 28, 2017 at 08:28:08PM +0000, Lorenzo Stoakes wrote: > 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? I have no idea. drm/via is unmaintained, it's a dri1 racy driver with problems probably everywhere, and I'm not sure we even have someone left who cares (there's an out-of-tree kms conversion of via, but it's stuck since years). In short, it's the drm dungeons and the only reason I merge patches is to give people an easy target for test driving the patch submission process to dri-devel. And to avoid drm being a blocker for tree-wide refactorings. Otherwise 0 reasons to change anything here. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- 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