From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC][PATCH] mm: fix page_mkclean() vs non-linear vmas From: Peter Zijlstra In-Reply-To: <1173291120.4718.40.camel@lappy> References: <1173264462.6374.140.camel@twins> <20070307110035.GE5555@wotan.suse.de> <1173268086.6374.157.camel@twins> <20070307121730.GC18704@wotan.suse.de> <1173271286.6374.166.camel@twins> <20070307130851.GE18704@wotan.suse.de> <1173273562.6374.175.camel@twins> <20070307133649.GF18704@wotan.suse.de> <1173275532.6374.183.camel@twins> <1173278067.6374.188.camel@twins> <20070307150102.GH18704@wotan.suse.de> <1173286682.6374.191.camel@twins> <1173291120.4718.40.camel@lappy> Content-Type: text/plain Date: Wed, 07 Mar 2007 19:24:39 +0100 Message-Id: <1173291879.14351.3.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Nick Piggin , Miklos Szeredi , akpm@linux-foundation.org, mingo@elte.hu, linux-mm@kvack.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, Jeff Dike , hugh List-ID: On Wed, 2007-03-07 at 19:12 +0100, Peter Zijlstra wrote: > On Wed, 2007-03-07 at 10:00 -0800, Linus Torvalds wrote: > > > > On Wed, 7 Mar 2007, Peter Zijlstra wrote: > > > > > > I'm not at all happy with this, but plain disallowing remap_file_pages on bdis > > > without BDI_CAP_NO_WRITEBACK seems to offend some people, hence restrict it to > > > root only. > > > > I don't think that's a viable approach. Nonlinear mappings would normally > > be used by databases, and you don't want to limit databases to be run by > > root only. > > It was claimed that they use it on tmpfs only, not on a 'real' > filesystem. More specifically, databases want to use direct IO (I know you hate it) and use the nonlinear vma as buffer area to feed this direct IO Mapped IO is unsuited for databases in its current form due to the way IO errors are handled. -- 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