From mboxrd@z Thu Jan 1 00:00:00 1970 In-Reply-To: <1192201105.27435.41.camel@twins> References: <11854939641916-git-send-email-ssouhlal@FreeBSD.org> <200710120257.05960.nickpiggin@yahoo.com.au> <1192185439.27435.19.camel@twins> <200710120414.11026.nickpiggin@yahoo.com.au> <1192186222.27435.22.camel@twins> <20071012075317.591212ef@laptopd505.fenrus.org> <1192201105.27435.41.camel@twins> Mime-Version: 1.0 (Apple Message framework v752.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Suleiman Souhlal Subject: Re: [PATCH] mm: avoid dirtying shared mappings on mlock Date: Fri, 12 Oct 2007 10:45:17 -0700 Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: Arjan van de Ven , Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, Suleiman Souhlal , linux-mm , hugh List-ID: On Oct 12, 2007, at 7:58 AM, Peter Zijlstra wrote: > On Fri, 2007-10-12 at 07:53 -0700, Arjan van de Ven wrote: >> On Fri, 12 Oct 2007 12:50:22 +0200 >>>>> The pages will still be read-only due to dirty tracking, so the >>>>> first write will still do page_mkwrite(). >>>> >>>> Which can SIGBUS, no? >>> >>> Sure, but that is no different than any other mmap'ed write. I'm not >>> seeing how an mlocked region is special here. >>> >>> I agree it would be nice if mmap'ed writes would have better error >>> reporting than SIGBUS, but such is life. >> >> well... there's another consideration >> people use mlock() in cases where they don't want to go to the >> filesystem for paging and stuff as well (think the various iscsi >> daemons and other things that get in trouble).. those kind of uses >> really use mlock to avoid >> 1) IO to the filesystem >> 2) Needing memory allocations for pagefault like things >> at least for the more "hidden" cases... >> >> prefaulting everything ready pretty much gives them that... letting >> things fault on demand... nicely breaks that. > > Non of that is changed. So I'm a little puzzled as to which side you > argue. I think this might change the behavior in case you mlock sparse files. I guess currently the holes disappear when you mlock them, but with the patch the blocks wouldn't get allocated until they get written to. -- Suleiman -- 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